A.O. Smith Water Heater HW-420

Attach the leads from a millivolt meter to the thermocouple and junction block and record the reading

Is the thermocouple reading above 14 to 18 millivolts?

Transfer the lead on the junction block to other terminal and record the reading

Is the voltage supply reading between 8 to 14 millivolts?

Check the junction block connections and the protector switch leads if the reading is less than 8 millivolts

Measure the millivolt drop across the contacts

Ensure the boiler is not connected to a common vent or chimney with solid fuel burning equipment.

Verify that the equipment room is not under negative pressure.

Inspect the venting system for the following issues

Is there sufficient supply and ventilation air in the equipment room?

Was the venting system inspection completed without identifying any unsafe conditions?

Oil the three oil cups (2 on the motor, 1 on the pump) as instructed on the oil tube supplied with the unit.

Ensure the circulator is oiled before operation.

Add 2 or 3 teaspoonsful of No. 20 non-detergent motor oil in bearing oil cups.

Add 10 or 12 drops of No. 20 non-detergent motor oil in motor oil cups.

Follow the same oiling procedure if a replacement circulator is installed into the system.

Inspect low water cutoff for proper operation

Inspect other safety devices associated with the boiler

Flushing of Low Water Cutoff Device

Flush the low water cutoff device of the float type

Is a more frequent inspection necessary based on water conditions?

Ensure the protector switch reset button is not depressed

Remove leads from the switch and attach to test flashlight leads

Testing with Model N22T Test Kit

Turn on the flashlight. Does the lamp light up?

Are the protector switch contacts open?

Depress reset button on switch if water temperature is below 200°F

Does the lamp light after depressing the reset button?