Just about everyone refers to the “stuff” moving around through the A/C system as “Freon”. But the term Freon, is actually DuPont’s trade name for their brand of refrigerant. In other words, it’s all refrigerant, but only DuPont’s brand is called “Freon”. Today, there are many different refrigerant manufacturers, so the refrigerant in yours might be any brand.
Refrigerant is the circulated substance that makes the A/C work. It’s kind of like the blood moving through your arteries. There are many different types of refrigerants. Most of the A/C and heat pump systems currently in use contain R22, which is currently being phased out due to concerns about its adverse effects on the ozone layer up in the sky. 2009 is the last year that systems containing R22 can be manufactured by federal mandate. The manufacture of new R22 itself, is due to be gradually phased out by 2020.
So a few years ago, the first systems containing R410A refrigerant started being manufactured. All of the new systems manufactured starting in 2010 will be R410A systems. (Update 7/23/11: AC manufacturers have started shipping units that use but don’t contain R22 when they leave the factory. They contain a nitrogen holding charge instead. The installer removes the nitrogen holding charge, evacuates the system, and charges it with R22. So it’s apparently an end run around a loophole in the law, which states that a system containing R22 can’t be manufactured).
The refrigerants R22 and R410A are not compatible, i.e. you can’t put R22 into an R410A system and vice-versa. The systems are manufactured specifically for the refrigerant they were designed to be used with. It’s like you getting a transfusion with the wrong blood type.
As some of you might recall, we went through the same thing with the refrigerants used in car air conditioners and household refrigerators back in the mid 90’s when R12 refrigerant was phased out in favor of R134A. And now, just as then it remains a highly controversial topic to say the least. Many of us in this industry continue to disagree about how wise these phase-outs truly were, and what the long-term prognosis for the replacement refrigerants is. I personally believe that the case against some of these phased-out refrigerants has been adequately proven, especially in the case of R12, which had a very high ozone depletion potential. The R134A replacement refrigerant, by comparison only had about 10% of the ODP as R12. But it’s much harder to make that same argument regarding R22, because the ODP of it is almost identical to that of R134A. And there are a lot more cars out there containing R134A than there are central A/C units containing R22. But this is a done deal, and there’s nothing to be gained by arguing the point.
There are major differences between R22 and R410A. One such difference is that R410A is under a much higher pressure than R22. But as far as the cooling capacities, they are quite similar, with the R410A actually delivering slightly more cooling than R22.
As for the future prognosis for R410A - nothing’s around forever. Plans are already being made to phase it out according to one of the primary refrigerant industry manufacturers. In 2008 they stated that while R410A has a very low ODP, it has been found to have a higher than desired global warming potential (GWP). So far, no refrigerants have been selected to replace it.
Does my A/C contain it?
Yes, unless it’s one of those very rare natural gas units.
Do I need to have more added every year?
Not unless there are leaks in the system. It goes nowhere in a sealed system.
How much does it hold?
That varies significantly depending on the size of the outdoor unit, the indoor cooling coils and the diameter and length of the refrigerant lines running from the outdoor unit to the indoor coils.
If I do have a leak, how long does it take for it to leak out?
There are too many variables involved to be able to predict it. It would be determined by how many pounds the system holds, how many leaks and what size they are and where each one is in the system. The system contains high pressure sections and low pressure sections. The higher the pressures are, the more refrigerant volume will be lost through the same size opening. In most systems, when the A/C is not running the pressure is the same through the entire system – the pressures equalize. So the pressure on the high pressure side drops and pressure on the low pressure side increases. So if the leak is in the high pressure side, it usually comes out faster when the unit is running. And conversely, if the leak is on the low pressure side, it will usually come out faster when the unit is not running.
How do you find the leaks?
We have several different methods of doing that. The most popular leak detection method is an electronic refrigerant detector, i.e. sniffer. It will give an audible and visual indication when a leak is sensed by the sensing probe. Another method is the injectable fluorescent dye which is injected into the system and it circulates around with the refrigerant and often comes out with the refrigerant when there’s a leak. We then use an ultra-violet light to illuminate the refrigerant system and the dye will glow a bright fluorescent green color where there’s a leak. Then there are the “ultrasonic” leak detectors that work on the principle that the leaks often make an ultra-high frequency sound when the refrigerant escapes. The sensor is basically a microphone, which picks up the sound and converts it to a frequency within the human hearing range. You put on a set of headphones and can often hear the sound of the gas escaping. The units also have visual indicators that can be used, i.e. LED lights, etc. to show you the intensity of the sound. There are also low-tech methods/devices, like soap bubbles. And there is also a device called a halide torch, which draws the sample in through a hose and sends it through a blue flame. When refrigerant is introduced into the flame, the flame changes from blue to green. (I have every one of these leak detection devices).
Do the leaks always show up when you look for them?
Unfortunately not – for numerous reasons. Leaks come in all sizes and shapes. These are not typically round holes. They can be any shape. Metals expand and contract. Leaks can close up completely at a given set of conditions and open up at another set of conditions. Obviously the ability to locate the leak is much greater when more refrigerant gas per unit of time is leaking out of them. There are situations where nothing in the leak detection arsenal will find some of them. But I’ve had excellent success in locating the majority of them with persistence and some really great devices. You’re only as good as your tools, and mine are the best money can buy. I don’t skimp in that area. (But my wardrobe is another matter according to my wife).
Where do the leaks usually occur?
There are 3 basic parts to the system, and they can occur in any of those parts. They can be in the outside unit, or in the refrigerant lines going to the inside coil, or in the inside coil itself. The least common place is in the lines. The most common place is typically in the indoor coil. Experience teaches us that some units have “favorite” places to leak.
Can you see the refrigerant leaks?
Almost never, unless they’re really big ones. But sometimes you can see indirect traces of them after the fact. Refrigerant isn’t the only thing being circulated through a system. There is also a small amount of refrigerant oil being circulated. You can often spot locations where there is an accumulation of oil on the surface. And that’s a very good place to focus your leak detection efforts. Refrigerant exists in 2 forms, i.e. states in the system – as a gas and as a liquid. You can’t see it in gas form, just as you can’t see air. But if trace amounts of oil are coming out with it, as in the case of a relatively large leak, you might see the oil bubbling around the leak. The refrigerant that’s leaking out as a liquid might be visible – but it turns to gas very quickly as it exits and reaches air. So it depends on how big the leak is, and the shape of the leak as to whether you’d be able to see it before it turns to a gas.
How do you fix the leaks?
There are numerous places for the leaks to occur. Some are relatively easy to repair and some are not. Some are as simple as tightening a connection, while others involve brazing or replacing the leaking component. If the leak is the indoor coil (the evaporator), the majority of the time they will occur in a location that is not repairable. So the entire cooling coil (evaporator) must be replaced. The same thing applies to the coils (condenser) in the outside unit). This is the worst place the leak can be, because the condenser replacement costs can be very close to that of the entire outside unit. And unlike indoor coils, where you have numerous replacement options for the replacement cooling coil, you are limited to the exact replacement condenser coil available from the manufacturer. And after a few years, they no longer sell them for each model. If the leak is in the lines running through the house, the line must obviously be accessed to repair the leak. It is almost never necessary to replace the entire line, as leaks in the copper lines can be easily brazed shut. I’ve seen this happen when a remodeler accidentally fired a nail or screw through a basement ceiling and punctured the refrigerant tubing.
The tubing in these lines generally has much thicker walls that the tubing used to manufacture condenser and evaporator coils. So when you see a leak in the lines, it is typically a “man-made” leak.
With a few exceptions, depending on where the leaks are located, all of the refrigerant typically must be “recovered” (removed and put in a recovery cylinder) for the leak to be repaired, because you can’t repair a leak when the leaking part is pressurized. Exceptions to this would be if the leak is in a Shrader valve core (I have a tool to replace it with without losing any refrigerant) or if the leak is not in the outside unit and the outside unit has “front-seatable” valves, which allows you to pump the refrigerant back into the outside and hold it there while the repairs are being made. Then after the repairs are made, you hook up a vacuum pump to the system and put the part of the system you had open (removed the refrigerant from) into a deep vacuum to remove any air and moisture from it. Then you release the refrigerant back into the system (if you stored it in the condenser with the front-seating valves).
Should I have a leak test if my unit is low on refrigerant?
There are a few different scenarios with different flow-charts involved for each one. It really depends on the age and history of the system as to whether or not you want to spend the money to have this done, and then go to the expense of having it repaired once the leaks are found. One thing’s for sure. The leaks won’t go away on their own. If you’re lucky, they’ll merely continue to leak at the same rate if they aren’t found and dealt with. But you have to balance this against the cost of adding refrigerant to it, or against the cost of replacing the system. Obviously if you sell the property, the new owners will not want to inherit a leaking system. Leaks come in all sizes, i.e. all rates of leakage. So it depends on how often it needs to have refrigerant added. The smaller the leak is, the less frequently it needs to have more added, and the more difficult it is to find. When I go after a leak, I usually find it, although sometimes the customer wishes I hadn’t when it’s in a really bad place. The bottom line is that it’s the customer’s choice whether or not the leak detection will be done. I typically ask them a few questions and based on that, throw in my 2-cents worth about what I’d do if I were in their shoes.
If my system is low on refrigerant, does that mean I have a leak?
It USUALLY does. But there are cases where it doesn’t. Not all technicians follow accepted procedures for checking refrigerant levels in the system. I’ve seen quite a few cases where the system was installed brand new without enough refrigerant in it. Central residential A/C systems are not plug and play devices. The amount of refrigerant in them must be tailored to that installation. The cooler it is outside the house or inside the house, the lower the refrigerant pressures become. There must be a minimum amount of heat outside and/or inside the house to accurately check the refrigerant levels. If the levels are adjusted during times when these temperatures aren’t above a certain level by experienced technicians using the proper diagnostic methods and the proper test equipment, the unit could very well have less than the proper amount of refrigerant in it. So that scenario would be a man-made problem of the system merely not having enough put in it. This same scenario can occur when a part of the refrigerant system is repaired or replaced by an inexperienced technician.
The problem is that when we visit your house for the first time and we find the system low on refrigerant we don’t know the history of it. So we don’t know if it was ever filled properly to begin with. But if it has a history of having refrigerant added to it, it’s extremely likely that there’s an ongoing leak, unless by some rare chance a leak was repaired before and they didn’t fill it completely afterward.
What causes refrigerant leaks?
Some of the causes for refrigerant leaks are “formicary corrosion”, acids in the refrigerant system, poorly manufactured components, thinner walled refrigerant carrying tubing, higher than normal refrigerant pressures, defective solder/brazing joints, improperly made repairs, punctures, excessive vibration/rubbing/chafing, long term immersion in fluids, and last but not least age. The evaporator (indoor cooling coil) usually has the hardest life, because it has water cascading down over it constantly when the system is running. It also typically resides directly above the heat exchangers in the furnace in most of the Greater Kansas City area installations. So it sees some amazingly fast changes in temperature, especially during the heating season.
Would I know if the system is low on refrigerant?
Yes, no and “maybe”. It depends on the system, the indoor and outdoor temperatures, how “tight” the house is, and how adequately sized the system is for that house. You’d obviously know there was a problem if it became extremely low on refrigerant or lost all of it, because it would no longer cool the house at all. Basically, the lower the refrigerant amount becomes, the less cooling per hour the system delivers compared to the amount of cooling per hour it would deliver under those same conditions (with all of the above-mentioned factors being the same) if the system was full of refrigerant. The cooling power (Btu per hour of delivered cooling) is not a constant in an A/C system. It varies with indoor and outdoor temperatures and humidity levels. And so does the amount of heat entering the house, which it must remove. And if the A/C system is oversized for the house, it might still be able to remove enough heat to maintain the temperature you have the thermostat set to. But the unit will have to run longer to do that. How much longer depends on all those other factors.
FUNNY REFRIGERANT LEAK SCENARIOS I’VE RUN INTO
As mentioned before, refrigerant leaks will sometimes ooze and even spray oil out of the source of the leak, leaving visual evidence (in the form of an oily residue) of their existence. I leak tested a system once and found an abundance of oil residue inside the outdoor unit. So I’m going over every square inch of the outside unit with a fervor trying to locate the leak. The customer returns home, and tells me, “Oh, I set a quart of oil on top of the unit and accidentally knocked it over.”
I leak tested an evaporator using my ultra-sonic leak detector. Immediately after turning leak detector on, I hear an incredibly loud noise coming from the headphones. I’m thinking that this must be the “mother of all leaks” to produce such a high intensity sound. But the farther away from the coil I get, the louder the signal becomes. The customer had plugged in one of those ultra-sonic bug repeller boxes into a nearby socket next to the light bulb. I don’t know if they actually keep the bugs away, but they definitely create a powerful high frequency sound. I’d put them all over my house, but it would be my luck that the bugs might be deaf. And it would be a lot of work and quite expensive to capture and outfit them all with little miniature ultra-sonic leak detector hearing aids. (As an interesting asides, some of these ultra-sonic leak detectors will pick up the sound of a bat nearby, because they make a sound in that frequency range for navigation purposes. They actually transmit that sound and it bounces off things and returns to them and this tells them the relative distance and size of things around them).
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Copyright 2011 Leonard Arenson Heating & A/C