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Old 10-07-2011, 02:52 PM   #31
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Heat pump starts initially but will not come back on to maintain temps


I do have a dual fuel configuration, and I do have an outdoor sensor on the side of the outside unit. I will trace and check the wiring. If there a way to check the sensor (ohms??)?
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Old 10-07-2011, 07:03 PM   #32
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Heat pump starts initially but will not come back on to maintain temps


There are too many hypotheticals going on here. Let's pick one problem area and start there.
You found 26v on the y terminal, and the condenser wasn't running. That's a malfunctioned defrost board. That will have to be replaced. You can wire the unit to test this theory if you wish, but you will not have the defrost option. Although the weather forecast for your area looks like you wont need any defrosting this weekend.

The thermostat jumping temperature after a short run duration could be a faulty stat. Or you could have air from the hole in the wall behind the stat. Couple that with the outdoor temp not reaching lock-out temp, and you have a cold house.

But I would start at the condenser and go from there.
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Old 10-07-2011, 08:11 PM   #33
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Heat pump starts initially but will not come back on to maintain temps


Agreed with the multiple theories, though I do appreciate all of the suggestions. I turned the heat on for the evening since the temp will drop overnight. Hopefully when I get up tomorrow the fan will be running. If it is I will check the voltages at the board and go from there.
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Old 10-08-2011, 08:11 AM   #34
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Heat pump starts initially but will not come back on to maintain temps


Got up early this morning and sure enough the temp had dropped and the system had run all night. Headed outside to remove the panel but first saw that one of the components in the compressor area was frozen. I have a picture but don't have a place to host it.

I proceeded to check the voltage of the yellow wire at the defrost board and it was registering a steady 26.70v (at the Y wire).

I then checked for voltage to the contactor from the two blue wires that feed into the side of it (to the coil??) from the defrost board and they didn't have power.

Lastly, I checked the voltage from the board to the two yellow wires (i still don't know the accurate name of this sensor/switch) and it was getting 26.50v. I also checked the ohms and it was OL or 0.000. Don't know if that means anything.

Link to pictures on Flicker

http://www.flickr.com/photos/johnniebravo2011/

Last edited by johnniebravo; 10-08-2011 at 08:22 AM. Reason: added photo link
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Old 10-08-2011, 09:33 AM   #35
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Heat pump starts initially but will not come back on to maintain temps


Y energized at board,pressure switch closed and no low voltage at contactor means you need a new defrost control board. Get that replaced along with the defrost sensor.
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Old 10-08-2011, 10:10 AM   #36
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Heat pump starts initially but will not come back on to maintain temps


Yes, time for a board..
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Old 10-08-2011, 11:14 AM   #37
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Heat pump starts initially but will not come back on to maintain temps


OK, tomorrow I will place an order for the following:

ICM304 Defrost Board
DT1172766 ICP Defrost Thermostat

and while I am in there I will also put in a new contactor.

And before the cold sets in I will have a Pro come out and check my refrigerant levels.

So I can better understand what's going on, why is the one particular part of the system freezing rather than the whole outdoor unit? My assumption the board is not telling the system to defrost??
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Old 10-08-2011, 11:17 AM   #38
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Heat pump starts initially but will not come back on to maintain temps


The part that is freezing looks like the txv(im on a mobile phone right now, I can't enlarge it).
The outlet of the txv assembly is the coldest part of the system.
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Old 10-08-2011, 12:28 PM   #39
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Heat pump starts initially but will not come back on to maintain temps


tvx restriction, power head should be stuck
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Old 10-08-2011, 12:39 PM   #40
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Heat pump starts initially but will not come back on to maintain temps


Quote:
Originally Posted by JJboy
tvx restriction, power head should be stuck
Will a new board and the sensor fix this?
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Old 10-08-2011, 12:52 PM   #41
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Heat pump starts initially but will not come back on to maintain temps


If your heating performance is good, don't worry about the txv.
The only other check would be to check the voltage at the contactor. I know you checked the blue wires at the contactor coils, but those are on the common side. I wold check the other side of the contactor.
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Old 10-08-2011, 01:18 PM   #42
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Heat pump starts initially but will not come back on to maintain temps


There are only contacts on one side of the contactor, the other side doesn't have leads similar to those that connect to the coil.

And yes, the system heats very well when that particular part is not frozen.
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Old 10-08-2011, 01:39 PM   #43
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Heat pump starts initially but will not come back on to maintain temps


Quote:
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If your heating performance is good, don't worry about the txv.
The only other check would be to check the voltage at the contactor. I know you checked the blue wires at the contactor coils, but those are on the common side. I wold check the other side of the contactor.
Maybe the check valve inside of txv is good in heating, but not the metering device in cooling......I'm no sure or the check valve is inside of the filter?????
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Old 10-08-2011, 02:04 PM   #44
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Heat pump starts initially but will not come back on to maintain temps


He has good heat when it runs. He is just running too long. The coil gets too cold and the txv shuts down. The little refrigerant that comes through is freezing at the orifice.
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Old 10-13-2011, 05:49 AM   #45
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Heat pump starts initially but will not come back on to maintain temps


With recent weather conditions I don't have much of an update. I replaced the defrost board (ICM304C), I don't know the part number for the defrost thermostat so i have not changed it yet. All the parts online look nothing like the one my unit uses.

After a bit of thinking about the logic behind this system, if in fact the board is bad, it would explain why the system no longer auto switches to aux heat. If a defrost cycle is never initiated it never gets the signal to switch.

As soon as the weather allows, I will be back with feedback.
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