4" ventilation Extractor Fan in ceiling regulations

Andy From Sligo

I find it strange about the building regulations for putting a 4" electrical extraction fan in a ceiling of a property and not in the wall.

This might never happen or be so rare that it was taken into account but if a fire (say electrical fire) ever broke out in a bathroom and the extractor fan was on, could that not suck the flames up into the loft space through the white plastic flexible exhaust pipe then set the loft alight?

Another rare thing but I suppose it could happen in extreme circumstance, if the actual 4" fan sparked and caught alight or overheated and went up into the flexible pipe and then up into the loft space - I know that the newer fans have a non resettable built in thermal cut out in the coil of the fan motor to stop overheating should the fan motor seize but what happens if the spark/overheating happens with the electronic timer or humidity board - that would only be protected with a 10 or 20amp mcb in the fusebox because they are normally wired up to the lighting circuits.

Any thoughts?

mikeoneilly

The best way to vent is straight up through the ceiling and roof.

You make a good point about the penetration of the ceiling fire barrier- I'd like to hear the answer to that from someone more qualified.

On the issue of fusing the fan control board .You will see that the instructions say to fuse at 3 amp which is generally not done.So you have a valid concern there

BryanF

Bathroom mech vent will be CE marked and IP65 rated,

In a domestic setting the plasterboard ceiling generally gives the required fire rating. The small percentage wise core/vent pipe to the external is deemed acceptable once certain separating distances from windows & adjoining properties are complied with as set out in the building regs.

Gumbo

In theory, in a 3 storey house, it should be boxed with Gyproc fireline board or similar as it passes vertically through the building.

Handsandtools

There's no problem in bathroom, as there's no need for spesific fire safety, but hallway and kitchen may need fire rated ceiling. In this case best practice is to fix fire boards straight to the joists and than lower the ceiling, so you can use the void for ventilation and other services. As long as the void, where vent penetrates fire ceiling, is sealed it must be ok for standard dwelling, as long it is within one dwelling.
There's minimum requirements for fire safety, so if you look for minimum, than you must be ok with standard vent and plasterboard.
Than there's another point to consider, distance from last step on stairs till exit doors.

metricspaces

Do the regulations specify exactly where in the ceiling the extractor fan must be? Does it have to be dead center?

Gumbo

metricspaces wrote: »

Do the regulations specify exactly where in the ceiling the extractor fan must be? Does it have to be dead center?

Your designer will calculate that.

metricspaces

kceire wrote: »

Your designer will calculate that.

Can they choose the location on the ceiling, with the only requirement being that it is on the ceiling?

Andy From Sligo

I have had two 4" fans with built in humidity sensors - they never come on when there is steam in the room! - thought it maybe a faulty one so fitted another one in its place (snip) and again dont turn on .. unless it was just a bad batch what else could it be? - have turned the adjusting screw on the electronic board both ways.

(sorry about large picture, i couldnt see how to reduce it for boards)
[snip]

BryanF

Andy
please don't derail the thread, start your own in future.

Also, please read to forum charter regarding naming companies thanks

Andy From Sligo

BryanF wrote: »

Andy
please don't derail the thread, start your own in future.

Also, please read to forum charter regarding naming companies thanks

ooops - apologies !