"Additional" ventilation on Baxi boiler

10 Oct 2006
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United Kingdom
My house boiler recently failed, requires new gas valve. However upon inspection we have been advised that there is insufficient ventilation for the boiler as we require "ventilation on an external surface".

I find this odd as:

1) the boiler has been serviced annually by the same company since we moved in (three years)

2) until we removed internal doors the only viable "external surface" would be the front door.

The boiler is situated in a dedicated cupboard in the hallway (which as natural air venting front and back into the hallway and kitchen).

Boiler IS very old however:

Baxi FS 501 OF (GC # 4107723)

Do I need to install forced air ventilation to one or more doors, can I just install a non-forced air vent to one or more (i.e. louver type), or is this "hokum"?
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Is your gas fitter on the gas safe register?

If he is he should be giving you correct advice which I advise that you follow.

Your manufacturer instructions will give you all the information you need regarding ventilation for your open flue appliance. which again needs to be followed.

Here's an extract..

The room in which the open flue unit is situated requires an air vent which should be direct to outside or to a room which itself has an air vent direct to outside

Thanks for the info.

Doesn't state that it requires forced air venting in the linked room(s) so I'll propose to install a simple one inplace of the cat flap. :LOL:

EDIT: Well, a little confused. The engineer "suggests" a Black Hole Ventilator through an external wall "which must be fitted prior to re-enstatement of the heating system".

However, once I suggested fitting a vent on the cat flap...they seem amenable to this (though they are to refer back to me with what they feel is vent capacity required).

...which confuses me as a Black hole ventilator system is significantly more involved AND has higher output than anything I could fit within the space of a cat-flap!

Obviously I need to locate the output rating for this old boiler so I can comply with the venting need.
vent to outside 57 cm2.

low compartment vent 353 cm2.

high compartment vent 176 cm2.
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Thanks for the reply again.

I have installed a passive vent to external with a rating in excess of 100cm2 free flow so that should be more than sufficient.

However, guess the task now is to save up the cash to have a new boiler installed! This old thing, whilst keeping this house nice and warm (and would most likely do so for a medium sized school! ;) ) won't keep going for ever and as a non-condensor type really needs replacement.

Thank you again for your input.

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