Skeptical A/C Issue
I am looking for some advice for an HVAC issue that I have been having at one of my rental properties. I am pretty well educated on the nomenclature and process for A/C systems, but am not up to speed on pricing and proper diagnostics.
My tenant told me in August that the A/C was freezing at the condenser, at which point I had contractor #1 take a look at it. He replaced the transformer/capacitor and added 1.2 lbs of R-22. A/C worked for a week and the problem recurred. Got a refund because the “repair” failed.
Contractor #2 found that the R-22 was a little low and added 1 lb, but saw no evidence of leaking. The A/C worked for about 2 weeks, but the system stopped outputting cool air.
Contractor #3 had fluctuations on his gauge so he sensed a leak or a bad metering device. He seemed very knowledgeable and I decided he’d be best suited to perform a leak check on my system. He performed a triple evacuation of the refrigerant to 500 microns and checked for leaks/noncondensables.
There were not leaks discovered and he recharged the system. This worked for about a month. He had a tech come over and diagnose the system again. This time they replaced the capacitor because it was reading low. No fix.
We are having a different problem. Here is what contractor #3 says:
“I just got a call from the distributor. They had to look up your coil info with the factory since its not made any more..it looks like that coil didn't come with a TXV..and for it to behave the way it is means basically that we caught the air in the refrigerant lines too late.
We may be able to replace the coil and flush the refrigerant lines...but if the compressor was too damaged and has shavings breaking off into the lines that may need to be replaced too. It was suggested that we perform an acid test and megohm the compressor to try and determine AC longevity since the system is a bit undersized”
After telling him that that only the fan was working and no cool air at all, this is what he said:
“When I first put my gauges on yesterday it was acting low on charge..then it acted like a Txv open and everything went normal for an hour or so. Then before I called you it seemed as a valve had closed causing really low suction pressure and high head pressure @ the same time.
I had told him to not use the AC and run fan only or set stat to ac and kill Pwr to AC unit for full fan speed ti prevent further damage.
I live in a house where my system is 3/4 ton undersized..for now it work ok...but when it starts giving me problems I'm just going to replace it all with high efficiency stuff properly sized.
I know were looking @ at least replacing the coil...possibly the compressor or condenser. It may be a good time to upgrade the system but that would require increasing the cfm by doing the furnace @ the same time. And that's your call. @ this point no matter the choice..we have to evacuate the refrigerants again. But if you upgrade the system we can credit the work we've already done to help out a bit.
Sorry for the novel, but I really would like some input from the community. I have the feeling that contractor #3 is trying the old “hook-line-and –sinker” method with trying to get me to pay for a complete system. Its only 7-8 years old!
Any thoughts? Thanks in advance!
Last edited by beenthere; 10-02-2012 at 10:02 PM.
Over 2 pounds added to teh system. but there was no leak? Hmm, sounds like a lot of taking shots in the dark.
Somewhat sounds like #3 is trying to sell you a new system cause they have no idea whats really wrong.
That's the feeling that I get. Especially becuase they changed out the capacitor and it did nothing. I can understand the upgrade if the system was 15-20 years old, but 7-8 years old seems a little pre-mature. What can I do in the mean time to squeeze some more life out of my current unit?
Originally Posted by beenthere
If it didnt come with a txv it most likely has a piston or fixed orfice. If it is clogged it can cause the low side pressure to drop and high side to rise, and if a tech just looks at the low side pressure and doesnt do a decent diagnosis he will assume it is low on refrigerant. This is only an assumption on my part. Unless the system lost all of its charge at some point I dont not understand how air could have compromised the system, unless when he evacuated it (I am assuming the refrigerant that was still in the system was either pumped down into the condenser or they recovered it into a clean empty tank) he accidently broke the vacuum with air before recharging system. I dont see a capacitor being an issue in this situation. Like has been said looks like every one is shooting from the hip and #3 wants to sell you a new system. I dont think a 7-8 yr old system needs to be replaced, just fixed as its major parts most likely still under warranty. I hope for the best.
I inquired about the piston or fixed orifice to the contractor and he stated that it was neither of those because they have been outlawed in California for a number of years. Which begs the question, what does my unit have? If the piston/fixed orifice was outlawed and, according to his email response to me from the distributor, my unit does not have a TXV, what is the device used in my unit?
Originally Posted by Rodney28334
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Assuming your system has no TXV, your tech may have been baffled why the system would appear to run fine, and then suddenly show signs of a restriction. What I did not read in your post is if any of the techs who looked at your system ever bothered to remove the charge and check the piston metering device for trash. It's not that hard to do. Even before getting to that point, all of these techs could have saved themselves heartburn had they taken superheat and subcooling readings. Maybe they did...but if so they may not be interpreting that data usefully. Who knows...we weren't there.
Originally Posted by moparman915
If you still want Contractor #3 involved, tell him you want to know what type of metering device you have (piston or TXV), and that you want it checked for trash. If he opens it up and finds none, tell him you want a new liquid line drier installed just upstream from the piston or TXV, if that's possible. If he agrees to do this, he will need to remove any old driers already in the system. This is important. Truth is, he should have already done things like this instead of you finding out about it on an internet forum. I may be barking up the wrong tree as it is, but I'm not inclined that direction at the moment.
- Electricity makes refrigeration happen.
- Refrigeration makes the HVAC psychrometric process happen.
- HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.
A building is NOT beautiful unless it is also comfortable.
This is all you need to do ^^^. These are basic refridgeration issues and should be fixed without having to replace the whole system, these companies kill me these days when it come to fixing your unit if its more than a capacitor lol
Originally Posted by Shophound
Originally Posted by Shophound
This is exactly why I wanted to engage with a forum, to explore my other options. Absolutely valuable information, Thanks.
It's good to get info from people who's not trying to sell you something
This is some information I found on the invoice about my A/C unit:
Model: FS3BA-036KA ( 3 ton unit; manufactured by Frigidaire in 2003 according to a Google search)
Line Temp 65
Sat Temp 42
Super Heat 23
Line Temp 110
Sat Temp 122
Sub Cool 12
Amb Temp 94or44
R-A Dry Temp 80
S-A Dry Temp 63
Temp Rise 17
Added 5 lb 1 oz of R-22
It’s funny you say this because on this latest service call one of hi tech’s came over and just swapped the capacitor because it read a little low. After I questioned that change but still no fix, he said that it was reading at 5% or 7%, something to that effect, and needed to get changed anyways. B.S.?
Originally Posted by hvacmike85
Do all units come with a piston, fixed orfice or TXV? Does it have to have at least one of the three to function...?
Originally Posted by Rodney28334