Vent requirements for gas fire.

[b33k34]

We've just had a gas fire fitted in the living room and understand there is a requirement for a vent. it's a victorian house which is far from sealed and I intend to get a carbon monoxide alarm. We're most of the way through fitting a secondary wood floor and the plan was to put a vent into it to the underfloor cavity (we've recently made sure all the air bricks to the cavity are clear).

So two questions:

1) Given the general draughtiness of the house do we really need the air vent?

2) if yes, how big. The figure of 100cm3 was mentioned but our local hardware stores don't carry stock and the minimum order requriements mean I'd look online. However the vents i've found (on andyplumb.co.uk) are measured, strangely, in inches. I'm presuming that 100cm3 does not equal a vent meauring 10cmx10cm but relates to the size of the holes.

[Brian Reay]

You need to allow for someone "draught proofing" it later.

Last time I checked (about 7 years) it was 16 sq in, which is about 100cm^2.

The area is the "free flow area" (ie area of holes) not the overall vent dimension.

Don't muck around with this, do it right.

[Dave Fawthrop]

| We've just had a gas fire fitted in the living room and understand | there is a requirement for a vent.

The manual for the fire should give the area required. Insist that the fitter give you the manual.

[b33k34]

OK, any clues on suppliers - i've only had a quick search but it didnt deliver me anything useful

[Uno Hoo!]

What is the consumption of the gas fire? Not all gas fires require vents - only those above a certain consumption level.

When I had an art-deco cast iron fireplace fitted a few years ago the inset 'decorative' gas fire required a vent and the fitter installed one by cutting a slot into the floorboards and fitting a grille. It was terrible - the draught coming up from the vent was like a hurricane - and freezing in winter! In fact I would say that the amount of cold air coming into the room from the vent was greater than the warm air coming into the room from the fire. In the end we placed a piece of carpet over the vent and just made sure that the lounge door was open a bit when using the fire. Never had any problems. We recently had a completely new contemporary fire installed (Brilliance 'slab' fire) and the fitter stated that the input was border-line for having a vent fitted. I questioned him about the need for a vent and he pointed out that the requirement for vents was only made in recent years and prior to that no-one fitted them! As I was installing a laminate floor I just removed the vent grille, placed a thin piece of aluminium sheet over the slot, and laid the laminate flooring over it. Again the fire works fine, no evidence of fumes coming into the room, and with the lounge door left slightly ajar, plenty of fresh air to feed the fire. If you are going to fit a vent into the underfloor cavity then I would think strongly about ways of preventing draughts - on windy days it will be horrendous!

Kev

[Grouch]

Whoever installed it should have checked and advised what ventilation was required; if they didn't I'd be very suspicious as to their qualifications to do such a job.

[powerstation]

Further to that it should not have been installed without correct venilation.

[Andrew]

What fire did the guy install? not all fires need extra ventilation. Are there any other appliances in the same room?

[Brian Reay]

Sorry, no. Last time I looked into this was just to check a fire already installed was OK- not actually installing one myself.

Really, I do advise you look into this very carefully. Check what the fire needs, then make sure that the room is so supplied.

Did the person who fitted the fire not check all this?

I noticed someone commented about draughts such vents can cause. Yes, they can cause draughts but they also stop you being killed, so don't skimp!. You can always position the vents so that the draught isn't drawn across the area you sit!

[b33k34]

The fitter did check, advised us 100cm3. The floorboards that were down at the time a) had up to 4mm gaps between them, and b) had a hole about 10cm x 10cm where a first, aborted, attempt had been made to fit the fire by another fitter so there was more than enough ventilation. There was no point in him insisting on a vent being added because he knew we were about to lay a secondary floor which would change the situation.

Hence my question:

1) in a draghty house is it still necessary (not to comply with the regs but to be safe) 2) where can i buy a suitable vent? (and if they're measured by external diameter rather than cubic airflow what size vent do i need?)

[John]

You can buy a variety of suitable vents from your local branch of Plumb Centre Round, rectangular and brass finish floor ones.

[Ed Sirett]

The manual will state the facts - this is the ultimate decider. If the manual does not state the vent requirements then:

If the fire has an input gas rate of less than 7kW then no purpose provided vent is needed PROVIDED the flue draws (which is will unless it's blocked).

If more than 7kW then 100cm^2 will be needed. If more than 14kW (which some display type models could be) then I would need to look some standard docs - however that would be very big if it's a grate burner.

Attempts to rewrite the regs based on pleading to special circumstances are a bit like trying to argue that you can bypass some of the electric regs "because you're only use lights".

[b33k34]

point taken - it was only in response to some comments i'd seen on here.

So can you point me to an online supplier (with the item i need - brass rectangular preferably) as the plumbing suppliers within walking distance were no help.

[fred]

In article , [e-mail] writes

Do you need one after all?, 7kW input is an absolutely huge fire.

[Ed Sirett]

In the world of grate burners 5-14kW is the typical range from the smallest to the largest models.

For display types 12kW is quite normal.

Inset fires and radiant outset types would typically be 4-7kW.

[b33k34]

Ed Sirett wrote: In the world of grate burners 5-14kW is the typical range from the

It's a Gazco Evolution VFC convector 22" which has an input of 12kw. manual says it needs 30cm2 of ventilation -

[Ed Sirett]

That's reasonable - the required ventilation would be 22.5cm2 if it were a 12kW boiler, but fires tend to need more ventilation to keep the chimney well aired and dry.