cancel
Showing results for 
Search instead for 
Did you mean: 
Replies are disabled for this topic. Start a new one or visit our Help Center.

Nest Dual Fuel and E heat configuration question with Zone Controller

Shawn_Kimble
Community Member

I have 4 zones with 4 Nest Gen 3 thermostats that are a bit overkill, as I also have an HZ432 zone controller, managing both a single stage heat pump, and a single stage oil furnace.  My issue is that my e-heat oil furnace kicks on when I would not expect it to, and instead would expect the heat pump to run down to 30F outside.  It's currently 50 outside, and the system continue to trigger the e-heat.  Unclear what is configured/wired wrong.

Here's the Nest setup:

Nests are wired as Dual Fuel, Heat Source 1 as Electric (Heat Pump), and Alt Heat as Oil.  Nest has them wired as Y1,  G, OB, Rc, W2 AuX and C, set as B type Heat Pump
They are wired to the zone controller for the thermostat as Rh, C, Y1, W2, G & OB
Nest is set at 30F cut over on fuel

Equipment is wired at the Zone Controller as:
Heat Pump: Y1, B, C to Oil C and Outdoor temp sensor to OT.  White is optional, and not connected.
Oil - W1/E, Rh/c, G

Zone controller is set to cut over at 30F

1 Recommended Answer

CoolingWizard
Platinum Product Expert
Platinum Product Expert

The Honeywell HZT432 uses the thermostat connected to #1 position as the system priority controller.  It only needs to know the duel fuel status in order set up the delay timers.  You still need the main thermostat to set the system mode. That is, control the call for heat on W1 and to disconnect the call on Y1 and O/B.  Make sure you move the wire from W2 and put it into W1 of your Nest Learning Thermostat. You might need to go into Pro Setup to define the W1 since it is not currently in use. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

View Recommended Answer in original post

3 REPLIES 3

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@Shawn_Kimble , the Nest Thermostat has no inclination of a zone controller being present.  Was the Honeywell HZ432 installed by the contractor or did you? The HZ432 my be optioned for Duel Fuel system as well.  You should have a Discharge Air Temperature Sensor attached to the DATS sensor connectors and the outdoor temperature sensor attached to the OT sensor connectors.  Your duel fuel setup should have your oil burning furnace should be attached to W1 and not W2/AUX. Unless your forced air handler has electric heat strips installed, there should not be any connection to the W2/AUX terminal when you have a heat pump.

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

It's a combo of myself and the last tech that upgraded me to a heat pump.  I'm not clear he wired things correctly, as it was cooling season, and now I'm seeing an issue in heating.  Yes I have a DAT sensor as well as the outside temp sensor from the heat pump.  No heat strips.  

I feel like it would be better to set the nest as "dumb", and have the HZ432 do all the fuel work, with the thermostat just providing the temperature set points and current temps.  But unclear how to establish that.

CoolingWizard
Platinum Product Expert
Platinum Product Expert

The Honeywell HZT432 uses the thermostat connected to #1 position as the system priority controller.  It only needs to know the duel fuel status in order set up the delay timers.  You still need the main thermostat to set the system mode. That is, control the call for heat on W1 and to disconnect the call on Y1 and O/B.  Make sure you move the wire from W2 and put it into W1 of your Nest Learning Thermostat. You might need to go into Pro Setup to define the W1 since it is not currently in use. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner. If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.