Miswired T-stat or Bad Heater Relay??

jusmerod · 11-05-2012, 02:12 PM

In March I installed a barely used, older matched Rudd split system in my Florida Mobile Home, that I have had in storage for 10 years. My nephew , in the business, wired my t-stat, and supplied the freon. Another friend, whom I had been paying for 3 years to anually add freon to my recently replaced split-system, realized that the electric heater was engaged while system was calling for cooling...He stated that it was his opinion that a heater relay was defective...We disconnected the three black leads going to heat coils and enjoyed a trouble free summer of cooling. Now the weather is beginning to cool and I will be in need of heat soon. I am looking for troubleshooting techniques to determine which relay may be defective, or is my t-stat miswired, or could it be a heat limiter bad(whatever that is).

Doc Holliday · 11-05-2012, 02:37 PM

What does the heater have, relays or contactors? Post the model number of the air handler and take some pictures of the stat wiring and post them as well.

Doc Holliday · 11-05-2012, 02:38 PM

You have heat sequencers which bring on one strip at a time so as to not trip a breaker but for power to come to those sequencers they need to go through a switch first, contactor or relay.

jusmerod · 11-05-2012, 02:49 PM

camera phone stopped working will borrow another and post pics soon I hope..
Ruud Model : UBEA-17J11NFDAI Serial : T M 0698
HTR. K.W.
Total 7.3/9.8

Doc Holliday · 11-05-2012, 02:53 PM

Can you open up the stat and tell me which color wires are on each labeled thermostat terminal? It could be a simple wiring issue, could be a bad thermostat.

What you can do is plug back in the heater wires in the unit, remove the face of the stat and jump a few wires to bring on either cool and /or heat. If with jumping the wires on either call with the heat strips wired in as normal the system works normally then the stat is bad.

You very well could also have power surges in your area which is taking out that defrost board.

Let me know the wires termination, I'll tell you which wires to jump.

jusmerod · 11-06-2012, 09:41 PM

Hi Pal,
thanks 4 your input so far....I am hot a hvac tradesman, so I really do not understand the correlation of wiring color to where ever or not that particular wire ends up where it is supposed to go...but here goes...
I was sort of hoping for someone to tell me if continuity may be checked or 2 of heat coils disconnect at a time to troubleshoot the defective part?/ my suspicions lay with t-stat wiring as the stat worked fine on old unit I replaced and my nephew did not review my diagrams I had sketched of previous connections..just went hogwild and connected saying he has installed literally hundreds...

carmon · 11-06-2012, 10:25 PM

wow.... that makes me dizzy.....

jusmerod · 11-07-2012, 07:51 AM

Molson Rules....