Immersion heater cut-out

Postby jack1m » Fri Nov 06, 2009 7:35 am

The immersion heater thermostat cut-out operates from time to time. I have replaced the thermostat and it happens on the upper and lower immersion, whichever happens to be in use. It can be reset and will then operate correctly for a few days or even months but then will cut-out again. It’s a regular problem. The tank is a Heatrae Megaflow HE Direct Unvented Cylinder DD210L Do I need to replace the immersion heater or is there an underlying problem?
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Simply Build It

Postby rosebery » Fri Nov 06, 2009 11:43 pm

What is the temperature set to for the tankstat?

It should be set to less iro 65 degrees, as any temperature above that causes furring-up of the cylinder and immersion element together with the risk of scalding. If the water temp is set too high the immersion heater trips out because there is now a legal requirement for all immersion heaters to have a safety cutout built into them. I think this operates at 95 degrees, is factory set and is not user adjustable.

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Postby jack1m » Sat Nov 07, 2009 12:24 pm

The thermostat is set to 4 on a range to 1-5. The water at that temp is normally OK and not too hot to be a problem. I did wonder is there was a problem with the pressure of the cold water and it not set high enough? Do you think that would cause it? Over the years I’ve had the water off at the stop cock for various reasons and may not have set it high enough, even though the pressure from hot and cold taps seems OK.
Tks for any ideas.
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Postby jack1m » Sat Nov 07, 2009 1:29 pm

Just to ad to the above, the hot water driven by the central heating boiler stat is set to 65. The normal operation is to use the immersion to heat the domestic hot water as the central heating is LPG and very expensive. The immersion is on 24 hours and controlled by the thermostat. Could the immersion just old and need replacing?
Tks for any ideas and advice.
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Joined: Fri Nov 06, 2009 7:29 am

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