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Thread: Lennox Heat Pump
01-07-2011, 10:27 PM #1
Lennox Heat Pump
I am running into problems with a Lennox heat pump that shows vacuum on low side and 0 on high side in heat mode. In air conditiong mode however I do have a compression ratio. Now for some background. This call started in july of 2010 with a no cooling call. I determined that the failure was a short to ground on the compressor. i ended up replacing the compressor and installed a new liq line filter drier. I did not do an acid test which I realize I should have done. I brazed in while purging with nitrogen perfored a standard leak test and pulled a 500 micron vacuum. Weighed in virgin r-22 according to manuf specs. Cycled in ac mode and test system was running perfect. Then the cold weather hit and the system does not heat. found both units operating but pressures showing 0. reclaimed r22 and found still had same amount from comp replacement. check id and od txv and found no problems. At this point i decided to change the txv and reversing valve which i know the rev valve is rarely a failure point. moved system into shop replaced parts leak check and now perform triple evac. re installed system and still have the same problem. Any suggestions would be appreciated as the cust has been extremely patient but i fear that will run out. I do have recorded pressures and temps if needed.
01-07-2011, 10:46 PM #2
Your post is difficult to follow?
"found both units operating"? are there two systems?
"vacuum on low side and 0 on high side" what ports are these? (where are they located)
"airconditioning mode compression ratio" are these refrigerant pressures?
What is the model #
Are you sure the I/D txv wasn't changed prior to comp replacement?
You may want to cross reference your part # of the I/D txv and make sure it's not cooling only with internal check.
Last edited by mgenius33; 01-07-2011 at 11:04 PM."The only true wisdom is in knowing you know nothing" Socrates
01-07-2011, 11:22 PM #3
sorry i meant both the air handler and heat pump were operating. when in ac mode i had a pressure difference between the high and low sides with the guages on the service ports at the service valves. in heat mode my low side was installed on the port off the reversing valve. these pressures basically read 0. i can get my recorded data tomorrow or monday depending on if i have chance to get to the office. i am almost positive the id txv has not been replaced as this system is only 7 years old.
01-07-2011, 11:28 PM #4
noncondensables or restriction. probably why comp shorted to ground in the first place
01-07-2011, 11:33 PM #5
If you had your gauges on common suction of compressor for low, and liquid line service port 3/8th's line for high, this is likely your problem, check the part # of the txv.
Did you have your high side gauge on the hot gas 7/8th service port?
If the compressor was running or not, the refrigerant has to go somewhere.
Unfortunately, I have probably overstepped the help boundaries as it is, due to this not being a DIY site. If you check with the site and get a Pro pass they discuss this stuff all day long."The only true wisdom is in knowing you know nothing" Socrates
01-07-2011, 11:46 PM #6
I am by no means a diy i have been in the field for 10 years and i am nate certified in air conditioning heat pump air distribution and gas furnaces. i had my guages in the right spot and i am saying the same thing, that the refrigerant has to go somewhere. I am desperate at this point and i figured this would help get my posts up to become a professionaL member. So having said that i would appreciate expert advise not limited advise
01-08-2011, 12:01 AM #7
01-08-2011, 12:42 AM #8
The filter dryer you installed, was it a biflow?Poor planning on your part doesnt necessarily constitute an emergency on my part.
01-08-2011, 12:48 AM #9
01-08-2011, 01:02 AM #10
01-08-2011, 01:08 AM #11
I have pumped it down successfully as well ran in ac mode and had pressures that show a compression ratio which tells me this compressor is able to function. I can list the data I recorded tomorrow
01-08-2011, 01:25 AM #12
u sure its the correct txv
01-08-2011, 01:37 AM #13
You have a cooling only txv in the evaporator (likely) or the evaporator check valve is stuck(less likely). Move your high side gauge to the large service valve and you will see positive pressure in the heating mode. I have said to much. Get pro status.