how to change a thermostat on an immersion heater

ONLY ATTEMPT THIS WORK IF YOU ARE CONFIDENT WHEN WORKING WITH ELECTRICAL CONNECTS

You will need to find the isolating valve, or stop tap, on the pipe that supplies the water tank that supplies the hot water cylinder. This is an immersion heater thermostat replacement guide for anyone who is looking to change their immersion heater thermostat and the heating element.I am a professional plumber and heating engineer – I get called out to The next step was to isolate the electric supply at the main consumer unit where all the fuses were.It’s best to just isolate the electric circuit or fuse that the immersion heater thermostat is connected to. Although I have not tried the newer Some people like to leave the water in the cylinder to keep it more solid and easier to turn the spanner, just to get crack it open and start the process off. It’s sometimes above the cylinder but could be in the loft with the supply tank.If you can not find one, then you will need to turn off the main stopcock that will turn off all the water to the property. You will be able to tell that it’s empty.First, you need to remove the cover off the immersion heater thermostat. Or, you may connect it to the ring main circuit, which has all the plug sockets connected.

I recommend getting a VDE insulated screwdriver that will protect you from any electric shocks.To remove the actual heating element from the hot water cylinder, you will need a blowtorch and an immersion heater box spanner. Make sure that the immersion heater being fitted incorporated a thermal cut-out (as well as the thermostat) to comply with current regulation. Check for leaks and if all is ok, turn the electric supply back on.Yes Richard, you should definitely get a plumber if you haven’t done anything like this before.Make sure you have done all the checks needed to find out the exact problem before replacing any parts.

To replace the thermostat in the immersion heater should your water get scalding hot all of a sudden, make sure the electricity to the immersion is off and the fuse in the isolator switch is out.

This should not be a concern if fitting a newly purchased heater, but don't fit an old, working heater if it does not have a thermal cut-out. You might only need to replace a fuse or find that the fault is somewhere else. Undo the top screw’s of the thermostat cover and you will usually see a cable clamp holding the mains flex in place.

A friend had a look and said it was a simple job but has just rung to say he forgot to make a note of the size of the one that he is to replace and has asked me to check and ring him back so he can buy the right one.. You will need to use an adjustable spanner, or pliers, to turn the square nut on the drain valve anti-clockwise until the water comes out.Draining down the cylinder fully will take a while, so you may as well do something else while it’s draining down. From April 2004, new and replacement Immersion Heater Thermostats need to incorporate an overheat safety cut-out so that if the water thermostat fails, the water in the cylinder will not overheat which could cause scalding water to come out of the taps. This is because the heating element seizes on the cylinder and you can easily damage the cylinder if you don’t use a blowtorch to heat it up first. My immersion heater overheats badly and apparently the thermostat is broken and needs replacing.

Immersion heater thermostats are available in various sizes (7, 11, 18 and 27 inches) depending on the manufacturer, model and type of immersion heater - only the correct sized thermostat should be used as a replacement. Tighten it up as much as you can with your hands, then use your spanner to tighten it.Then you can insert the thermostat and wire it up using the instructions supplied with the thermostat.Then put the cover on and tighten the small nut up.Now just close the drain off valve where the hose is connected, close all the hot water taps, and turn the water supply back on. Then, open all the hot taps to drain down the water from the header tank.Then, you will need to find the drain off valve.

Fitting of the replacement thermostat is just the reverse of the removal. You might rip the sealing washer, which can prevent you from tightening it back up if it leaks.

This will be a little brass valve connected to a pipe at the bottom of the hot water cylinder.