WRM1086A Master Thermostat with a Dual Voltage Power Module is required for all floor heating system installations utilizing more than 240 square feet of floor heating product when operating on a 240 volt circuit. Use also when operating a floor heating system on a 120 volt circuit with more than 120 square feet of floor heating product. Each Master Thermostat requires a minimum of one Dual Voltage Power Module. Each additional Power Module provides an additional 15AMPS of service and up to 10 Power Modules can be added to each Master Thermostat. Specifications: * Master thermostat 12VDC programmable with sensor * Dual voltage power module with GFCI, 5mA, 15AMP * Systems are expandable * 3-Year warranty * Width: 1"" * Thickness: 4"" * Length: 3""