What is the difference between a double pole and a single pole thermostat?
Single pole thermostats breaks only one side of the power line to your heater and cannot be turned off. Therefore, power is continuous to the heater even if it is not running. The control knob will have a low temperature setting without an off position. Single pole Thermostats uses only two wires. This means that even if the temperature dial is turned all the way down, voltage is still going into the heater through one line. This may pose a hazard to anyone who might perform electrical work on the heater without realizing that the circuit was still on. You will need to turn off the power at the circuit breaker before electrical repairs can be made safely.
Double pole thermostats breaks both sides of the power line; therefore all power to the heater is interrupted. This acts as a safeguard for people performing electrical work on the heater. However, to be on the safe side, you should always turn off the power at the circuit breaker, not at the thermostat, before making any electrical repairs. A double pole will uses four wires and has a off position on the thermostat.
Since they are inherently safer, double-pole thermostats are preferred and may be required by code. Another advantage of a double-pole thermostat is that you can turn it completely off and the heat will not come on no matter how cold your room gets. But with a single-pole unit, the thermostat will turn the heat on even if set on the lowest setting.
CHECK YOUR LOCAL CODES FOR BUILDING REQUIREMENTS IN DETERMINING IF YOU NEED A SINGLE OR DOUBLE POLE THERMOSTAT BEFORE PURCHASING OR INSTALLING.