Is New Compressor Needed?
Symptom: Had an 80* OAT day and turned on AC. 83* inside. Inside set at 77*. While vent air seemed reasonably cool, took 1-3 hours to drop to 80* inside. Hours later, dropped to 79* inside.
Gas Furnace: 92.2 AFUE York/Unitary P3URC14N09501D
Coil: York/Unitary G1UA036S21C R22 or R410A option but don't know which is being used
Compressor: Goodman CKJ30-1A
Don't know furnace/coil age but booklets for furnace/coil are copyright 1999-2000. Service guy says compressor is from 2000, but I did not see on label (I wasn't present for service call).
Service guy told wife 2-ton compressor worn out from age. $$$$ to replace but no specifics on brand/model.
Question-do I need a new compressor? If so, do I replace compressor or start with a new system from scratch (say a heat pump). Thank you for any help.
Last edited by jpsmith1cm; 04-10-2012 at 10:57 PM.
I'd be looking for a second opinion.
a. If it's cooling at all, the compressor is probably fine.
b. A 12 year old compressor isn't "worn out from age"
Originally Posted by jpsmith1cm
If a 12 year old compressor is dead, it wasn't old age, it was murder.
If more government is the answer, then it's a really stupid question.
Today, I talked with the service guy. He said the low pressure is 52 and the high is 68, indicating bad valves and necessitating replacement of the compressor. Although he charged me for a full routine AC service, he said he never looked at the inside unit other than to check the filter.
He had also suggested to my wife yesterday that replacing the whole sytem makes more sense than just replacing the compressor. I'm not sure how he came up with that recommendation if he didn't look at inside system (furnace/fan/coil).
This is a 2 1/2 ton unmatched system. At 12 years of age, I'd not recommend replacing the compressor. Replace the entire system with a matched system (inside and outside units).
I do not accept this diagnosis.
Originally Posted by scouts22
I would expect MUCH different pressures from a failed compressor.
If you've got the cash, a new system is a good way to go, but I'll bet that this one can be repaired for less money.
Have a look at our Contractor Locator Map and see if there is a contractor near you.
Those pressures don't indicate any bad valves to me, something is wrong if it has those pressures, but bad valves?
Originally Posted by jpsmith1cm
Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law
"Never let success go to your head, and never let failure go to your heart". - Unknown
My quoted post above needs some clarification.
Depending on outdoor dew point, frost should be indicated on filter-drier & down-stream from it, if no frost due to very low dew point temp,the drier & down-stream tubing should be a lot colder than up-stream toward condenser coil. [That was an incorrect statement by me!]
Dew point is relevant to when a suction line sweats or not.
It's not relevant to when a line gets below the freezing point.
Let' take an R-22 TXV metered evaporator set for 12-F superheat.
First load is very light & you read only 62-psig suction that's only 35-F Saturated Suction Temp (SST), add 12-F Superheat & the line temp is 47-F, usually the dew point is going to be well above that temp. That is even above beer-can cold.
Second load is an 85-psig with a 51-SST add 12-F SH 63-SLT.
The dew point could be below that temp & therefore NO sweating on the line; also a 63-F suction line is not going to feel beer-can cold.
We have to take both the suction & high-side refrigerant line temps & pressures & do the math to get both Superheat & Subcooling so we know what we're doing; beer-can cold & a sweating line does not work, it's even more critically important on high SEER systems that operate at higher suction pressures & line temps, with a given heatload....
Last edited by udarrell; 04-12-2012 at 10:20 AM.
Reason: [That quote was an incorrect statement by me!]
I presume your comments are directed at your fellow techs as they're over my head. Nonetheless, they raise another question. Is there a minimum OAT to troubleshoot this or other issues?
Originally Posted by udarrell
Thanks to everybody that replied. This is one of the best forums on any subject anywhere.
I wish I could retain one of you experts for my HVAC needs. I looked at the contractor locator map but there is only one listing in the Kansas City area, but that contractor only has a Facebook page with no info about the company other than a phone number. He may be great, but the lack of info about the company doesn't inspire confidence. Not sure how I could search for postings on this forum by the contractor. I searched the company name, but no luck.
Originally Posted by scouts22
With bad valves normally the low side is not a low 52-psig pressure, but a high low side pressure; with bad compressor valves the high-side head pressure drops & the suction pressure rises way above normal. That reported scenario sounds fishy to me...may just be wanting an equipment change-out...?
scouts22;Today, I talked with the service guy. He said the low pressure is 52 and the high is 68, indicating bad valves
and necessitating replacement of the compressor. Although he charged me for a full routine AC service, he said he never looked at the inside unit other than to check the filter.
He had also suggested to my wife yesterday that replacing the whole system makes more sense than just replacing the compressor. I'm not sure how he came up with that recommendation if he didn't look at inside system (furnace/fan/coil).
Small chance, but perhaps the valve core was not depressed enough to get an accurate high-side reading; but I question what took place by the service guy.
If the pressures were as he indicated there would be no cooling. What is the temperature of the air coming off the condenser as compared to the outdoor temp; list both temps.
What is the temps of supply air & return air in your home?
There are other indications that don't make sense with what you were told...
There are other diagnostic checks that a PRO could use. A blocked filter-drier inside the condenser could cause a very low high-side reading at the liquid high-side port as the liquid refrigerant merely builds up in the condenser; a condenser can hold all of the liquid refrigerant in the system.
By all means find another contractor for a more comprehensive diagnosis & opinion; don't tell them what the other guy said.
Last edited by udarrell; 04-11-2012 at 01:11 PM.
Reason: think it's R-22...
udarrell: "If the pressures were as he indicated there would be no cooling."
jpsmith1cm: "If it's cooling at all, the compressor is probably fine."
The service guy did mention when I called him today that he was "surprised" I was getting some cooling. Guess that means he realizes there may be a flaw in his diagnosis but he didn't follow up on it.
BTW, I can't figure out how to make the multi-quote thing work here. I'm maxed out at one quote. Thanks.