A dual fuel system which is comprised of a gas furnace and a heat pump should be connected to a thermostat or control system that can accommodate the specific heating set points.
Single stage furnace thermostat wiring.
If you have a two stage heat pump then you will also utilize terminal y2 for the second stage.
This controls the second stage of heating.
So you may have to fish an additional four strand cable from the furnace room to the thermostat location photo 1.
How to choose the right furnace thermostat.
The thermostat only kicks in the second stage if the furnace can t maintain 6 to 8 degrees per hour.
The new thermostat doesn t have these because it isn t designed for this type of installation.
So that s the easiest way to identify single stage conventional hvac systems which would be furnace based or boiler based.
Single stage hvac system thermostat source.
Verify that the red wire is connected to the r terminal green wire to the g terminal and white wire to the w terminal.
A two stage thermostat may need more wires than your current programmable thermostat.
Strip the brown thermostat wire back one half inch and connect it to the w2 terminal on the furnace.
Furthermore this thermostat wiring diagram is specifically for a system with two transformers your system likely only has one transformer as most typical residential systems only use a single transformer for control.
One which is common is the single stage heating system and the other one is multi stage heating system.
1 know your heating system.
The first and foremost thing you must do is to check what kind of heating system you are using at your home.
The thermostat you purchased is designed for a single stage system such as an air conditioner and a single stage gas furnace.
If not connect them in this manner.
The terminals are usually marked r and w.
A basic two wire thermostat can be compared to a simple single pole switch that you will find throughout your home only instead of you turning the switch on and off as required a mechanical or electronic temperature controlled mechanism is the operator of the switch.
Conventional single stage systems will have one wire leading into w or w1 terminal for heating and one wire leading into y or y1 terminal for cooling.
That is a basic honeywell thermostat wiring diagram for a single stage heat pump.
A two stage or variable speed system may only be operating at a single speed because the thermostat or control system doesn t allow for two stage wiring.