"Roger Mills" wrote in message
...
On 12/11/2011 17:33, David WE Roberts wrote:
Just to check - I have a system boiler which provides central heating
and heats a hot water cylinder.

The programmer is off and there seems to be no power to the boiler
(problems with downstairs lighting circuit).

So does all the power to the system flow from one connection i.e. the
boiler takes its power directly from the programmer or are the two
independantly powered?

If it is all one feed then I can find where the power goes in and
connect in temporarily from a ring main to get the CH working.

If the boiler and programmer are powered independantly (and both off the
downstairs lighting circuit) then that is more of a challenge.

I am assuming the pump is either powered off the same circuit or off a
seperate 13 amp feed.
Either way I might be able to make a temporary repair.

Moral - even if it is broke don't try to fix it.


If it's been wired conventionally, everything should be fed from a single
supply - usually with a fused connection unit (FCU) spurred off a
ring-main - so that you can isolate the whole system by throwing a single
switch.

How the programmer and boiler are wired after that depends on what flavour
of control system you've got. If you've got an S-Plan system, the
programmer - along with the associated room and cylinder stats - will
power a couple of zone valves - but will *not* power the boiler and pump
directly. The zone valves have auxiliary switches which close when the
valves are fully open. These have a permanent live feed (from the same FCU
as the programmer) and switch on the boiler and pump when either or both
zones are demanding heat.

If your system is powered from a lighting circuit, that makes it pretty
unconventional to start with - so there's no telling how it's been done!

The moral is actually to get to fully understand the system when it *is*
working, so that you will be able to fix it when it *isn't*!


Thanks - useful info.

The whole shooting match upstairs is powered off a fused isolating switch
which goes into a wiring loom inside a big box.
From this comes wiring to/from the programmer and the pump and the valve
(AFAICS it is Y plan) plus at least one wire which goes off somewhere "down
below".
So just about everything is off one circuit.
Once our guests (including cute little girl just less than one year old)
have departed I will switch off the power at the isolating switch and check
if there is power to the boiler.
Much of the panic yesterday was because I had a house full of guests and no
central heating.

So - by direct testing at the circuit breaker the CH is off the downstairs
lighting.
By observation I can see that everything bar the boiler is powered off this
circuit.
I will need to test to confirm the boiler is also powered this way.

I would like to share my thoughts with whoever wired this into the lighting
circuit instead of using the spare fuse way in the main box and also put it
on the lighting circuit which is much less able to cope with any initial
load surge than the 13 amp. Long gone, however, before we bought the house.

Fortunately we are getting rid of the whole shooting match next year.

Cheers

Dave R

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")