My friend lives in a rented house with hot water from a cylinder with
an electric immersion heater.
There is no programmer and no thermostat, the element is wired to a
fused outlet and is on all the time (although there is a switch on the
The water is dangerously scalding hot.
What's the simplest way to fit some sort of temperature control?
So far as I know all immersion heaters have a thermostat built in.
There should be a small rotatable control on top of the round housing
for the thermostat. Perhaps this has failed? Its usual not to have a
Have another look. I'm afraid that if the temp can't be turned down it
looks like a replacement. Scalding water is wasting money as well as
being dangerous. I love those hotels where it says, 'Caution. This water
is hot for health'. Hope the landlord is not one of those slow types.
Any immersion heater should have its own built in thermostat, usually under
a plastic cover held on by a couple of screws. There won't necessarily be a
stat on the side of the tank if that's what you've been looking for - those
are used for controlling a boiler system. The immersion I fitted a year ago
had a max temp of only 60C which is just about hot enough for a bath or
dishes but nothing like as hot as the boiler used to get the water if I
wanted it to. Maybe older immersions have a higher temp, I think my previous
one did anyway, but should never get the water scalding. If the stat on
yours has broken then a complete new immersion is the only cure but they are
only £25 or so. Of course that's if you can get the old one out. They tend
to corrode into the thread in the tank and sometimes won't budge even at
levels of force which are starting to buckle the thin metal of the tank
Then I'm afraid it's new tank time which ain't cheap.
Many thanks for all the replies.
I managed to find a temperature control of sorts, under a metal cover (about
7' off the ground). The range was 50-80C and appeared to be set to 65C. I
will try 50C later and see what happens.
unvented system with no safety features - hardly typical of a normal
domestic installation. The second reference is far more unnerving. The
combination of a permanently on immersion filling the header tank with
boiling water and that tank being (a) plastic not able to withstand boiling
water and (b) suspended over the bed is the stuff of nightmares! Not nice
I think the OP has now found the stat control on the Immerser .
As an addition someone mentioned that these can sometimes fail "On" .I
believe that new ones have a safety cutout to prevent this and this
needs to be reset by pressing a small button on top