Re: HW cylinder star question (update)

> >>> Whilst our CH is on the blink we've been using our immersion heater, a very

>>> rarely used item in our mains pressure HW tank. >>> >>> The overheat stay tripped out last night and when I looked at the >>> temperature setting on the Theeta WT7 stat, it was already screwed down to >>> 20 degrees! I might have done this sometime in the past to deal with >>> over-hot water when on the immersion and then forgotten about it. >>> >>> Anyhoo, the stat doesn't seem to be doing it's job, but, before I replace >>> it is it normal for a stat to be very loose in its sleeve (into the tank)? >>> Just wondering if there ought to be some sort of thermal goo/paste etc to >>> conduct the heat better from the tank to the stat. >> >> IME the slide in and out freely (a slightly loose fit). No goo or other paste necessary. >> > > Cheers. New stat it is then. > > Tim

Well I picked up a new stat and everything's fine. I was curious to see what was wrong with the old stat so I opened it up.

Before doing this you could turn the temperature knob from min to max without any audible clicking. With the cover on, it's mechanically restricted to about 270 degrees of rotation. With the cover off I was able to rotate it by 360 degrees+ and low and behold, it now clicks on and off in an appropriate temperature range.

I suspect that this is a manufacturing fault and that it's never worked properly. We've never left the immersion on long enough to find out prior to this.

Does this sound plausible or is this a recognised failure mode (ie working temperature range moving out with the control adjustment range)?

Tim

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