"Steve Gouldstone" wrote in message
news
Thanks for reply Brian.
"Brian Sharrock" wrote:
"Steve Gouldstone" wrote in message
. ..
My hot water tank has wiring for an immersion heater, but one isn't
fitted. The tank, I would guess is about 20 years old.
I don't understand what you've written: - "wiring for ... "
but "is not fitted ... ".
A hot water cylinder - 20 years old may be 'naked'
copper with an external insulation blanket or foamed
insulation clad - should have a large boss on the top
for accepting an immersion heater. The immersion heater
assembly should fit directly into, and replace, the boss.
From what you've said - you should see a big nut
hexagon on the top of your cylinder.
Yes I see a big hexagon nut near the top at about 11:30 o'clock which
fits this description of a boss.
I'm answering this _and only this _ point. What you see
is the blanking plug for the immersion heater. That hexagon
plug/boss is stopping water (hot) from pouring out of the
top of the cylinder.
Immersion heaters usually, when fitted have a cylindrical
'can' -all those I've encountered have been black -
normally secured by a knurled nut off-centre within the
'can'. 'Wiring' normally makes contacts with terminals
under the can. It's fitted on an installation -specific
basis to the feed/source of the 'immersion heater' supply.
Where does your 'wiring for ..' start and finish?
what is on the hot-water cylinder top?
Sorry, I could have been clearer. There is a mains wire going into the
airing cupboard, but it terminates in a thermostat attached to the
outside of the tank. There is no output cable from the thermostat.
Presumably this is meant to continue on to an immersion heater?
It ain't neccessarily so: - immersion heater _assemblies_
screw into the aperture we've decribed above, making a
water tight seal. The assembly contains one or two
elements each froming a 'U' shape [there can be a top-up
heater and a longer full-cyclinder heater] on top of the assembly
can usually be found a knob with an arrow pointing to a demand
temperature for the heated water- this is sensed by a thermo-couple
which itself is a long thin sensor fitting into a tube penetrating
through the heating elements. In other words, the heating-sensing
thermostat is contained within the 'Immersion Heater' assemby.
An external clamped thermostat is _usually_ indicative of
a boiler supplied heating system - in this case the thermostat
is telling the boiler to cease producing heat for the water.
You _may_ be looking at a 'wire' coming from and returning
to the boiler. It may not be the 'mains wire' that you think;
although it _may_ be switching 'mains' in a similar fashion to
a light switch. Be very careful when examing this cable,
dependant on the boiler control circuitry it may be at
mains voltage ... and probably changes dependant on whether
your boiler is 'ON' 'OFF' CH HW or CH+HW ....
The nut on the boss is slightly bigger than my biggest spanner, so
I've not tried to remove it, also I don't want to introduce a chance
of a leak until I've got a fair idea I can just put an immersion
heater in there.
'Immersion spanners' are quite cheap and have only one use ....
they can usually be found in the sheds adjacent to the cylinders
in the plumbing sections. They are big hex cut-outs from cheapish
metal usually with a shortish cranked handle. They're not pretty;
but necessary.
What you _will need is an electrical feed for the immersion heater,
Locating, and routing for such a service is IMHO beyond the scope
of this post.
--
Brian