Baxi Bermuda 552 Back boiler

[Mike2007]

Do I have to change my back boiler or are British Gas trying to make more work for themselves? It needs more ventilation but I do not want to change the boiler or fire for that matter. Yes, its not condensing and has no whistles and no bells attached, but works ok!
View report:
http://i64.photobucket.com/albums/h197/artymike8/Gas3.jpg
http://i64.photobucket.com/albums/h197/artymike8/Gas2.jpg
http://i64.photobucket.com/albums/h197/artymike8/Gas1.jpg

Where can I get a new one from old stock?

 

[Agile]

I find it difficult to understand from the BG report why they consider its at risk.

They appear to be saying it needs 90 cm² but it already has 100 cm².

Perhaps one of the BG guys can explain?

These boilers are not very efficient ( 55% ) and need room ventilation which causes cold draughts and need regular servicing otherwise they quickly become very dangerous.

My view is that if it really needs more ventilation then that can be provided but its better replaced soon with a wall mounting condensing boiler which will be about 93% efficient.

Tony

 

[bobthebender]

Put in the correct size vent and sort out whatever is wrong with the flue terminal.
What do they say is wrong with the flue ?
Is it lined ?

 

[giblets]

That's odd, I didn't think it was permissable/possible to carry out a combustion test on a bbu.

Why don't you just increase the ventilation to the required amount?

 

[Mike2007]

I will increase the ventilation. A reasonable site for a combi is a pain as my house a strange design, as in tiny kitchen/ bathroom (above it) and 4 bedrooms. Other properties in the row have it in the already small bathroom!
There is the attic room, where the cylinder presently is what would water circulartory problems be like?

 

[gas_man_gaz]

by the looks of ya paperwork the vent he has listed (in the top box) is the one he recomends ya get installed and in the bottom box he's made a note of the ventilation requirement for ya boiler. he's not trying trying to make work as iam a bg engineer and ive been briefed that the regs are changing soon and if ya havnt got 90% of the ventilation requirement we have to list it as "at risk"

just get a bigger vent put in!

 

[gas4you]

I agree with Tony about the air vent size. The stadium 5" vent will give 70cm2 free air with the draught excluder fitted or 100cm2 with it removed.

An average BBU is around 20 Kw heat input, so deducting the 7Kw for adventicious air = around 13Kw, 13 * 4.5 = 58.5cm2, so the stadium even with the draught excluder fitted is adequate.

What terminal have you on the chimney? I would have thought that this should be NCS at the most from what you have posted, without seeing the terminal.

 

[Mike2007]

I agree with Tony about the air vent size. The stadium 5" vent will give 70cm2 free air with the draught excluder fitted or 100cm2 with it removed.

An average BBU is around 20 Kw heat input, so deducting the 7Kw for adventicious air = around 13Kw, 13 * 4.5 = 58.5cm2, so the stadium even with the draught excluder fitted is adequate.

What terminal have you on the chimney? I would have thought that this should be NCS at the most from what you have posted, without seeing the terminal.

You know the chimneys are high up and I am really not sure I can see a gas cowl up there, just nets? Should it definitely have to have a cowl?

 

[gas4you]

Yes it should have a gas terminal which is connected to the s/s liner.

 

[Mike2007]

So it needs 190 cm² of free air? Maybe should not have bought new draught excluders recently!
Back to a combi. Would a combi in the attic room where the cylinder is pose a functional problem in any way. That is, low pressure on the DHW and CH pumping?

 

[nickso]

a 552 bbu needs 89cm2 per the manufacturers instructions.

if you have 100cm2 ignore his advice. if you dont then get at least 90cm2 and get whatever is wrong with the flue sorted. im betting the flue annulus isnt sealed.

rightly or wrongly BG policy is its up to the engineer to determine if its at risk when you have a flue and vent defect on the same appliance. some will put it at risk with 2 ntcs to cover their arses. some wont.

 

[nickso]

I
20 Kw heat input, so deducting the 7Kw for adventicious air = around 13Kw, 13 * 4.5 = 58.5cm2,

erm i would use a 5 instead of that 4.5

 

[gas4you]

5 is for gross and 4.5 is for nett. It was only a rough calculation for guidance.

 

[namsag]

Dave you are forgeting the fire would take up the adventatious ventilation and also converting from gross to net.. Manufacturers instructions i have ask for 90cm2 or 14inches2.
And its 5cm for net..

Mike2007 stick a picture of your vent so we can see it cheers

 

[gas4you]

Dave you are forgeting the fire would take up the adventatious ventilation and also converting from gross to net.. Manufacturers instructions i have ask for 90cm2 or 14inches2.
And its 5cm for net..

I never realised the fire front is 7Kw

And yes I have got my nett and gross muddled up

But 100cm2 would still suffice.

It only becomes AR if there is less than 90% of the required ventilation.