best approach for CAC refrigerant leak
I have a Lennox Central A/C system that appears to be leaking refrigerant. My contractor's approach is to send two guys @ $$$/hr, fill the system with Nitrogen ($$) and try to track down the leak. I spoke with a friend whose contractor pumped in a sealant product that he said will seal a pin-hole leak and in his case, he has been good for two years since doing this.
Looking for advice on the best way to proceed. The system is about ten years old.
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The only thing that belongs in there is refrigerant and refrigeration oil.
Leak Seals do as much damage as good. It's a 50 / 50 shot at best.
How have they been leak checking? How long does it take between topping it off?
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not an ac expert but they make electronic leak detectors for freon if is there any pressure left in system you might be able to find it that way
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Thanks. We fully charged the system on September 6th, and when we just tested it a week ago the compressor was cycling on/off again, which is the same thing it did right before refrigerant was added last September. The system seemed to work fine for the week or two of use we got out of it for the remainder of the summer season. Thus I don't have any real sense of how quickly it is leaking out, but it seems likely that it would not last us through the summer on a new charge.
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that tells me it’s a small leak but still detectable.
isolating and N2 pressurizing is last resort.
Open there eyes and look for signs of oil.electronic leak detection
Infra red dye
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It sounds like you are saying that there are better methods and that I would be best off finding another company that utilizes these better methods? I'm assuming the better methods are for time efficiency so as to save cost?
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Unless you get lucky, it's a time consuming process. If it's in a wall, you might never find it.
It really doesn't take two people, though…
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It does if they want to get $$$/hour. Unfortunately I cannot dictate how they should do their work. I can only choose which company to use. If they recharge the system, they charge $$/pound here. 8.8 pounds = $$$. I can buy a 25 pound canister for $300. I don't know what prices are like outside the New York Metro area.
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Find someone else.
A good technician with an electronic leak detector should find that leak unless it is buried in a wall. If it is in a wall your going to have to open the wall for a new line set anyhow (new unit or old)
It is not a 2 man job to leak check. Don't put any dye or leak stop in the system.
At 10 year old it is worth a shot to fix it
Notice I said good technician. Most don't want to take the time to leak check. They want to sell new equipment.
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@lbeachmike , we really aren't supposed to talk about money like that. You can edit your post by touching the "…" icon in the upper right of your posts.
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Lennox systems are notorious for leaks in the evaporator coil. 9/10 times I find them there. A tech equipped with an electronic leak detector should be able to find it. If that doesn't work then I would do a nitrogen pressure test and check with leak detector soap. As a last resort I would try dye. I would never use ant type of "leak sealer ". It's definitely more likely to do more harm than good in my experience.
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Thanks for the really great info. I hope we are the 9/10 case. My contractor mentioned this was a relatively common possibility and they would be looking there first. He also mentioned they are about $K and hard to get right now (about five weeks?) Is an electronic leak detector standard for most HVAC contractors to have?
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Yes. I own two different electronic leak detectors, I like to have good quality tools that I know are well taken care of. Even if a tech doesn't own his own leak detector his company should be able to provide him with one. Because leak detection can sometimes be time consuming and involve spending time in a hot attic, lazy/bad techs will tend to try to take the easy way out and use leak sealer or dye before trying anything that takes effort.
Or they will try the salesman routine. "You need a new system ".
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start with dish soap and water at all the connections, look for bubbles that get bigger or a stream of bubbles. i think you'll sea a stream/growing foam in your case
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How big is this system that it has 8# of refrigerant in it?
There are 3rd parties that make replacement evaporators too, that might be a better route if Lennox can't get it right.
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It's a 3 ton compressor. I included a pic of the model and specs at the start of this thread.
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From my experience with this company's techs, I don't expect they will try to sell me a new system. They have always been extremely hard-working and seeming to try to do the right thing.
It sounds like an electronic leak detector makes the process of finding the leak far more efficient? I will try to find a YouTube video to see how they work.
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Your contractors willingness to resort to putting leak sealer in the system should taken as a major red flag and not knowing best practices for locating the leak is strike two.
I'm glad they didn't jump to the sales pitch routine, give them one more chance and after strike three they're out! Get another opinion.
Some coil leaks are field repairable too...
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My contractor did not recommend leak sealer.
My original post says "I spoke with a friend whose contractor pumped in a sealant product"
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» Some coil leaks are field repairable too...
Could you expand on this?
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Depends on where the leak is. If it is someplace accessible like on the bends that connect the tubes together or someplace you can get to without cutting too much of the fins away then you can braze it shut.
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An electronic leak detector is just a device with a probe on it that sniffs the air and beeps and lights some lights in varying intensity if it detects refrigerant. it gets you to the general area then especially for a leak your size soap bubbles and looking for oil will find the exact leak.
Also note if someone didn't tighten the caps on the service valves and the access valves that it will slowly leak through those.
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Re: electronic leak detector - how do we sniff for refrigerant if the refrigerant has largely leaked out already? I think that's why they said they would be pumping in nitrogen.
Re: leak at the service valves - when the tech filled the system last September, he took his gauge off and it was spraying out of the service valve. He fixed or replaced the pin on the service valve and said that hopefully that was the source of the leak. He mentioned that he was fortunate to have a tool with him that was able to deal with the pin situation. I don't think the valve itself was replaced but just the pin. Possibly a bad valve with slow leak, even after the pin was addressed?
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We usually leave it up to the client, depending on the situation.
The leak seal can be a big expense without guaranteed results. We use a seal that also has a dye, so if the seal doesn't seal, then the leak should be visible with IR. Most of our clientele also have refrigerant lines that are 80% inaccessible without major demo or digging. So not all leaks are addressed equally.
Sectioning and nitro testing will leave you without AC until the leak(s) are located and repaired. It's at least 2 visits. One for the recovery, sectioning, and nitro charge. Second visit to see where the pressure dropped.
Now let's say the leak is found, and it's in the condenser coil. That's not a repair. That's a coil replacement at minimum. Now you're waiting for a new coil. For how long? IDK. Your condenser is 12 years old, not 10, and out of warranty. So now do you go through the expense of a new condenser coil now (plus refrigerant) and hope the compressor doesn't take a poop in August, or do you replace the whole condenser? Or roll the dice and do the seal? Isn't being a homeowner fun?
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Repair vs replace normally favors repair, especially when you consider the time value of money. You frame it as if the chance of further near term failure is more than 50%.
Though it does seem like an argument could be made to do no troubleshooting and simply replace the compressor, if odds are significantly favoring the issue to be at the compressor (given the troubleshooting costs.)
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The compressor is unlikely to fail unless you do something extreme to it. Another leak is a possibility.
Someone who is doing refrigeration service should have the tool to replace the valve cores without losing the charge. Worst case they could pump it down(close the liquid service valve then run the condenser to pump all the refrigerant in to the condenser), replace the core, then re-evacuate the system, but the tool to replace the core without losing the charge is a standard service tool.
If the high side hose is removed with the system running sometimes the pressure can keep the schrader valve from closing. Liquid refrigerant in the high side hose of the manifold set can be mistaken for a sticking schrader as well.
The access valves(the schrader valves that the manifold gauge set connects to), should have metal caps with a metal to metal flare seal that goes over them and is wrench tightened to make the long term seal. There should be similar caps over the service valves (the valves used to trap the refrigerant in the condenser or to allow it to circulate in the system). Without the metal to metal seal the refrigerant will slowly escape.
If it is cycling there is at least enough refrigerant in the system to close the low pressure switch until the compressor starts trying to make it a solid column of liquid through the condenser and in to the evaporator so it will be leaking some but not as fast as if you added nitrogen to to increase the pressure or if it had a full charge. It should be possible to find the general area of the leak at least without adding anything to the system.
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No, that's not what I'm saying. A leak could be anywhere. If a leak(s) can't be found and repaired without sectioning, the time and expense of sectioning and repair, considering equipment age, might not be worth it. Like I said, each situation is different.
Whatever is done, make sure a new liquid line drier is installed.
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Why make sure re: new liquid line dryer? What does that do?
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It may be worth noting that my home is three blocks from the ocean. Things corrode a lot more quickly here, though I don't see any obvious corrosion on the unit.
I am interested in better understanding if the leak could be at my schrader valve, given the pin was stuck/defective last time the tech was here - and he used a tool to resolve that, but he did not replace the valve as far as I am aware.
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Wondering if the piping looks like a concern in any of the below shots …
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These caps have to be wrench tightened, it is the flare connection on these caps that keeps the refrigerant from leaking at the service and access valves. The schrader cores almost always leak a little bit so without the caps being tight the refrigerant will slowly leak out.
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It would be my assumption that the caps were properly tightened by the tech who was last here to charge the system. Are you suggesting that I should check them? If so, I'm not sure how tight they should be. And are you talking about the large caps facing up?
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the large caps and the small caps. usually if the tech didn't tighten them you can turn them by hand. the large caps are the service valves and the small caps are the access valves.
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