This is something I'll figure out on my own before long, but confirmation would be nice. And unfortunately, hvac-talk frowns on DIY anything.

I have a Rheem/Ruud heat pump and 80% furnace as backup. Control is via a Honeywell VisionPro thermostat. It's about 3 years old.

Unfortunately, when it was installed, a dual fuel kit was put in at the HP, outside. I haven't been too convinced that the lockout setting on this is 100% accurate. That's mainly because I've seen the gas running when it made no sense that it should've been. I'd like to run the HP more and reduce the NG bill this winter.

I've put in an outdoor sensor for the Honeywell. My plan is to take the dual fuel thermostat out of the loop and let the Honeywell lock out the HP at 30 or 35F. I've already changed the setting to look for the sensor, and I'll just change that to allow control once I'm ready.

The question is this- is the thermostat at the heat pump just a switch inserted in the run signal for the HP (opens below setting)?

I'll finish tracing the wiring and sit down and figure this out here soon, but I thought I'd ask.