Bear with me while the facts are presented. Heat pump with 40K BTU 92% propane furnace for the supplementary/auxiliary, dual fuel kit set to operate at 28 deg or lower. Today's temp was up to 35 deg.
In July, installed interlock for generator input for outages. Today used the 4000 watt portable generator during snow storm outage. Everything worked as expected except for the furnace. The furnace is on a 120 volt dedicated circuit and that circuit also powers the electronic thermostat for the system. Shut off the 240 volt breaker for the outdoor unit as the generator will not power it-- produces too few amperes.
The furnace did not work. Apparently some of the furnace control power/signal comes from the outdoor unit- the dual fuel kit? Or did the 5 minute delay come into play?
Electric wiring I know, HVAC controls, I know little.
Your suggestions welcomed about how to power this furnace with the generator.
One thought is to put switches in the conductors to the outdoor fan and compressor between the contactor(s) and the motors. That way the outdoor unit would be powered but not drawing the amperes for the motors.
Or would switching some of the control wires do the job? If so, which ones and how many? .
I do need help with this one.

This post was edited by bus_driver on Thu, Feb 13, 14 at 21:55