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White wire connected to Aux bridged with E

Community Member

My current Honeywell thermostat has a White wire connected to the heat pump AUX, additionally there is a short red wire connected to both the AUX and E. Where would the white wire connect on a Nest thermostat?


Community Member

Did you figure this out?  I have the same set up.  The W controls the additional heat source (e.g. AUX or E (Emergency heat) (inside in the furnace) when it's very cold the heat pump doesn't do well, and I assume the thermostat looks at the delta between the desired heat and actual heat to make that determination.  SO, I think you just plug the W (White) into the single W on the regular NEST.  The more expensive Learning version has additional inputs (e.g. W1, W1, Y1, Y2) to support systems with multi-stage cooling and heating options.  I just have 1 yellow and 1 white coming out of the wall so I think the regular NEST will work fine, and the configuration checker agrees (if I don't check both the AUX box and the E box, which would indicate 2 separate wires)).  Note: I also have the Orange wire to tell the heat pump to switch between heating and cooling.