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Cooling Mode air feels warm

6K views 19 replies 4 participants last post by  ROBERTSIY 
#1 ·
I have a Trane XR12 that I switch to cooling mode. I can feel the condenser unit fan blows warm air, which I presumed that my cooling mode is working fine. However, I felt the air coming out the vents is warm. I thought I might have the thermostat setting on cooling and heating temps close to each other, which I presumed would kick in the heating elements. On the other hand, if my thermostat setting is in cooling mode, then the heat should not come on. Can someone please tell me what to check? I change the air exchange unit's relay early in January and everything runs well during the heating mode. So what can go wrong between the lag time when I last used the heating mode and the first time I switched to cooling mode after almost two months of the unit being off because of the good weather we have here in NE Texas?
 
#9 ·
The defrost board could be sending a 24v signal to the air handler to turn on the backup when it shouldn't be on - usually elements are turned on during defrost cycles.

Short between Y and aux/w2 in the low voltage wiring.

Maybe an issue in the air handler.

Maybe faulty thermostat.

If you know what terminal/wire does what in the air handler, try disconnecting the wire which energizes backup up. (terminal labelled w2, w1, or aux)

post the model number of the air handler so we could find a schematic.

if u have an ammeter, check the amp draw of the heat strips in cooling mode.

volt meter needed to troubleshoot this.
 
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#2 ·
I take it you have a heatpump with electric backup and a hrv or erv?

Feel the refrigerant lines - big insulated one should be cold, smaller one should be warm.

If the big line is very hot and the small one warm, it's running in heating mode. Otherwise the heat strips and a/c could be running at the same time.

Check the supply and return air temperatures.

Cooling but not enough could also be caused by a refrigerant leak, or disconnected return air duct if your ducts r in the attic. (hopefully they're not!!)

Best thing to do is get a pro with this system unless you're familiar with heatpump controls and wiring - not going to try to help troubleshoot it online. there r 2 many things that it could be.
 
#6 ·
Can't tell if the charge is off without getting it checked - can have a cold suction line but still have a refrigerant leak. Electrical problem can cause heat strip to be on when it shouldn't.

Get this system checked out.
 
#8 ·
User_12345a, putting my problem in another form of question, what causes the contactors in the air exchange unit to close (or what part that triggers it) and activate the heating elements when the unit is turn on to cooling? I noticed that this is the only reason why the air coming out of the vents is blowing warm.The A frame evaporator is cold, so I think the cooling system is working fine. This is really more of a challenge for me to learn. I am guessing that there is some defective electrical component that is mistakenly calling for heat. As I mention, the unit was last use in heating mode before it was turned off for two months and nothing was done to the unit. Any additional thoughts is highly appreciated and thank you for your patience.
 
#12 · (Edited)
defrost is in the outdoor unit - a 5+ conductor wire runs from the defrost board to the air handler's low voltage connections. thermostat is also connect to low voltage connections.

disconnecting the right wire will rule out everything outside of the air handler - not sure about terminals or wire colours, haven't look for a manual yet. terminal labels/letters aren't standardized on all heatpump systems.


when did this problem start? did it cool fine last summer?
 
#14 ·
Can't seem to find a manual - trane product literature aside from consumer brochures is hard to find online. i'm not too familier with air handlers (have only opened furnaces), but can help if you post a picture of:

1. the air handler schematic, usually on the back side of the access panel
2. the air handler circuit board, if the t-stat wires directly connect to it
3. the t-stat wire connections, if they're wire-nutted to other wires in the air handler
4. the wire connections at the t-stat sub-base

----------
things i know of to check:

1. disconnect and tape off aux heat wire at the heatpump, turn on a/c with line voltage off, check for 24 vac at aux heat/w1 terminal on defrost board

2. disconnect aux heat wire at t-stat, tape off, test a/c - if this doesn't work...
disconnect both aux heat control wires at air handler; if the heat strips are still coming on in a/c mode, the issue is in the air handler itself.
 
#15 ·
here are some pictures. I hope these will help. I can't remember if the sets of wires I am holding where connected before to the board(don't remember disconnecting them before either. I usually mark them if i disconnect them). I strongly believe that they were not. I thought to include this pic just in case.
 

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#19 ·
Hello
The same thing you described happened to me this evening. The Nest should be in cooling mode, however all of we felt hot air start to circle. We could understand warmed air happening to the vent. I checked the Nest. It demonstrated it was in cooling mode and set at 75, however it was currently 79 in the house. I did a Restart of the Nest. Afterwards, everything came back to normal. I think about whether a software upgrade or something is the issue.
Thanks
ZaraJohn@
 
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