Heat Pumps and Electric Heating - Auxillary heat clicks on every few minutes - Please help!

I'm running a trane electric heatpump w/ Honeywell TH5000 Stat.
Outside unit was icing over the coils evenly last week. Head pressure was high @ 360 (unit spec is 300). LED at control board was showing no fault blinking once every second.

I attempted force defrost at the control board but no response, no defrost. Replaced the defrost control board with Trane "upgraded" part CNT05001 that superceded my original board.

I had to call trane tech support during install because the new control board had no post soldered at the T1 point as my old one did. Trane tech explained that no brown T1 wire should be used if using a digital thermostat without mercury (which I assume I'm not). So, I capped off the brown T1 wire and ran force defrost at the control board while ON in heat mode. Fan stopped and I heard what sounded like the reversing process. The coils got hot. Sucess, I thought. I buttoned the unit and walked away happy.

:wall: Now, this evening the auxillary heat is clicking on at the thermostat every 5 minutes or so with a dull thunk sound coming from what sounds like the outside unit. Thermostat setpoint is 72, thermostat reads ambient temp @ 72, and yet the heat pump is blowing almost constantly and the auxillary heat strips are clicking on every few minutes. What's the deal?

what are your outside temps?

Outside temp is 14F and snowing. It's been 24 hours with no ice or frost on the outside unit so far.

Additionally, the supply register temp @ the nearest register is around 80F with heat pump only, and about 130F when auxillary heat is running.

if it is that cold, your auxiliary should be running quite often.

Surely not every three minutes. Maybe it should come on more than I thought but that seams like it would be hard on the system. I can hear the pump click on with a typical "clunk" sound every time. Am I just being paranoid?

The electric strips kicking on should have nothing to do with your heat pump starting and stopping. They should be kicking on and off as needed while the heat pump keeps on running. Electric strips starting and stopping often is not hard on them. They have no moving parts.

The heat strips will kick on when the heat pump goes into defrost if they are not already running, but that would be the only sound associated with elec. strips.

If the system is maintaining temperature properly, then it is most likely running properly. If you want to reduce how often the strips kick on you can get a thermostat that has adjustable CPH settings for the Aux heat, OR you can reduce the heat loss in your house through better insulation and reduced infiltration.

Good to know, thanks so much for your help.

Is this your t-stat:

http://www.forwardthinking.honeywell.com/related_links/thermostats/focuspro_5000/install/69_1922es.pdf

If so, you can try setting your CPH to 6 or 3 and see if that helps at all. You might check to make sure the HP itself isn't kicking off and on often and it is just going in and out of defrost.

Also, you might want to check the setting #26 and make sure it is set to 1 and not 0. if it is on 0, it will use the auxiliary more to maintain comfort.

That is my thermostat. Was set to 9 CPH per the manual. But now that you mention it if I do the math thats a cycle every 6.6 minutes. So, I switched to 3 CPH and will monitor.

I'm still confused why the heat pump and/or the auxillary heat would still be running after reaching the thermostat setpoint. Shouldn't the system shut down after reaching the setpoint?

The thermostat also has an "emergency heat cycle rate" option, set to 9 CPH per the manual. Should this remain as it is? Thanks again for all your help! This damn thing has been driving me crazy. Maybe I just need to up the meds or something this week :thumbup:

I'd change the emergency rate, too, and set function #26 to economy mode. I think that will make the biggest difference.

Also, typically, honeywell t-stats maintain temperature instead of using temperature swings. The heat loss in your house is great enough that at this point your system needs to run constantly to maintain temperature. The only way it wouldn't run constantly is if it used a temperature swing. That would mean it would heat up to (example) 72 degrees, kick off, then kick back on at 70 degrees. That isn't how the honeywells work.