Question about 2 stage heating thermostats

[kcroat]

I have a dual fuel system (heat pump and gas boiler) that I want to control with the same thermostat. I'm looking at a cheaper White-Rodgers model (1f85-277) as I don't think I need any of the features on the more advanced models. This t'stat is two-stage and has W1 and W2 terminals for heat pump and gas boiler, respectively. However as I understand it the normal configuration for heat pump t'stats is for W2 to be hooked to supplimental electric heat, which is called for only when the heat pump (on W1) can't keep up. When it is too cold, I'd like to be able to not use the heat pump and go straight to the gas boiler (on W2). Do the typical 2-stage heating thermostats allow you to do this or do I need a more expensive model (other White-Rodgers or Honeywell)?

Thanks.

[Grady]

You need a "Fossil fuel kit". Installing one on a boiler, especially if it is mult-zone is usually not a DIY job. The wiring can get fairly complex & if you mess up, you can fry some expensive components.