Hole for downlights

[maypen]

Hi guys,
I am fitting some 85mm downlights, but the holesaw i have is 89mm. The downlights have a lip of about 10mm.

1) Does the holes have to be exact
2) what difference will 4mm make

cheers!!

 

[Lectrician]

Yoy can get hole saws of any size.......but if you want to make do - try it on an off cut of plaster board or thick cardboard or something first. 4mm shouldn't make too mush odds - 2mm either side.

 

[ban-all-sheds]

1) They should be as close as possible

2) Possibly nothing, possibly draughts, possibly dust falling out, possibly the lights falling out.

What do the instructions say? Maybe you need a slightly bigger hole to allow the clips to pass through.

Why not get a bit of scrap plasterboard and see how well it works?

 

[maypen]

Cheers guys, i tried it on some hardboard and it works perfectly. Another question though. Does the 2mm gap affect the acoustic and fire rating of the fixture.

 

[gingervit]

of course you have remembered to install fire hoods too???

 

[ban-all-sheds]

Why do you think he needs them?

 

[Taylortwocities]

Don't start that firehoods thread again. Pleeeeeeeeeeeeeeze...

 

[ban-all-sheds]

It just amazes me how many people fit firehoods with (clearly) no idea whatsoever about if/why/when they are needed..

 

[didthathurt]

One reading of this suggests they're not necessary at all in domestic premises where a 30 minute fire resistance is required.
http://www.iee.org/Publish/WireRegs...nstalling_recessed_luminaires_in_ceilings.pdf

 

[Softus]

of course you have remembered to install fire hoods too???

Why would you do that? Is this a flat?

[Edit - oh, sorry - just noticed that b-a-s had this covered]