House A/C question for you guys that know it

alank2

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Towards last fall it seemed like my house A/C wasn't running as well as it usually does, but the hot days ended and I haven't messed with it until now. Today I started it up and the delta T between the return air and closest vent is around 13.5 deg F. After running for 10 minutes or so, I measured the outside suction line temperature and it is not very cold - 77 deg F. It is a 19 year old system, but are there any tests that a non-HVAC person can do to see if it is just low on refrigerant or if the compressor has weak valves or something?
 

scott024

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Is the outside unit fan running? If it's not running or not running fast, it might not be able to cool the condenser adequately. Hopefully it's this and you only need a capacitor or a fan motor. These are easy to change out even if you've never done it before. There's probably 10 videos on Youtube on how to do it.

I had a rent house with a similar problem and the duct had separated between the air handler and the vent. It was letting in hot air from the attic into the duct work. Might be worth a look if you were checking a vent in the ceiling.

Other possibilities are that it could be low on freon. 19 years old, probably an R22 system. Probably not something you are going to be able to check unless you have a set of gauges. Should be some info on high pressure/low pressure operating ranges on the outside unit. It's an easy fix, but the HVAC companies are going to hit you with a diagnostic charge and then about 100-200/lb for the R22.
Worse case scenario is that the compressor is on it's way out. (not likely, but it's a possibility). I'm not sure how you can check this and be absolutely sure that's what the problem is.
 

alank2

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Fan is running and is blowing warm air. A friend already recommended checking the duct work so that is on my list!

That is what I was wondering too low freon or compressor failing. I think it is R22. Someone I know with gauges is going to help me this weekend. What will the gauges show if it is low freon vs. compressor issues?
 

kirk1978

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Careful with the advice you get from shade tree HVAC folks. Being in the business for 22 years I have heard and seen some good stuff.
 

2busy

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That is only part of the equation . Suction temperature doesn't mean anything without evaporator temperature. 13 degree temp difference between supply and return air may or may not be ok.
 

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