Need Help Troubleshooting Trane Heat Pump Auxiliary Heating Strips

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Old 07-17-13, 07:07 PM
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Need Help Troubleshooting Trane Heat Pump Auxiliary Heating Strips

Being pro-active to get my heat ready for the upcoming winter months. I have a Trane heat pump, model TWR036D100A0, and air handler model TWE036C140BO with a Honeywell VisionPro TH8320U1008 thermostat. The system is 12 years old but works good except for the auxiliary heating. I have always noticed that when the system goes into defrost mode cold air blows out of the vents. I am in need of help to remedy this situation. Based upon my research, when the system goes into defrost mode the condenser is supposed to shut down and the auxiliary heat strips are supposed to come on. I don't believe my system has the heat strips engaging when in defrost. I opened up the cavity where the heat strips are located to see if I could see any obvious issues. The installer did not mark an X in the box to designate which heat strip(s) are installed on the outer panel. When I pulled the metal access panel to the heat strip bay there is a wiring diagram on the back that shows BAYHTR1408 and BAYHTR1410. It appears that I have two different heat strip banks but there are no markings on the outside of the metal housing. There is one 2-pole contactor and one 2-pole limit switch that has L155F on it. I pulled the wires off the four white ceramic circles and did a continuity test. I found continuity between two pairs. Each pair with continuity shows 14.7 ohms. Does anyone have knowledge on how to test this setup to see if all the components work properly and the wiring is correct at the condenser and air handler? I have attached a crude diagram to show the wiring I found.
 
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Old 07-17-13, 10:03 PM
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first you need to make sure X2 from the heat pump is wired back to AUX on the thermostat. If your heat strip work other wise and it is only during defrost that you have a problem then it is most likely a low voltage wiring issue as that is field installed.
 
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Old 07-18-13, 06:57 AM
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Thanks for the reply. That is the issue. I am not sure if the heat strips are working properly. In the air handler two of the white wires W2 and W3 are cut off from the plug and are just dangling. The other white wire in the plug W1 is wire-nutted to the black X2 wires. At the heat pump the black X2 wires are connected. There is a white wire at the heat pump that is not connected to anything. I looked at the wiring schematic on page 13 and it shows X2 should be connected to W2. Here is a link to the manual: http://www.trane.com/webcache/un/spl...5_04012001.pdf
 
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Old 07-18-13, 03:59 PM
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w2 and w3 are for a system with 2 or 3 heat strips banks. Yours only has one contactor and 2 strips for a total of about 8 - 10 kw. X2 from the HP should be wired to W1 in the ahu.
 
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Old 07-18-13, 05:03 PM
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hvactechfw, thanks for the info. I believe that is the way it is wired. I believe I have two BAYHTR1405 heat strips, but I am not totally sure. I have searched and searched for information on how my heat strips should work but I have been unsuccessful. I have been unable to find any reference concerning how the 2-pole L155 limit switch actually works. With this limit switch I can't determine if these two heat strips operate independently or together when a call for auxiliary heat is made. With W1 wired to X2 at the air handler when the heat pump goes into defrost mode or has a call for auxiliary heating would both strips come on or just one? I have attached a photo of the wiring. Thanks!
 
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Old 07-18-13, 05:05 PM
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They work at the same time.......................................
 
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Old 07-18-13, 06:41 PM
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Once again, thank you for outstanding knowledge and assistance! I truly appreciate it! One final question: the numbers on the 2-pole limit switch have the numbers 64TX11, L155F. L005, 208485 and 21C711344P41. I researched using those part number(s). I found that 64TX11 designates it is a 2-pole limit switch and a certain size and L155F designates it opens at L155 degrees farenheit. I could not find a part based upon the numbers 208485 or 21C711344P41. I couldn't find this part listed under Trane. I like to plan ahead for future problems and have a solid plan where to get part. I always like to have a spare contactor and a run capacitor on hand for my condenser and air handler for these hot summers. It paid off recently on my heat pump. I have found a 2-pole limit switch that has the same 155 degree rating and looks exactly like the one on my heat strips but is not the same part number. It is a Nordyne 6264090 or 626409R. Do you happen to know if the original part is available from Trane/American Standard or is it acceptable to use the part that looks the same and has same specs? I do not want to create any safety/electrical hazards by installing an incorrect limit switch (if needed). I have attached a photo of the limit switch I have installed and the possible replacement. Thanks!!!
 
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Old 07-18-13, 07:26 PM
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The trane part number is THT02210
 
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Old 07-18-13, 08:11 PM
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Thanks for the Trane part number. Unfortunately, I researched for an hour trying to find this part on-line. The only two places that popped up were amazon.com (no image) for a price of $71.10 plus $7.49 shipping and another place where you have to be registered to log in and shop. That seems crazy as normally when you surf the net for a part you get all kinds of "hits" for an opportunity to locate/purchase. Any alternative/substitute part numbers? I'll keep looking. Appreciate it!
 
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Old 07-19-13, 08:41 AM
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try

PEX - Radiant Heat - Radiant Heating - Plumbing Supplies - PexSupply.com
not much description offered but I've had luck on the 'phone with them in the past .


also:

Thermostat; control, temp, open 155f, close 115f, s THT02210 Order now for same day shipping. 365 day return policy. RepairClinic.com

and they have a good return policy ....
 

Last edited by dsomerv; 07-19-13 at 08:53 AM. Reason: additional link
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Old 07-19-13, 09:15 AM
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dsomerv,

Thanks for the sources for the part. I appreciate it!
 
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Old 12-12-13, 07:31 AM
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working on the same heater.

just curious was you contactor pulling in? mine is and I have continuity on the element but no heat, the whole heater assy only $115 so I guess Im getting a new heating strip.
 
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