The dial controls heating duty cycle, so measure current during an ON period.
Electrical access and live measurements are for a qualified electrician. Turn off the circuit at the electrical panel before opening the box or arranging the test. Restore power for measurement only with the required electrical safety precautions.
The TH113-R-GA uses a 15-minute heating cycle. Dial 5 gives about 7.5 minutes ON and 7.5 minutes OFF; dial 10 requests 100% output for the cycle. For a brief professional test, turn the regulator on and set the dial to 10. Return it to the normal setting afterward.
A qualified electrician can measure AC load current with a suitably rated clamp meter around one insulated load conductor, following the meter’s safety instructions. Clamping around both outgoing and returning conductors can cancel the reading. Compare the reading during an ON period with the heating product’s rated current at the installed voltage. Do not use a household multimeter’s current input as a substitute for a correctly rated clamp.
The regulator is rated for a maximum 15 A resistive load: 1,800 W at 120 V or 3,600 W at 240 V. A lower dial setting changes ON time, so a zero reading during an OFF interval is not proof of a fault. Do not use a promised relay-click time as the pass/fail test.
Sources: TH113-R-GA user guide (Operation and Technical Specifications) and Fluke clamp measurement guidance.