Boiler won't switch off

[sturmey]

I've just fitted a new Worcester 30 cdi system boiler at home.
It's an S plan system controlled by a programmer,wired room stat, cylinder stat and two Honeywell zone valves. It's up and running without any problems and responding to all controls but the on/off switch on the boiler itself doesn't turn off the boiler or stop the boiler when it's running. I'm having to switch off at the fused spur instead(or use the external controls)
I realise that there will always be power to the boiler while the fused spur is on but I would have thought the boiler on/off switch would at least do something.As it is presently it has no function!

I wired it as per the book with mains power into the boiler direct from the fused spur and also as instructed took three cores from the boiler to the wiring centre ,as follows:
LS terminal in boiler to permanent live supply in wiring centre.
LR terminal in boiler to live return in wiring centre (zone valve orange cores)
NS terminal in boiler to neutral terminal in wiring centre.

Following link shows wiring instructions on page 26/27 of installation manual

http://www.worcester-bosch.co.uk/installer/products/gas-boilers/greenstar-30cdi-system

The system is operating as it should with the boiler responding to all the heating and hot water controls. It's just the boiler that won't switch off at the on/off button.

The only thing I can see that might be an issue is with the mains supply from the fused spur. The load side from this fused spur goes to another fused spur next to the wiring centre which is supplying power on IT'S load side to the programmer- this was the way it was done at the time the previous boiler was installed. Obviously I didn't supply the mains power to the boiler from the load side, just wired in to the supply side of this second fcu. The previous boiler was wired slightly differently and its mains power also came from the supply side of this second fcu but the neutral went via the neutrals in the wiring centre before going on to the boiler. Does this make a difference?
Sorry for long post. Any ideas welcome.

 

[D_Hailsham]

the on/off switch on the boiler itself doesn't turn off the boiler or stop the boiler when it's running.

There is back feed to the Ls terminal.

Here is a sketch of your wiring from your description. Is it correct? If so the problem must be in the wiring centre as that is the only place that back feed can come from. I have not shown the wiring from programmer to wiring centre.

What happens if you turn the programmer OFF? Does the boiler ON/OFF switch work then?

Whose wiring diagram did you use to wire up your S Plan? Did you follow it exactly?

Untitled

• D_Hailsham
• 13 Dec 2009
• 1

 

[freddyuk]

I have the same problem with my Greenstar. ????

 

[D_Hailsham]

I have the same problem with my Greenstar. ????

The problem may be similar but the solution may not be the same

Start a NEW TOPIC

 

[sturmey]

sorry for late reply.

your sketch is correct though the mains live to boiler goes via the supply side of the second spur if that makes any odds.

If I switch off second fused spur I can then turn boiler off via on/off knob (all neons go off) and the programmer display then goes blank(though this will only happen if I turn boiler off first)

the S plan arrangement is what was there already and seems to be done according to Honeywell wiring plan unless I have missed something.

The previous boiler had a pump overrun and the switch live came back from boiler to zone valve orange cores.

Could this be a case of me wiring the LS and LR to the wrong terminals? i.e LS should be to orange and LR to permanent wiring centre live?

Forgot to say - programmer does not have its own on/off switch- it is a honeywell ST6300a.

 

[D_Hailsham]

your sketch is correct though the mains live to boiler goes via the supply side of the second spur if that makes any odds.

That, in effect is what my diagram shows, though it might suggest that the boiler is fed from the "out" side of the main spur and not from the "in" side of the second spur. Electrically, they are the same thing.

Forgot to say - programmer does not have its own on/off switch- it is a honeywell ST6300a.

The second spur acts as the on/off switch.

Could this be a case of me wiring the LS and LR to the wrong terminals? i.e LS should be to orange and LR to permanent wiring centre live?

Ls and Ns are the Live and Neutral Supply to the wiring centre. Lr is the Live Return, i.e switched live, to the boiler. So that part is correct; no need to change it.

The previous boiler had a pump overrun and the switch live came back from boiler to zone valve orange cores.

Presumably you changed the wiring as the boiler has a built in pump.

If I switch off second fused spur I can then turn boiler off via on/off knob (all neons go off) and the programmer display then goes blank (though this will only happen if I turn boiler off first)

The bit in green is OK. It's the bit in red which does not make sense.

The problem is in the wiring of the programmer and/or the wiring centre. The programmer gets its L and N supply from the second spur. Make sure that it is not also getting another feed from the wiring centre (usually terminals 1 and 2).

Here is the standard S plan wiring diagram. In your case, terminals 1 and 2 should be connected to Ls and Ns only.

View media item 72

 

[sturmey]

I seem to have found the solution!

Turn off power at second spur and boiler works fine (as previously ) but with the added bonus that it will now switch on and off using the fascia button!

Too many lives then and I obviously don't fully understand all the principles of central heating wiring! Funny though as I followed the text book as far as I know.
Terminals 1 and 2 in the wiring centre are indeed taking the LS and LR connections respectively from the boiler.
the 2nd fused spur IS turning the power off to the programmer FROM the wiring centre -that cable is dead as you would expect ,but if I then press the boiler on/off button on the fascia (which appeared to go off when i switched off the fused spur) the boiler and programmer come on again with live going back down the LS wire from the boiler and presumably feeding the programmer also.
What a waste of good cable.

Thanks for your patience.