Author Topic: Tempstar heat pump won't initiate defrost cycle  (Read 9779 times)

Offline lgmccoy1

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Tempstar heat pump won't initiate defrost cycle
« on: December 20, 2010, 07:50:06 PM »
My Tempstar SmartComfort 2000 heat pump will not initiate the defrost cycle.  I had a hole develop in a refrigerant line at the condensor unit outside after some wires lying against the line rubbed a hole from constant vibration and all the refrigerant leaked out preventing unit from operating.  Some HVAC techs came and repaired the hole and refilled with refrigerant.  Unit worked fine for about a week and while checking on it I noticed it had iced over.  Defrost cycle wasn't working.  I put the jumper in test mode on the defrost control board and it initially went into defrost cycle but now it will not even go into defrost cycle in test mode.  I replaced the defrost control board with a new one but apparently that wasn't it as it still won't initiate defrost cycle.

Smart Comfort 2000 TCH048AKD1

Offline JWWebster

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #1 on: December 20, 2010, 09:02:23 PM »
Did they measure the refrigerant or go by gauges?
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Offline lgmccoy1

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #2 on: December 20, 2010, 09:13:31 PM »
They used guages.

Offline JWWebster

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #3 on: December 20, 2010, 09:25:41 PM »
Get em back out there. I bet it needs a shot. let me know.
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Offline jumptrout51

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #4 on: December 21, 2010, 06:03:45 AM »
What did the wires that rubbed go to?
Possibly the defrost thermostat?
Check the defrost thermostat with a ohm meter.
Do you have continuity?
Is it connected to the coil or has it come loose?
It must be cold to check this.
Is the reversing valve working correctly?
Check for power to the RV when you do the test pins.
The board may be dropping power to the RV as it should and the valve is sticking.
JW is correct. The refrigerant charge should have been weighed in from a scale.
« Last Edit: December 21, 2010, 06:05:49 AM by jumptrout51 »
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Offline lgmccoy1

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #5 on: December 23, 2010, 03:29:31 PM »
Ok I installed a new line thermostat.  It will initiate defrost cycle.  I have it set for 30 minutes but it is still freezing up.  The main line coming from house into unit is hot to touch and I can watch steam coming from coils but it's not completely melting all the frost.  After a couple hours it has a good amount of frost coverning the coils.  Oh and I contacted the tech that refilled with refrigerant and he said they did weigh the refrigerant amount before the charged the lines.  I am going to readjust the line thermostat as it is kind of loose on the line and see if that helps.

Offline jumptrout51

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #6 on: December 23, 2010, 03:43:31 PM »
Make you a jumper wire for the board to bypass the defrost thermostat and see if it works correctly.
Set the defrost time for 1 hour.
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Offline lgmccoy1

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #7 on: December 23, 2010, 08:04:46 PM »
I did use a jumper wire to bypass thermostat while power was off and had the timed jumper set to "test" instead of one of the time increments "30" "60" or "90" and I could here a clicking on the defrost board.  I assume that would be the relays.  When I turned power on to unit and initiated indoor thermostat to "heat on" it went into defrost mode and cycled on and off.  When I removed the jumper on the timer side it stayed in defrost mode.  I think it possibly may be the reversing valve  as the large copper tube coming from inside the house and going into condenser is warm when in defrost mode.  It goes straight into reversing valve.  To this point there isn't any ice accumulation on line but once it gets to reversing valve all the lines on the other side of reversing valve are iced over.  How can I unstick the valve if it is sticking.  I've tried running in air conditioner mode but no luck.  Also the temperature outside now is in the 20's.

Offline jumptrout51

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #8 on: December 24, 2010, 06:52:08 AM »
The large line(suction line) is supposed to be hot when in the heat mode.
You may not have let it run long enough in defrost to cool down.
Unless you turned off power to the air handler when you made the jumper connection you will hear noise at the board.
If the valve is sticking you can set the unit to run in COOL,lower the thermostat as low as it will go(usually 50 degrees).
At the defrost board remove one wire going to the RV.
Continuosly touch and remove the RV wire to its' terminal until you hear the swoosh sound on the valve changing over.
If you hear the swoosh sound as soon as you remove the wire,it is not stuck.
Since it is cold at the unit,use your meter to check continuity through the defrost thermostat to verify it is good.(remove the wires from their terminals first)
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Offline lgmccoy1

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #9 on: December 24, 2010, 11:05:04 AM »
Ok I did what you said and I noticed on my defrost control that the terminals connecting the reversing valve, one is abbreviated Y-RV and the other one is R-RV.  There is one wire attached to each coming from the reversing valve.  I removed the wire from Y-RV and continued touching it but no "swoosh" sound.  I noticed right below Y-RV there is a terminal marked "RV" with no wire attached.  I touched the wire that was on Y-RV to RV and reversing valve initiated with the noticeable "swoosh".  When I replaced the old defrost control with a new one  I was careful to make sure i reattached the wires to correct terminals as I did them one at a time but I guess it's possible I attached this to the wrong one.  What is the difference between the two Y-RV and RV.  Can it damage anything if I leave it attached to RV instead of Y-RV. I attached a .pdf of a similar board to mine the only difference is terminal "B" in diagram is labeled "O" on mine.

Offline lgmccoy1

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #10 on: December 24, 2010, 11:10:54 AM »
Also I forgot to mention when I first started having all the problems I had switched the programmable indoor thermostat I have with an older one thinking the newer one might have went bad and when it turned out that wasn't the problem I switched them back.  Does anything at the indoor thermostat control the reversing valve?  Because I remember there was one wire that I wasn't sure where it went when I reinstalled the newer tstat.

Offline jumptrout51

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #11 on: December 24, 2010, 11:38:14 AM »
The indoor stat sends a signal usually on orange(o) to the control board to energize the RV in the cool mode.
On your diagram the orange wire would connect to the r/rv on the board where the other t-stat connections are made.
Because you heard the swoosh sound,your problem is in your mis-connected wires.
« Last Edit: December 24, 2010, 11:43:26 AM by jumptrout51 »
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Offline lgmccoy1

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #12 on: December 24, 2010, 12:21:16 PM »
Yep fixed it that was the problem.  After looking at my wiring diagram on my control panel I had it connected to the wrong terminal.  Thanks for all your help.  Have a Merry Christmas!

Offline jumptrout51

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Re: Tempstar heat pump won't initiate defrost cycle
« Reply #13 on: December 24, 2010, 12:53:31 PM »
 :cheers: :pint1: :santa_cool:
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