Control problem? - http://www.hvacmechanic.com/ Forums
Original message
| RainzWA
 |  "Control problem?"
, posted Sun 2 Nov 15:05  
I have a 3-mo old Trane Weathertron Heat Pump, 3 ton. It is controlled by a Honeywell T8611G Chronotherm IV Deluxe Programmable Thermostat installed at the same time. The unit was retrofitted on a Bryant Gas Furnace using propane. The gas furnace is the emergency heat.
It has been cold here the past couple of nights and the night setback to 64 F to wake at 68 F seems ineffective. The compressor unit is dutifully churning constantly in the morning but apparently does not put out warm air. In fact, I have to turn the unit to emergency heat (from 62F interior on Sat morn; from 64F interior on Sun morn) to reach 68F. Thereafter, the system seems to work as advertized. I have checked the thermostat programming and it seems correct for temperature, day and time.
Why does the unit not produce heat when it is most needed? I have to manually switch to emergency heat using the gas furnace, then return to the heat pump program mode. After that, things seem to work. Is this operator error or do I need the installers to come back to check the installation/wiring?
I believe the system seems to work on other days where the temperature difference (in/out door) is not great. Oh, and I don't know why or if the emergency heat actually turned on when the outdoor temperature approached freezing (where the installers set it, and tested it for switching on as I watched).
Thanks for your insight.
RainzWA
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Replies:
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| Xenos
Webmaster 
| "Re(1):Control problem?" , posted Sun 2 Nov 19:25
I say call them back, first off a heat pump it’s self cant heat your home in cold weather and when used with setback again does not have the capacity to produce enough heat to quickly raise you homes temperature. It requires back up heat for these times. You furnace should turn on automatically from the thermostat when required therefore something’s wrong. You should never have to switch your thermostat to emergency unless your heat pump breaks down. Of course you could live in Texas where a heat pump would be fine on it’s own.
Its sounds to me as they may be using a change over thermostat to save the cost of a fossil fuel kit.
Xenos.
The best way to escape a problem is to solve it.
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| | RainzWA
| "Re(2):Control problem?" , posted Sun 2 Nov 21:29
Thank you very much. I'll ask them to come back.
The system has no electric heat. Heat is provided by the heat pump and the gas furnace.
Because there is no "auxiliary heat" available, I suppose the gas furnace should bring the interior to the desired temperature after a programmed lower temperature, then let the heat pump maintain that temperature from that point? Presently, I think they programmed the gas furnace to kick in at freezing.
What does a fossil fuel kit look like?
Thanks for the help!
RainzWA
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| | hvt
| "Re(3):Control problem?" , posted Sun 2 Nov 21:49
You are right about the gas furnace quickly heating your house after setback(morning) and then allow the heat pump to maintain temperature during the day.
The fossil fuel kit is used to achieve the above,for example, when your thermostat calls for second stage heat, the "fossil fuel kit" turns off the heat pump and runs the gas furnace unitl the FIRST stage is satisfied, then it returns to normal operation, the house will cool down until there is a call for first stage heat,the heat pump will turn on and run until either the call for first stage heat is satisfied, or until there is a call for second stage.. and the process starts again.
Xenos is probably right about the changeover stat(operating as a fossil fuel kit), if this is the case, you may be able to access the changeover stat and raise the temperature at which your system will changeover to gas from the heat pump.
BTW, you would not be able to see the ffk,it is just a couple of relays and t-stat I believe.
JC
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| | RainzWA
| "Re(4):Control problem?" , posted Sun 2 Nov 22:14
Thanks for the tips. I'll be able to converse a little better with the techs whenever they come over. I know, because they told me, that there was no aux heat when the thermostat showed "aux heat". They said that the heat pump could handle it. So that might be the problem. Now, will they fix it...
Thanks again!
RainzWA
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