Intelli-Vent Controller Failed

[RonAKA]

I am new here and spend the day finding and installing a new White Rogers Intelli-Vent controller on my power vented natural gas water heater. It came up with a code this morning that said the only option was to replace it with a new controller. "The high temperature thermal cutoff is open". Powering it down did not reset it, so I bought a new controller for a not insignificant price. It seems to work, and the heater is warming up now.

Why I am posting is to ask why this controller would fail? What I found when I removed the old controller was that there was a plastic tube over the copper looking temperature sensing (bulb?). On the new one there is open space between the copper bulb and this plastic tube for the last 1" or so. The one I removed was packed solid with white scale. I am thinking that this scale caused the bulb to overheat and fail?

If that is the case does this mean that with my water, which is fairly hard, does the heater need to be cleaned periodically? With vinegar or ? If scale is the cause of the failure it would seem just letting the controller fail will be very expensive. This controller cost half the price I paid for the whole water heater. It is just over 10 years old.

I welcome all thoughts and suggestions,
Ron

 

[RonAKA]

I've done a bit more research on this issue, and it appears I have been somewhat negligent in not periodically flushing the water heater tank. My first basic water heater lasted 30 years, and still had not failed when I replaced it. I only took it out to put in power vent unit that could go out the side of the house like my high efficiency furnace. I wanted to get rid of the combined flue which went up through the roof. I attribute the long life to regular replacement of the anode rod.

In any case this newer heater, and in particular the temperature sensor, seems to be very susceptible to scale. I have flushed the tank the best I can with the factory tank drain valve but am going to order a brass ball valve made for flushing so I can get more flushing flow. Until it arrives I will have to do more research on whether or not I should do an acid clean. A.O. Smith have an interesting article called "Why? When? & How? to remove lime scale from tank type glass-lined water heaters". I may rig up a method similar when I do the drain/flush valve upgrade.