BAXI Bermuda problem....

[stulew]

OK.... The story so far... " Along time ago in a galaxy far far away" (Not sure if Orpington in Kent counts as a different Galaxy but I'm sure it is not of this world.. MMmmm)
I get asked by a friend of mine to service his back boiler because "It has been over a year since it's last Service" not quite sure why I wasn't asked to service it a year ago, but I suppose it is a free country isn't it..
So I go down there and strip it down and let my Henry hoover and my soft brushes have a field day, and to be honest the sooting on the heat exchanger was awful but I just put it down to the fact that 12 months since it's last service was probably more like 108 months and the poor old thing was just choked up. I cleaned everything thoroughly and then did the standing and working pressure and it was exact 22 mb standing and 11mb working. So I reassembled it all and left with a whole load of sooty dustsheets and looking more like one of the black and white minstrals than Stuart from Surrey.
He calls me today saying the heating is now not working, so off I trundle again and take off the fire and to my dismay the cast iron is in a really bad state again, the soot is all over the heat exchanger.
So gentlemen I need a bit of help with this one..
1... The Standing pressure is fine
2... The working presure is as it should be.
3... The flue liner is pulling a smoke match and pellett with no probs.
4... There is lots of ventilation..
5... The flame does very occasionally appear to be poking it's head over the top of the Heat Exchanger.
I am wondering (Is it possible) that even though the gas valve is sending the right volume of gas to the burner, is it possible that this has some cracks.
It is Friday Night but I would appreciate some help on this one..
Thanks

 

[B.O.B DOLE]

I am wondering (Is it possible) that even though the gas valve is sending the right volume of gas to the burner, is it possible that this has some cracks.


your asking us your the one that serviced it did you check the burner only you can answer if ther is cracks in it

OK.... The story so far... " Along time ago in a galaxy far far away" (Not sure if Orpington in Kent counts as a different Galaxy but I'm sure it is not of this world.. MMmmm)

sounds to me your not of this world

 

[stulew]

Yes BOB I did have a look at the burner, It looked OK to me, and the flame seemed to be behaving as it should, there were no flames leaving the burner and going off at strange angles, and they were also nice and blue.

 

[Mikeyboy]

Linting in the primary injector , is the normal cause of incomplete combustion .

 

[stulew]

But Mikey, the flame picture is very good, the flame does occasionally climb up the H/E so I would gather that that means it is to high. but there are no signs of visible cracks and the injectors look very clean.

 

[Slugbabydotcom]

The flame does very occasionally appear to be poking it's head over the top of the Heat Exchanger.

Has someone been cleaning the injectors with big pointy things ?
This would result in too much gas getting through, more than the burner was designed to aerate hence the big flames

 

[chrishutt]

standing and working pressure and it was exact 22 mb standing and 11mb working

Do you mean the inlet pressure is 22 mb while the boiler is firing, and the burner pressure is 11 mb? My understanding is that standing pressure is when there is no gas consumption (this figure is not really relevant) and working pressure is the same as inlet pressure when boiler firing.

Also you should check the gas rate via the gas meter. And what about checking the primary air ports of the burners? These are all standard procedures that any Corgi person should know well. You really need to brush up your act (assuming you are corgi reg).

 

[bobs yer uncle]

I agree with chris, I'm a little confused about stulew reference to working pressure being 11. I take it he means burner pressure. With reference to the problems my thought are....
1. Stripping the burner out completely, often the mesh within the burner is
partially blocked.
2. Performance testing the combustion gases.
3. Turning down the BP based on the results of the PT. You would be
amazed the effects that reducing the BP can have. Start at the lowest
within range and work up.

If the flame is reaching the HE then the flame picture is plainly wrong????? The flame is (probably) chilling on the cooler HE surface and this causing incompete combustion.

Your comment .. There is lots of ventilation.... but is the ventilation correct. revised unsafe situation etc. I have seen x venting causing combustion problems.

Bob

 

[ollski]

Is the annular space sealed?, you could be getting secondary flue pull under certain atmospheric conditions. Presume the spillage test with the fire connected up was convincing?

 

[Agile]

I seem to recall that the flames should NOT be TOUCHING the heat exchanger because of the risk of excessive cooling causing incomplete combustion, sooting and CO. Its AT RISK !!!

Before you reduce the burner pressure do a gas rate at the meter.

Then reduce the burner pressure until the flames do NOT touch the HE ( after desooting again ).

Surely "Working Pressure" is the pressure at the inlet to the appliance when its working, unless its been qualified as the "working pressure at the meter" which should be within 1 mB of the WP at the appliance.

Its all this which makes the rest of us have to redo ACS every five years when people forget basic things.

Tony

 

[corgiman]

as tony says "chilling" aint good, must say that burner pressure may not be the problem, what about the burner injector has that been eroded??

 

[kevplumb]

check the gas rate

 

[stulew]

Thanks for the replies gents. Sorry about the confusion.. yes I checked the pressure at the appliance without it working just to check the amount of gas pressure before doing anything else, I then attached my gauge to the other test nipple on the Honeywell Valve and with the appliance working there was a reading of 11Mb which backs up the setting highlighted on the data plate. And yes I am registered Chris. I am going back tomorrow to have a look at this. The Gas rate was showing a Heat input of 58,000 BTU/hr and the flue liner puled a match and then a smoke pellett with no problems at all. I will strip out the burner and inspect the injectors and then if that seems clean and free from lint then I will turn down to 43,000 BTU'hr and see how high the flame is then.

 

[corgiman]

Good luck mate

lets us know what the upshot is wont you?

 

[stulew]

I will of course return with my findings tomorrow night..