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boiler / central heating problem - main burner weak and cuts out



 
 
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  #1  
Old March 15th 04, 12:51 AM
SledgehammerSteve
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Default boiler / central heating problem - main burner weak and cuts out

Im in need of some help in trying to figure out a boiler problem.
Do the following facts and observations point to anything to anyone here.

- 3 days ago the boiler (an old fashioned gas fired standard boiler -
Stelard Ideal Mexico Super Model CF65 - about 13 years old),
pilot light shut off automatically. I relit it, it stayed on, main burner
came on. Then after 1 hour the pilot again shut off automatically.
I adjusted the pilot screw to increase pilot flame size, and boiler
has worked normally for 3 days.

- 3 days later, pilot shuts off, I relight it, pilot stays on, main burner
comes on, after 1 minute, Main burners AND pilot both go out.
If I relight the pilot, it stays lit. NOTE it only goes out 1 minute
AFTER main burners come on.
Also Note that the main burner flames look fairly weak and the second of
the 2 main burners comes on say 20 seconds after the 1st main burner.

- I now replace the thermocouple. Makes no difference. Anyhow, the pilot still
stays lit as long as main burners dont come on so surely its not the
thermocouple.
The voltage at the gas valve terminals is 240v ALL the time including when
the burners and pilot cut out, so I am assuming there is no problem with
the controller or thermostats. I also assume there is no problem with the gas
valve as the main burners come on for 1 minute.
Note I hear a click from the gas valve when the main burners and pilot shut
off automatically after 60 seconds. (Everything is still cold at this point)

- I now clean out the 2 main burner jets and pin prick flame holes (There is
no dirt I can see)
I DIDNT clean the pilot.

- Still same problem.
- I now notice that when the main burners come on the pilot flame seems to
go out and is therefore not covering the thermocouple tip as it does when
the main burners are NOT on.
- I now adjust the pilot screw again to increase the pilot flame even more.
Now when the main burners come on, I can see a pilot flame which does touch
the thermocouple tip. Also the main burners and pilot now STAY ON.
GREAT - BUT the radiators arent getting hot - only slightly warm, and the
pipes coming out of the boiler that should be hot are only warm, even though
both main burners are now on and running for 30 minutes.
NOTE I can hear and feel that the pump is on and humming.
Also NOTE - the main burner flames still look fairly weak to me but Im not
too sure what they usually look like.

-Bit stumped at this point. Think it could be restricted incoming flue/airways
I blow into the main burners from below.
The second burner actually goes out now, but I can see a small flame at the
bottom of the second burner- below the pin prick flame holes.

-Both main burners are now working again last time I looked - but pipes and rads
are just luke-warm

-Last resort - SOS message on uk-d-i-y

Any ideas greatly appreciated

(The one comforting thought is the weather forecast over the next few days)

SledgeHammerSteve
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  #2  
Old March 15th 04, 11:42 AM
SledgehammerSteve
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Default boiler / central heating problem - main burner weak and cuts out

Ive just spoke with a rather unhelpful chap on the Caradon Stelrad
Ideal Boilers helpline.
But just before he sussed I wasnt a qualified heating engineer
and bottled up, he said "Have you checked the burner pressure?"

I asked if he meant the gas pressure going into the gas valve,
and he said no.

Does anyone hear know how and where to check the burner pressure and
tell whether its too weak. And if it is what might be the cause.

Im now starting to thing this is a weak burner pressure problem.
The gas hob appears a bit weak as well.

Is this a problem I can get British Gas to check and fix no-charge.
Could it be their Gas meter and is testing it and fixing it included
in our gas bills.

Steve
  #3  
Old March 15th 04, 12:43 PM
Andy Hall
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Default boiler / central heating problem - main burner weak and cuts out

On 15 Mar 2004 03:42:01 -0800,
(SledgehammerSteve) wrote:

Ive just spoke with a rather unhelpful chap on the Caradon Stelrad
Ideal Boilers helpline.
But just before he sussed I wasnt a qualified heating engineer
and bottled up, he said "Have you checked the burner pressure?"

I asked if he meant the gas pressure going into the gas valve,
and he said no.

Does anyone hear know how and where to check the burner pressure and
tell whether its too weak. And if it is what might be the cause.

Im now starting to thing this is a weak burner pressure problem.
The gas hob appears a bit weak as well.

Is this a problem I can get British Gas to check and fix no-charge.
Could it be their Gas meter and is testing it and fixing it included
in our gas bills.

Steve


It could be a faulty regulator at the meter.

For this one, call Transco and ask them to come and test it. There is
a test point at the meter, and there should be a specific pressure of
21mBar there.

At the input of the appliance, when all appliances are running. there
should be a pressure drop of no more than 1mBar relative to the meter.
There should be a test point on the inlet side of the appliance for
that.

The burner pressure will be listed in the installation instructions of
the boiler. It may be a single setting, or the appliance may be
range rated, in which case the pressure is set to a value in the range
to produce different output power levels. The pressure setting for
that is normally a screw on the gas valve. However, that should not
be touched until the pressure on the meter side is known, because if
the supply is out of spec and you have adjusted the valve, when it is
brought back into spec. the burner will be firing at too great a rate
(not safe).

There are normally test nipples for the pressure to use with a
manometer on the gas valve or the inlet pipe and pipe to the burner.
Obviously it is important to know which is which. Some boilers don't
have a test point on the input side.

The man at Caradon was not really being unhelpful. Legally, you are
required to be competent to work on gas systems, and if you were doing
it for someone else, trained and a CORGI member. If he felt that you
were not competent, then it is not unreasonable for him not to help
you get into trouble.

If you are 100% certain that you know what you are doing, then the
question of competence arises. A qualified fitter would have made
the checks on the supply and the burner pressures.

Another factor in all of this is whether the flue and the ventilation
provisions are OK. If either are insufficient or blocked, then the
appliance will be generating carbon monoxide, and I am sure you are
aware of the effects of that.

As a next move, I would call Transco and get them to come and check
the meter and pressure. There should not be a charge for that.





..andy

To email, substitute .nospam with .gl
  #5  
Old March 15th 04, 07:33 PM
SledgehammerSteve
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Default boiler / central heating problem - main burner weak and cuts out

Thank you very much for that advice Andy.
I will get in touch with Transco asap.
Thanks again
Steve

(I now fully appreciate theres a lot more to fixing boilers than replacing
the thermocouple)
  #9  
Old March 16th 04, 12:32 PM
SledgehammerSteve
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Default boiler / central heating problem - main burner weak and cuts out

5 minutes after reading Andy's first message, I rank Transco (9.00pm).
2 hours later one of their guys was round checking the gas pressure at the
meter - It turned out to be 12mb (should have been 20mb) so youre dead right-
there is a supply side problem.
1 hour later there were 3 guys digging up the supply pipe in the front garden.
(past midnight now).
When they cut through the supply pipe there was virtually no hiss coming out
at all.
They then stuck a flexible rod down the supply pipe towards the road.
It hit a blockage where it joins in the main supply that runs under the
pavement.
Now its 1:00am in morning - said they'd be back next morning to dig up the
pavement.
End of story.

Thanks very much for everyones help, advice and suggestions.
-I must remember to think of the system as a whole, and not concentrate on
most obviously affected part. And the real cause of a problem your
looking at can be miles away. (priceless lesson)

Thanks again - (hope someone finds this thread useful in future and saves
themselves a sunday taking the boiler burner to bits)

Steve
 




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