______________________________________________________________________ I have seen several posts on thermostats, however nothing that relates to my situation. I installing a T8320 honeywell in replace of a T841A. Set up on old T841A is as follows R – Red wire – power Y – Yellow wire – compressor G – Green wire – Fan O – Orange wire – Cooling change over relay B – Blue wire – Heating change over relay W – White wire – Aux heat T – Brown wire – ? I think this is defrost control New connections for T8320 RC – Power O/B – change over valve G – Fan Y – compressor C – Common (optional) E – emergency heat relay AUX – Auxillary heat. Blue and Orange wires are the problem. I would think blue was the E (emergency heat)and no common wire. However, I only getting the unit to run cold air. I can’t seem to find the right connection to change over to heat. Replies: mastertech “Re(1):Trane Heat pump” , posted Tue 13 Dec 16:10 ______________________________________________________________________ Blue should be Common or C, and O should be orange or O/B. Think u blew up the T-stat. Go ahead and try it but i have a feel you will need to exchange it. mastertech “Re(1):Trane Heat pump” , posted Tue 13 Dec 16:02 ______________________________________________________________________ Do u have the full m# off the T841a T-stat. There are several models. One use B as comon(which trane noramlly would sell for there heatpumps). M# T841A1498 and T841A1606 use B as common. mastertech “Re(1):Trane Heat pump” , posted Tue 13 Dec 15:55 ______________________________________________________________________ If u have a 5/16″ nut driver. Go to the outside unit remove the panel that says service(or some writing on it like that). look at the control wires coming down from the electrical panel. The orange control wire should be connected to the orange control wire going to the house. Im almost tempeted to say try blue wire at O/B but im afraid it would blow something. Either you have a bad new T-stat or orange and blue wires got crossed. bugse12 “Re(2):Trane Heat pump” , posted Tue 13 Dec 16:07 ______________________________________________________________________ Yes, I as well was tempted to put that blue there. consequently, curiosity got the best of me. Fortunately, I did and was able to shut it down before I let the smoke out of the thermostat. lol. I have been outside to the condensing unit and even found the schematic for both handler and condensing unit. Orange does run to a relay and blue connects to a darker blue and then runs to another relay/transformer. mastertech “Re(1):Trane Heat pump” , posted Tue 13 Dec 14:50 ______________________________________________________________________ I assume you had no problem before switching T-stats. Vision pro set should be 170 to 7.(telling the T-stat u have a heat pump) 190 to 0.(std mode) Is this correct? mastertech “Re(1):Trane Heat pump” , posted Tue 13 Dec 13:47 ______________________________________________________________________ B is not used on either the old or new T-stat.(O is used for Trane) T is no longer used. E is the same as Aux(there technically different but for your applications there the same) Just make sure u jump E and Aux together. Hope that helps bugse12 “Re(2):Trane Heat pump” , posted Tue 13 Dec 14:07 ______________________________________________________________________ I set the blue and the brown to the side and connected the O to O/B. I have the White wired to the Aux with a jumper to the E. I am getting Cold air when calling for heat. I am also getting cold air when calling for A/C. I tried swapping the installers set up on 0190 to 01(reversing vlv in heating) and 00 (reversing in cooling) neither made a difference. mastertech “Re(3):Trane Heat pump” , posted Tue 13 Dec 15:09 ______________________________________________________________________ When u turn the heat or cool on is the outside unit running? Im wondering if your getting just fan only because maybe outside unit is not coming on either by tripped breaker or other problem. If you put T-stat in emergency heat will the heat come on? mastertech “Re(4):Trane Heat pump” , posted Tue 13 Dec 15:28 ______________________________________________________________________ Remove the orange wire to O/B tape off and then retry system check. What happens now? bugse12 “Re(5):Trane Heat pump” , posted Tue 13 Dec 15:34 ______________________________________________________________________ On thermostat, in both modes heat/cool It said “wait”. I waited 5 minutes on both. Neither would kick the unit on. bugse12 “Re(4):Trane Heat pump” , posted Tue 13 Dec 15:21 ______________________________________________________________________ Yes, the outside unit does come on. I also check the line to see if it was warming. Line is ice cold. With the old stat on and heat mode the line is warm. I also tried putting it on aux heat with new stat. I noticed that air doesn’t come out quite as cold, which i think means the cool air is running through the heat strip and warming to a point. bugse12 “Re(3):Trane Heat pump” , posted Tue 13 Dec 14:56 ______________________________________________________________________ Yes, no problems before setting up and all installer options are correct. mastertech “Re(4):Trane Heat pump” , posted Tue 13 Dec 15:40 ______________________________________________________________________ What is the model # of the outside unit and is a Trane too? Do u think Blue wire could have gone to O instead of the orange wire? Do u have the common wire hooked up ? bugse12 “Re(5):Trane Heat pump” , posted Tue 13 Dec 15:48 ______________________________________________________________________ condensing unit – TWR060C100A – Air Handler – TWE060C15C The blue wire seems to be killing me. At first, I though this was the common. Result, all stages cooling. I put in the O/B eliminating Orange. Result, system would not run (“waiting”). I put the Blue into the “E” terminal. Result, all stages cooling. However, tried the old stat. Blue to B and Orange to O. All stages running normal. This is where, I see might be the problem. On the unit it self it says 2 stage thermostat. On the TH8320 figure (#15) that I am wiring off of is a Typical single stage heat pump w/aux (2H/1C). Should it Multi stage?