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Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 22018
Experience:  Licensed Master plumber with 40+ yrs. experience.
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I have a Rheem power vent water heater model #21VP40E-1. It

Customer Question

I have a Rheem power vent water heater model #21VP40E-1. It lights and the burner runs for just a few seconds before shutting down. It makes me think it is the thermocouple but this model doesn't seem to have a easy to identify one. Does it have a thermocouple? Is there another reason? It is a more complex model than I am used to dealing with.
Submitted: 2 years ago.
Category: Plumbing
Expert:  Rick replied 2 years ago.

This unit doesn't have a thermocouple but you're on the right track, that it's not detecting the flame. Instead of a thermocouple this unit has a flame sensor (see attached pic for similar). You can try cleaning off the metal rod of the flame sensor with fine aluminum oxide sandpaper or steel wool. Also vacuum out the combustion chamber since a stray rust flake can also foul the flame sensing. Also check the electrical connections on the flame sensor lead. If that doesn't work the next thing to try is to replace the flame sensor.