Hi all,

I've a Worcester oil fired condensing combi boiler that I've complained
about here on previous occasions. This time it's gone tits up as a result
of a suspected electrical fault. I suspect it's electrical since the 230v
terminal which supplies an external room stat has gone right down to just
a few volts. But I've lost hot water as well as heating so it must be a
fault that's common to both sub-systems.
The boiler 'power' light is illuminated; the 'lock out' light is not, and
the on1/on2/off/time lcd panel is likewise showing the usual correct
indications. When I turn the hot tap on, just one of the relays on the pcb
activates and there's a faint hum from the boiler's internals, but
nothing from the fan/burner etc.
One clue is that the boiler has recently been taking progressively longer
in firing up after switch-on until its now got to where it doesn't fire
up at all. Any troubleshooting suggestions, guys?

cheers,

cd

Cursitor Doom wrote in
:

Hi all,

I've a Worcester oil fired condensing combi boiler that I've
complained about here on previous occasions. This time it's gone tits
up as a result of a suspected electrical fault. I suspect it's
electrical since the 230v terminal which supplies an external room
stat has gone right down to just a few volts. But I've lost hot water
as well as heating so it must be a fault that's common to both
sub-systems. The boiler 'power' light is illuminated; the 'lock out'
light is not, and the on1/on2/off/time lcd panel is likewise showing
the usual correct indications. When I turn the hot tap on, just one of
the relays on the pcb activates and there's a faint hum from the
boiler's internals, but nothing from the fan/burner etc.
One clue is that the boiler has recently been taking progressively
longer in firing up after switch-on until its now got to where it
doesn't fire up at all. Any troubleshooting suggestions, guys?

cheers,

cd


A faint hum from the guts of the thing, I would say.

1. Knackered oil pump.

2. Jammed fan.

3. Capacitor kaput.

In that order.

Replace capacitor.Cheap.

Take off oil pump and start boiler. If it revs up then it's the pump.

If it still hums then motor stuck.

On Fri, 07 Feb 2014 00:20:09 +0000, Heliotrope Smith wrote:

A faint hum from the guts of the thing, I would say.

1. Knackered oil pump.

2. Jammed fan.

3. Capacitor kaput.

In that order.

Replace capacitor.Cheap.

Take off oil pump and start boiler. If it revs up then it's the pump.

If it still hums then motor stuck.

It's not clear to me which capacitor you're referring to here.
You may be right about the other parts, but I'd be surprised, since the
boiler was installed brand new only just over 2 years ago (warranty
timer's kicked in, predictably) although I have discovered it's not been
serviced since then, if that's relevant.

Also even good looking relays can deceive one into thinking its actually
connected. Could be poor regulation of supply to relay or just knackered
or tarnish on the contacts.
I hate boilers..
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Heliotrope Smith" wrote in message
. 116...
Cursitor Doom wrote in
:

Hi all,

I've a Worcester oil fired condensing combi boiler that I've
complained about here on previous occasions. This time it's gone tits
up as a result of a suspected electrical fault. I suspect it's
electrical since the 230v terminal which supplies an external room
stat has gone right down to just a few volts. But I've lost hot water
as well as heating so it must be a fault that's common to both
sub-systems. The boiler 'power' light is illuminated; the 'lock out'
light is not, and the on1/on2/off/time lcd panel is likewise showing
the usual correct indications. When I turn the hot tap on, just one of
the relays on the pcb activates and there's a faint hum from the
boiler's internals, but nothing from the fan/burner etc.
One clue is that the boiler has recently been taking progressively
longer in firing up after switch-on until its now got to where it
doesn't fire up at all. Any troubleshooting suggestions, guys?

cheers,

cd


A faint hum from the guts of the thing, I would say.

1. Knackered oil pump.

2. Jammed fan.

3. Capacitor kaput.

In that order.

Replace capacitor.Cheap.

Take off oil pump and start boiler. If it revs up then it's the pump.

If it still hums then motor stuck.

On Fri, 07 Feb 2014 11:15:21 +0000, Brian_Gaff wrote:

Also even good looking relays can deceive one into thinking its actually
connected. Could be poor regulation of supply to relay or just
knackered or tarnish on the contacts.
I hate boilers..
Brian

IMO (knowing very little of boilers but quite a tidy bit about
electronics) shorting out the relay secondaries to get some reaction is
the first line of investigation here after checking the more obvious
things like circuit board fuses and whatnot. It's just a bloody nuisance
the things appear to be hard wired onto the main pcb rather than the plug-
in type which would have made life so much easier.

I guess there must be a voltage regulator here somewhere that should also
be checked, but I've yet to find one...

Cursitor Doom wrote:
On Fri, 07 Feb 2014 11:15:21 +0000, Brian_Gaff wrote:

Also even good looking relays can deceive one into thinking its actually
connected. Could be poor regulation of supply to relay or just
knackered or tarnish on the contacts.
I hate boilers..
Brian

IMO (knowing very little of boilers but quite a tidy bit about
electronics) shorting out the relay secondaries to get some reaction is
the first line of investigation here after checking the more obvious
things like circuit board fuses and whatnot. It's just a bloody nuisance
the things appear to be hard wired onto the main pcb rather than the plug-
in type which would have made life so much easier.

I guess there must be a voltage regulator here somewhere that should also
be checked, but I've yet to find one...

I've wondered if there is potential for a replacement pcb with simple
discrete logic and plug in relays. US gas fired hot air heaters seem to
have used this system for ever and are very easily repaired. Are the
modern pcbs multi layer? For reliability and cost, IBM IME always used
single sided boards with links where necessary when handling power.

On Fri, 07 Feb 2014 11:54:02 +0000, Capitol wrote:

I've wondered if there is potential for a replacement pcb with
simple discrete logic and plug in relays.

All the scope in the world, I'd say. But it does demand a good deal of
time to perfect such a replacement control system. The main drawback with
your idea is the extra cost of a decent power supply. As things stand it
seems like everything just runs off 230v!

US gas fired hot air heaters seem to
have used this system for ever and are very easily repaired. Are the
modern pcbs multi layer? For reliability and cost, IBM IME always used
single sided boards with links where necessary when handling power.

Single sided board with surprisingly few components; just four (Chinese)
relays and a bunch of strip connectors to interface to the off-board
components (again, not much at all in the way of electronics). I'll bet
they want a mint from a new main pcb, though!