480-volt A.O. Smith electric water heater repaired at Rancho Cucamonga dental office

The call: A dental facility in Rancho Cucamonga had no hot water. For a dental office, that can’t wait. Staff need hot water for hand washing and cleanup between patients.

The equipment: An A.O. Smith Custom Xi (DSE) commercial electric water heater running on 480-volt power, with a recirculating pump and aquastat that keep hot water at the faucets. This is high-voltage commercial equipment, not a typical home water heater.

What we found: Our technician performed a full electrical diagnosis, testing the power and the heater’s control circuit step by step instead of guessing at parts. The cause was a bad fuse that had shut the heater down.

What we did: We replaced the fuse and re-energized the heater, and the controller showed it heating back up toward its 120°F set point. We then checked the recirculating pump and the aquastat for proper operation, and tested the water at the faucet for proper flow and temperature.

The result: Hot water restored for the patients and staff, with only the failed part replaced.

Tip for facility managers: If a commercial electric water heater goes cold, check that its disconnect switch is on, then call us. Fuse and element testing on 480-volt equipment should be left to a qualified technician.