[2BirdDogs]

Thanks for your reply Jack.

I think the black box is a timer that is there to keep the AC's from coming back on all at once in the event of power failure. It is somehow connected into the AquaHot Electric Heat mode too since the element amp draw is so high Leg 1 and 2. I think the black box timer and relay may also be part of the system that locks out the heat pumps when AquaHot is on electric element but I am not sure.

The bathroom and 1/2 bath aquahot heat vents ONLY pulsate when the electric AquaHot element is energized. 

Once the AquaHot comes up to temp and the element is not drawing any current, the bathroom heat vents blow normally. The bathroom aquahot heat vents are controlled by stand alone "old style dial" thermostats.

Zone 1 (kitchen Aquahot vent) and Zone 3 (under the bed Aquahot vent) blow normally all the time regardless if the electric element is energized or not. Zone 1 and 3 are controlled by the main AC thermostat via gas heat setting.  

The relay pulses anytime the AHot electric element is energized (even if the bathroom heat vents thermostats are turned all the way down / off).

Thanks again,
Paul