Where is the high limit switch on a Trane XE90?

High limit switch tripped: do I need to clean air filter in hot water heater? (Bradford White)?

• I have a Bradford White hot water heater, about 7 years old, model MI5036FBN2. The pilot light went out and I found out it was the high limit switch that had shut the unit off. I can replace the high limit switch, but I was told that the high limit switch often trips and shuts the heater off when the heater gets too hot, due to the air filter being clogged...or possibly not enough oxygen getting in because the air filter is clogged. As far as I can tell, the inlet holes to let oxygen into the sealed combustion chamber are below, just about 1/2 inch above the ground at base of the tank, and I can't get any type of brush in there to clean this out. Does the air filter actually need to be cleaned, and how do I do that, or is there some other reason the high limit switch would trip that I need to take action on?

• Answer:

  You should be able to remove the air filter for cleaning. It just snaps in place. You don't have to have the filter on it, it is something I usually leave off when I install them. Your vent pipe could be blocked. Check it to ensure a bird is not building a nest in it. A blockage on this vent would cause your high limit switch to trip. I just saw a picture of your model, you cannot remove that filter. Blow it out with compressed air.