combi in a cupboard

Dont know about your specific boiler but the one weve got installed is a sealed unit and therefor does not require any ventilation if place in a cupboard. just have to make sure approp distances around the boiler are met "stuart noble" be in a cupboard providing the "ventilation requirements" (which it

"stuart noble" be in a cupboard providing the "ventilation requirements" (which it doesn't

The "ventilation requirements" mentioned are given by BS 5440 Pt 2.

As it is a room-sealed boiler with a fan-assisted balanced flue, the requirements are just for ventilation of the cupboard to the room. (All room-sealed devices in a "compartment" still need this.)

The figures you give look a bit high, 40 sq inches for each of the high and low level openings (1100mm2 per kW) but the bit extra won't harm it

In message , The Question Asker writes

Thanks for that. Can only find references to it by various manufacturers from which it would appear that, providing there are certain clearances round the boiler, no ventilation is required. Still like to see the full details of the above if anyone can oblige. TIA

"stuart noble"

Many thanks. Seems slightly dotty in that it doesn't define "confined". A small, draught free room could be considered a confined space. Worcester Bosch say that, with the required clearances (and they're not all that generous), no ventilation is required. If they and Saunier Duval are both interpreting the same BS requirements, one of them has to be wrong

Part J of the Building regs gives all the details you need.

It is available from

Hope this helps.

Sorry, just realised it's an oil boiler in which case you need to look at page 48 onwards. Page 49 has details of the requirements for various installation configurations. You need 1100mm2 per KW for internal venting and 550mm2 for external venting, again at both the top and bottom of the compartment.

"stuart noble" small, draught free room could be considered a confined space.

Trouble is, I believe the term "compartment" is defined in the separate British Standard 6798 ("Specification for installation of gas-fired boilers of rated input not exceeding 70 kW net").

IIRC from when I looked at it, a compartment can be quite a large volume and would include most cupboards.

Potterton say of a similar gas-fired appliance:

"A cupboard or compartment used to enclose the boiler must be designed and constructed specifically for this purpose. An existing cupboard or compartment may be used provided that it is modified for the purpose. Details of essential features of cupboard/compartment design including airing cupboard installations are given in BS6798 and BS5546 and should be complied with."

Overall Potterton appear to agree with Saunier Duval re. the requirement. But I agree with you. It is dotty -the whole thing. I'd tend to bet against Bosch being correct here.

However, I fail to see the logic for it, unless it is an extra fail safe measure in case the fan fails but the supply to the burner isn't cut due to a problem with the air pressure switch etc. I can understand why there might be a need for it with devices that have pilot lights, but the requirement applies to **all** RS devices - I have seen it explicitly spelt out in the manual of a boiler with electronic ignition.

You were right the first time, the Thelia is a gas-fired appliance. Thrown by my link to the Oil-fired site?

Thanks. Nice to know the laws we are bound by can be tracked down eventually :-) .

I think I'm going to ignore these regs. It sounds like they haven't got round to re-drafting them to cover modern boilers. Whoever fitted the thing obviously had his own interpretation of the rules. He knocked one 4" hole in the outside wall and fitted a non-return plastic flap.

In message , The Question Asker writes

AIUI the info to be found in BS5440 is superceded by the Manufacturers Instructions. The Manufacturers have the option of designing the boiler to release less heat through its casing thus avoiding excessive temperature rise within the confined space. This is often done by improving the inner casing insulation. Of course if the particular manufacturer doesn't wish to do this then BS ventilation requirements apply. If you are in any doubt then you should consult the manufacturer then you must follow the info you are given.

A word with the manufactruers may be called for. Most but not all modern boilers require little or no additional ventilation.

Heverthe default which might just be the case here is 5cm^2 per kW at low level and high level from outside air which is a little over 100cm^2 This is likely more than what a 9"x9" terracotta air bricks provides!

If the cooling is from a room then the vents are doubled. Again two large plastic grills EACH at high and low level.

I don't know this model but if it's not room sealed then even more about the same ventilation as for cooling is required at low level for combustion.

I would be surprised if this is the case. The manufacturers have to comply with the relevant British Standards in order to get the appliance certified. There may be several ways of doing this, and the standard will generally lay down the requirements rather than the way of achieving it. However, if the standard mandates air flows as it does, then it is not for the manufacturer to modify them, they have to meet those standards. They can have higher recommendations, but not lower ones. All the manuals I have seen ( including Saunier Duval and Worcester Bosch) have a section that with a list of British Standards which must be complied with during installation- including BS 5440 and 6798.

Looking again at a Worcester manual, it appears that BS6798 may provide an alternative way of meeting standards by providing enlarged clearances. This may explain the difference.

You will find if you study the various options available that many newish, room-sealed boilers are designed and built with the express intention of allowing installation within a confined space i.e. an unventilated compartment. Having obtained type approval (GC Number or CE approval) before launch onto the UK market these are quite legal to install without compartment ventilation. I believe it is highly unlikely that any UK manufacturere would lightly print "wrong" requirements in their installation and maintenance instruction documentation if only because of the financial implication of liabilty claims by the hundreds of installers who find themselves being hauled over the coals by zealous authority.

My copy of BS5440 is filed away in the office at the moment but have you actually "read" what you are asserting or are you making an assumption?

This enlarged clearance allows an airspace between the casing and the surrounding enclosure to allow escape of heat from the exterior of the appliance but cannot be considered to "ventilate" the confined space. The intention is to maintain a harmless surface temperature and keep any control electronics within the boiler casing safe from heat damage. I suggest we agree to differ as I intend to continue to operate to the manufacturers instructions until advised to the alternative by CORGI or a professional and recognised reliable source.