HAI omnistat problems

[hgupta1]

I finally got around to installing my HAI omnistat RC80b thermostats both upstairs and downstairs.

For some reason, the thermostats will sort of freak out briefly whenever they are connected to downstairs HVAC unit. It almost looks like it is resetting itself with all of the lcd "lights" on the thermostat turning on briefly. Then it will shut down for about 8 minutes.

This happens with either thermostat when they are connected to the downstairs HVAC unit, so I think there is either a setting on the thermostat that I need to adjust, or maybe my wiring is incorrect? The thermostats work fine on the upstairs unit.

When I don't touch the buttons on the thermostat it appears to work okay.

Any idea what may be wrong?

 

[pete_c]

From the specifications:

RC-80B has power stealing capability for retrofitting 4-wire heating and cooling systems, or can use "common" wire to disable power stealing (All other models use a transformer common wire).

With my thermostat I initially tried:

30A00-1 Thermostat Power Supply Module (TPSM) is used for RC-80B and retrofits where a 5th “common”
wire is needed, but not available. Increases current to thermostat using existing wires.

Didn't work for me but the following did and is working fine after a few years.

29A00-1 Thermostat Isolation Module (TIM) is used when continuous 24V power is not available from the HVAC equipment. It completely isolates an RC-80B series (Rc-8x) thermostat from the heating and cooling system and allows a separate 24 VAC transformer (not supplied) to power the thermostat.

 

[hgupta1]

From the specifications:

RC-80B has power stealing capability for retrofitting 4-wire heating and cooling systems, or can use "common" wire to disable power stealing (All other models use a transformer common wire).

Initially tried:

30A00-1 Thermostat Power Supply Module (TPSM) is used for RC-80B and retrofits where a 5th “common”
wire is needed, but not available. Increases current to thermostat using existing wires.

Didn't work for me but the following did and is working fine after a few years.

29A00-1 Thermostat Isolation Module (TIM) is used when continuous 24V power is not available from the HVAC equipment. It completely isolates an RC-80B series (Rc-8x) thermostat from the heating and cooling system and allows a separate 24 VAC transformer (not supplied) to power the thermostat.

This forum is awesome! Thank you so much. For whatever reason, the HVAC installer didn't use the common wire, even though it in the wiring bundle, and there was a spot on the HVAC circuit board for it. So I hooked it up, and everything worked great!