Immersion heater thermostat tripping

[garynortheast]

Any of you knowledgeable folk out there know why the thermostat on our immersion heater keeps tripping when the round metal cover is on it? If I take the cover off it heats the water without tripping. It's a Backer Backersafe immersion heater element with the 18" thermostat. The cover is the right one for the device so it's got me baffled. It obviously overheats with the cover on but surely it shouldn't?

[embee]

I've had to replace a couple of the dual safety thermostats because of tripping out. I suspect it's a fine line between tripping too early and too late. If it was mine I'd bite the bullet and just replace it, they're not hugely expensive.

Out of interest what temperature setting do you have the stat set at? You could always try it with the temp set 10C lower as a start. Have you checked whether the stat temp dial switching actually corresponds reasonably with the water temp using an independent thermometer/thermocouple ?

[garynortheast]

I have just bought another thermostat to be on the safe side but it’s not yet fitted. Don’t know what temp it’s set at as although it has lines to denote hotter or colder it doesn’t have any numbers on it. Think I might set it back a notch and see what happens. It’s currently on the factory setting.

[SV650rules]

Hot water tank control stat should be at 55 to 60 deg C - any hotter risks scalding any cooler risks legionella. Safety trip is probably set at 80 to 90 degrees just to stop water boiling, they normally work on a capillary tube where the contents expand as temperature rises. If there is loose connection on immersion heater terminals or contacts it could cause higher temp inside case.. as said previous replace stat as they are not megabucks..

Factory setting on stats normally 60 deg C.

[garynortheast]

Thanks chaps. I have a new one here. I’ll add the fitting of it to my ever expanding list of jobs for tomorrow

[SV650rules]

If you mark factory setting with permanent marker as 60 you have a reference to go back to..

[svenrico]

The thermostat on my hot water cylinder was set at 60 degrees for years ,then it went haywire so was replaced, then set it at 50 because water was scalding hot, recently turned it down below 50. I assume numbers on dial don't bear much relation to actual water temperature. British Gas engineer said just adjusting them can sometimes stop them working properly !

[Bibio]

stop feeding it shrooms then...

[svenrico]

stop feeding it shrooms then...

:confused:???

[johnnyrod]

The thermostat on my hot water cylinder was set at 60 degrees for years ,then it went haywire so was replaced, then set it at 50 because water was scalding hot, recently turned it down below 50. I assume numbers on dial don't bear much relation to actual water temperature. British Gas engineer said just adjusting them can sometimes stop them working properly !

See above, it needs to be about 60C to keep the system free of nasty bugs. Any higher and you start dropping scale out in the tank, if that is a problem in your kettle as well.

[svenrico]

See above, it needs to be about 60C to keep the system free of nasty bugs. Any higher and you start dropping scale out in the tank, if that is a problem in your kettle as well.
Yes ,I know the actual water should be about 60C, as it used to be when the thermostat on the cylinder was set at 60C. The problem is the gauge isn't accurate. I have set it at below 50C on the thermostat to get the water feeling about right. (Set at 60C on the thermostat the water was coming out of the taps scalding hot )

[SV650rules]

See above, it needs to be about 60C to keep the system free of nasty bugs. Any higher and you start dropping scale out in the tank, if that is a problem in your kettle as well.


IIRC +/- 70deg C is the point where scale starts to come out of water, hot water deffo needs to be stored above 55C and preferably 60C.

[svenrico]

IIRC +/- 70deg C is the point where scale starts to come out of water, hot water deffo needs to be stored above 55C and preferably 60C.

As far as my comments are concerned I am not disputing the hot water should be at 60C. The problem is getting the water set at 60C by the thermostat on the hot water cylinder because it isn't accurate.

[SV650rules]

I popped a kitchen thermometer into one of the spare thermostat pockets on our cylinder to check temp. Otherwise can check water temp coming out of hot tap nearest to storage cylinder.