RTH8500 not locking out heat pump...

[tlmartin84]

I was in the shop today and noticed my heat pump running and the air handler continually running to keep up.

At one point it dropped to 62 degrees and never did recover to 65. Needless to say it was -1F outside.

I manually switched it over to Auxiliary.

How long should it cycle before it automatically kicks to the Auxiliary Heat on its own?

It is an RTH8500 HONEYWELL wifi. I cycled through the setup and there is not a lockout temperature setting.

 

[rooster59]

Outdoor sensor & Fossil Fuel Kit?

 

[PoorUB]

Yup, you need an outdoor thermostat, (fossil fuel kit) that will switch over to aux heat when it gets somewhere around 15-20 F.

Bill Porter controls makes an inexpensive one.

 

[fitter30]

Doesn't have a outdoor sensor or a setting in the program
Under system set up check
0170 #7
0240 # cycle rate
0250 # stage 2 cycle rate
0250 #

 

[tlmartin84]

Doesn't have a outdoor sensor or a setting in the program
Under system set up check
0170 #7
0240 # cycle rate
0250 # stage 2 cycle rate
0250 #

Mine skips 240 and goes to 250 which is set on 9(electric furnace).

There is no sensor. I assumed it would pull the temp from wifi. Or auto switch over after it wouldn't catch up.

About to just switch thermostats.

 

[fitter30]

Any other numbers in that model # . Honeywell probably makes revisions at least once or twice a year. Didn't see any additional number on the web.

 

[danski0224]

Download the manual for your thermostat and make sure that it is dual fuel compatible.

You also need to know the economic balance point to do it properly, or guess.