Hi All,

I have a newly installed Worcester Bosch CBi boiler (- a conventional,
not combi). This was installed to replace an aging myson appollo
fanfare, into the existing system. Both systems have pump over-run so
I think the wiring ought to be identical ....

Once installed it fired up without any porblems, however did not shut
off as expected with the room stat. I left it running so that at least
there was some hot water and heat in the house!

After the hot water cylinder had warmed up I completed the other
tests, e.g. lock-out etc, all of which were fine

I started the boiler up again, running it in the normal way, and after
a while it shut off as expected - however the cause was not the room
stat etc - the fuse in the mains isolator switch had blown. Replaced
the fuse and same again. I investigated for the short circuit and
found the resitance across the pump was 0 - not good!. I checked the
wiring and it all seems to be correct for "Y-Plan" style wiring. -
also bear in mind that the wiring hadn't change, just the boiler
connections. I had an old pump lieing around which i fitted, and again
the circuit (fuse) blew and the pump again - without the system even
starting up.

Their is one variance from the worcester-bosch instructions and my
wiring, in the the pump neutral goes to the common neutral in the
wiring centre (which just a a connector box - not a special one),
rather than to the boiler, but i don't see that this should make any
difference, and i want to avoid recabling! If that neutral connection
is vital i was thinking a link between boiler mains neutral and pump
neutral aty the boiler would suffice

To test the system, i disoccnect each component (mid-position valve,
cylinder state, room stat, pump) and connected each in turn to check
the fuse didn't blow, and it is ok until the pump is connected

Any help would be greatly appreciated

Thanks in advance

Dave

In an earlier contribution to this discussion,
D Simmonds wrote:

Hi All,

I have a newly installed Worcester Bosch CBi boiler (- a conventional,
not combi). This was installed to replace an aging myson appollo
fanfare, into the existing system. Both systems have pump over-run so
I think the wiring ought to be identical ....

Once installed it fired up without any porblems, however did not shut
off as expected with the room stat. I left it running so that at least
there was some hot water and heat in the house!

After the hot water cylinder had warmed up I completed the other
tests, e.g. lock-out etc, all of which were fine

I started the boiler up again, running it in the normal way, and after
a while it shut off as expected - however the cause was not the room
stat etc - the fuse in the mains isolator switch had blown. Replaced
the fuse and same again. I investigated for the short circuit and
found the resitance across the pump was 0 - not good!. I checked the
wiring and it all seems to be correct for "Y-Plan" style wiring. -
also bear in mind that the wiring hadn't change, just the boiler
connections. I had an old pump lieing around which i fitted, and again
the circuit (fuse) blew and the pump again - without the system even
starting up.

Their is one variance from the worcester-bosch instructions and my
wiring, in the the pump neutral goes to the common neutral in the
wiring centre (which just a a connector box - not a special one),
rather than to the boiler, but i don't see that this should make any
difference, and i want to avoid recabling! If that neutral connection
is vital i was thinking a link between boiler mains neutral and pump
neutral aty the boiler would suffice

To test the system, i disoccnect each component (mid-position valve,
cylinder state, room stat, pump) and connected each in turn to check
the fuse didn't blow, and it is ok until the pump is connected

Any help would be greatly appreciated

Thanks in advance

Dave

When you found the resistance across the pump to be zero, was that with the
pump in circuit - or with it disconnected? If the former, my guess is that
you've somehow managed to wire a short circuit by misconnecting something.
If you disconnect the pump and put a 13A plug on the end of its lead (with a
3A fuse) and plug it into a normal socket, what happens? I suspect that it
will work, and that you haven't 'blown' it at all!

Come back with some answers, and we'll try to work out what's happening.
--
Cheers,
Set Square
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On Fri, 7 Jan 2005 15:08:16 -0000, "Set Square"
wrote:

In an earlier contribution to this discussion,
D Simmonds wrote:

Hi All,

I have a newly installed Worcester Bosch CBi boiler (- a conventional,
not combi). This was installed to replace an aging myson appollo
fanfare, into the existing system. Both systems have pump over-run so
I think the wiring ought to be identical ....

Once installed it fired up without any porblems, however did not shut
off as expected with the room stat. I left it running so that at least
there was some hot water and heat in the house!

After the hot water cylinder had warmed up I completed the other
tests, e.g. lock-out etc, all of which were fine

I started the boiler up again, running it in the normal way, and after
a while it shut off as expected - however the cause was not the room
stat etc - the fuse in the mains isolator switch had blown. Replaced
the fuse and same again. I investigated for the short circuit and
found the resitance across the pump was 0 - not good!. I checked the
wiring and it all seems to be correct for "Y-Plan" style wiring. -
also bear in mind that the wiring hadn't change, just the boiler
connections. I had an old pump lieing around which i fitted, and again
the circuit (fuse) blew and the pump again - without the system even
starting up.

Their is one variance from the worcester-bosch instructions and my
wiring, in the the pump neutral goes to the common neutral in the
wiring centre (which just a a connector box - not a special one),
rather than to the boiler, but i don't see that this should make any
difference, and i want to avoid recabling! If that neutral connection
is vital i was thinking a link between boiler mains neutral and pump
neutral aty the boiler would suffice

To test the system, i disoccnect each component (mid-position valve,
cylinder state, room stat, pump) and connected each in turn to check
the fuse didn't blow, and it is ok until the pump is connected

Any help would be greatly appreciated

Thanks in advance

Dave

When you found the resistance across the pump to be zero, was that with the
pump in circuit - or with it disconnected? If the former, my guess is that
you've somehow managed to wire a short circuit by misconnecting something.
If you disconnect the pump and put a 13A plug on the end of its lead (with a
3A fuse) and plug it into a normal socket, what happens? I suspect that it
will work, and that you haven't 'blown' it at all!

Come back with some answers, and we'll try to work out what's happening.


Thanks for the above. I measured the pump with it out of circuit, and
get a zero resistance. There is definately a short somewhere, as even
with the pump disconnected from the circuit i am still blowing the 3
amp fuse. I am going to try and chase the short down, but none of the
wiring has changed from the original setup as far as i'm aware - of
course i'm only human! luckily i was away for the weekend so got heat
and hot water!!!!

The cylinder stat has resistance as i'd expect, - but i'm not sure
how (which wires) to check for the mid position valve .... - i presume
they are capable of shorting out as well. I shall see if i can
discover more .....


Dave

In an earlier contribution to this discussion,
D Simmonds wrote:


Thanks for the above. I measured the pump with it out of circuit, and
get a zero resistance. There is definately a short somewhere, as even
with the pump disconnected from the circuit i am still blowing the 3
amp fuse. I am going to try and chase the short down, but none of the
wiring has changed from the original setup as far as i'm aware - of
course i'm only human! luckily i was away for the weekend so got heat
and hot water!!!!

The cylinder stat has resistance as i'd expect, - but i'm not sure
how (which wires) to check for the mid position valve .... - i presume
they are capable of shorting out as well. I shall see if i can
discover more .....


Dave

Any chance you can post a link to an installation manual - or wiring
diagram - for your new boiler. I'd like to try to work out just how the pump
is supposed to connect - particularly since you've done it differently!

Do you mean there is zero resistance across the pump itself, or across the
terminals where it connects but with it disconnected? With what did you
measure this resistance?

Have you tried connecting the pump directly to the mains? What was the
result?
--
Cheers,
Set Square
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On Sun, 9 Jan 2005 20:04:38 -0000, "Set Square"
wrote:

In an earlier contribution to this discussion,
D Simmonds wrote:


Thanks for the above. I measured the pump with it out of circuit, and
get a zero resistance. There is definately a short somewhere, as even
with the pump disconnected from the circuit i am still blowing the 3
amp fuse. I am going to try and chase the short down, but none of the
wiring has changed from the original setup as far as i'm aware - of
course i'm only human! luckily i was away for the weekend so got heat
and hot water!!!!

The cylinder stat has resistance as i'd expect, - but i'm not sure
how (which wires) to check for the mid position valve .... - i presume
they are capable of shorting out as well. I shall see if i can
discover more .....


Dave

Any chance you can post a link to an installation manual - or wiring
diagram - for your new boiler. I'd like to try to work out just how the pump
is supposed to connect - particularly since you've done it differently!

Do you mean there is zero resistance across the pump itself, or across the
terminals where it connects but with it disconnected? With what did you
measure this resistance?

Have you tried connecting the pump directly to the mains? What was the
result?


I measured the pump across the terminals - so suspect its the
capacitor thats blown perhaps? I was thinking that replacing the
capacitor (if its cheap) might fix the pump .... - thoughts?


Anyways - i found the cause of the short one of the cables in the
wiring had nicked insulation, AND by coincidence the sleeving on the
earth wire adjacent to it also had a nick - and hence the short
occured - i'm mystified why it ran and then blew rather than just
blowing - however its all solved now. For the wiring i used std Y
plan, however when looking at it again it also had the HW off feed to
the programmer missing!!!!!!!, - and had been that way for years .....

Thanks for your help

Dave

In message , D Simmonds
writes
I measured the pump across the terminals - so suspect its the
capacitor thats blown perhaps? I was thinking that replacing the
capacitor (if its cheap) might fix the pump .... - thoughts?

It depends whether it's the capacitor which has gone, doesn't it. It's a
motor start capacitor, so the usual problem with a dead pump capacitor
is just that the pump won't start



Anyways - i found the cause of the short one of the cables in the
wiring had nicked insulation, AND by coincidence the sleeving on the
earth wire adjacent to it also had a nick - and hence the short
occured - i'm mystified why it ran and then blew rather than just
blowing

It depends what the cable was connected to. If its to e.g. the fan, it
would blow when the fan was powered up and not when the boiler was on
without a call for heat

--
geoff

In an earlier contribution to this discussion,
D Simmonds wrote:


Anyways - i found the cause of the short one of the cables in the
wiring had nicked insulation, AND by coincidence the sleeving on the
earth wire adjacent to it also had a nick - and hence the short
occured - i'm mystified why it ran and then blew rather than just
blowing - however its all solved now.

I suspected it was in the wiring rather than the pump. Glad you've fixed it.

For the wiring i used std Y
plan, however when looking at it again it also had the HW off feed to
the programmer missing!!!!!!!, - and had been that way for years .....


Not good! However, it will still work as long as the HW is on at the
programmer whenever the CH is on, and provided the cylinder stat has
change-over contacts which are wired correctly.
--
Cheers,
Set Square
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