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Homeowner here...I have a 2 stage heat pump split system with the ducting zoned for 2 zones. The units are as follows:

Compressor: Goodman GSZC16 heat pump
Zone control board: Honeywell HZ322
Thermostats: Ecobee 3 (zone 1) & Ecobee 4(zone 2)

My issue is that when the thermostats are calling for aux heat it's not actually turning on. I took readings of the W wire terminals at the zone board on the thermostat side and get 30v, so the aux heat call is getting to the zone board, but when i measure the W terminal on the heat pump/air handler side of the zone board I only get 10v so the board is preventing the call for aux heat. After reading the zone board manual I found that it doesn't actually support 2 stage compressor systems with aux heat (only 2 stage without aux heat for some reason).

I was thinking that maybe if I jumped the W wire terminals between the thermostat sides and the equipment sides that the aux heat call would actually come through and turn on. Would this work? If not is there any other solution besides replacing the zone board with one that does support 2 stage compressors with aux heat? Thanks!

  • That looks like an expensive controller. Shorting two terminals on it without knowing what I was doing, is not something I would do. It sounds like you need to learn more. How are you measuring voltage? One probe on W, and the other probe on what exactly? – Harper - Reinstate Monica Nov 16 '19 at 18:35
  • I was grounding it on one of the open DATS sensor terminals. – StephenT Nov 16 '19 at 18:53
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    Wait, what? There's no such thing as ground in thermostat wiring, which is isolated. You need to measure off normal current return, which is C in that grouping of terminals. – Harper - Reinstate Monica Nov 16 '19 at 18:55
  • I didn't know that. However, using the DATS terminal for the second probe was giving me readings that I would expect based on what the thermostat was calling for at the time. Using the C terminal was giving me the same results. Which terminal should I be using for the second probe when measuring on the left (i.e. HP/air handler) side? – StephenT Nov 16 '19 at 19:18
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    You need to measure off normal current return, which is C in that grouping of terminals/wires. The reading you saw at the furnace was not what you expect. – Harper - Reinstate Monica Nov 16 '19 at 19:28

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