Why do heat exchangers fail?

Why do heat exchangers fail

Why do heat exchangers fail? I have been called out to many homes to troubleshoot why a homeowner’s furnace isn’t working. I’ll get in there and find a part that has failed and needs to be replaced. As an experienced technician, I always make sure I inspect the firebox or heat exchanger inside the furnace. The reason why every good technician does this is to make sure the furnace is safely operating to factory specs. The manufacturer would never send out a cracked heat exchanger, so we want to identify to homeowners when we see something like a cracked heat exchanger.

So, how & why do heat exchangers fail? It can be a bunch of different reasons. Operating a furnace in any of these conditions can cause a heat exchanger to fail because it puts a lot of stress in the form of expansion and contraction over several years. Knowing that, you can surmise that cracks and breaks will form over time because of the constant bending of the metal.

  1. Why Heat Exchangers Fail - Serpentine designsFurnace is Oversized – It’s normal for the cool metal firebox, or heat exchanger, and a hot flame to temporarily create a bit of condensation inside the tubing or chamber of them. An oversized furnace will not evaporate that condensation completely because oversized furnaces tend to short cycle. They turn on and off more frequently than they should because they’re so powerful they warm the house up very quickly. Too quickly! Too much rust over time will drill a hole in the tubing or chamber, and you’d have a failed heat exchanger.
  2. Not Enough Return Air – The system wants to give you a certain amount of air to warm your home. The furnace will only give you what it gets from the return duct (the duct or plenum attached to the grill where you change your filter). Those of us in the industry know that a lot of systems installed before, let’s say, 2015, were installed with return ducts that were too small. The heat exchanger is designed to see a certain amount of air pass over it with the correct amount of gas input and heat the heat exchanger emits. Too small of a return duct will restrict the amount of air that can enter the furnace and cause the firebox to expand and contract too much, causing it to break sooner than it should.
  3. Dirty Filters – Another way to slow down the proper amount of air flowing across the heat exchanger is to have a dirty filter. Filters come in several thicknesses. 1″ all the way to 5″. You can have any size and thickness for a filter. But if it becomes impacted with dirt, dust, skin, hair, and whatever else clings to it, the filter restricts airflow like the return duct we discussed in number two.
  4.  Check out our blog on how the newer MERV 13 filters can cause problems for your heat exchanger and the rest of the system
  5. Why Heat Exchangers FailHousehold Chemicals – Believe it or not, corrosion can form on the heat exchanger. Things like hair spray, fabric softeners, and bleach can enter the air stream, pass the filter, and attach to the heat exchanger for good. Over time, the chemicals bore a hole through the metal and cause it to fail.
  6. Off-Gassing – Let’s say you have a home remodel or new construction. Running the furnace during the construction and even afterward will expose the heat exchanger to off-gassing. What is off-gassing? Like the smell of that fresh paint? Off-gassing. New carpet smell? Off-gassing. And many of those new products keep off-gassing long after that new smell wears off. It’s just more subtle. And just like household chemicals, it will contribute to the overall degradation of the furnace heat exchanger. Frozen Evaporators Coils – Ever had a refrigerant leak cause your air conditioning system to freeze up? Vertical furnace/evap coil combos leave the heat exchanger below the evap coil drain pan. When a frozen evap coil melts, it tends to melt rapidly enough that it overflows or straight drips right down onto the metal heat exchanger. And that causes corrosion over time.
  7. Missing Eyelet on Serpentine - Why Heat Exchangers FailPoor Manufacturing Design – There are clamshell, serpentine, and tubular heat exchanger designs.
    1. Clamshells tend to fail in the back of the chamber. But it’s tough to get an inspection mirror back there for inspection purposes. A process called hydro-scan is used to identify cracks in these types of heat exchangers. And it’s very effective if done right and if the professional is looking in the right spots. It takes a trained eye!
    2. Serpentine designs are pressed together with the middle areas held together with rings or eyelets. The eyelets on serpentine designs tend to deform, pop off, and crack. And if the manufacturer wouldn’t send a heat exchanger out into the field with cracked or missing eyelets, a technician who later finds them like that should fail your heat exchanger for not meeting the manufacturer’s specs.
    3. Tubular designs are a newer design and, in my opinion, superior to clamshell and serpentine designs. They are usually made with stainless steel and bent into form at the factory. The ends of those tubes are stamped into the collector box and faceplate of the burner compartment. At that connection is where some tubular designs fail. Corrosion plays a big part in tubular heat exchangers failing. Eventually, that moisture, condensation, chemicals, and gasses we discussed earlier can infiltrate the tubes and cause them to fail. And 90% of the time, those failures happen at the back of the tubes on the first bend.

Gas furnaces are very safe. Most people prefer the warmth emitted by gas furnaces. They’re cozy! Ensuring the furnace is installed correctly is almost 100% of the battle. Choosing a reputable contractor is important because they will read the manuals and abide by the building codes that mandate a proper installation. Homeowners need to make sure those filters are replaced regularly.

Hopefully, this helps you understand more on “Why do heat exchangers fail?”

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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!

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How Long Should My Furnace Last?

furnace replacement

How long do furnaces last?

Most people don’t know that 95% of furnaces out there are not going to last much more than 20 years. Anything past 20 years and your furnace are likely operating on borrowed time. The warranties from the builder of those furnaces were made with 5-year parts warranties, so even they were only thinking 10, 15, maybe 20 years. I get asked that question a lot. How long should my furnace last? I tell them most furnaces last about 20 years.

Can furnaces last longer than that?

It is true that we run across service calls on systems that have safely made 35-40 years.  So, it can happen! As long as the parts are still available to make repairs that allow the machine to operate at or above original factory specifications. Also, if the system is still safe to operate, meaning the fire box or heat exchanger is NOT cracked, potentially releasing carbon monoxide through the supply registers in your rooms, it’s safe to operate. Fox Family techs take a special class every year to ensure we are capable of inspecting any heat exchanger to ensure the safety of your family.

Maintain your furnace

If the furnace is maintained properly over the years, like mine, the furnace can easily last 20 years. Sure, some things may break along the way, but a properly trained HVAC technician can get your furnace up and going again. Some other major parts that can break on a furnace are the inducer motor, blower motor, gas valve, and control board. Some of the minor repairs are the pressure switch, capacitors, ignitors, roll-out and high limit switches.

How do I know my furnace is not working?

Inducer Motor

An inducer motor that doesn’t work is going to cause the flame and its exhaust not to shoot into the furnace the proper way. This can cause a serious safety issue in the home. Fortunately, there are safety switches all along the firing up sequence to make sure this doesn’t happen. The control board knows what should work and when it should be working. It’s a very intelligent furnace that has been made over the last 20 years.

Blower Motor

Another component that the furnace can tell is not working is when the blower motor stops working. The blower motor pulls the air from the room and pushes that air through the hot furnace and into your rooms. It’s supposed to be running at a very specific speed. If the blower is running too slow, or not at all, the furnace will overheat. This lets one of the safety devices in the furnace to sense the high heat and shut the system down.

Gas Valve

The gas valve is another major component that must be checked on a regular basis. It’s responsible for emitting the proper amount of gas to the burner assembly which shoots the flame into your heat exchanger. The gas valve is capable of getting stuck in the open position too. Sometimes we get calls where the homeowner is smelling gas in the house, or near the furnace. We have come in to diagnose the system and found that the valve is actually stuck in the open position, albeit ever so slightly. This is obviously a dangerous situation to have. An odorant is added to natural gas and propane gas to help homeowners/customers sniff out leaks. If you smell gas, and no stove burners were left on, evacuate the house and call 9-1-1. Then, call your natural gas provider (your utility).

Control Board

Finally, the control board is one of the major components of your furnace that can go out. If it does, the system just won’t know what to do and when to do it. The control board is the brains of the system. The symptom I see the most on controls boards that have failed is when the solder connections on the back of the board have started to fracture. They started out as complete solder points relaying signals to other parts of the board. But these fractures make it difficult to send the electronic signal. This causes a slow and sometimes very annoying failure of the system because sometimes the system works and sometimes it does not. Maybe in the mornings, it will work but in the afternoon it does not. This usually indicates something is wrong with the furnace control board. Not always, but in my experience has been a good place to start.

Make sure you are getting the proper maintenance done on your HVAC system so it can last up to 20 years. If you don’t, chances are you will be replacing your furnace sooner, because of neglect, just like your car. Let Fox Family come out and get your furnace tuned up for the season every year. My system is so perfectly clean and functional year after year because I clean it and check all the components every year. My system is 19 years old this year too!