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-   -   AC not cooling, but numbers look good (http://www.diychatroom.com/f17/ac-not-cooling-but-numbers-look-good-110547/)

wetbar 07-12-2011 07:03 PM

AC not cooling, but numbers look good
 
Hey I have a split system that is not cooling. I checked the super cooling and all the numbers look good to me. Here are the numbers I'm getting:

Outside temp 97
Suction line 90 psi 62
Liquid line 225 psi 103

inside
Suction line 56
Louid line 82.7
Wet bulb 71
ambient temperature in the house is 80 degrees.
the air coming out of the vents is 75
the ir temperature of the coils is 59
the air coming across the coils is 67
the air as it leaves the fan compartment entering the heating coils is 71.5

so I seem to be losing so little bit of the cold air in the vents. I would take the statue in said I would think the coils would be lower than 59 degrees.
I checked the air handler for leakage, but didn't find anything wrong. Any clues what to check next?

Thanks for the help!

Marty S. 07-12-2011 07:35 PM

Since the refrigerant is cooled by air going through the condensor coils the liquid line can not be colder then ambient. You have a restriction,possibly in the condensing coils or a kink in the lines.

wetbar 07-12-2011 07:40 PM

Sincethe liquid line at the condenser is 103 and lower at the evaporator would the blockage be near the evaporator coil?

Artco 07-12-2011 07:47 PM

With the high suction and lower head pressure it sound like the compressor has some internal problems possibly a bad valve bypassing gas internal.
What is the amp draw?

What does the suction line feel like right at the compressor? Is it cold?
When you shut off the compressor do the pressures equalize fast between the suction and discharge line at the compressor ( not the liquid line)

Marty S. 07-12-2011 08:26 PM

Quote:

Originally Posted by wetbar (Post 684968)
Sincethe liquid line at the condenser is 103 and lower at the evaporator would the blockage be near the evaporator coil?

Could be more then one issue. Do the lines run through a hot attic by any chance? I noticed the suction line is picking up quite a bit of heat between indoors and out. With a low subcool the refrigerant might also be picking enough heat in the liquid line to flash off. If so add a bit of gas and take the subcool to 14. If the lines don't run in the attic then there's a kink in the liquid line or the compressor is having issues as artco stated. Suction pressure of 90 is pretty high but not out of line with a 71 degree wet bulb return temp,that's a mighty big load.

wetbar 07-12-2011 11:43 PM

The lines do not run in the atic, they run under the house to the air handler. I will check the amp draw and for kinks in the morning.

beenthere 07-13-2011 05:51 AM

Is there a LLFD inside the condenser cabinet.

wetbar 07-13-2011 02:50 PM

If you mean a in line drier or filter no.

Ok this gets stranger: I decide to pull out the freon and only 2 pounds was recovered. But look at the numbers from before. the factory charge is 6. I'm recovering from both sides, so it can't be a clog right? Man im really lost now.

JJboy 07-13-2011 03:39 PM

I think you should start to open the linesets and isolate evap, condenser, linesets.

wetbar 07-13-2011 04:00 PM

The black wire that goes from the compressor to the contactor is pulling 8.5 amps. The blue wire from the cap has 4.8 - the yellow wire to the contactor had 6.8 amps.

Marty S. 07-13-2011 05:47 PM

That is a strange one. Being short 66% of the charge should have the suction pressure in the 20's and no subcool. Get the leak detector out and find where the 4 pounds went first. Second close the LL valve and see if the unit pumps down to test the compressor. I also think it would be a good idea to test the calibration of your guages,thermometer and scale. Something is way off.

wetbar 07-13-2011 06:04 PM

My guages and my fieldpiece said the same at all times. My scales could be off, but I would think the time it takes to recoved 6 pounds would be the real tell. I was drawing a vacuum in less than 5 min or so. Once I got her down to -30, I let it sit there for 30 minutes - and it held! WTF ? I filled it back with 6 pounds and the temp did drop about 2 degrees. Still I am only getting a 10 degree drop from the intake to the vents.

JJboy 07-13-2011 06:23 PM

Have this system working good by any chance?

If I were you I'll start from the beginning: Recover, pumpdown, leak test, pump down to 500 microns. etc

wetbar 07-13-2011 06:59 PM

jjboy yeah that is what I did today. I didnt understand your first question. Did you mean has this ever worked? yes it worked lest year, when all this was installed.

Tomorrow I think I am going to remove the LL at both ends and blow compressed air through it. Can I blow air through the evaporator coil? I cant do that with the compressor because of the oil, right ?

JJboy 07-13-2011 07:50 PM

Quote:

Originally Posted by wetbar (Post 685585)
jjboy yeah that is what I did today. I didnt understand your first question. Did you mean has this ever worked? yes it worked lest year, when all this was installed.

Tomorrow I think I am going to remove the LL at both ends and blow compressed air through it. Can I blow air through the evaporator coil? I cant do that with the compressor because of the oil, right ?


air + oil = explosion......better to use N2 :thumbsup:


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