How I Add Refrigerant to a Central Air Conditioner

How I add refrigerant

Hey HVAC techs! I’m Greg Fox, and today we’re going to talk about adding more refrigerant to an air conditioner.  I wanted to expand on our recent AC troubleshooting series by going into each part of its sequence of operations.  This week, it’s the refrigerant.

Now, I’m not going to get into the legalities and moral issues here of refilling refrigerant on a system that is leaking, but you should know a few things:

  • Refrigerant is expensive for the customer – If you have to keep refilling their refrigerant, which we do not know how often that will be, it can add up quickly.
  • They know their air conditioner better than us.  If we’ve never been to their home to refill their refrigerant before, there’s no reference for knowing how BIG their refrigerant leak is or WHERE the leak is.
  • The customer could lose all of their refrigerant tomorrow if they have a significant leak… or if it is a small leak, the refrigerant could last them all year or longer.   

Let’s go over some basics to charging an air conditioner on your average 90-degree day in the middle of summer.  Upon arrival at the house, your customer tells you the air conditioner worked just fine last year, but this year the system seems to run non-stop, especially as the summer days get hotter and hotter.  You ask the customer, “Have any other technicians been out to make repairs on your system since last year?” It’s very likely the customer will say no.  

There’s a lot of things that can affect the refrigerant charge.  Just remember, for the sake of time, we’re keeping this dialogue short, so we can get to the point of charging the system up.  

I like what Bryan Orr mentioned in an article I read.  He said,

“We need to set up equipment so that it won’t freeze during normal operating conditions.   At the very least, the typical residential A/C system should be set up so that the return air temp can get all the way down to 68° and still be just above freezing at the evaporator coil.

Let’s say it’s 78° in a house on an R410a system, and your suction pressure is 108 PSI.  That means your suction saturation (coil temperature) is 35°… so the coil won’t freeze.

However, the coil temperature will drop approximately 1° for every degree the return temperature drops. 

Remember, at 78° inside, the evap coil was at 35°, So if the customer sets it down to 74°, the saturation would get down to 31°, and the will start to freeze.

Knowing this, let’s grab your temperature probe and check the return air and the supply air.  Here you notice the difference between the two is about 8 degrees.  As a tech, you know the split should be around 18 to 22 degrees.  

Next, you head outside and feel the suction line to see if it’s cold. Now, there is some validity to the old term, “beer can cold” but it should not be the measure you go by to check the refrigerant charge. It can, however, give you a clue as to the condition of the system.  In this case, the suction line at the AC is barely cold.  Now, I’m not always a huge proponent of hooking my gauges up to a system every time I go out to diagnose a system, but in this case, we can tell something’s not right with the cooling system, so in this case, I want to see what is going on inside of it.

Hook your hoses up to the liquid and suction lines.  Be careful of blowback so you don’t freeze your hands.  Follow all safety precautions. 

Now, what do you see on your suction side?  I like my techs to talk to me about the evaporator coil’s TEMPERATURE and the TEMPERATURE of the condenser coil.  When I’m on the phone trying to help a tech out in the field, it’s hard for me to remember all the pressure-temperature ratios between the different refrigerants we use. 

So if someone tells me the evaporator coil is 40 degrees, I can immediately tell the coil is not freezing.  If someone tells me the temperature of the condenser coil is 140 degrees, I can immediately translate that to an outdoor coil that is under some seriously high pressure.

On the refrigerant gauge, the outer circle and those numbers are the pressures.  The inner rings of numbers reflect the temperature.  This is how I want my techs to communicate pressures to each other. It’s more efficient this way.  Most gauges these days have a green ring for R22 and a pink ring for R410.  The pink ring’s numbers are what we are using for evap and condenser coil temperatures on a 410 system.

Here we see that the evaporator coil is at about 20° F.  For proper refrigerant levels, the image I want you to project in your mind is this.  Our end-goal here is to have liquid refrigerant reach all the way to the TXV at the evaporator coil to meter the refrigerant appropriately.  Right now, there’s not enough liquid in the system to do that.  This means vapor is making its way to the metering device, and we’re not giving the coil enough refrigerant to interact with the speed of the blower air moving across it.

We need the perfect balance of airflow and refrigerant pressures to create that 18 to 22-degree temperature split we are looking for.

Let’s suppose this system holds 10lbs or R-410a.  In my mind, I’m thinking the system is about halfway charged. It’s an approximation, but we have to let the customer know about how many pounds we want to add, so they give you the okay to move forward.  Of course, you don’t know for sure, but they should be aware it could be around 5 lbs, and that will cost (whatever, $100 a pound). We need to let them know it could be a couple of pounds more or a couple of pounds less, but either way, we need permission to move forward.

Using a scale is the only way we can know for sure how many pounds of refrigerant we are adding. And it’s cool to let the customer know you’ll be using this too. It’s reassuring to them. This is great for preventing you from overcharging the system too.

My service hoses are already hooked up.  I’m going to start by putting my charging hose on the tank of refrigerant.  Next, I open the refrigerant tank valve and place it upside down on the scale. With the gauges closed on the manifold, I crack open the connection where the charging hose meets the manifold.  Not too much, though.  We just want the refrigerant to prime itself up to that point so we get rid of excess moisture and air in the hoses.

Reset the scale back to zero, so we know how much we are adding as the refrigerant enters the system.

I recommend you put an amp clamp on one of the wires leading to the compressor.  If you’ve seen my video on diagnosing a bad compressor, you know that the compressor’s amp draw correlates with the refrigerant pressures inside the system.  The healthiest compressors will run at around 60 percent of their RLA.  When you’re charging up the system, you’ll see the amp draws fluctuate as the refrigerant goes in and settles down.  Use your knowledge about the compressor amp draws to monitor your charging process.

Okay! We’re ready to charge!  With the charging hose valve open, we’ll start opening the suction side valve.  A quarter to half of a turn is enough.  There is no approximate amount of time it’ll take to insert 1 lb. of refrigerant.  Each situation is different.  To know for sure, use your scale.  

In this situation where we think the system is about 4 or 5 lbs low, let about 2 lbs flow into the system and wait for 5 to 10 minutes for the system to equalize.  Question.  How long does it take for the refrigerant to cycle through a typical residential split system? I’d say about 3 or 4 minutes.  If you have a different answer, let me know in the comments.

So we see now the low side has come up to about 27 degrees or 92 psi.  Our evaporator coil is still freezing.  Let’s add two more pounds and wait.  I know there’s a lot of pressure on techs to get their calls done quickly so they can get to the next one, but it’s essential to let the system stabilize before adding more refrigerant.  If you add too much, too soon, you could see the pressures skyrocket insanely fast.  And now you have to recover some refrigerant into a separate tank which takes even more time!

Now we are getting close to 32 degrees or about 100 psi on the suction side.  From here, we want to start dialing our subcool to whatever it is the manufacturer recommends.  This system says 10 degrees subcooling on a 95-degree day.  Let’s get a temperature probe on the liquid line and start getting our reading from it. We’re going to be subtracting the high side’s temperature and the liquid line’s temperature to come up with our subcooling.  

Add refrigerant a little at a time until the difference between those two numbers is 10 degrees. There’s nothing tricky about this.  Just don’t add too much too fast.  Add refrigerant and wait for the numbers to stabilize. 

You’re going to be looking for the low side pressure to be around 40 to 42 degrees or 125 psi.  The high side pressure/temperature will likely settle around 15 degrees above the outdoor temperature.  So on a 90-degree day, you may end up with a high side temperature around 105 degrees.  If you can get your numbers around this area, you’re close!  But let’s really get it dialed in.  Get that subcool to 10, plus or minus 2 degrees.

I will tell you; it takes longer to move the needle on your gauges when there’s less refrigerant in the system.  As the system starts getting close to the proper subcool, you’ll want to finesse the time you keep the manifold open, allowing refrigerant into the system.  Overcharging can happen quickly, especially on a hot day.  

Getting close to your 10 degrees subcool?  Cool!

Once you get it to this point, check your temperature split inside.  Is it around 18 to 22 degrees?  Great! You’ll notice the liquid line is a little bit warmer than the outdoor temperature.  Also, the suction line will be damn near “beer can cold!”

Test the system while it’s running.  Get your amp draws on the condenser fan motor and compressor.  Cycle the system on and off at the thermostat to make sure the system is operating correctly.  If it is, you’re good to go.

Well, I hope this has helped you when it comes to the charging process.  I make my videos for my technicians to reference when they are in a bind out in the field.  But if this can help anyone else, that’s great.

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

Life or Death: Flammable Refrigerants Used in Homes Will Be the Norm

flammable refrigerants

The global warming potential of R410 is leading to the use of flammable refrigerants for indoor comfort

With the complete phase-out of R410A already underway, the industry is looking for new alternatives.  These alternatives are required by the Kigali amendment to the Montreal Protocol to start using a refrigerant that not only has no ozone-depleting potential, but significantly lower global warming potential.

Ozone-Depleting Potential

R-22 refrigerant (freon) is a Chlorodifluoromethane that has ozone-depleting potential.  As it escapes a refrigerant system, chlorine is released with R22.  It’s been proven several times over that freon escaping into the air gets carried to the stratosphere with updrafts.  Once high enough, the freon bonds break down when UV rays from the sun hit them, releasing the chlorine from its bond where it lingers in the ozone layer for years.

The California Air Resource Board says, “releasing one 30 lb. jug of R22 is more potent, if released, than the CO2 emitted to the air by driving nearly 7 more fossil-fuel-powered cars each year.”  Not only that but its global warming potential (GWP) is 1810.  That means R22 released into the air has 1800 times the potency as the same amount of carbon dioxide.

Just as a reminder, we all know CO2 is a once naturally-occurring greenhouse gas that has significantly increased since the late 1700s with the start of the Industrial Revolution.  Humans and their machines have elevated once balanced CO2 levels to almost twice what it was.  What once was a normal amount of CO2 in our atmosphere, helpfully trapping heat in our atmosphere, has now risen far beyond normal.  This contributes to an abnormal rate of global warming.

As for R410A refrigerant, while it has no ozone-depleting potential, it does have a significant amount of global warming potential.  Would you be surprised to know that its GWP is even higher than R22’s, at a little over 2000?


This has led to Kigali mandating the HVAC industry to elevate its standards for refrigerant usage in residential and commercial systems.  Further, the state of California has passed legislation requiring the phase-out of what most of us thought to be the “environmentally-friendly” refrigerants (R-410a, R-134, etc.) by the year 2023.

And if HVAC manufacturers have to change the refrigerants to satisfy the state of California, they likely will have to change the refrigerants in all the equipment they sell throughout the entire United States and elsewhere.  It makes no sense for these companies to manufacture two different types of equipment lines.

Future Alternatives

So, what refrigerants would we move to?  Well, they’re already being used in HVAC applications today.  Actually, since 2012, R32 is a refrigerant that Daikin has been using as its non-ozone depleting refrigerant with very low GWP.

Carrier also has one called R454B.  The other name for it, Puron Advanced, is strangely familiar to us all.  It implies ozone-depleting and easy to switch to.  Carrier has already declared by 2023 that all their ducted air conditioning products in North America will be manufactured with this product.

But most of us who have been following the phaseout of R410A are concerned about the composition of these refrigerants.  Put in the category of “Mildly Flammable,” these refrigerants are listed as A2L refrigerants.

Mildly Flammable?  As opposed to what?  R22 and R410A are considered to have low flammability levels and are listed as A1.  A and B are the toxicity levels of the refrigerant; “A” being lower than “B”, while 1,2 and 3 are the flammability ratings, with 1 being the lowest and 3 being the highest.

What is Mildly Flammable?

According to an article written for the Department of Energy Technology, author Pavel Makhnatch described a comparison as to what Mildly Flammable means.  “To be deemed a mildly flammable refrigerant, a substance must burn at a velocity no greater than 10 square meters per second. By comparison, Usain Bolt’s world record 100-meter time equates to 1043 square meters per second, while hydrocarbons burn many times faster,” Makhnatch said.

R32 is described as having a lower flammability rating than ammonia which is already known for being a difficult substance to ignite.  That makes me feel all warm and cozy, but when ACHR News and Indoor Comfort News started releasing stories about the dangers that could arise when switching over to an A2L refrigerant, it made my ears perk up.

One article I read said we technicians will have to switch to recovery machines that vacate any accumulating nearby fumes.  Machines that have a source of ignition like something as little as a spark.  I realize I don’t fully understand the mechanical breakdown of a recovery machine or vacuum pump, but I do realize they need electricity to run.  The article I read reports that most common recovery machines won’t be suitable for A2L refrigerants.

Another concern of mine and many others is “mildly flammable” still means more flammable than non-flammable.

Upcoming Code Changes

The International Code Council recently met and discussed routine changes to the upcoming code.  These changes rarely make as big of an impact on the community as this topic does.  Usually they just change some wording for new emerging technologies.  But Jay Peters for Indoor Comfort News wrote, “seldom does a standard update change the level of safety for a particular product, like the one happening with using flammable refrigerants.”

He’s concerned that the administration of the Code Council doesn’t really debate the technical aspects of the updated standard.  Peters said, “the flammable refrigerants issue has become a very big subject of debate in the codes covering HVAC and fire safety nationwide.”  He found that many proposals to add these refrigerants to direct in-home systems were all rejected.

Citing a deadline to get this new refrigerant mainstream, the companies are trying to get it pushed through to the International Code Council via the Fire Code, Mechanical Code and Residential Code.  Well, no governmental agency is pushing them.  This particular refrigerant is not mandated to be used by a certain time.  It’s the companies themselves that are saying it.

Protection and Training for Flammable Refrigerants

These companies should be looking out for the real people who will be using it every day as well as those protecting us from it.  HVAC mechanics and firefighters should be protected, fully trained, and prepared to handle and battle a potential fire breakout.   This will require the International Fire Code, International Mechanical Code and the Uniform Mechanical Code to all get the facts to adopt the required wording for Mildly Flammable refrigerants.

Peters asks, “what will stop others from timing their standards the same way that has been done here – circumventing all technical and safety debate of the industry and the membership of the ICC?  This sets a very bad precedent, raises safety concerns, and conflicts with the votes of the International Mechanical Code, Uniform Mechanical Code and International Fire Code committees.”

Jay Peters stresses to the ICC Membership that, “the committee must be overturned so that flammable refrigerants will not be allowed in homes without a single technical or safety provision in place to ensure public safety.”

Flammable Refrigerant in the Hands of Amateurs

My main concern when I heard all this wasn’t so much for our own technicians.  I can train them!  My concern is Side-job Bob, out on his first “mildly flammable refrigerant” call.  Bob may seriously injure himself or causes major damage to the home he’s working on.  Side-job Bob sure does take a lot of my business away, but I wouldn’t wish that on my worst enemy.

One refrigerant that does meet current non-flammable refrigerant ratings is Honeywell’s Solstice N41.  R466A has no ozone-depleting potential and very low GWP.  Even 65% less than R410A, Honeywell has partnered with Midea, China’s leading home appliance maker.  They’re replacing R410A with Solstice N41 in HVAC applications.  Honeywell has answered the the Kigali amendment mandate to produce a low GWP refrigerant.  It’s also non-flammable which makes everyone safer for it.

It’s currently running in third place as the replacement for R410A.  I feel this is due to its production cost.  R32 is apparently cheaper to make than Honeywell’s R466A, which is a blend and therefore costs more to produce.  Shutting out Solstice N41 just puts more money in the pockets of the big guys.

Are big companies like Daikin and Carrier willing to put people in danger to further pad their own pockets?  It seems to me that they’re pressuring themselves to get this refrigerant out too quickly.  Why?  One, to beat everyone else to the punch, and two, to gain recognition and profits.

A Temporary Solution to Flammable Refrigerants

Daikin, Carrier and Honeywell all admit this refrigerant update is only a medium-term solution to the problem.  Other refrigerants will be next as the drive to bring global warming potential to seemingly never-ending lows moves on.

Believe it or not, Daikin is already looking to replace their own R32 with a newer, lower GWP product.  If that doesn’t chap your hide I don’t know what will.  We just began the R410A phase-out.  If R32 is truly our next refrigerant to be used, it’s already on its way out.

Flammable Refrigerants: Who is Most at Risk?

Let me know what you think in the comments below.  Who pays the highest price by having to use an HVAC system that uses flammable refrigerant?  Is it the technicians in the field, the HVAC company owners, or the end-user, the homeowner?  There are more important things in life than money.  There are lives at stake here, and I just hope the authorities get this one right.

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

Using (or Abusing) the R-22 Phaseout as a Sales Tool

Some contractors selling equipment on fears that refrigerant will be illegal

I was pleased to contribute to this 11/18/2019 article in – Greg Fox

As of January 1, 2020, it will no longer be legal to produce or import virgin R-22 in the U.S., but that does not mean the refrigerant will be unavailable, unaffordable, or illegal to use. It just means that after that date, contractors who service R-22 systems will have to rely on existing stocks of virgin refrigerant or else use reclaimed refrigerant, both of which should be readily available (and affordable) for a long time, according to industry experts.  Go to article»

R-454b Will Be the New (New) Refrigerant Starting January 1st, 2023

how to handle a refrigerant leak

In 2010 when I started my venture into the HVAC industry, I was coming in during a time of transition.  Our industry was changing from systems that had R-22 refrigerant circulating through their lines to R-410a.  This new refrigerant has no chlorine in it, which R-22 had.  When chemicals like chlorine rise into the atmosphere in the form of an HVAC system leaking refrigerant, it damages the ozone layer.  This is what we’re talking about today on Fox Family Heating & Air.

The new-new refrigerant coming very soon is R-454b, also known as Opteon XL41. It’s just funny right now.  When I go into people’s homes, and they say the technician was talking about the “new” R-410 refrigerant, in my mind, I already know that 410 will be phased out very soon.  Just like R-22 was phased out. 

Environmentalists found the “new” R-410a has less ozone depletion potential (ODP) since it doesn’t carry chlorine in its composition.  But the global warming potential (GWP) of it was still too high. In fact, the “new” R-410a’s GWP is actually higher than the old R-22!

In response to this, manufacturers have been trying to figure out a better refrigerant to use—one with no ozone depletion potential and less global warming potential.  And to bring you up to speed on these gasses as they’ve changed over the last few decades — only a generation ago, the refrigerant R-12 was commonly used to cool houses before R-22 took its place. Then, R-22 was replaced by the new R-410a as recent as 2010.  Now, 13 years later, R-410a is being replaced by R-32 and R-454b.  All to decrease 1. ozone depletion potential and 2. global warming potential.

The goal is to get the global warming potential of refrigerants below 500.  The potential of these refrigerants is:

Halons were once the holy grail of fire suppression for sensitive items like IT rooms, data centers, museums, and libraries that would otherwise be damaged by sprinkler systems.  But they’re banned now and being replaced by alternative suppression systems.  I give you that information as a reference to the refrigerants used in the HVAC industry. They’re not as bad, but much more refrigerant is released into the atmosphere than fire suppression halons.

Even though R-22 only has an ODP of 0.5 per metric ton, its effect on the ozone layer isn’t suitable for future generations.  And like I said before, while the “new” R-410a has no ODP, it has a little higher global warming potential.

R-454b offers pressures much more similar to R-410a and requires a little bit less of a charge.  R-32 was another option for use as a low GWP refrigerant, but its potential of 675 is higher than 500.  A dip below 500 will likely become the industry standard soon, so it makes sense to choose R-454b now.

New Refrigerant Not Up to Residential Building Code

If we’re going to be using this refrigerant, some things will have to change.  Most importantly, the residential codes that are currently in effect.  Nothing in it allows for the use of A2L (mildly flammable) refrigerants to be used in residential cooling systems.  

Mildly flammable refrigerants can’t be used in existing R-410a and R-22 systems. Compressors must be upgraded.  Systems designed for R-454b will require less of a charge than today’s R-410a systems and will be about 5% more efficient than current refrigerants.  410a systems will need some extra protection and usage standards not used in today’s equipment.  So if people think they’re just going to drop in some XL41 into 410a systems, which do operate at similar pressures, they have some more training to do.

When Will the NEW Refrigerant Be in Use?

The EPA has approved the refrigerant for use in light commercial and residential applications for new equipment.  This is why the major brands are already planning for new equipment in the future to use the “new-new” refrigerant on January 1st, 2023 (which is the date the 2022 California Energy Code begins.)  And if manufacturers have to start making it for California, they’re not going to keep making 410a systems AND 454b systems.  Essentially, when this happens in states like California and Washington, it will happen around the rest of the country too.

New Refrigerant Training Will Be Required

AHRI and ESCO have already created classes that will teach today’s technicians all about the new-new refrigerant.  NATE will also have certification testing available for technicians.  Even though we’ll be using the same types of equipment to handle XL41, they must be approved for use with A2L refrigerants, which use features like fans to dissipate fumes from the electric motors.  For that reason, we need training.

All of this training will cover safety, as well as requirements for proper installation and maintenance of equipment that use A2L refrigerants.

Will R-22 and R-410a Still Be Available to Use?

Will R-22 and R-410a still be available to service existing HVAC equipment?  Absolutely.  But some HVAC companies will use this as an opportunity to convince the unsuspecting customer that R-22 and R-410 are “illegal” to use now, and they can’t repair their existing system. It’s a common tactic I hear from customers about the “new” R-410a.  And shame on the “technicians” that do that.  They give the industry a bad reputation. 

Warehouses will be full of perfectly legal R-22 and other alternative replacements for R-22 until at least 2030.  And 410a will be available for much longer.  The protocols that are in effect to stop global warming are there to phase out the production of new, virgin refrigerant.  Recycled refrigerants and current inventory will be around much longer after they stop making it.

R-32, R-454b, and R-466a have been the leaders as possible replacements for the current ones because they have no ozone depletion potential and much less global warming potential.  It looks like R-454b has emerged as the winner.  Leading manufacturers were forced to decide which refrigerant they were going to use that was also approved by the environmental authorities.

Certification for 454-B

The residential codes that just came into effect on January 1st, 2020, are already established.  Nowhere in the codes is the use of A2L, mildly flammable refrigerants, approved, so some changes will have to be made for the codes beginning January 1st, 2023, for that to happen.  Training will also be made ready for the transition over to 454b, and certification might be mandatory when that happens.

Now you’re up to speed on the upcoming industry change over to the new-new refrigerant. Thanks so much for stopping by. We’ll see you on the next blog post.

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