What is the maximum current allowed on line voltage thermostats?

• A. 10 amps
• B. 22 amps
• C. 15 amps
• D. 30 amps

Answer: (B)

Line-voltage thermostats must switch the full load current that powers the heater, so their internal contacts and insulation must be sized for that current. For typical residential electric heating controlled by a line-voltage thermostat, the standard maximum rating is 22 amps at 240 V. That corresponds to about 5,300 watts of heat, which fits common baseboard heater circuits. Ratings lower than this would be undersized for standard heaters, while higher ratings exist but are less common, so 22 amps is the conventional maximum used in practice and on exams.