Ever since we moved into this house 5 years ago we've had to top the
central heating system up more often than I would have liked. Once a
month or so.

Now it's suddenly got a lot worse, as in once per day. I've just
checked the expansion vessel. Now, the system was hot, but there was
plenty of pressure in it and no water. Unfortunately I don't have tyre
pressure gauge, but from years of cycling I would guess it was well
over 20PSI.

I've looked for a relief valve test knob but can't find any red knobs
and can't find anything that I would be confident in tweaking. Odd, I
can strip down and rebuild your average Ford engine without any
worries. With combi boilers I start getting really nervous though.

Whilst I was fiddling about with this (a period of no more than half
an hour) about 3/8 of a pint of water came out of the boiler overflow
pipe (yikes!).

The boiler is a Worcester Bosch 240.

I'm guessing that it's time to try to find a professional to fix it,
but is there anything else I can do before I go spending serious
money?

I've got some photos of the boiler that I can put on the we if that
would help.


Thanks,

Andrew

"Andrew Collins" com.hotmail@bflfcbb wrote in message
...
Ever since we moved into this house 5 years ago we've had to top the
central heating system up more often than I would have liked. Once a
month or so.

Now it's suddenly got a lot worse, as in once per day. I've just
checked the expansion vessel. Now, the system was hot, but there was
plenty of pressure in it and no water. Unfortunately I don't have tyre
pressure gauge, but from years of cycling I would guess it was well
over 20PSI.

I've looked for a relief valve test knob but can't find any red knobs
and can't find anything that I would be confident in tweaking. Odd, I
can strip down and rebuild your average Ford engine without any
worries. With combi boilers I start getting really nervous though.

Whilst I was fiddling about with this (a period of no more than half
an hour) about 3/8 of a pint of water came out of the boiler overflow
pipe (yikes!).

The boiler is a Worcester Bosch 240.

I'm guessing that it's time to try to find a professional to fix it,
but is there anything else I can do before I go spending serious
money?

I've got some photos of the boiler that I can put on the we if that
would help.


Thanks,

Andrew

The pressure relief valve is right at the back/bottom of a 240 (drop the
control panel down to see it), and is normaly a red one with the pressure
gauge directly attached (just trace the relief pipe up to find it). It
sounds like it is leaking, thus dropping pressure - flushing it though may
help (give it a twist, then repressurise), otherwise drain the boiler and
replace (again, twist it to drain fully, no need for mains water isolation,
DO NOT isolate the boiler via its own isolation valves as these WILL leak.
Not expensive, part no more than £5, you can DIY.

Angus

On Sat, 31 Dec 2005 17:00:12 -0000, "Fentoozler" nospam@mapson
wrote:
The pressure relief valve is right at the back/bottom of a 240 (drop the
control panel down to see it), and is normaly a red one with the pressure
gauge directly attached (just trace the relief pipe up to find it). It
sounds like it is leaking, thus dropping pressure - flushing it though may
help (give it a twist, then repressurise), otherwise drain the boiler and
replace (again, twist it to drain fully, no need for mains water isolation,
DO NOT isolate the boiler via its own isolation valves as these WILL leak.
Not expensive, part no more than £5, you can DIY.

Pressure valve located and duly twisted. Cheers!

I don't think it's made any difference though. I think it might be
time to find a new valve.

Thanks Angus!

Andrew

wrote in message ...
On 31 Dec,
Andrew Collins com.hotmail@bflfcbb wrote:

On Sat, 31 Dec 2005 17:00:12 -0000, "Fentoozler" nospam@mapson
wrote:
The pressure relief valve is right at the back/bottom of a 240 (drop
the
control panel down to see it), and is normaly a red one with the
pressure
gauge directly attached (just trace the relief pipe up to find it). It
sounds like it is leaking, thus dropping pressure - flushing it though
may help (give it a twist, then repressurise), otherwise drain the
boiler and replace (again, twist it to drain fully, no need for mains
water isolation, DO NOT isolate the boiler via its own isolation
valves
as these WILL leak. Not expensive, part no more than £5, you can DIY.

Pressure valve located and duly twisted. Cheers!

I don't think it's made any difference though. I think it might be time
to
find a new valve.


If the pressure is rising rapidly when heating, then it is likely that the
pressure vessel has lost charge. It's easy to check but the system needs
to
be cold and not pressurised. You will require a pressure guage (car type
is
adequate) and a foot pump or similar to re-charge. About 10psi (0.7bar) is
normal.

Or a blockage in the connecting pipe system to expansion vessel

On Sat, 31 Dec 2005 22:33:51 GMT, wrote:

If the pressure is rising rapidly when heating, then it is likely that the
pressure vessel has lost charge. It's easy to check but the system needs to
be cold and not pressurised. You will require a pressure guage (car type is
adequate) and a foot pump or similar to re-charge. About 10psi (0.7bar) is
normal.

Heh... That's actually the *first* thing I did!

It does pressurize quickly, so the amount of pressure in the expansion
vessel could be wrong, but there was plenty of pressure in there when
I tested it. I will try to find out what the pressure should be for
the boiler and make sure it is correct.

It also leaks when the pressure is well under 2 bar (the maximum it
gets to), and I believe for this boiler the pressure relief valve
opens (or rather should open) at around 3 bar.

I *think* it is slightly better since I tweaked the valve yesterday. I
shall try it again later, but I suspect it needs replacing anyway.

Thanks,

Andrew

"Andrew Collins" com.hotmail@bflfcbb wrote in message
...
On Sat, 31 Dec 2005 22:33:51 GMT, wrote:

If the pressure is rising rapidly when heating, then it is likely that the
pressure vessel has lost charge. It's easy to check but the system needs
to
be cold and not pressurised. You will require a pressure guage (car type
is
adequate) and a foot pump or similar to re-charge. About 10psi (0.7bar) is
normal.

Heh... That's actually the *first* thing I did!

It does pressurize quickly, so the amount of pressure in the expansion
vessel could be wrong, but there was plenty of pressure in there when
I tested it. I will try to find out what the pressure should be for
the boiler and make sure it is correct.

It also leaks when the pressure is well under 2 bar (the maximum it
gets to), and I believe for this boiler the pressure relief valve
opens (or rather should open) at around 3 bar.

I *think* it is slightly better since I tweaked the valve yesterday. I
shall try it again later, but I suspect it needs replacing anyway.

Thanks,

Andrew
Pressure raising quickly is usually one of 4 things on a WB:

1. Blockage - unusual;
2. Pump stuck - unlikely if you're getting any CH and/or HW;
3. No pressure in expansion vessel - more likely;
4. Split in water-water heat exchanger - had this on later models (CDi
range), not on a 240 however.

The PRV requires replacing (again flushing it through (twist until it clicks
shut again)) - you can do this as often as you like until it stops leaking
or you get ****ed off. Remember to recharge when necessary.

If you do need to recharge the expansion vessel, use the guide above, but
remember to leave an open end when pumping it up (e.g. crank the PRV open
just before it clicks shut - it should stick open).

Angus