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FixedIT 05-29-2012 03:45 PM

Heat pump blowing both hot and cold air in cool mode
 
Hi,
I have a heat pump that is not cooling. I checked the compressor and refrigeration line and they are good. I opened the air handler and the coils in there are getting cold too. When I turn the unit on to cool I realized that the heating elements are getting turned on as well. This heat is negating the cold air. I disconnected the heating elements and the temp dropped from 88 degrees to 76 degrees overnight. The thermostat was replaced last year so I do not think that this is the problem. I thought that it could be the heat sequencer sticking open ? The sequencer has 15s2 H24V 309562 printed on top. I went to Grainger and they have a replacement but I need to figure out the delay times to get the right replacement. Before I proceed I wanted to see if I could get some advise as to if I am on the right track or not. Thanks in advance.

Marty S. 05-29-2012 04:38 PM

The way to check is with a volt meter. Is there 24V between W and C with a call for cool?...yes= thermostat or thermostat wire problems
If no then we get in the touchy area where you get to stick hands in live 240V which is fused many times higher than it takes to kill you. For that reason I do not suggest DIY checking it. Sequencers are cheap ,match the H and C numbers on the old sequencer. Eliminate the thermostat and wires as a possible cause first though.

sktn77a 05-29-2012 06:21 PM

Quote:

Originally Posted by FixedIT (Post 931518)
The thermostat was replaced last year so I do not think that this is the problem.

Actually, that could well be the problem. Heatpump thermostats control the backup strips so if it was not wired correctly, it could be turning them on thinking you're calling for heat.

Did you replace the thermostat and were the terminals on the new thermostat identical to the old one? (Not that it makes much difference - pros can wire them incorrectly too!)

:eek:

beenthere 05-29-2012 06:37 PM

if the thermostat was replaced in the winter. its possible its wired wrong, and you never took notice.

FixedIT 05-29-2012 07:38 PM

Quote:

Originally Posted by Marty S. (Post 931562)
The way to check is with a volt meter. Is there 24V between W and C with a call for cool?...yes= thermostat or thermostat wire problems.

Can you tell me where I should check this ? outside or in the stack inside ?

With regard to the thermostat... I should have mentioned that we turned the AC on a few weeks ago and it had been working a.ok.
We came home from vacation and that is when we discovered the problem.

The thermostat was set at 74 today and that is where the temp was when I checked it this evening.
So...it seems to be working ok with the heating elements disconnected.

one more question... how can I tell the type of sequencer if it is not marked on the outside of the component ? would this be somewhere in the schematic?

Thanks again for the help !


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