have a 20 year old boiler- gravity flow, pilot light, with a hot water
cylinder in the airing cupboard.
recently (a week ago) had a plumber drain the boiler to sort out problems
with radiators (also fitting thermostatic valves all over the house on the
radiators).
since then (maybe coincidentally?) the boiler is misbehaving.
on manually lighting it, the pilot comes on, the boiler fires up, can see
the flames clearly, then the flames gutter and go out. (i can see a lot of
yellow flames- is that unusual? i thought they would be all blue.)
after repeated attempts, the boiler stays on when left on a continous timer
setting. leaving it on a twice a day setting, the pilot goes out and the
boiler does not heat up.
what could the possible problems be? is the boiler kaput?
any help appreciated.

"Zax" wrote in message
...
have a 20 year old boiler- gravity flow, pilot light, with a hot water
cylinder in the airing cupboard.
recently (a week ago) had a plumber drain the boiler to sort out problems
with radiators (also fitting thermostatic valves all over the house on
the radiators).
since then (maybe coincidentally?) the boiler is misbehaving.
on manually lighting it, the pilot comes on, the boiler fires up, can see
the flames clearly, then the flames gutter and go out. (i can see a lot of
yellow flames- is that unusual? i thought they would be all blue.)
after repeated attempts, the boiler stays on when left on a continous
timer setting. leaving it on a twice a day setting, the pilot goes out and
the boiler does not heat up.
what could the possible problems be? is the boiler kaput?
any help appreciated.

If you told us what make and model of boiler it is we might be able to make
a sensible contribution. Also when was the boiler last serviced and is all
ventilation clear?

If the pilot keeps goin out I'd suspect the thermocouple.
That's the bit that sticks into the pilot flame and is connected by a
thin copper tube to the gas valve. It's job is to keep the gas valve
open (and hence the pilot lit) as long as it is 'warm'.

You can replace the thermocouple yourself for about 4 quid. (See
www.screfix.com and search for 'thermocouple' )

"John" wrote in message
...

"Zax" wrote in message
...
have a 20 year old boiler- gravity flow, pilot light, with a hot water
cylinder in the airing cupboard.
recently (a week ago) had a plumber drain the boiler to sort out problems
with radiators (also fitting thermostatic valves all over the house on
the radiators).
since then (maybe coincidentally?) the boiler is misbehaving.
on manually lighting it, the pilot comes on, the boiler fires up, can see
the flames clearly, then the flames gutter and go out. (i can see a lot
of yellow flames- is that unusual? i thought they would be all blue.)
after repeated attempts, the boiler stays on when left on a continous
timer setting. leaving it on a twice a day setting, the pilot goes out
and the boiler does not heat up.
what could the possible problems be? is the boiler kaput?
any help appreciated.

If you told us what make and model of boiler it is we might be able to
make a sensible contribution. Also when was the boiler last serviced and
is all ventilation clear?

its a glow-worm balanced flue boiler 100B
last serviced 2 years ago
all ventilation clear.

"Zax" wrote in message
...

"John" wrote in message
...

"Zax" wrote in message
...
have a 20 year old boiler- gravity flow, pilot light, with a hot water
cylinder in the airing cupboard.
recently (a week ago) had a plumber drain the boiler to sort out
problems
with radiators (also fitting thermostatic valves all over the house on
the radiators).
since then (maybe coincidentally?) the boiler is misbehaving.
on manually lighting it, the pilot comes on, the boiler fires up, can
see
the flames clearly, then the flames gutter and go out. (i can see a lot
of yellow flames- is that unusual? i thought they would be all blue.)
after repeated attempts, the boiler stays on when left on a continous
timer setting. leaving it on a twice a day setting, the pilot goes out
and the boiler does not heat up.
what could the possible problems be? is the boiler kaput?
any help appreciated.

If you told us what make and model of boiler it is we might be able to
make a sensible contribution. Also when was the boiler last serviced and
is all ventilation clear?

its a glow-worm balanced flue boiler 100B
last serviced 2 years ago
all ventilation clear.



If it's a Glow Worm balanced flue 100B (like mine) and the flames are all
yellow, the heat exchanger fins are all blocked up with soot. This is
marginally dangerous as there will be partial combustion and poisonous fumes
(but only marginal as it's a balanced flue and they all go outside.

It is possible to do it DIY (I've just done mine) but I cannot recommend
this to anyone for obvious reasons. It MUST be done, however. Whoever does
it has to remove all the internal covers and laboriously clean between the
fins (lolly sticks just fit between them, and a stiff paint brush). The
stuff that comes out is ultrafine carbon, the dirtiest substance known to
man. You are in for a right pasting from SWMBO (probably). Don't use the
best vacuum cleaner (I did - once { ).

As an aside they ususally last 5 years before sooting up (this is my one's
second event). This means the "service" you had was the usual quick hoover
round and didn't involve cleaning the heat exchanger properly.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

In article . com,
kmillar wrote:
If the pilot keeps goin out I'd suspect the thermocouple.
That's the bit that sticks into the pilot flame and is connected by a
thin copper tube to the gas valve. It's job is to keep the gas valve
open (and hence the pilot lit) as long as it is 'warm'.

Think it's possibly more likely the pilot jet is partially blocked so the
flame is too weak to keep the thermocouple happy.

--
*The closest I ever got to a 4.0 in school was my blood alcohol content*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Zax wrote:
on manually lighting it, the pilot comes on, the boiler fires up, can
see the flames clearly, then the flames gutter and go out. (i can see a
lot of yellow flames- is that unusual? i thought they would be all
blue.) after repeated attempts, the boiler stays on when left on a
continous timer setting. leaving it on a twice a day setting, the pilot
goes out and the boiler does not heat up.

There shouldn't be any yellow when it's burning correctly - apart,
perhaps, for a brief moment at ignition.

Does the pilot light look a healthy size? It's possible the act of
ignition of the main burner is blowing it out.

First thing I'd try is to remove it and make sure it's clean. Give it a
good scrub in hot water and washing up liguid, and use a bristle from the
brush down the jet. Examine the jet with a magnifying glass to see it's
clear - but don't use anything metallic to try and clear any crud.

--
*Failure is not an option. It's bundled with your software.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Bob Mannix wrote:
As an aside they ususally last 5 years before sooting up (this is my
one's second event). This means the "service" you had was the usual
quick hoover round and didn't involve cleaning the heat exchanger
properly.

Wonder what influences how fast this happens? My experience is that my
boiler does over twice that before needing attention. Mine's on the first
floor, so may get a cleaner air supply?

--
*Life is hard; then you nap

Dave Plowman London SW
To e-mail, change noise into sound.

"Zax" wrote in message
...

"John" wrote in message
...

"Zax" wrote in message
...
have a 20 year old boiler- gravity flow, pilot light, with a hot water
cylinder in the airing cupboard.
recently (a week ago) had a plumber drain the boiler to sort out
problems with radiators (also fitting thermostatic valves all over the
house on the radiators).
since then (maybe coincidentally?) the boiler is misbehaving.
on manually lighting it, the pilot comes on, the boiler fires up, can
see the flames clearly, then the flames gutter and go out. (i can see a
lot of yellow flames- is that unusual? i thought they would be all
blue.)
after repeated attempts, the boiler stays on when left on a continous
timer setting. leaving it on a twice a day setting, the pilot goes out
and the boiler does not heat up.
what could the possible problems be? is the boiler kaput?
any help appreciated.

If you told us what make and model of boiler it is we might be able to
make a sensible contribution. Also when was the boiler last serviced and
is all ventilation clear?

its a glow-worm balanced flue boiler 100B
last serviced 2 years ago
all ventilation clear.

It sounds as though the flue is not discharging the products of combustion
so the main flame is "smothering" itself because either the outlet is
blocked or the combustion air inlet is blocked. Can you see any possible
obstruction at the balanced flue terminal?
If not and you are competent to do so I suggest you look inside the boiler
to check if the burner and its air supply ways are clean and clear, the heat
exchanger is clean and clear, and the path for the egress of the flue gases
via the balanced flue is also clear. I can't recall the exact construction
details of this model but it may be that a fibrefrax combustion chamber
lining could have fallen off and be lying on the burner upsetting the
combustion.
Balanced flue boilers are inherently very reliable and simple so its most
likely something stupid