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Thermostat and Furnace Compatibility

By Bob Formisano, About.com

9 of 10

Electric Heat and Cooling Systems - Low or High Voltage

Condensing Unit


Type: Electric Furnace
Number of Thermostat Wires: 2; with air conditioning 4 or 5
Voltage: 24 Volts AC
System Attributes: Forced air furnace


Type: Electric Air Conditioning
Number of Thermostat Wires: 4 or 5
Voltage: 24 Volts AC
System Attributes: Outdoor condensing unit; cooling coils in furnace ductwork


Type: Electric Baseboard Heat
Number of Thermostat Wires: 2 or 4
Voltage: 120 Volts AC or 240 Volts AC
System Attributes: Localized heating with line voltage thermostat in each room

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