Immersion heater makes the water in header tank BOIL!

[Rotten78]

Hi, I hope someone can help?

I have an immersion heater that, if it is left on for more than 45mins, will start to boil the water in the header tank in the loft! So, I have to time how long to have the heater on and then switch it off manually or have the oil central heating on but thats a waste and heats the radiators at the same time (too hot for that in the summer!)

It got so bad once that water started ****ing through the ceiling and I had to turn all the taps on to drain the boiling water from the header tank. I read some horror stories about people being killed by scalding water coming through the ceiling after the boiling water and weakened the plastic walls of the tank!

Could this be the immersion heater of the thermostat controlling it? Or something else?

Any help will be greatly appreciated.

Many thanks

 

[jackpike]

it'll be the stat in the immersion, best to change the whole thing though, and quick, the tank is not built to withstand boiling water, it will collapse and cause much damage, turn it off till you can change it

 

[45yearsagasman]

A year or two ago there was a young child fatally scalded with just the same scenario.Get the whole immersion changed without delay.Use with extreme caution until then but better still as suggested turn it off.

 

[namsag]

Why change the whole thing its obviously working ,
Just change the stat cost about a tenner and takes 5 minutes usual size if at top of the cylinder is 27 inch

 

[jackpike]

in my experience, shortly after the immersion stat goes wrong, the element burns out, so while you're doing the change you might as well change the whole thing,

 

[Rotten78]

Thank you for all your speedy replies. I wonder why the tanks are made to only withstand the lower temperatures when this is a problem that is potentially fatal?!

Is it a big deal changing the stat? It seems accessible enough but do you have to drain the tank ?

I am happy to get a plumber in but around here (quiet area), it can take a while for someone to come out.

If you think its a job for a pro and not an amateur DIY man then please say!

Thank you all again very much.

 

[Rotten78]

Just a quick addition to the last post :


There is an adjustable thermostat on the side of the immersion tank set to 60 degrees C (its about half way up on the tank and towards the front) - Is that the one for the immersion element or would it be under the cap as most are?

Thanks

 

[kevplumb]

Is it a big deal changing the stat?

no

It seems accessible enough but do you have to drain the tank ?

no its in a dry pocket

There is an adjustable thermostat on the side of the immersion tank set to 60 degrees C (its about half way up on the tank and towards the front) - Is that the one for the immersion element or would it be under the cap as most are?

the one on the side is for the 3 way valve when the boiler is running

the one you want as you say will be under the cap on the immersion heater

dont forget to turn the power off first

 

[jackpike]

that one on the side will be to control the hot water when heated from the boiler,
if you just want to change the immersion stat, its under the electrical cover of the immersion, its a five minute job as namsag said, but you will need to isolate the power, if you want to change the whole immersion, you better getting a plumber,

 

[OwainDIYer]

More modern immersions have two thermostats - one for everyday operation and a second one with a manual reset.

 

[gasbanni]

Why change the whole thing its obviously working ,
Just change the stat cost about a tenner and takes 5 minutes usual size if at top of the cylinder is 27 inch

Take the old stat out when youv'e isolated the power and removed the cover cap measure the length as they come in different sizes depending where the boss is on the tank and the lenght of the pocket.

If the elements working which it is why change it as namslag says.