My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

In the hope that it is either the spark electrodes or flame sensor
that are to blame (i.e. not a more complicated/expensive cause like
the control board, gas valve or gas supply etc) I purchased
replacements whilst it was convenient to obtain them (and negligible
cost too).

Can anyone tell from the following photos whether it looks like the
spark electrodes and/or flame sensor are in need of replacement? I
appreciate it may be hard to tell given that most of the time the
boiler works fine and so if either is to blame it must be due to a
borderline condition.

http://www.newtonnet.co.uk/permanent/IMG_8099.JPG
http://www.newtonnet.co.uk/permanent/IMG_8100.JPG
http://www.newtonnet.co.uk/permanent/IMG_8102.JPG

I have verified the correct gaps (3-4mm spark electrodes and 5-6mm
flame sensor) and the boiler is at least 5 (possibly 7 or more) years
old now if that helps.

Unfortunately the replacement of the flame sensor requires the removal
of the burner, i.e. disconnection from the gas valve, and I didn't
feel competent that I could ensure (through testing) gas soundness of
the reconstructed burner/valve union. That said, how would one test
the soundness given it is on the low pressure side of the valve?

I replaced the spark electrodes anyway given I had the part and,
whilst I may be imagining this, the new spark certainly seems more
pronounced.

I am now keeping an eye on the boiler in the hope that it is either
now fine or I will catch it in the act of entering the burner lockout
state so I can determine at what stage it occurs and hence rule in/out
potential factors.

Any thoughts/opinion would be most welcome.

Mathew

In message
,
Mathew Newton writes
My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.


Well, that's the crux. isn't it




I am now keeping an eye on the boiler in the hope that it is either
now fine or I will catch it in the act of entering the burner lockout
state so I can determine at what stage it occurs and hence rule in/out
potential factors.

Any thoughts/opinion would be most welcome.

Check the flame sense lead - physically give it a bit of a tug


--
geoff

On Dec 16, 5:34 pm, geoff wrote:
In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it


I think I may be getting somewhere... but it's a place I don't like...

I managed to catch it in the act today - the stat called for heat, the
pump/fan activated and the electrodes started sparking but nothing
else. After 10 seconds or so the boiler gave up and entered burner
lockout.

I am assuming the valve did not open, or is its mode of operation more
complicated than this?

The service manual fault chart says that if resistance across the two
sets of wires to the valve (main valve connections as opposed to
regulator according to the book) is not 100 ohms (they were both 75
ohms) then 'replace control board - if problem not solved replace gas
valve'.

Am I right to infer from that that the control board is the more
likely of the two to have failed? I know probabilities mean little
given both could fail, but perhaps you might know that the valves tend
not to fail, for example?

Of course I ought to be just getting someone in right now but given
the time of year I'm not looking forward to fighting for an
appointment and indeed if I can source the parts cheaper beforehand
then that might take the sting out a little.

Mathew

On Dec 18, 6:55 pm, Mathew Newton wrote:
On Dec 16, 5:34 pm, geoff wrote:

In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it

I think I may be getting somewhere... but it's a place I don't like...

I managed to catch it in the act today - the stat called for heat, the
pump/fan activated and the electrodes started sparking but nothing
else. After 10 seconds or so the boiler gave up and entered burner
lockout.

I forgot to mention; if you can this a 'test' I did confirm the gas
supply was okay as the hob is working (I'm sure there's more to a
supply than that though).

Mathew

On 18 Dec, 18:55, Mathew Newton wrote:
On Dec 16, 5:34 pm, geoff wrote:

In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it

I think I may be getting somewhere... but it's a place I don't like...

Well... I've moved on now.. and I'm *definitely* in a place I don't
like.

A few years back I replaced the control board following some problems
with the overrun not working properly (pulsing fan). I forgot that I'd
kept the old board so I've just fitted it and... occasional burner
lockouts.

So, I'm assuming it's the gas valve so will get someone out to replace
it. I'm not comfortable doing it myself, not least the setting
pressures aspects.

Cheers,

Mathew

In message
,
Mathew Newton writes
On Dec 16, 5:34 pm, geoff wrote:
In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it


I think I may be getting somewhere... but it's a place I don't like...

I managed to catch it in the act today - the stat called for heat, the
pump/fan activated and the electrodes started sparking but nothing
else. After 10 seconds or so the boiler gave up and entered burner
lockout.

I am assuming the valve did not open, or is its mode of operation more
complicated than this?

The service manual fault chart says that if resistance across the two
sets of wires to the valve (main valve connections as opposed to
regulator according to the book) is not 100 ohms (they were both 75
ohms) then 'replace control board - if problem not solved replace gas
valve'.

Have you measured the volts on the gas valve when it's sparking ?

When it's sparking the GV has to open

That would, IMO, be an obvious thing to do

volts to valve - valve problem

no volts to valve - pcb problem
--
geoff

In message
,
Mathew Newton writes
On 18 Dec, 18:55, Mathew Newton wrote:
On Dec 16, 5:34 pm, geoff wrote:

In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it

I think I may be getting somewhere... but it's a place I don't like...

Well... I've moved on now.. and I'm *definitely* in a place I don't
like.

A few years back I replaced the control board following some problems
with the overrun not working properly (pulsing fan). I forgot that I'd
kept the old board so I've just fitted it and... occasional burner
lockouts.

So, I'm assuming it's the gas valve so will get someone out to replace
it. I'm not comfortable doing it myself, not least the setting
pressures aspects.


Just a minute, as I read your post

new board - boiler doesn't fire

old board - boiler fires sometimes

Take one step back, and reassess your deductions


--
geoff

On Dec 18, 9:54 pm, geoff wrote:
In message
,
Mathew Newton writes



On 18 Dec, 18:55, Mathew Newton wrote:
On Dec 16, 5:34 pm, geoff wrote:

In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it

I think I may be getting somewhere... but it's a place I don't like...

Well... I've moved on now.. and I'm *definitely* in a place I don't
like.

A few years back I replaced the control board following some problems
with the overrun not working properly (pulsing fan). I forgot that I'd
kept the old board so I've just fitted it and... occasional burner
lockouts.

So, I'm assuming it's the gas valve so will get someone out to replace
it. I'm not comfortable doing it myself, not least the setting
pressures aspects.

Just a minute, as I read your post

new board - boiler doesn't fire

old board - boiler fires sometimes

Take one step back, and reassess your deductions

Sorry, perhaps I wasn't clear. Both boards fire most of the time...

I haven't checked the voltage at the valve - I simply can't get round
the back of it to do so!

I've now booked a Worcester engineer for Friday - it's a flat rate fee
of £185 inc. labour, VAT and upto 2 major parts (exc. heat exchanger).
I figured that if it's either the PCB or valve then I'm reasonably
happy with the price, particularly given they ought to be able to fix
it and ensure everything is hunkydory. I'm a little worried about when
he sees my new spark electrodes - do you think they'll kick up a fuss
given I've been 'meddling'?

Thanks for you advice so far, it's just a shame I'm not managing to
pinpoint the problem myself even with it.

Mathew

In message
,
Mathew Newton writes
On Dec 18, 9:54 pm, geoff wrote:
In message
,
Mathew Newton writes



On 18 Dec, 18:55, Mathew Newton wrote:
On Dec 16, 5:34 pm, geoff wrote:

In message
,
Mathew Newton writes

My Worcester Bosch 24CDi combi boiler keeps occasionally entering its
'burner lockout' state. The problem is so intermittent that resetting
the boiler always brings it back to life and I have so far been unable
to observe/determine whether the boiler is entering this state as a
result of it failing to ignite, partial ignition, igniting but failing
to detect the flame or the flame extinguishing when it shouldn't.

Well, that's the crux. isn't it

I think I may be getting somewhere... but it's a place I don't like...

Well... I've moved on now.. and I'm *definitely* in a place I don't
like.

A few years back I replaced the control board following some problems
with the overrun not working properly (pulsing fan). I forgot that I'd
kept the old board so I've just fitted it and... occasional burner
lockouts.

So, I'm assuming it's the gas valve so will get someone out to replace
it. I'm not comfortable doing it myself, not least the setting
pressures aspects.

Just a minute, as I read your post

new board - boiler doesn't fire

old board - boiler fires sometimes

Take one step back, and reassess your deductions

Sorry, perhaps I wasn't clear. Both boards fire most of the time...

Ah - I thought it was the other way round


I haven't checked the voltage at the valve - I simply can't get round
the back of it to do so!


Do you need to ?

measure it on the connector on the pcb

This introduces loom wiring as an unknown, but on a relatively new
boiler, it shouldn't be a problem



--
geoff

On Dec 18, 10:45 pm, geoff wrote:

Sorry, perhaps I wasn't clear. Both boards fire most of the time...

Ah - I thought it was the other way round



I haven't checked the voltage at the valve - I simply can't get round
the back of it to do so!

Do you need to ?

measure it on the connector on the pcb

This introduces loom wiring as an unknown, but on a relatively new
boiler, it shouldn't be a problem

True. I'll give it a shot tomorrow.

There are six wires to the valve - 2 x blue for 'regulator', 2 x brown
for 'main' and another 2 x violet for 'main'. Given my testing time is
limited (intermittent fault, 10 second window) can you advise on which
I ought to be concentrating on? It would help if I knew the principle
of exactly how the valve works but Googling failed me.. (or rather I
failed it!)

Given the service manual speaks of measuring the resistance of the two
'main' pairs (brown and violet) so I'm assuming these are two
solenoids? (why two?) What does the regulator consist of?

Sorry for all these questions, I'm sure you must be doubting my
competence but I just want to understand as much as possible to get
the most of this situation.

Mathew

In message
,
Mathew Newton writes
On Dec 18, 10:45 pm, geoff wrote:

Sorry, perhaps I wasn't clear. Both boards fire most of the time...

Ah - I thought it was the other way round



I haven't checked the voltage at the valve - I simply can't get round
the back of it to do so!

Do you need to ?

measure it on the connector on the pcb

This introduces loom wiring as an unknown, but on a relatively new
boiler, it shouldn't be a problem

True. I'll give it a shot tomorrow.

There are six wires to the valve - 2 x blue for 'regulator', 2 x brown
for 'main' and another 2 x violet for 'main'. Given my testing time is
limited (intermittent fault, 10 second window) can you advise on which
I ought to be concentrating on? It would help if I knew the principle
of exactly how the valve works but Googling failed me.. (or rather I
failed it!)

Given the service manual speaks of measuring the resistance of the two
'main' pairs (brown and violet) so I'm assuming these are two
solenoids? (why two?) What does the regulator consist of?


ITYF the two main valves are a two stage main valve - 240 volts

the "regulator" is what's known as a modureg, it's a 24v modulating
valve which adjusts it's flow rate according to the voltage on the
solenoid. It's purpose is to fine tune the output depending on the
demand so that e.g. you get a constant temperature hot water
irrespective of the flow rate through the tap
--
geoff

On Dec 19, 12:03 am, geoff wrote:

There are six wires to the valve - 2 x blue for 'regulator', 2 x brown
for 'main' and another 2 x violet for 'main'. Given my testing time is
limited (intermittent fault, 10 second window) can you advise on which
I ought to be concentrating on? It would help if I knew the principle
of exactly how the valve works but Googling failed me.. (or rather I
failed it!)

ITYF the two main valves are a two stage main valve - 240 volts

the "regulator" is what's known as a modureg, it's a 24v modulating
valve which adjusts it's flow rate according to the voltage on the
solenoid. It's purpose is to fine tune the output depending on the
demand so that e.g. you get a constant temperature hot water
irrespective of the flow rate through the tap

Thanks for that - very useful.

I gave this a shot this morning and found that, during (attempted)
ignition the voltage across each of the main valve points on the PCB
(MV1 and MV2) rose to 135v AC (I suppose it could've been on its way
to 240v AC but the digital meter update refresh may not be quick
enough) and this coincided with a small thud from the valve. During
the 10 seconds of sparking the voltage remained steady at something
like 15v AC. Does this sound right? It was the same for both valves
points. At the end of the ignition period it gave up, the valve gave
another small thud, the sparking stopped and it enter buner lockout.

Remember I am seeing the same issues with both boards, so I'm assuming
it's definitely the gas valve. The small thuds I hear are worrying
though - that to me suggests it is opening or is there more to the
successful operation of the valve than that?

Mathew

Mathew Newton wrote:
On Dec 19, 12:03 am, geoff wrote:

There are six wires to the valve - 2 x blue for 'regulator', 2 x brown
for 'main' and another 2 x violet for 'main'. Given my testing time is
limited (intermittent fault, 10 second window) can you advise on which
I ought to be concentrating on? It would help if I knew the principle
of exactly how the valve works but Googling failed me.. (or rather I
failed it!)
ITYF the two main valves are a two stage main valve - 240 volts

the "regulator" is what's known as a modureg, it's a 24v modulating
valve which adjusts it's flow rate according to the voltage on the
solenoid. It's purpose is to fine tune the output depending on the
demand so that e.g. you get a constant temperature hot water
irrespective of the flow rate through the tap

Thanks for that - very useful.

I gave this a shot this morning and found that, during (attempted)
ignition the voltage across each of the main valve points on the PCB
(MV1 and MV2) rose to 135v AC (I suppose it could've been on its way
to 240v AC but the digital meter update refresh may not be quick
enough) and this coincided with a small thud from the valve. During
the 10 seconds of sparking the voltage remained steady at something
like 15v AC. Does this sound right? It was the same for both valves
points. At the end of the ignition period it gave up, the valve gave
another small thud, the sparking stopped and it enter buner lockout.

Remember I am seeing the same issues with both boards, so I'm assuming
it's definitely the gas valve. The small thuds I hear are worrying
though - that to me suggests it is opening or is there more to the
successful operation of the valve than that?

Mathew

When we had a WB engineer he replaced the faulty item plus a couple of
other things that "might go", so it was probably a good deal compared to
a local engineer

On 19 Dec, 10:50, Stuart Noble
wrote:

When we had a WB engineer he replaced the faulty item plus a couple of
other things that "might go", so it was probably a good deal compared to
a local engineer

That's good to hear - I was wondering how it might work, not least
given £185 doesn't go very far when it comes to many boiler parts. I
suppose it may depend on the engineer but I'll certainly try to ease
the process with tea and choccy biccies. Might even train the cats to
shiver too.

My biggest concern is that the problem won't manifest itself on the
day. I've taken a video of it happening so hopefully that might help
should this happen.

Mathew

On Dec 18, 10:32 pm, Mathew Newton wrote:

I've now booked a Worcester engineer for Friday

He came out today and firstly replaced the air pressure switch - not
sure why. Anyway, that didn't sort it so he then put a new gas valve
in. Job done... at least so far - I'll be absolutely gutted if I wake
up tomorrow to a cold house!

Thanks for all your help Geoff - much appreciated.

Cheers,

Mathew

Mathew Newton wrote:
On Dec 18, 10:32 pm, Mathew Newton wrote:

I've now booked a Worcester engineer for Friday

He came out today and firstly replaced the air pressure switch - not
sure why. Anyway, that didn't sort it so he then put a new gas valve
in. Job done... at least so far - I'll be absolutely gutted if I wake
up tomorrow to a cold house!

Thanks for all your help Geoff - much appreciated.

Cheers,

Mathew


I'd be interested to know if you get any kind of written confirmation
from WB about what's been replaced and what kind of warranty applies to
the new bits. I was given no paperwork at all and, although I have the
bank debit and the original bits as proof, it's not a very professional
way of carrying on.

They replaced a leaking pump on mine in March and the same fault appears
to be developing again. I somehow thought it might because the auto air
vent (which apparently often leaks, but costs tuppence and is easily
replaceable ) is right at the back of the pump. Nice one, WB.

On Sat, 22 Dec 2007 13:25:16 GMT, Stuart Noble
wrote:


I'd be interested to know if you get any kind of written confirmation
from WB about what's been replaced and what kind of warranty applies to
the new bits. I was given no paperwork at all and, although I have the
bank debit and the original bits as proof, it's not a very professional
way of carrying on.

We had a WB engineer in here this morning. He didn't leave a service
report either. He said it was on his laptop and the office would be
sending me a printed copy. We'll see.


They replaced a leaking pump on mine in March and the same fault appears
to be developing again. I somehow thought it might because the auto air
vent (which apparently often leaks, but costs tuppence and is easily
replaceable ) is right at the back of the pump. Nice one, WB.

We had also had an odd intermittent water leak on our 4 year old
condensing boiler which came and went away. It came from a joint in
the flue ! The engineer said whether it actually leaks or not depends
much on patterns of usage inside / outside temperatures etc.

DG

Derek Geldard wrote:
On Sat, 22 Dec 2007 13:25:16 GMT, Stuart Noble
wrote:

I'd be interested to know if you get any kind of written confirmation
from WB about what's been replaced and what kind of warranty applies to
the new bits. I was given no paperwork at all and, although I have the
bank debit and the original bits as proof, it's not a very professional
way of carrying on.

We had a WB engineer in here this morning. He didn't leave a service
report either. He said it was on his laptop and the office would be
sending me a printed copy. We'll see.


All I got as a follow-up was an invitation to take out a yearly service
agreement. I think their long term plan is to leave you no other option.
If their stupid £120 pump is going to fail annually because of a design
fault, they would seem to have one by the short and curlies.

++++++++++++++++++++++
Dear Mathew

I have a WB 24CDI and noted that I have the same problems as you. Did the boiler function for long with the new Gas Valve? Did you have any problems with it in the months/years following?

Many thanks
Coco