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Posted By Topic: HWC thermostats failing

me
Sep 06 2012 20:26

Have a client which i have now replaced their hot water cylinder thermostat for the 3rd time in 12 months, its a stainless steel cylinder - mains pressure, with a standard 11 inch probe hwc thermostat that uses the stat tube in the element pocket. i don't understand why they keep failing, in 20 years in the trade i've never struck this before and infact could count the number of failed t/stat on less than one hand (other than loose connections cooking them up) until now, any ideas folks ??????

   

The Don
Sep 07 2012 10:41

Not enough information to be of any help , the current rating of the thermostat in relation to the element is the only thing I can think of other than crap thermostats in which case I would be talking to the supplier .
Its not a WH with dual elements is it ? and the thermostats have been connected incorrectly ?
   

Killy
Sep 07 2012 15:52

There is/was a 'bad' batch of stem stats. Suggest talking to your wholesaler.
   

me
Sep 07 2012 20:08

Thanks kelly, interesting that there has been a bad batch.
The Don, the HWC is a 3kw SS cyclinder mains pressure on town supply. the thermostats have all been 20amp rated 7inch models - the std types not the dairy scale ones. there is no wet back or internal water coils for any other energy source, hope this additional info helps.

   

Linz
Sep 08 2012 07:56

Using a 7" stat in an 11" pocket is not a totally good idea, have found over many years of dairy and domestic work that for some reason, dont really know why, the dynamics/physics conspire to mean that the stat will fail to operate and the tank will boil. The only thing I have been able to come up with is the space left vacant in the pocket (4") is insulating if you like the probe. Have occasionally had the same issue with capilliary stats, not right to the end of the pocket the calibration is out. This all of course is irrelevent if the stat is going open circuit.
   

me
Sep 08 2012 09:27

thanks linz, could be worth a try changing to a 11inch model, my wholesaler mainly only has the 7's, so i'll get them to order 1.