Rayburn heating an immersion heater.

[BigSi]

Just got back from one of my customers, after replacing a thermostat in her immersion tank. Now the problem is, that this is a regular occurrence that happens every six months or so. As the thermostats should last a lot longer than this, I’m wondering if something else is at play?

She also has a coal fired Rayburn oven that also heats the water, and stores it in the immersion tank. She mentioned (could of told me earlier), that on a few occasions she has had to come down during the night to open the hot water taps to drain out the boiling water, as there is nothing on the Rayburn to regulate the water temperature.

Now, could this be causing damage to the thermostat? I couldn’t get through to her that the thermostat only controls the heating element in the immersion tank, and not the temperature of the water from the Rayburn.:skep:

 

[Top Cat]

Sounds quite feasible for it to damage stat but never come across it before. Sounds like you could do with another stat on tank to run a pump round a pipe loop to dissipate the heat but how you would explain that to her is another mater!

 

[telectrix]

tell her to put less coal on.

 

[Guest123]

Sounds quite feasible for it to damage stat but never come across it before. Sounds like you could do with another stat on tank to run a pump round a pipe loop to dissipate the heat

Absolutely!!!

Wood/coal burning appliances require a LOT more though and planning on the plumbing/electrical side of things as they dont just shut down when a stat is satisfied, they keep on burning.

@ OP, I'd advise your customer to get a proper heating engineer that has experience with rayburns & aga's etc to have look at the current setup and advise accordingly as it sounds to me like it's dodgy at best!!!

 

[Rockingit]

Just a thought - and I know nothing about AGA's - but I guess there must be a pump in it in order to get the water to the tank. It might be possible to have the immersion stat control that pump via a contactor.

 

[alanl]

It'd more likely be a gravity feed to the hot water tank.
I've had it a few times where the stat inside the immersion has overheated, and caused it to pop the over-temp switch, which just needs to be reset on top of the stat, but I can't see how over-temperature alone can ruin an immersion stat, considering it woudl only get to around 100 degrees before it boiled over into the header tank.

 

[Lighthouse Phil]

I've come across this problem a few times over the years. Its even happened at home to me a number of times. Does the stat your using have a thermal cut-out ?. Some stats come with a small cut-out on the top and unless they are switched off, this trips due to the high heat output of the stove. During the winter months when my own stove would be burning, I'd swithch off the Immersion heater altogether.

 

[Guitarist]

All new stats will have this cutout. Don't mean to sound insulting, but have you tried resetting this before replacing the stat? Also, do you use just one particular brand or have you tried different ones?

 

[Knobhead]

The AGA should have a loading radiator with no thermostatic control. I’ve always fitted them in the bathroom.
Get the customer to buy some “slack” coal to damp the fire overnight.

 

[Guitarist]

The AGA should have a loading radiator with no thermostatic control. I’ve always fitted them in the bathroom.
Get the customer to buy some “slack” coal to damp the fire overnight.

I remember decades ago when we bought a house with a Parkray solid fuel fire. Was spring, I was young and naive, and the house was getting warm but I didn't want to let the fire go out. Came home one day to water spitting out of the overflow....
I'd only turned off the loading rad and the poor heat had nowhere to go. In a rush to reduce the heat I quickly pulled the ash pan out and started shovelling the coals into it. After a few minutes I smelt burning....ruined the edge of the carpet. Never made that mistake again.