[vicki n]

Heat Pump w/ Aux Gas-Incorrectly cycles on and off

When on HEAT the unit goes on and off according to the temp. When on AUX it cycles on and off on a 3 min on/8 min off cycle regardless of temp (and thermo clicks each time). So then I switch it back to HEAT and it just blows cold air. Then I turn the system off, wait 10 minutes and put it back on HEAT (and it works on HEAT).

The repair folks have been here 3 times. Replaced thermo once, replaced wire at furnace once, and tightened wire at furnace third time.

Still has this cycle in aux mode after 3 repair bills! What would cause this cycle in the AUX HEAT mode?

 

[nap]

so when in aux it continues to heat the premises even beyond the set point of the thermostat?

 

[zappa]

Is your thermostat compatable with dual fuel? Can you set the cycles per hour (CPH) independently for both modes?

 

[Bob Sanders]

There is a safety lockout on the heat pump which disallows it to restart immediately. This is to prevent the compressor from attempting to start while there is still pressure in it. When you turn the stat to AUX and then back to HEAT I suspect your running into this safety lock out and that's why it's blowing cold air right afterwards. Switch back to heat and leave it and see if it starts on its own again after 10 minutes

As for fast cycling in AUX, my guess is that Zappa is on the right track... you're running too high a CPH (cycles per hour). Some stats allow you to customize this setting. See if your stat allows you to change the CPH

 

[vicki n]

Thanks Bob, nap, and zappa!

Honeywell Focus Pro 5000 series.

alpinehomeair.com/related/Honeywell%20TH5220D%20Install%20Instructions.pdf

Diagram 2H/1C heat pump system pg. 9

It cycles on/off like clockwork in AUX regardless of temp - air not always hot.

I have been reading about the CPH. Is it correct that AUX/HEAT should come on based on the temp setting vs room temp (which it appears to do in HEAT)? If that is correct, what prompts the CPH to take priority when in AUX mode?

I really appreciate the education as I have no way to confront the repairman without it. He put the system in and has always been great but this is getting to be expensive (not only in repair bills - but the inability to run on gas 100% - Electric bill shows that!).

 

[vicki n]

Thanks Bob, nap, and zappa!

Honeywell Focus Pro 5000 series.

alpinehomeair.com/related/Honeywell%20TH5220D%20Install%20Instructions.pdf

Diagram 2H/1C heat pump system pg. 9

It cycles on/off like clockwork in AUX regardless of temp - air not always hot.

I have been reading about the CPH. Is it correct that AUX/HEAT should come on based on the temp setting vs room temp (which it appears to do in HEAT)? If that is correct, what prompts the CPH to take priority when in AUX mode?

I really appreciate the education as I have no way to confront the repairman without it. He put the system in and has always been great but this is getting to be expensive (not only in repair bills - but the inability to run on gas 100% - Electric bill shows that!).

 

[Bob Sanders]

I have been reading about the CPH. Is it correct that AUX/HEAT should come on based on the temp setting vs room temp (which it appears to do in HEAT)? If that is correct, what prompts the CPH to take priority when in AUX mode?

Thermostats always work on temperature. They have a low limit where the heat is turned on, and a high limit (the temperature setting on your thermostat) where the heat is turned off.

The CPH however sets kind of like the 'sensitivity' of the system if you will. You're still operating between that low and high I mentioned above (or close to it anyway). The more cycles per hour, the shorter they will be and the more even the heat will feel. The temperature swing will be much smaller and much less noticeable with a higher cph. The downside is that the system will go off/on quite a bit.

Honeywell thermostats by default have a pretty high cph setting with electric/gas heat (too high in my opinion) and needs to be set down a little. Heat pumps however by default have a pretty low cph setting because they are not great at cycling off/on and that's why you notice the difference in the cycling rate between you heat pump and your gas AUX heat.

I believe the focus pro DOES have a settable cph. Try setting the gas heat CPH down to 3 or 4 and see if that's better

 

[Houston204]

The Honeywell FocusPro thermostats should be used with an external fossil fuel kit with dual fuel applications.

The Multistage VisionPro TH8320, the Honeywell IAQ and the Honeywell Prestige IAQ will control a dual fuel system without an additional fossil fuel kit.