The following only applies when you are using a Z-300-HPS or Z-600 and the dipswitch is set to "FOSSIL". This will NOT work if the dipswitch on our zone board is set to conventional.
Typically we tell contractors when using our Z-300-HPS or Z-600 for fossil fuel applications that the thermostats should be set up as conventional heat pump thermostats (heat pump with electric auxiliary heat). This might be the simplest thing to do; however it is not absolutely necessary to set the thermostats up this way. The thermostats can be set up for heat pump stats with fossil fuel backup and the zone board should work fine. Also, when setting up thermostats such as the VisionPRO 8000 or the IAQ you have the option in the advanced installer menu to select "external fossil fuel kit controls backup heat" or "thermostat controls backup heat". You can choose either option and the zone board should work fine.
We still recommend setting the stats up as conventional heat pump thermostats (heat pump with electric auxiliary) for simplicity and consistency.