Boiler only fires for CH

26 Nov 2010
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United Kingdom

Just moved into a new house, and haven't had has before - so sorry for the dumb question.
When we put the CH on via the timer controller, the boilers fire up and heats the rads and water no problem.
(Same as above when putting both Hot Water and Heating on)

However, when we select only the Hot Water on, the boiler doesn't fire up and so no hot water in the tank.

Question, should the boiler be able to heat the water in the hot water tank indepdently? There are two, 2 way valves so would presume this would they should be able to be controlled seperately?

Boiler: Convetnial - Potterton Suprima HE 60
Timer Controller : Honeywell ST6400C
Tank Stat : Honeywell l641a1005
Pump: ups-15-50 130
Two way valves: 2x Honeywell v4043h1056
Room Stat: Wickes analog
& a
Pullin 3kw immersion heater with a standard 3 way plug

Thanks, Ash.
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Based on the presence of the wickes bit, chances are that the previous owner did some dodgy diy and hooked it all up wrong.
Your timer is fully independent if I recall correctly, so would allow you to have the heating and dhw on at different times which gives a much better performance.
The fact that you mention it was on both indicates a complete botch job.
Sounds like a faulty powerhead on the Hot Water motorised valve to me -no output on Orange wire = no hot water unless heating on as well!! ;)
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... Thanks, that does explain why permanent marker on the plug says "Immersion heater DO NOT PLUG IN".
Doesn't explain a thing to me. If you insist something must not be plugged in, why put a plug on it?? :confused:
Pullin 3kw immersion heater with a standard 3 way plug

Do you mean a 3 pin plug?
If so, it should really be an independent 15A circuit as it's a fixed appliance over 2KW.

From an electrical stand point then no. I totally agree the immersion should be hard wired into a double pole switch and be backed up by a 16 amp MCB

In theory a 3kw load converts to 13.5 amps therefore would hold in on a standard BS 1362 just.

A 2kw load converts to 9 amp therefore in theory whilst not best practice could easily run from a plug top.

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