
The PC8900 includes a SYSTEM light, which is lit when the heating or cooling system is running, and a CHECK light, which lights as a prompt to check messages on the CHECK list. These models will replace most heating/cooling system thermostats. Check Table 1 to make sure the thermostat is compatible with the intended system. Table 1. Compatibility Chart. System Type Compatible with PC8900 Gas—Standing Pilot Yes Gas—Electronic Ignition Yes Gas-Fired Boilers Yes Gas—Millivolt See Note a Oil-Fired B