dac122,
mmmh I don't recall saying/indicating that I only had 4 wires hooked up ? I did mention that the New IAQ would be installed where the original T'stat (pre heat pump install) was located because the current visionpro was installed right near the front door and 2 heat registers. ( There are only 4 wires where the old T'stat was so the IAQ solves 2 problems. I can move the T'stat back where it should be (without having to pull more conductors)and I don"t have to listen to the relays clicking as they'll be in the EIM on the furnace.
Just to clarify, the system is wired as per HP15A with one exception, L is not hooked up between the either furnace or the heat pump. That would have required 9 conductors at the HP and they only pulled 8 conductors. ( Quote" Oh no-one hooks that up because it's just confusing for the average homeowner ... it's not needed") Ya, I can see why no-one would want any error reporting
I'll either run another couple of conductors or just replace it with 10 conductor plenum cable. Then I can complete the wiring (L) .
I've checked the T'Stat outputs and they operate correctly for what's indicated on the display. EM heat, Aux heat, heat, cooling etc.
I did find a new PDF for the Defrost board that now makes reference to the HP and furnace running together ( for 30 sec) if the outdoor temp is below the BP but above the LTCO
but further down it states that the HP and furnace will not operate together without a bonnet sensor installed ?? seems contradictory to me.
I'll do some more reading tomorrow.
Gary