Immersion Heater Replacement Question

[Turtle Shed]

My immersion heater stopped working. (I use it on overnight cheap electricity). The reason it stopped is that there's a thermal fuse between the thermostat output and the heater input and it has failed. (It can't be reset).

You can't buy/aquire the thermal fuse, and given that it failed I wouldn't want to just chuck a new one in anyway.

So...whilst a new heater is cheap enough, there's a risk that I break the tank when trying to fit one. Picture of tank shown below (ignore the top heater, I only want to replace/use the bottom one).

Question 1 - How likely is it that the tank will break if I try to replace? (How long is a piece of string..?)
Question 2 - Is there anything I can do to minimise the risk of breaking it?

I'd like it working as a backup to oil, but given that a new cylinder is £400 and fitting it probably another £300, I'm very wary of replacing unless the concensus is that the chances of breaking the tank are very very low.

p.s - For those interested the blanked off circuit was connected to an open fire back burner, and I believe the tank was installed in the early 1990s.

[119]

When I did mine I shut off the water supply to it, used a blow torch around the outside Of it and then used a decent box spanner to brake the seal.

Keep an eye on it and watch you don’t twist the tank!

Tighten it up, drain the tank and the then Remove and fit a the new one.

I believe you will want an 11” heater

Edit: might be tricky as you dont appear to have a drain off on the cold water fill the bottom?

[.:ian:.]

Screwfix do a big box spanner for immersions, but I found even with this it wasn't shifting. Even 3/4 full of water it was just moving the tank!

What I ended up doing was tapping the corner of the hex face with a small sharp cold chisel. (Tapping the chisel with a hammer rather)
This acts a bit like an impact driver, shock it loose rather than monkey on a breaker bar torque.

[Turtle Shed]

Thanks both.

I've discovered that you can buy replacement thermostats with built-in thermal protection, so I'll go down that route. Less wiring and hopefully will solve the problem.

The heater measures 20 ohms so bang on the money and should still be working fine. As to why the thermal fuse failed, no idea, but it could be 30 years old and just decided to give up.

Worst case is that the thermal fuse trips in the new stat, in which case I will have to look at a replacement, or just not bother with using the immersion. The downside of that being it's harder to heat a full tank for a bath because the oil boiler loop only does the top half.

[clockworks]

I had to replace the immersion heater in my last house.

I ended up drilling a few holes to make room for a hacksaw blade, and sawing through towards the threaded part.
A quick twist on the hex with molegrips to collapse the threaded part inwards, and it came out easily.

[megaphone]

Ensure the tank is full before you loosen the element, the water pressure will help to stop the tank buckling.

Obviously drain it before you actually remove the element!