Best Gas Furnace for 2023

Best Gas Furnaces 2023

One of the most common questions I get as an HVAC contractor in Sacramento is, “Which gas furnace systems are the best?” Or more specifically what are the best gas furnace for 2023?  I see a ton of articles online about this topic – many that someone who’s not even in the HVAC industry wrote! Some compensated blog writer wrote it or gave you a list of top-rated systems. Systems they’ve never even touched. These bloggers are telling people that nationally recognized economy line systems are better than those that will truly last you a long time.

Best HVAC Systems

Just like my summer post in 2022 on Which AC Systems are the Best, I have always felt like three manufacturers have had the best reputation for the last few decades. And in no particular order, they are:

  • Trane/American Standard
  • Carrier/Bryant
  • Lennox

Best Gas Furnace for 2023A Special Note:

Before I list the rest of the systems, I want to mention furnace systems come fully assembled at the factory and are ready to work. However, it takes experienced technicians to modify the unit per the manufacturer’s instructions to conform to your specific home’s demands. The last step of installing it “in the field” and adding whatever additional parts to bring it up to the proper building code in your area is up to the contractor you choose.

That’s an important point because buying a Trane, Carrier, or Lennox includes buying it from a professional, detail-oriented, reliable contractor you trust and are comfortable with bringing to life. If someone is going to install it for you, but you can’t find them after the installation because they sell systems so cheap they’re out of business, or they simply won’t pick up the phone, that’s not going to help you when you need some follow-up.

You can buy any system, but if the blower settings, gas pressures, static air pressures, high and low voltage wiring, fuse sizes, a precision refrigerant charge, airflow, water drainage, gas piping, intake air, exhaust system, thermostats, and other safety codes aren’t set up correctly, you’ll find your new system not lasting nearly as long as it could have. It can be the difference between your system lasting ten years or 20 years.

Consumer Reports

So, Consumer Reports asked over 36,000 gas furnace owners who had their system installed between 2005 and 2021. Their owner satisfaction ratings are based on the percentage of members who are extremely likely to recommend their gas furnace brand to friends and family.

The manufacturers of today’s residential heating and cooling systems are:

  • Rheem, who also makes:
    • Ruud
  • Daiken, who makes:
    • Goodman
    • Amana
    • Daiken
    • Janitrol
  • Bosch recently started making their own systems. Pretty good ones too. We sell their inverter split systems and package units.
  • Nortek, who makes:
    • Intertherm
    • Maytag
    • Frigidaire
    • Nordyne
  • Johnson Controls, who makes:
    • York
    • Coleman
    • Luxaire
  • International Comfort Products (ICP) who makes several brands. The most prominent are:
    • Day & Night
    • Tempstar
    • Comfortmaker
    • Heil
    • Keeprite
  • Lennox also makes:
    • Armstrong
    • Ducane
    • Aire-Flo
    • Concord
  • Carrier also makes:
    • Payne
    • Weathermaker
  • Trane also makes:
    • Ameristar
    • RunTru
    • Oxbox

Isn’t it crazy the limited number of true manufacturers but the 30+ brands we have to choose from? No wonder it’s hard to determine the best gas furnace for 2023!

Here is where they fall as far as owner satisfaction. And keep in mind that some of these brands like Bosch, Daiken and others didn’t make the Consumer Reports survey results due to their obscurity and low number of installations during that 2005 to 2021 timeframe.

Highest Rated for Owner Satisfaction:

  • Trane rated 5/5
  • American Standard rated 5/5

Second Place for Owner Satisfaction:

  • Carrier rated 4/5
  • Bryant rated 4/5
  • Lennox rated 4/5

Mid-Tier HVAC Systems

  • Rheem rated 3/5
  • Ruud rated 3/5
  • Armstrong rated 3/5
  • Concord rated 3/5
  • Ducane rated 3/5
  • Amana rated 3/5
  • Comfortmaker rated 3/5
  • Day & Night rated 3/5
  • Heil rated 3/5
  • Keeprite rated 3/5
  • Tempstar rated 3/5
  • Payne rated 3/5
  • Goodman rated 3/5
  • Coleman rated 3/5
  • Luxaire rated 3/5
  • York rated 3/5

Lower-Tier HVAC Systems

  • Frigidaire rated 2/5
  • Maytag rated 2/5
  • Westinghouse rated 2/5


When it comes to deciding which gas furnace systems are the best, you have three systems perennially at the top of the list. Trane, Carrier, and Lennox. While their single-stage and two-stage systems have the same capabilities, efficiencies, and life spans, it’s the higher-tier variable speed systems where you’ll start seeing the differences.

When you start looking for a vehicle, you pretty much have a brand name in mind. You might get a higher or lower-end model with fewer bells and whistles, but maybe you’ve always felt comfortable driving a GMC truck over a Toyota truck.

In another post, let’s talk about the other heating systems in homes across America – Best Heat Pumps for 2023

Let me know what you think about this in the comments below. I see a ton of articles online about this topic – many that someone who isn’t even in the HVAC industry wrote. Some paid blog writers wrote it. You’ve got to take it from someone who actually installs them and services the equipment out in the field.

If this is your first time watching our videos, please click subscribe down here on the bottom right, and if you click that little bell next to it, you’ll be notified of all our videos as they come out.

Thanks so much for watching, and we’ll see you on the next video.

What to do When Your Heater Stops Working After a Storm

Heater Stops Working after a Storm

Heater Stops Working after a StormIt’s that time of year again when severe weather is a possibility. One of the dangers of thunderstorms is the potential for lightning strikes. A lightning strike can cause all sorts of problems for your home, including knocking out your furnace or heat pump. If you find yourself in this situation, don’t panic! Here are some troubleshooting tips to help you get your heater up and running again when your heater stops working after a storm.

Is Your Thermostat Displaying Properly?

It doesn’t mean your furnace should be working properly if it does still display right; it’s just where I always start. Some thermostats only run on the 24 volts provided by the furnace, and some thermostats have AA battery backup. (I just want to know if the system is calling for heat or not.) You’ve probably already tried this, but if you haven’t, observe what condition the stat is in. Is it blank, looks normal, and calls for heat? If it’s blank, the thunderstorm could have taken out the low voltage to your furnace. But before opening up the furnace or air handler, let’s check the high-voltage power source.  This can also be a reason your heater stops working after a storm.

Check the Main Electrical Panel

Your furnace is supposed to receive 120 volts from the breaker panel on the side of the house. (Some people have high voltage panels located inside the house.) Heat pumps have 240-volt power supplied to them. As a reminder, the air handler or furnace will be located in a closet, the garage, the attic, or maybe you have a package unit on the roof or side of the house. But the first thing you’ll want to do is check to see if the power to your furnace is turned off at the breaker box.

If the breaker is “Tripped,” flip the switch to the “Off” position, then to the fully “On” position. Wait a few minutes to see if the furnace turns on. If it doesn’t, there may be an issue with the power supply to your home. In this case, you’ll need to contact your HVAC contractor to investigate and make any necessary repairs.

Inspect the Furnace for Damage (Charring, Soot)

A bolt of lightning hitting near your home can send an enormous amount of damaging heat and energy through your home’s electrical system. If the breaker is still on, but there doesn’t seem to be any power flowing to the furnace, the next step is to inspect the unit itself for damage. Start by looking for any signs of damage to the exterior of the furnace, such as burns or melted plastic. If you see any black charring or soot, it’s possible one of the components inside the unit blew, like a control board, relay, or safety switch. If you see any damage, it’s probably best to call in a professional heating and cooling technician to take a look and perform any necessary repairs.  Fox Family can always help finding out why your heater stops working after a storm.

Check for Error Codes

While you’re checking the unit, see if there is a sight glass, maybe an inch wide, on the front cover. Without opening the cover, see if any red or yellow LEDs are flashing. Count those flashes and make a note of it. Your HVAC contractor will thank you for having that flash code. Maybe it blinks three times long and two times quickly. That would be an error code of 32. Maybe you just see five steady flashes. The error code would be 5. Each brand is different in how they display error codes, but once the outer panel is removed, a sticker is usually attached to the inside that identifies what those error codes mean. You should really know what you’re doing before removing any panels, though. You have to think about your safety first.

Reset the Furnace

What to do When Your Furnace Doesn't Turn on After a Lightning Storm

If you’ve checked both the power supply at the main panel and the furnace itself for damage and error codes, and everything seems to be good, the next step is to reset the furnace itself. The easiest way to reset the furnace is to unplug it from the outlet, wait for 30 seconds and then plug it back in. While you’re doing that, observe the condition of the outlet cover and plug. If it has burning and soot around it or on the plate, the wiring inside of it could be charred. If you feel comfortable, take a small screwdriver and take the cover plate off to inspect the wiring. If it looks clean, it’s probably okay, but I would still replace the plug and cover plate as soon as possible. The cord that leads to the plug should not be melting or discolored either. If it is, that’s another thing I would consider having replaced soon.

After you plug the furnace back in, make sure the thermostat is still calling for heat and wait up to five minutes to see if the furnace turns on. Some types of systems have protection that forces the system to lock out for up to five minutes. To us technicians, this can be the longest five minutes EVER!!!

DIY Troubleshooting

Some people are brave enough to move on with troubleshooting their heat pump or heater is not working after a storm, but I have some pretty good articles and videos already posted about how to do that.

Lightning strikes can cause all sorts of problems for your home—including knocking out your furnace or heat pump. If this happens, don’t panic! Follow these troubleshooting tips, and you might be able to safely get your furnace up and running again in no time. And remember, if you’re ever unsure about what to do or how to fix something, it’s always best to call in a professional who can help. Stay safe!

If this is your first time watching our channel, please click subscribe down here on the bottom right, and if you click that little bell next to it, you’ll be notified of all of our videos as they come out.

Thanks so much for watching, and we’ll see you on the next video.

Turning on the Furnace for the First Time Each Year

Turning on the Furnace for the First Time Each Year

What is that burning smell when turning on the furnace for the first time each year?

As the winter season approaches, a lot of you will turn on the furnace for the first time this year.  That can be a very intimidating situation for some people.  You may have just moved into your first apartment.  Or perhaps you’ve just moved into your new home this past summer.  The AC worked fine, but now it’s time to see how the furnace is going to work this winter.

Whether you walk over to the thermostat or turn it on manually, what’s that burning smell the first time you’re turning on the furnace for the year?  In this week’s blog, let’s break down the gas furnace, and some of the sounds and smells you get when it comes on for the first time each year.

About Turning on the Furnace

You should understand the nature of the furnace is to provide warm air for your home.  And it does that with a gas flame.  But that gas flame isn’t just flying around uncontrolled the way it does in a fireplace for example.  A very structured flame is sent into the furnace.  If the flame were to roll out or overheat the furnace, a series of safety switches will engage, turning off the furnace.

Whether you walk over to the thermostat or turn it on with your smartphone, the sounds and smells that you experience can be confusing.  That’s not how the air conditioner sounded when it came on, and that’s definitely not how the air conditioner smelled when it was working.

When the furnace gets turned on, the thermostat on the wall tells the furnace which is in your attic, your garage, or your closet in the hallway to initiate a sequence of events that will ultimately shoot a gas flame into the firebox, or heat exchanger.

Turning on the Furnace:  the Basic Parts

There are a few parts that come on before that flame starts to heat the home.  The thermostat tells the control board inside the furnace to come on.  The control board is the brains of the system that will control the following events.

The first motor to come on will be the inducer motor.

Not a large motor by any means, but it’s the one that gets rid of the fumes spent by the flame that warms your home.  The control board and a pressure switch acknowledge that the inducer has come on and is working properly.

The ignitor will come on next.

Usually, it’s a hot surface ignitor made of silicon carbide that glows red hot.  About 2500 degrees.  The timer on the control board then allows the gas valve to open up and pour a controlled amount of gas over the red-hot surface ignitor.

Creating the Flame

This creates the flame we were talking about earlier, that shoots into the metal firebox, which is better known as a heat exchanger to us technicians. A small flame sensor then verifies the flame is on and sends a signal to the board that everything is burning properly, and the system is safe to continue heating the home.

Blower Fan Comes On

If the flame sensor says everything is okay, the control board then tells the blower fan to come on.  The sequence is complete.  Warm air will then start flowing into the rooms until it gets to the desired temperature.

That whole sequence of events that happens takes about 1 minute from the time thermostat tells the furnace to start, to the time the blower turns on and gives you heat through your registers.

When the thermostat senses the room’s warm enough, it tells the control board to end the call for heating, which then cuts the flame.  Meanwhile, the blower stays on just long enough to cool the furnace down quite a bit, about 60 to 90 seconds.  This helps extend the life of the system.

So how does the heat exchanger work?  Well, it “exchanges heat” by keeping the flame and its fumes inside the metal box while a fan blows air over the outside of the metal.  The heat that comes off that metal and the air from the blower is then carried into your rooms where you feel the warm air.

What’s That Burning Smell?

Folks call in every fall when they’re turning on their furnace for the first time and say the system IS working but there’s a strange smell coming through their vents. Almost like a burning smell.  When we get out to their home and verify all the motors are working properly, we let them know something most people don’t know until it’s happened to them.

So what’s that smell the first time you turn on your furnace each season?  It’s just a fine layer of dust that’s settled onto the heat exchanger.  The dust from your house has made its way past the air filter and blower assembly to the metallic heat exchanger.  As the metal heats up, the dust burns off and creates that burnt smell.  It can happen the first few times you turn the system on, but after that, you shouldn’t get that burning smell any more.

If the smell bothers you, you can just open the doors or windows to your house and let it vent out that way for about fifteen minutes.  But rest assured it’s not carbon monoxide.  That odorless gas can only be picked up by a carbon monoxide detector.

Safety First

If you do turn your furnace on for the first time or ANY time this year and your home’s carbon monoxide detector does go off, don’t just remove the batteries.  Don’t treat it like it’s some nuisance alarm, either.  Go ahead and step outside of the home and call the Fire Department.  Let them come out to make sure everything is okay before going back inside.  It might cause a big show for everyone in the neighborhood, but who cares?  It’s your family’s life on the line.

If you don’t currently have a carbon monoxide detector on each floor and the main hallways of your house, now would be a good time to pick those up from your local hardware store.

About Detectors

Speaking of detectors in your homes – if you haven’t done so already this year, it’s time to change out the batteries in those detectors around your home.  Your local fire department usually will come out for free and help you replace those batteries if you have trouble reaching those detectors on your own.  If they won’t and you’re in our area, just provide the batteries and we’d be happy to come out and change them for you.  Otherwise, any handyman in your area would be up to the task.

As a reminder, the single-most-important-thing you can do to keep your furnace clean is to change those air filters.  If the system can’t breathe in because of a dirty air filter, then it won’t be able to breathe out for you at the supply registers in your rooms either.  Again, if you can’t do it because you’re elderly or physically unable to reach the filter, give us a call!

Remove Flammables Before Turning on the Furnace

Another bit of advice we’d like you to consider is to make sure there are no flammables around the furnace.  Remember, we said that the furnace is either in the attic, the closet, or the garage. These are common places to store items that tend to be forgotten over time.

A metal flue pipe that gets very hot when the furnace is turned on can be dangerous if left unattended.  Broomsticks, cardboard, newspapers, clothing, and other materials can scorch over time if they’re resting on the flue pipe.  Setting away from the furnace any flammable varnishes, lacquers, oils, and gasoline will help keep your home safe.

Don’t Wait to Turn on the Furnace

Although you might be nervous to turn your furnace on that first time every year, do it.  Turn it on when it’s still mild outside.  Maybe don’t wait for the first winter snap to hit before finding out your furnace doesn’t work.  If you do wait, you might find yourself at the end of a long line.  Other homeowners and property management companies may be requesting service at the same time you are.

Taking Care the Easy Way

If you don’t already have someone coming out to your house each year just to make sure everything is running safely for you and your family, we’d love to be the company that gets to do it for you.  Fox Family offers an easy way to automate this. You won’t even have to remember to call us. We take care of it all.

Your furnace runs better when it’s been cleaned and maintained, much like your car. Every Fall or Winter is a good time to get the required maintenance done on your heating system. Don’t have a desire to be on an automatic program? Call for a furnace tune-up. A typical cleaning lasts 45 minutes to an hour and a half. It’s usually about a 30 point checklist, but I’ll go into that on another post.

Turning on the Furnace: a Recap

The nature of a gas furnace is to use a controlled flame to warm your house.  It’s done in a VERY controlled way by a series of safety switches.  Any unexpected events within the furnace components tell the control board to shut down the unit.

Thanks so much for stopping by, and we’ll see you on the next blog post!

Don’t miss our video on this topic:

8 Reasons Hot Surface Igniters Fail

How Does a Gas Furnace Work

The Hot Surface Igniter has become an industry standard in gas heating systems in the Sacramento Valley.  To technicians and furnace manufacturers everywhere, the sequence of events that takes place for a gas furnace to start a flame that jets into the tubes of the heat exchanger is like a well-choreographed dance.  Stick around while we talk about an integral part of the sequence to bring heat into a home: the hot surface igniter.


As the winter season approaches, we are going to be using our gas furnaces more and more.  A lot of those furnaces won’t be lighting up when they’re turned on for the first time this season.  The hot surface igniters that start the flame in a gas furnace often fail.  It’s almost as common as replacing a capacitor in air conditioning systems all over the city every spring.

How They Work

Hot surface igniters are a resistance element made of silicon carbide or silicon nitride.  Anywhere from 80 to 240 volts are applied to the wires attached to the igniter.  A ceramic base insulates the wire connection to the carbide element which looks like the letter M on most applications. Spirals are another shape I see.  Most nitride igniters are formed in the shape of a 1.5-inch flat stick or a 2-inch long cylinder.

When the voltage is applied to the wires, the element starts to glow because of the resistance the carbide creates from one wire to the next.  When it glows long enough, gas is poured over it, and the flame ignites.

Hot Surface Igniters are Resistance Heaters

As mentioned earlier, hot surface ignitors, or HSI’s, are resistance heaters.  The element itself glows orange when the voltage is applied.  How hot that element gets depends on the voltage being applied to it.  A 120-volt HSI will glow at around 2500 degrees Fahrenheit.  Most gas fuels will ignite around 1100 degrees, so 2500 degrees is a little excessive.  A 240-volt igniter burns even hotter.  Several control boards these days are made to support an 80-volt igniter.  This way the carbide breaks down slower, adding life to the system.

Hot Surface Igniters are Better Than a Pilot Light

Before hot surface ignitors and spark ignition was around, we had gas pilot lights that would stay lit burning a 1 to 2-inch flame year-round whether the heat was on or not. When the heat was turned on, the gas valve would flow more gas over the pilot to ignite the burner assembly that carried the flame.

For a pilot to stay lit all year, it could cost up to $150 dollars a year depending on where you are in the US.  Some of you reading this post have pilot lights still going strong on your 35-year-old furnaces!  Although very reliable when needed, and not a truly major expense, it’s not a great use of resources to just let that gas flame just burn all year.

On-Demand Efficiency

You might be okay with a small pilot burning in your furnace all year, but it really freaks out some of our customers.  A lot of people don’t even know that new furnaces these days don’t have pilots anymore.  They come with on-demand ignition components like an HSI.  Meaning the ignitor only comes on when needed and even then, it only comes on for less than a minute at a time.

Hot Surface Igniters are Silicon Carbide

Silicon Carbide is one of the most common components that make up a hot surface igniter.  Not only are these igniters used to light gas furnaces, but they are used for lighting stoves, boilers and other appliances that heat things around your house. Carbide is used as an abrasive, as a cutting tool, and has some automotive applications as well.   The first carbide igniters were actually produced in 1969.  From then until now they have become one the main choices for manufacturers to use as their ignition source.  The other source being spark igniters, which we’ll talk about on another blog post.

How Long Do Hot Surface Igniters Last?

Just like most components on your HVAC system, these parts last about five to ten years.  Yes, you can get lucky and have one last for twenty years, but it’s few and far between.  Different hot surface igniters last longer than others.  The trend over the last five to ten years has been to use the more durable silicon nitride igniters.  They seem to be less brittle, making them better able to stand the test of time.

Why are Hot Surface Igniters Such a Common Replacement Item Each Year?

So why do these silicon carbide igniters break so often?  The fact is, a gas flame pours over these ignitors which applies a lot of damaging heat to them.  The same thing that makes them work also destroys them!

8 Reasons Why Hot Surface Igniters Break Down Prematurely:

1. Brittle HSI’s

Just today as I was called by one of my techs who said they accidentally broke an HSI as they were cleaning the burner assembly on a routine maintenance call.  It happens.  If you took your index finger and thumb and brought them together even somewhat quickly, that would be enough force to break the carbide tip of a hot surface igniter to pieces.

2. Overuse

A furnace that cycles on and off excessively will reduce the lifespan of an HSI.  Making sure the system is properly sized for the house is probably a good idea.  We say it all the time, but an improperly sized unit is going to cause all kinds of problems.  Maybe not in the first year of its life, but long after the contractor who installed it is gone, and not responding to the customer’s phone calls anymore.

3. High Voltage

If an HSI is exposed to higher voltages than it’s supposed to receive, they will surely break sooner than they should.  An 80-volt HSI should have about 80 volts applied to it.  Applying 120 volts to that HSI will cause it break, and sometimes almost immediately.  Having too low of voltage may not let the igniter burn hot enough.

Once, in my early service years, I replaced a 240 ignitor for a package unit with a 120 ignitor.  Not only did the HSI break on the first start-up, but the high voltage backfired to the control board and took it out as well, which put my employer in the position of having to now replace the customer’s control board.  I never did that again…

4. Contamination

Some field experts say that the oils on the hands of technicians will cause the carbide tip to break down earlier than it should.  Other experts say it won’t.  One thing is for sure, the fewer contaminants that touch the surface of this red-hot igniter, the better.  Other contaminants around the house that can get on the hot surface igniter are sheetrock dust, condensation, dirt, rust, and fiberglass.

5. Gas valve pressure

An overfired gas valve will cause the flame to be hotter than it should be.  Any kind of heat is going to break down the HSI naturally.  It’s parts can last longer if you make sure the system is set up properly.

6. Faulty control board

In most cases the ignitor on the furnace is lined up with the flame that shoots into the heat exchanger.  It starts glowing red-hot when the control board tells it to come on.  If the board doesn’t tell the HSI to turn off, it will continue to glow red hot. You’d likely have a faulty board in this case, and that won’t be good for your HSI either.

That hot surface igniter will be energized in about a minute.  Most igniters achieve maximum temperature in less than 15 seconds.  Some ignition sequences can leave the igniter burning for about a minute.  The less the igniter has to be on, the longer the lifespan of the igniter.  Some things can’t be changed on a furnace such as this designed ignition sequence, so sometimes we’re just stuck with what we’re given.

7. Propane gas

Propane is a very viscous gas.  If you were to compare a natural gas furnace to a propane gas furnace after just five years of use, you would see the burner assembly on the propane system looks like it needs to be cleaned more than the natural gas burners.  I’ve seen hot surface ignitors that stand in the stream of a propane flame have the top half of the carbide tip ripped off after just 3 to 5 years.

8. Radiant heat

A heat exchanger that is overheated at shutdown could radiate extra heat on the ignitor to damage it or its ceramic base, especially in closed combustion systems like those Coleman or Intertherm downflow furnaces you find in modular and mobile homes.  A fan cools the heat exchanger once the call for heat has been satisfied.  Making sure the fan stays on for more than 90 seconds might be a way to correct this.

Standing pilot lights are a thing of the past.  Furnaces these days have spark igniters or hot surface igniters.  I don’t know that one is really better than the other.  Hot surface igniters are replaced about every five years.  Spark igniters have their downfalls too, though, which is why the industry hasn’t dedicated itself to one technology or the other.

Thanks so much for stopping by, and we’ll see you on the next blog post.

Smart Thermostat Installation Guide

How to install a smart thermostat

Thermostat technology has advanced so much that programmable thermostats are now looking like obsolete technology after smart thermostats were introduced on the market. Are you still undecided about the appropriateness of this device for your home? Read the smart thermostat installation guide below and decide whether it is time for you to call Fox Family Heating and Air for a discussion of the available options of smart thermostats.

Best Smart Thermostat Options

If your thermostat looks like this, it might be time to upgrade
If your thermostat looks like this, it might be time to upgrade!

Smart thermostats do what any other thermostat can do and a lot more. They not only regulate the heating and cooling of your home, but their functionality also extends to the indoor air quality as well. Smart thermostats can be linked by Sacramento air conditioning repair professionals to your home automation system. Smart thermostats are internet-enabled and you can access them using a mobile device like your smartphone.

Popular brands you may be familiar with are the Nest, Honeywell, and Ecobee4. It’s really up to you to determine which one is the best fit for your home but by now most brands are on their 3rd or fourth version so they are pretty well tried and tested. Our technicians always keep a few new smart thermostats on their trucks in case you haven’t had time to head to the store and pick one out.

Smart Thermostat Advantages and Capabilities

Smart programming.  These new Smart thermostats can learn your preferences and adjust the air conditioning settings automatically to address your needs. For example, the smart thermostat will “notice” that you tend to increase the temperature settings as you leave your home each morning. The smart thermostat will begin making those adjustments on its own when the time you leave approaches so that you no longer have to do it or program it into the memory of the smart thermostat. The smart thermostat can also adjust the furnace and AC settings depending on how many people are in the home at a given time. This goes beyond what you see in programmable thermostats that work based on the settings that have been pre-programmed.

You Will Love The Remote Connectivity This Winter

Smart thermostats enable you to adjust them even when you are not in your Sacramento home.  Any internet-enabled device such as your smartphone or computer will work. You will, therefore, be in a position to conserve energy even when you aren’t at home.

Energy reporting. Smart thermostats have the capability to collect data about the energy usage patterns of your home. You can monitor this data for energy use.  You’ll see when most energy is used in your home and when it is minimal. You can also ask a Sacramento heating and air conditioning repair technician to help you to make sense of that data in case you aren’t comfortable analyzing such information. You can take corrective measures based on this data.

How the Smart Thermostat Can Be Installed

Manufacturers of smart thermostats usually have a user manual that has step-by-step installation instructions. You can follow that installation guide to install the smart thermostat on your own. However, it is not advisable to attempt a DIY installation if you lack appropriate training and experience. This is because the process requires electrical knowledge as well as technical knowledge to put together the different components.

We recommend you seek an installation by an experienced technician, like Fox Family Heating and Air. The cost of a professional installation is well worth it to avoid problems with a DIY installation.

Either way, you will enjoy a warmer home with convenient temperature controls in your home this winter!

Top 5 Reasons Why My Furnace is Blowing Cold Air

furnace is blowing cold air

Whеn the chilly weather fіnаllу аrrіvеѕ in Sacramento аnd you turn on your furnасе аftеr mаnу months оf non-use, thе last thing you want tо find is that it’s not wоrkіng. Or, even wоrѕе, discovering thаt your furnace is blowing cold аіr! As exasperating as thіѕ ѕіtuаtіоn mау bе, the solution mау bе a simple fix.

Hоw Dо Gаѕ Furnасеѕ Work?

Undеrѕtаtіng how furnaces wоrk іѕ kеу tо finding рrоblеmѕ like one that’s blowing cold air, аnd having a professional fіx thеm. Thіѕ wіll also hеlр you kеер соѕtѕ dоwn because knowing whаt thе problem is рrоtесtѕ you from bеіng taken advantage of bу contractors whо trу to rір уоu оff. If you want to learn more, check out Wikipedia on this topic.

A gas furnace works by taking іn соld air, сlеаning іt out thrоugh a fіltеr, and then hеаting thе аіr wіth a gаѕ burnеr. Tурісаllу, thеу use a “steel hеаt exchanger” that converts the air frоm сооl to wаrm. It will thеn blоw оut аnd dіѕtrіbutе thе air іntо уоur hоmе wіth a fan or blоwеr роwеrеd by a mоtоr.

Top 5 Reasons a Furnace May Blow Cold Air

A dirty air filter can also be to blame.

When they become clogged and dirty, they block air flow and can even cause the system to overheat itself. When the system overheats, a safety switch will tell the furnace to shut down and retry when the furnace has cooled back down. If this happens more than three times in a row, most furnaces will start blowing cold air.  This lets the homeowner know something is wrong with the furnace. Clean the filters or change them with inexpensive replacements every two months. If the filter is not perfectly white, it’s time to change it. Remember, that’s the air you’re breathing, too! So keep it clean!

The Flame Sеnѕоr іѕ Dіrtу.

Newer furnасеѕ uѕе a flаmе ѕеnѕоr tо kеер thе furnасе burning, оnсе it starts. If thе flаmе sensor іѕ dіrtу, your furnасе will turn оn аnd begin hеаtіng but then turn соld rеlаtіvеlу quickly.

If уоu’rе familiar wіth furnасе соmроnеntѕ, уоu can сlеаn the flаmе sensor уоurѕеlf, which ѕhоuld rеѕtоrе your furnасе’ѕ heating funсtіоn. Or, уоu соuld enlist the services of a Fox Family Heating and Air Conditioning expert tо сlеаn the sensor fоr уоu. It’s typically just the cost of a regular service call for us to come out and do that for you.

The Gas Valve is Not Working.

Another culprit behind your furnace blowing cold air may be a closed or blocked gаѕ valve. Sometimes moisture or sand in the gas lines will work itself into the gas valve. This valve is constantly opening and closing every time your heater turns on. If sand was to get in there, it could cause the gas valve to seat improperly. This obstruction could cause a small amount of gas to start leaking around the furnace. If this gas began to seep out into the combustion chamber, it’s possible that the flame could “roll-out” and cause an unsafe situation. It іѕ bеѕt to have a рrо look at thіѕ, as any time уоu hаvе tо mеѕѕ around wіth gas, there іѕ a potential for danger.

An Old Control Board.

A faulty control board is аnоthеr common рrоblеm. It саn bе саuѕеd bу the solder connections on your board fracturing, causing intermittent operation of the furnace. These can be tricky and annoying to a homeowner because the system is not working one day, but does the next day. Finally, after a few of these nuisance appointments, it finally goes about for good. Those solder connections get warm with the electricity flowing through the circuits until they start to fracture. At this point, it’s time to replace that control board. You’ll want an experienced technician for changing your control board.

Pressure Switch.

A pressure switch is a safety switch that lets the furnace know the exhaust from the gas burners is venting properly to the outside of the house. This pressure switch opens and closes with the on and off operation of the furnace. Sometimes that switch inside fails to open or close on a consistent basis and will need to be replaced. These can be changed out fairly easily, but it should be noted that proper suction from the inducer assembly is needed and should be verified with a manometer before turning the system back on safely.

So There You Have It.

These are your top 5 reasons why your furnace is blowing cold air. Furnaces are trickier and have more intermittent failures than air conditioners do. This is because your symptoms will typically show up gradually instead of all at once. With furnace repairs, we ask our homeowners to be patient sometimes because we may not put a diagnosis on a unit the first time we are out to the home. We don’t want to start replacing parts and waste your money. We want to catch the component that’s failing while it’s in the act.

If уоu lіvе in the Greater Sacramento area, the HVAC professional tо call is Fox Family Heating and Air Conditioning. Your technician wіll wоrk thrоugh a series оf tеѕtѕ tо pinpoint the еxасt source оf trоublе, and get уоur hеаtіng ѕуѕtеm uр аnd running аgаіn аѕ ѕооn аѕ possible.

Thanks so much for taking the time to read this blog post. We’ll see you on the next one.

Don’t miss our video on this topic:

my furnace is blowing cold air

How Does a Gas Furnace Work?

Easy Guide to gas furnace troubleshooting


Understanding How a Gas Furnace Works and the Sequence of Operation

Hey guys, how are you doing?  Today I’m going to describe for you the sequence of events that needs to happen for your furnace to start blowing warm air into your house. We’ll start at the thermostat and go all the way to the blower turning on, forcing air into the rooms of your home. Furnace troubleshooting is the topic coming up today on Fox Family Heating and Air.

Furnace Troubleshooting Safety

First, I want to give fair warning to anyone watching this that isn’t already an experienced technician in the HVAC industry.  This furnace troubleshooting video is for educational purposes only.  Fox Family Heating and Air does not recommend anyone other than a professional start opening up the furnace to try to diagnose the failure going on with your system.

There are high and low voltages that can shock a person.  There are also lots of moving parts that can damage body parts—namely, hands and fingers.  The furnace also produces hot surfaces within the furnace compartments and around the housing, potentially causing severe burns.  An actual flame produced by the ignition and startup of a gas furnace can cause severe burns and damage to a person or property.

When your house reaches a point where the heat needs to come on to keep you comfortable, a series of components work in a specific order to produce that heat.

The Thermostat

The thermostat is the first part of the sequence that engages, making the furnace work. There’s 24-volt power at the R terminal of the stat already.  Within the workings of the thermostat, 24 volts closes a switch at the W terminal.  That signal is sent to the control board back at the furnace.

The Furnace Control Board

The control board is a printed circuit board with various switches, resistors, and terminals that act as the quarterback of the heating system.  It calls the plays as they need to happen.

Low Voltage Wires

The control board has a terminal block with screws on it, with a set of thin low voltage wires coming from the thermostat.  Typically, the colors of these wires are red, yellow, white, green, and blue.  The wires are going to R (red), Y (cooling), white (heat), green (blower motor), and blue (common).

Note: the wire colors don’t matter here. They’re still copper on the inside of the sheathing.  So if we use a brown wire for R at the control board, brown needs to be hooked up to R at the thermostat.

The Inducer Motor

Once the control board receives the thermostat signal to turn the heat on, it tells the inducer motor to come on.  The inducer motor is a major component that removes the carbon monoxide from the flame of the gas furnace.  It draws the spent gasses into the metal or PVC flue pipe, which transfers those fumes from the furnace to the atmosphere through the roofline.  You may have seen the metal pipe sticking out of the roof of your house in the winter, exhausting steam into the air. That’s the exhaust we’re talking about here.

The Pressure Switch

This safety device proves that the inducer motor is on and doing its job properly.  If it’s not, the sequence shuts down and retries again.  This pressure switch is actually measuring the suction the inducer motor is producing and sends a signal back to the board, letting it know that startup is working so far.

Roll Out and High Limit and Pressure Switches

Meanwhile, other low voltage safety switches are sending a signal of all-clear back to the board.  There are a couple of “roll-out” switches and a high-temperature limit switch that must confirm to the control board all is well there, too.  The wires leading to the roll-out, high limit, and pressure switches are usually all wired in the same series circuit with each other as a safety control.  If any of these safety switches sense anything wrong with the heating system’s startup, the sequence stops, and retries.

The Ignition Sequence

Next, three components engage in lighting the flame and proving that it is lit. When the pressure switches and other safeties tell the control board all is well, the board starts the ignition sequence.  First, the board sends a signal to the ignitor.  This could be a hot surface ignitor that glows orange or a spark ignitor, which produces an arc between two metal forks lasting for several seconds.  (My blog post and video discussing why hot surface ignitors fail might be of use for you, too.)

Whether the ignitor glows or sparks or not, the next component, 24 volts, is sent to the gas valve, which opens the diaphragm inside of it. It opens, allowing natural or propane gas to flow on to through the metal burner assembly.

The Heat Exchanger

The gas now flowing through multiple orifices in the burner assembly reaches the ignitor, causing a flame to ignite and burn in a controlled fashion straight into the firebox or heat exchanger.  For the purposes of this post, we’ll call it the heat exchanger.

Crossover channels within the burner assembly allow the gas to flow from the first burner to the last one, where the flame pours over a thin metal safety rod called the flame sensor.  The flame meeting the rod creates a millivolt DC signal to the control board that allows the gas valve to remain open.  No flame being sensed means gas is flowing uncontrolled throughout the furnace cabinet, which is not good.

At this point, we have power, a good thermostat, a functioning inducer motor, ignition, flame, and flame sensor to verify it.

A delay now occurs to allow the heat exchanger to warm up so cold air isn’t sent through the ducts and into the air.  The heat exchanger is a hollow metal box with individual chambers.  The flame pours into each chamber, warming the metal to an extreme temperature.

Once hot enough, the air that flows over and around the metal box warms quickly from room temperature to about 100 to 140 degrees.  The temperature is set by the manufacturer and must be closely adhered to.  This will keep the system operating safely and to proper specs.

The Blower Startup

After this delay completes, the blower starts up, sending forced room temperature air over the correct speed of the metal heat exchanger.  If the air is sent over too fast, the air entering the room won’t be warm enough.  Too slow of air or not enough air and the system gets too hot.  Too hot means the high-temperature limit we discussed earlier will open, telling the control board something’s not right. So, this blower motor has to be dialed in just right.

Furnace Troubleshooting Tips

Here are some things that can happen when the furnace isn’t starting up correctly.  The following troubleshooting tips are not all-inclusive and are not to be taken as scripture that what is going with the furnace you’re working on is the problem.  These are general problems only.

No power to the board – If the unit is plugged in correctly and the breaker at the main panel is in the on position, there should be power to the furnace control board.  A transformer can fail between the outlet and the control board, and they can and do regularly.  The board with proper power can send the high and low voltage signals it needs to be the quarterback and run the plays.

Power, thermostat, no inducer motor – Low voltage power is sent from the control board to the R terminal at the thermostat.  Assuming you have 24 volts there, the thermostat closes the W switch, which now has 24 volts applied to it.  If the 24-volt signal is getting back to the control board’s W terminal, the control board will send the high voltage signal to the inducer motor.  If voltage is getting to the inducer motor but it doesn’t run, you likely have a bad inducer motor or capacitor for the inducer motor if it has one.  If you’re not getting voltage to the inducer motor from the board, you have a bad board or faulty wiring connection between the two.

Power, thermostat, inducer, no ignition – If the inducer motor is running, the ignitor should start glowing or sparking.  The gas valve should open, allowing the gas to flow, the gas flame should crossover to the other burners in line, and a signal should be received at the flame sensor telling the board everything is good to go.

As with many components in furnace troubleshooting, if the part is getting power but not operating, it’s likely failed.  If it’s not getting power from the control board, it’s likely a bad board.  I have a great video on why control boards fail for more information.

Power, thermostat, inducer, ignition, flame, sensor, but no blower – If everything works as it’s supposed to, except the blower motor hasn’t turned on after the flame ignited after about a minute or so, something is going on there.  If the motor is getting power but not working, the motor or its capacitor may have failed.  If the motor is not receiving power from the board, the board is likely bad.  Not all blower motors have capacitors, either.  This is especially true for systems made in 2020 or later.

Power thermostat, inducer, ignition, flame, sensor, blower, shuts down on high limit or roll-out – Lastly, if the blower motor comes on and the system starts heating, but after a few minutes or even several minutes the system shuts down, the high-temperature limit switch may have opened causing the system to retry again, after the heat exchanger cools off.  If the chamber that houses the heat exchanger gets too hot, this high limit switch will shut down the system.

So What Causes a Shutdown?

First, we have to check that the blower speed settings are correct.  Next, the air filter could be dirty, ductwork could be too small or even collapsed, or the evaporator could be clogged with dirt. (Check out one of my most popular videos that shows what kind of problems a dirty evaporator coil can create.)

All of these items have one thing in common:  not enough air flowing over the heat exchanger.  This causes the inside temperature of the furnace to go over the recommended setting established by the manufacturer.

Although many things can go wrong with the gas furnace, sometimes in combination with each other.  Not much else can go wrong unless something in this sequence goes wrong.  I sure hope this answers some questions you have about troubleshooting a gas furnace.  Be safe and use your head out there. Don’t get in over your head if you don’t know what you’re doing.

Thanks so much for stopping by, and we’ll see you next time!

Don’t miss our videos related to this topic:


Troubleshooting a Furnace Pressure Switch: 5 Easy Things to Check

Troubleshooting a Furnace Pressure Switch

Today we’re going to talk about troubleshooting a furnace pressure switch.  I want to expand on our recent gas furnace troubleshooting series by going into each part of a furnace’s operation sequence.  I’ll fill you in on what the pressure switch does and why it’s important.  And to wrap things up, I’ll give you five easy things to check when you’re troubleshooting a furnace pressure switch.  That’s coming up here on the Fox Family Heating & Air Blog.

First, I want to give fair warning to anyone watching this that is not already an experienced technician in the HVAC industry.  This video is for educational purposes only.  Fox Family Heating & Air does not recommend anyone other than a professional to start opening the furnace up and trying to diagnose the failure going on with your system. 

There are high and low voltages that can shock a person.  There are also lots of moving components that can damage body parts—namely, hands and fingers.  The furnace also produces hot surfaces within the furnace compartments and around the housing, which can cause severe burns.  An actual flame produced by the ignition and start-up of a gas furnace can cause severe burns and damage to a person or property.

The Furnace Sequence of Events

First, as a technician, you must know the sequence of events for a gas furnace to start properly. It’s very straightforward, and you should have this memorized before you can even consider being qualified to troubleshoot.

  1. Power to the furnace control board
  2. Thermostat signals the call for heat
  3. Inducer motor kicks on
  4. Pressure switch proves the inducer operates correctly
  5. Ignitor activates
  6. Gas valve energizes
  7. Flame pours across burners
  8. Flame sensor proves all burners are lit
  9. The blower forces air through the ducts

First, the Inducer Motor Starts

When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on.  120 volts is applied through the wires coming from the control board.  This starts the inducer motor for up to 60 seconds before anything else even happens. It’s a safety feature that creates a negative pressure or draft which purges the heat exchanger of any poisonous gasses, namely the byproducts of combustion.  It makes the air inside the hollow tubes of the heat exchanger cleaner when the flame kicks on. When we have cleaner air inside the heat exchanger at the time of combustion, the furnace’s efficiency increases.

Next Up, the Furnace Pressure Switch Activates

Next, a safety device called a pressure switch activates when the diaphragm inside it recognizes the inducer motor’s suction or purging action.  The pressure switch is a normally open switch that closes upon the manufacturer’s specifications for required negative pressure.

If the inducer turns on and is working normally, the furnace pressure switch should activate. There’s no time lag on this either.  The inducer motor creates this draft quickly.  Within 5 to 7 seconds in most cases – and the rest of the furnace starts up from there.

If the pressure switch doesn’t activate, the furnace will then shut down, wait a bit, and try again.  If the pressure switch doesn’t close after 3 to 5 tries, the control board will stop sending voltage to the inducer motor, essentially locking it out from attempting it anymore.

You can tell the system is on some sort of safety lockout when the furnace’s fan (or blower) pushes room temperature air through the ducts and into your rooms.   No one likes cool air blowing into their house when it’s heating season, so this happens to alert the occupant that the system isn’t working right, and they should call an HVAC company to come out and troubleshoot the system.

How to Troubleshoot a Furnace Pressure Switch

Let’s assume the inducer motor is running correctly. But the pressure switch doesn’t seem to be closing.  Using your meter, you can trace the 24 volts coming from the control board, through the safeties, and on to the pressure switch.  Place one lead on ground or a solid piece of metal attached to the furnace.  Place the other on the incoming terminal of the switch.  If you have 24 volts on the incoming terminal but not at the terminal leaving the switch, you can assume the pressure switch has not closed. 

Another way of doing this is by testing with your leads across the two terminals.  When the pressure switch is open, your meter will read 24 volts. When the switch closes, you’ll read 0 volts.

Remember, the pressure switch doesn’t close until the inducer motor comes on and provides the necessary suction for the pressure switch to close. The required suction is listed on the pressure switch.

Furnace Pressure Switch Not Closing

When we’re troubleshooting a furnace pressure switch, we can do a few things.  We can take our manometer and make sure the inducer motor is creating the vacuum by hooking up the meter’s hose directly to the collection chamber that the pressure switch tubing is connected.  Take that pressure switch hose off and put your manometer’s hose on the same port.

Once you put the hose on and start the system up, the inducer comes on, and the manometer should start reading the induced draft as it begins to rise.  This number on the meter needs to be greater than the number on the pressure switch.  For example, suppose you’re testing a pressure switch that closes at -0.7 inches water column. In that case, the suction reading on the meter should be around -1″ wc.  It could be less, it could be more, but it can’t be less than the number on the pressure switch.  Meaning, if you’re reading -0.4″ wc, something is causing a low pressure reading. 

Five Easy Things to Check

Let’s check out some of the things that could be going on here. Some of the more common reasons I’ve seen furnace pressure switches either fail or not close to allow the rest of the system fire up are:

  1. A clogged port on the collection chamber to the pressure switch
  2. An obstruction in the flue
  3. A diaphragm that’s ruptured or stuck
  4. The pressure switch hose is damaged
  5. The pressure switch hose has water in it

1. A clogged port on the collection chamber to the pressure switch

On the collection chamber, check to see if the port itself is clear of any calcium deposits, dirt, or other debris that would prevent air from flowing through the port.  If there is, take a small wire — like some thermostat wire — and clean that port out.  Whatever the substance is, it should be brittle enough to be scraped off, allowing the port to become clear.

2. An obstruction in the flue pipe

Remember, the inducer motor causes a draft to allow the gasses to be drawn out of the heat exchanger and into the flue pipe where it terminates outside the building—usually the roof.  I have found that bees, wasps, and birds like to build their nests in and around the flue pipe. It’s not likely to happen during the winter, but for sure can happen over the summer.  So, if the season is early and the furnace hasn’t been run yet, it’s good to check at the roof vent. It’s also not uncommon to see that the nest (or the bird) has fallen all the way down to the base of the pipe, where it meets the furnace. 

3. A diaphragm that’s ruptured or stuck

Commonly, the pressure switch fails because the diaphragm inside the casing has become stuck or it has ruptured.  Ruptured diaphragms can sometimes make a flapping noise.  Stuck diaphragms just won’t budge on the required draft.  Sometimes a little tap with your finger on the flat part of the casing will free the stuck part, and that’s great!  But your switch is on borrowed time, and nine times out of 10, the switch will fail again. If I tell you it will fail tomorrow, it will last for years.  If I tell you it will last for years, it’ll fail tomorrow.  I recommend trying to convince the customer to replace the pressure switch now, so there are no surprises.

One way to see if the pressure switch is stuck open or closed is to breathe lightly into the hose leading to the switch. You’ll hear the diaphragm open and close.  It doesn’t mean the switch will work properly, but it gives you more information to troubleshoot a furnace pressure switch.

Because pressure switches are almost impossible to rebuild, a new switch should be ordered.

4. A pressure switch hose is damaged

There have been diagnostic service calls that I’ve been on where I could tell the port was clean, the flue pipe was clear, the inducer motor was pulling a proper draft, and the diaphragm was functional.  But, the pressure switch would still not send 24 volts across to the other terminal.  Is the hose itself in good condition?  Rats like to chew these hoses up and leave holes in them. Other hoses can become brittle and crack.  Keep some extra tubing in your service van for cases like this.

5. A pressure switch hose has water in it

Another possibility is that water could be stuck inside the tubing to the pressure switch.   Condensing furnaces send the flue gasses up the pipe, but latent heat will turn that gas into moisture that flows back down the flue pipe and into the inducer motor assembly.  Remember that naturally flowing water flows downward.  If there is a low spot in the hose leading to the pressure switch, you’ll find it won’t close.  Try draining the hose by unplugging it from the port.  Just be careful; there can be a lot of water in the hose so maybe have a bucket handy. 

Installing a Furnace Pressure Switch

During the pressure switch installation, you want to make sure it’s mounted in the correct position.  The pressure switch you took out was in a vertical position for a reason.  Diaphragms don’t activate as easily when they must fight gravity.  I once replaced a pressure switch with a universal and mounted it horizontally, parallel with the ground, and the switch failed a few days later.  Of course, it didn’t happen when I tested it the day I installed it, but another tech had to come out and fix the problem a few days later.

I could have avoided this had I read the section in the installation instructions that said not to mount it in the horizontal position.  I never did that again!

OEM switches will usually just screw right back into their old spot, but universals sometimes need to be creatively mounted. You may need to use a longer hose to get to the switch—another good reason to have an extra hose on your van.  And make sure there are no dips in the hose, so water doesn’t accumulate, causing the switch to fail again in a couple of days.


So, just to recap.  When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on. A safety device called a pressure switch activates when the diaphragm inside of it recognizes the suction or purging action of the inducer motor.  The pressure switch is a normally open switch that closes upon the manufacturer’s specification’s required negative pressure.

If the pressure switch closes normally, the rest of the furnace sequence of operation will continue.  If the pressure switch won’t close, the system will go into safety mode, try a couple more times, and eventually just start blowing cold air in your room, letting you know something is wrong with your furnace.

Be patient and check the things we went over today before condemning a pressure switch.  It could be one of a few things.

Thanks so much for stopping by, and we’ll see you on the blog next time.

Don’t miss our video series related to this topic:

Troubleshooting a Furnace Gas Valve

Troubleshooting A Furnace Gas Value

10 Easy Things to Check When Troubleshooting a Furnace Gas Valve

Hey guys, today we’re going to talk about troubleshooting a furnace gas valve.   I wanted to expand on our recent gas furnace troubleshooting series by going into each part of a furnace sequence of operation.  I’ll describe what the gas valve does and why it’s important.  And towards the end, I’ll give you ten things to check when you’re troubleshooting a furnace gas valve.  That’s coming up here on Fox Family Heating & Air.

The Furnace Sequence of Events

First, as a technician, you have to know the sequence of events that occurs for a gas furnace to start up properly. It’s straightforward, and you should have this memorized before you can even consider being qualified for troubleshooting a furnace gas valve.

  1. Power to the furnace control board
  2. Thermostat signals the call for heat
  3. Inducer motor kicks on
  4. Pressure switch proves the inducer operates correctly
  5. Ignitor activates
  6. Gas valve energizes
  7. Flame pours across burners
  8. Flame sensor proves all burners are lit
  9. The blower forces air through the ducts

First, the Inducer Motor Starts

When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on.  One hundred twenty volts are applied through the wires coming from the control board.  This starts the inducer motor for up to 60 seconds before anything else even happens.

Next, a safety device called a pressure switch activates when the diaphragm inside it recognizes the inducer motor’s suction or purging action. 

When the “all clear” signal arrives at the control board, high voltage is sent to the ignitor – be it a hot surface ignitor or a spark ignitor.  The hot or sparking ignitor stands in the way of the gas that is getting ready to pour over it. 

This is Where the Gas Valve Comes Into Play

Modern gas valves typically have a printed circuit board in them that receive a 24-volt signal to activate the valve inside of it.  Remember the video I did on printed circuit boards?  If not, I’ll attach it below so you can brush up on what they are and the things that can go wrong with them.

This sequence will happen in three stages – and even if one step of this doesn’t perform, each part is still going to do its thing sequentially once the board gives the signal.

So, after the board senses the pressure switch and inducer motor are working:

  1. 120 volts is given to the ignitor (on some package units, it’s 240 volts.)
  2. 24 volts is given to the gas valve.
  3. The flame sensor starts detecting if there is a flame or not.

The ignitor is supposed to come on for a set amount of time: 30 to 60 seconds. (See our video on ignitors for an in-depth explanation of this topic.)

Next, the gas valve opens.  The gas coming from the utility company or the propane tank in the back yard is free to flow on to the ignitor.  That gas valve is what’s regulating the flow of the gas.

The flame sensor senses whether the flame is correctly burning.  At the opposite end of the burner assembly, the flame sensor also stands in the way of the flame.  The rod, which should be cleaned annually, by the way, will heat up and send a millivolt signal down to its ceramic base and on to the control board.

Only a certain amount of gas can be allowed to pass through the manifold and on to the burners.  The manufacturer of the furnace determines what that will be.  It is pretty standard, though—about 3.5″ water columns (wc).  The natural gas pressure coming from the street is somewhere around 7″-10″ wc, but the gas valve itself specifically allows that 3.5″ wc onto the burners. 

There are some situations and equipment where I’ve been told to bring the outlet pressure down to 3.25″ wc.  But I only did it on the advice from the technical support rep from that equipment.  Specifically, it was Ruud equipment.  The rollouts were getting too hot because the hood covering the flame would trap the heat and make the safety open.  Modifying the hood and adjusting the gas pressures were recommended to us, which seemed to fix it.

Furnaces differ, so please check your furnace installation and service guide for your system’s specifics.  This is something you don’t want to get wrong.

The gas valve is adjustable.  And usually, the installer of the equipment will dial in the outlet pressures on start-up.  Because the gas valve manufacturer – Emerson, White-Rodgers, Honeywell, and other valves makers will usually have it pre-set to that 3.5″ wc, some installers forget to do this.  We can’t assume the valve is correctly adjusted each time. That’s why you can have issues with your furnace related to your gas valve – because it wasn’t set up right by the installer during its first use.

Troubleshooting a Furnace Gas Valve

If 24 volts is coming from the board to the gas valve terminals and you don’t hear that little clicking noise the internal valve makes, you could have a bad gas valve.  To double-check, take the leads off to the gas valve and check there.  Got 24 volts?  Then something downstream of that 24 volts is not working. 

What’s the next thing that’s supposed to be working?  The printed circuit board or electric solenoid attached to the gas valve isn’t telling the valve to open, OR that gas valve board IS telling it to open, but the valve is stuck somehow.

If something is wrong with the internal components of the gas valve, it should be replaced. The gas valve cannot be repaired in the field. Only the gas valve manufacturer or someone certified by the gas valve manufacturer can make these repairs.

Some people will literally take a wrench and bang on the gas valve to get it to open up.  This is extremely dangerous.  Gas is nothing to toy with.  If you decide to try this and it kicks on, please replace the gas valve now rather than later. 

If we try to fix these ourselves and something goes wrong with the gas valve, and it somehow caught the house on fire, the investigation could come back to the furnace.  If they wanted to know who last worked on it and what was done to it, the gas valve manufacturer could claim innocence, and the homeowner’s insurance could deny the customer’s claim.  I know that sounds a little drastic, but it could happen.  Why put yourself in that situation?

I see people try to fix control boards, ignitors, and such, but we shouldn’t try to fix gas valves ourselves with such a sensitive instrument.

Here are ten things we can check when we think we have a bad gas valve before condemning it:

  1. Check the wires to the gas valve.  Are they cracked or frayed?  That could mean a couple of things.  You have a REALY old furnace, or something could have scorched the wires—things like that.  Replace the wire and continue your diagnostic.
  2. Check the coil at the gas valve.  If you check the coil’s resistance by putting your two-meter leads on each terminal and you get a reading of OL, you have a bad coil. There are more complicated things here but let’s keep this straightforward. 
  3. The gas coming into the valve should be at utility line standards.  It’s around 7″-10″ wc for natural gas in my neck of the world. There’s a port on the inlet side to check it.
  4. You may have plugged burner orifices.  A furnace that’s been off all summer can be the victim of a spider spinning a web inside the burner orifices.  Now, that’s a tiny spider, I know, but I promise, it happens!  Take a small piece of thermostat wire and gently poke inside the holes of the orifices attached to the manifold and try to fire up the system again.
  5. The flame might be coming on for a few seconds but then shutting off.  Is there a dropout of voltage or gas pressure to the gas valve?  That’s something to check for sure.  And you can do that by putting a “T” fitting in line with the hose to connect to your manometer.  Check the inlet and the outlet side to see if the pressure is dropping on either side of the valve. 
  6. Another reason the flame could drop out after only a few seconds of burning is the flame sensor.  If the sensor doesn’t detect the flame, the control board will signal the gas valve to shut down.
  7. If the flame does anything but shoot directly into the hollow metal heat exchanger, a safety can trip.  One safety trip is the rollout switch.  Sometimes you’ll get a little part of the flame that drifts off to the left or right, sending the switch off.  That doesn’t mean you should remove the switch.  It means you need to fix the problem.  Clean the end of the burner assembly nearest the heat exchanger.  Rust will sometimes build up on the crossover channels.  Use a wire brush to clean and see if that solves it.  Then place the burner correctly into the channel.
  8. The other safety trip that can cause the system to cut the gas off to the valve is the high limit switch.  If the furnace runs for a few minutes, then shuts off, something could be causing the inside of the furnace to get too hot. The first thing I would check is to see is if the evaporator coil is dirty.   I have a great video that shows what a dirty evaporator coil looks like and what it takes to clean it.
  9. The other reason the high limit could open is the blower motor speed could be set too low.  Check your installation guide as a reference for where the settings should be.
  10. Check the ductwork too.  These last three have all dealt with airflow.  If the return duct is crushed, then we’ll have low airflow again.  Visually check the return duct and feel around it if it looks questionable.  If the duct is not perfectly round, then this could be the problem. The furnace is suffocating.

What else should folks check when troubleshooting a furnace gas valve?  Leave me a comment down below to share your expertise.

When you’re installing the new gas valve, there are few things to keep in mind. It’s a like-for-like change out, but gas leaks are a serious issue, so make sure to use some pipe dope or pipe tape to seal the fitting. 

Also, don’t bend the manifold when you’re trying to remove the gas valve or put the new one back on.  Use two wrenches to get a proper hold on the manifold and the gas valve.

I strongly recommend not over-tightening the gas valve to the manifold.  You could bend the manifold, but also remember, someone might have to get that thing off someday, and you’d be creating a challenging situation for a tech that has to come out and service it in a few months.  Some guys get a little over the top and really crank down on it.  Not necessary. 

Check for gas leaks with an electronic gas sniffer or soap bubbles.  This will assure you the fittings are snug and leak-free.  And don’t forget to check the outlet side when the gas valve is on.  It doesn’t help when the valve is off because no gas is flowing through it.

If it’s a natural gas set-up, the spring that comes inside the valve will already be the right one.  If you’re using LP gas, you’ll need to make sure you put the right spring in it. It’ll come in the box.  Check the manifold orifices to ensure they are the right ones for LP too. And put the sticker on the gas valve that says LP.  This will help future HVAC technicians when they service the furnace.

And lastly, check the gas pressure on the new valve after you’ve replaced it.  I can’t say it enough. It’s simple to do with the right tools, don’t just change the valve and not check the pressures.

When it comes to troubleshooting a furnace gas valve, there’s also a setting for low fire on two-stage units that needs to be checked.

If the gas pressure is too low, your furnace’s efficiency will go down.  More condensation than usual will build up because the air in the air-fuel mixture will be too high.  The condensation can cause corrosion, possibly creating the need for a heat exchanger replacement in the future.

High gas pressure can be just as bad for your furnace because it dramatically increases the furnace’s overheating risk. When this happens, high limit switches will start opening, causing intermittent operation.  It can also crack your heat exchanger since it’s only rated to handle a certain amount of heat.  And cracked heat exchangers can introduce the spent gasses inside the heat exchanger to be carried along with the heat blowing into the house.

So, to recap.  When a furnace begins a new cycle, the inducer motor is the first thing you should see kick on. A safety device called a pressure switch activates when the diaphragm inside it recognizes the suction or purging action of the inducer motor.   Next, the three parts of the ignition sequence begin.  The ignitor kicks on, the gas valve opens, and the flame sensor senses that the flame exists.  If this all goes well, you have heat blowing into the house about a minute later when the blower kicks on.

What else should folks check when troubleshooting a furnace gas valve?  Leave me a comment down below to share your expertise. Thanks so much for stopping by, and we’ll see you at the next blog post.

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