Immersion heater stopped working

[blackrose]

A few years ago I installed a thermostatic mixer on my system, it was a high-quality domestic model by Caleffi, but it kept giving trouble. I eventually discovered that it included a safety cut-out to shut off completely if the temperature of the incoming water exceeded 85 degrees, so when the engine was working well I kept finding that I had no hot water. Apparently all domestic mixing valves include this feature, so maybe the immersion cut-out is set to a similar value.

 

I replaced the mixer with one designed to be used on calorifiers, purchased from Midland Chandlers, which doesn't include the over-temperature cut-out; so I now have the first mixer bringing the temperature down to 65 degrees for general use, but with the second mixer to the washbasin tap set to a comfortably hand-hot lower temperature.

 

I think my TMV has that same 85 degree C maximum water temp input specification but I'm not sure what happens if it's exceeded? Usually my engine temperature is about 90 deg C as displayed on the gauges but isn't that the oil temperature? I'm sure the water in the calorifier is a bit cooler.

 

Anyway, so far the TMV has been great - no more scalded hands when you forget that the engine has been run.

[Keeping Up]

I think my TMV has that same 85 degree C maximum water temp input specification but I'm not sure what happens if it's exceeded? Usually my engine temperature is about 90 deg C as displayed on the gauges but isn't that the oil temperature? I'm sure the water in the calorifier is a bit cooler.

 

Anyway, so far the TMV has been great - no more scalded hands when you forget that the engine has been run.

The gauge would normally read the engine coolant temperature. The water in the calorifier will eventually reach that temperature.

 

My TMV starts to close down as it approaches that temperature, ie it reduces and then shuts off the water output completely, whilst maintaining its temperature.

[RobinJ]

Mine's fitted at the bottom.

No, the only thing I did down there was install a thermostatic mixing valve.

If the engine and immersion were on at the same time could this cause the thermostat totrip?

Can't see why fitting a thermostatic valve would increase chance of tripping when immersion is at the bottom? (presumably at the top - heat rises - more chance)

However if both the engine and immersion were being used to heat at the same time, could possible produce more heat and exceed thermostat setting?

[chris w]

That happens at home... the immersion heater is timed to come on overnight, to take advantage of the very cheap electricity, and then the normal oil-fired boiler comes on in the morning. When the two times overlapped a bit the safety trip sometimes blew on the immersion heater.

 

Chris