Insufficient cooling Carrier 42000 BTU R22 scroll compressor

bighankJune 11, 2014

Have a Carrier scroll compressor R22 3 1/2 ton unit outside and a 4 ton piston coil inside at furnace. R22 charge is 7 pounds. Original coil was a thermal expansion type but was leaking R22 and was replaced with a piston type 4 ton coil about 2 years ago. Cooled fine for 2 years. Started AC intermittently 2 days ago as humidity is high and temp only in the 80s. Now noticed that air coming out of 1st floor outlets not very cold.
Pressures measured at charge ports on the compressor are 140 PSI on the high side or compressor output and 97 PSI on the low or suction side of the compressor.
High side tubing is not hot and low side tubing to the inside coil is not cold.
Coil is not very cold either as I accessed it thru the holes where a humidifier is used in the winter with the furnace.

Are these pressures OK for R22 with ambient air temperature of 88 degrees F?

What are potential causes for insufficient cooling given the data supplied above?

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"Are these pressures OK for R22 with ambient air temperature of 88 degrees F?"


The only valid measure of charge at this point is to measure sub-cooling. Google it - there are good explanations for how it's done.

Once you have done that, If the charge is low, find the leak.

    Bookmark   June 12, 2014 at 9:29AM
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As pointed out by the folks at the other forum, the compressor is bad. the charge numbers you have are all wrong. You may have to buy a new compressor or new condenser. Call a tech...Good luck.

    Bookmark   June 12, 2014 at 4:04PM
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"the charge numbers you have are all wrong. You may have to buy a new compressor."

I secound the motion and asking on forums is not going to reveal some silver bullet to cure it. Were you an apprebtice tech stumped by the odd combo of pressures,one of the old hands might give you things to test for ( such as obstruction or wacked valve) . Under the circumstances,it would be far to cumberson to guide you,call a tech and let him find what's going on.

    Bookmark   June 12, 2014 at 9:58PM
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Was a bad start/run capacitor which failed after the system was running for 2 days last week.
As for why I am posting in a forum; KNOWLEDGE IS POWER.
I have learned AFTER THE FACT some facts which if I had the prior knowledge would have made my cause of action much different. I do not like to be bamboozled or lied to about something which I am not familiar with. Had to fight with a contractor charging $1800 for a $300 EVAPORATOR COIL.
Coil supplied was a cheaper piston type and not a TXV which it replaced. The real difference in price for a piston vs TXV coil was less than $100. While I might not be a HVAC tech I have worked on AC systems for over 30 years. Don't appreciate comments which are not helpful but demeaning in nature. Think twice before you supply criticism and not information.
Thanks for the informative comments. When I post in a forum to try and help someone I try to be factual.

    Bookmark   June 13, 2014 at 3:41PM
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The high/low PSIs (97/140) is not normal. It should be some where around 70/220 for a normal R22 system. The narrow span indicates a weak compressor. not sure how old the unit is, and because compressor is a sealed device, there is not much you can do. In most cases, you will have to purchase a new compressor as mentioned by other posters.

    Bookmark   June 13, 2014 at 11:44PM
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After replacing capacitor and running compressor for 10 minutes the high system pressure was 250 PSI and the low pressure was 75 PSI. Can't explain the pressures measured a few days ago as if the compressor was not running I would expect both high and low pressures to be low and equal. System ran for about 10 hours yesterday and did cool the house. Outside temp was only in the low 80s so system was not stressed. High side piping was just warm not hot and the low side was cool not cold. The evaporator coil was cold. Next week ambient temps should be in the 90s so the system should get a good test.

    Bookmark   June 14, 2014 at 9:22AM
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On a 10 or 12-SEER condenser; the head pressure is too high with only low 80's outdoor temp.

Head pressure with a light indoor heat-load shouldn't be over 100ðF or no more than 200-psig; or about a 17ðF rise over outdoor temp.

    Bookmark   June 14, 2014 at 12:14PM
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