The HW (hot water) Series was intended for use as a 2 circuit thermostat controlling a circuit pump and fan on a hydronic coil heating system, though it could be used when needing a 2 circuit control with 1 minute delay on the second circuit. This control solves the historic problem of using a standard 22 Amp bi-metal heating thermostat on a hydronic system which require high Amp loads to be accurate.