boiler ventilation

[Fred]

Hi,

I have an oil fired boiler with a balanced flue. It's in the kitchen and all the valves, pump, etc are alongside it. "the boss" thought it looked ugly and wanted it all hidden away, so I have made a box of veneered chip around it.

The box is slightly higher than the boiler and about work top height. I have made a lid from the same sheet of chipboard. The box has a front and rightthand side but no back because I couldn't get behind the boiler due to pipes etc.

There is no lefthand side as the lefthand side butts against the kitchen units; these obviously have a gap under the plinth and behind the units so heat can escape from the box into these spaces.

Now we've been running the boiler like this and everything has been ok, but the manual states that if you run it in a "compartment" you need to add a vent at the bottom and a vent at the top to allow air to circulate so the boiler does not overheat.

The manual says each vent should have a free area of 232cm^2 or 36in^2 which seems absolutely massive! The area required to "feed" an open flue boiler is half that!

Many catalogues I have looked at don't give you the free area, only the overall size of the louvre, which is useless. I've found BES states the free area but only sells large sizes in white; I would have liked brass or as a second choice brown plastic (to match the wooden finish of the box).

My worry is that by the time these are fitted, there will be more vent than box! Any idea who sells big brass louvres or any idea what to do next?

TIA

[Ronald Raygun]

Instead of metal or plastic louvres, have you considered setting a

*wooden* louvred panel into either the front or side? This panel would be large, taking up most of the area of the front or side. Such panels are often supplied for use as kitchen unit doors.

It'd then just be a matter of staining/varnishing/painting it to match your veneer. Or more likely to contrast tastefully with it. Be sure to involve the boss in the cosmetic aspects, or there'll be hell to pay!

[John Rumm]

will need a couple of those... they do a non hooded version as well)

[Baz]

I think you will find that the Free Area is Square cm and Square Inches. Not 232cm Square or 36 Inches Square.

36 Square inches is 6 Inches x 6 Inches. 36 Inches Square would be 1296 Square Inches.

Baz

[Ronald Raygun]

That's what he said. "cm^2" doesn't mean "cm square", it means "square cm".

That's not what he said. Otherwise he would have had to use brackets, like this: "(232cm)^2", because, in conventional notation, exponentiation (denoted by "^") binds more tightly than multiplication (denoted here by juxtaposition).

Hence "36in^2" means "36(in^2)", not "(36in)^2".

Indeed, and 232 sq cm is 15 and a bit cm x 15 and a bit cm, and 232 cm squared would be nearly 54000 sq cm.

Luckily there is a sanity check built in, so one could tell, if one had any doubt, that one interpretation is wrong and the other right. It is that 6 inches is the same length as about 15cm, but 1296 sq in is not the same area as 54000 sq cm.

I think you'll find that, in context, the OP reckons that 72 sq in is "massive", and that his statement that there would be "more vent than box" was not serious but just an exaggeration.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Fred saying something like:

A two-brick size louvre would do, top and bottom. Or make two

3"x12"minimum.

[Fred]

Thanks. This is curious. These have 119cm^2 free air flow but BES sell part 18449, which is 241 mm x 241 mm and yet only has 88cm^2 free air flow. I thought they were the same part since they had the same overall dimensions but that would not explain the different air flows; perhaps the openings in the Ironmongery direct part are bigger?

The problem is that, as you say, I would need two, and then when you consider I would need two at the top and two at the bottom, that becomes four, at which point I think it will look rather silly.

[Fred]

Thanks. I think the one John found is two-brick sized 24cmx24cm? And yet on paper that only has half the flow required. I'm wondering whether to ignore the manual and just fit one of these top and bottom. It's got to be better than nothing hasn't it.

I'm not convinced they will do a great deal for convection since they are going to be on the pump and valve side, so away from the boiler anyway.

It hasn't blown up yet without any ventilation.

[Fred]

Thanks. That's a good idea. It may be the way forward. Thanks.

[Fred]

Ronald is right. According to the manual I would need four of the

10"x10" louvres that John Rumm found. When you consider I would fit these to a side that is roughly 3'x4' I think they take up a massive proportion of the side. There would strictly speaking be more wood than vent, I was exaggerating, but four big vents seem "massive" to me.

[Ronald Raygun]

Or dispense with louvres (which have the unfortunate property that the "free flow", being the sum of the areas of the individual louvre slots, is very much less than the overall area of the whole louvre fitting. Instead you could make up a grille, using some sort of chicken wire, held by a nice wooden surround made from the kind of battens one makes picture frames from. That way your "free flow" will in effect be equal to the area of the cutout.

The other thing in your favour is the fact that your boiler is not strictly in as snug and tightly enclosed "compartment" as the manual writers have in all likelihood envisaged, but the air space in your box is open to the space under and behind the adjacent kitchen units.

With the bigger air volume this gives, there will be quite some air circulation within that space, and this reduces the need for external ventilation. It could even eliminate it.

[Fred]

That's what I had hoped. Certainly nothing has gone wrong yet without vents fitted. Sadly the manufacturer hasn't replied to my emails. The diagram in their manual shows their illustration of a compartment being floor to ceiling height. Why would anyone hide their boiler behind a wall?! If they think a room-height compartment needs ventilation, I would think that a box a fraction of that size would need it even more. I wonder whether to compromise and fit some ventilation as that would be better than nothing rather than the four louvres the manual suggests. Thanks.