What is the maximum current allowed on line voltage thermostats?

• A. 12 amps
• B. 22 amps
• C. 30 amps
• D. 5 amps

Answer: (B)

Line-voltage thermostats are switches that must safely interrupt the full current drawn by the heating load. The rating on these thermostats indicates the maximum current they can carry and interrupt without overheating. For typical residential line-voltage thermostats, the standard maximum current is about 22 amps at 120/240 V, which translates to roughly 5 kW of heating at 240 V. If the heater needs more current than the thermostat can handle, you’d use a higher-rated thermostat or a contactor controlled by the thermostat to switch the larger load. While some devices exist with higher ratings, 22 amps covers most common electric heating applications, and 12 amps or 5 amps would be too low for many heaters, whereas 30 amps is less common for standard line-voltage thermostats.