downlights and joist

[james king]

hi all i know there are maunfacuer distances but how many of u actully go as close to joinst as possible. i have never heard of a joist catching fire befor. any one put one touching a joist ?

 

[Deleted member 26818]

Not seen one actually touching, but have seen it where the joist was cut awayto allow room for the fitting.

 

[mayfair]

10 downlighters yesterday managed to hit 4 of the metal plasy board supports, only just bit hit them all the same. But its evenly spaced and the client is happy

 

[james king]

i too have seen one cut away a few actyully but they were firerated with a cap on is this safe?

 

[IQ Electrical]

i too have seen one cut away a few actyully but they were firerated with a cap on is this safe?

The limits on joist-notching (for cables/containment) are 0.125 X joist depth.

This is NOT for luminaires that can present a fire risk by dissipated heat.

 

[james king]

so will 50w gu10 down light be a fire risk?

 

[IQ Electrical]

so will 50w gu10 down light be a fire risk?

Absolutely, check out 422.4.2 quite stringent requirements.

 

[james king]

so could u put a fire cap over them to prevent the joist burning?

 

[PC Electrics]

Also check out downlighter research on the ESCs website. Quite a bit of concern there for poorly installed units causing a fire risk.

Downlighters and fire safety : Electrical Safety Council

 

[IQ Electrical]

so could u put a fire cap over them to prevent the joist burning?

That's not really the purpose of fire-rated downlights and/or firehoods, they are to prevent the propagation of fire rather than limit heat transfer.

 

[james king]

ok... so would LED lamps prevent the risk of fire so therefor u could install the DL closer to a joist

 

[IQ Electrical]

ok... so would LED lamps prevent the risk of fire so therefor u could install the DL closer to a joist

Yes, they should have an 'F' symbol inside an inverted triangle to show that they burn cool and can actually be mounted on combustible materials.

 

[KEVINDOE]

I have also seen a 100mm x 100mm ceramic wall tile screwed to a joist , with a GU10 down lighter sitting 5mm away from the tile,

 

[mogga]

Not doing domestic much this isnt a problem Iv come across much But when fitting challis type fittings in a plasterboard celing Iv hit the celing support grid a few times (even though the celing fixers had lighting layout Worst case theyv had to build a support ring As for joists and "notching" in thats a deffinite NONO both due to weakening joist and the heat dissapation as IQ says firehoods and firs capped fittings arent meant to disipate heat but to prevent spread of fire they are also NOT meant so you can cover fitting with glassfiber(or other) insullation the amount of that Iv seen scortched above commercial fittings where they have pin hole tiles with blanket above

 

[nickblake]

A fire rated down lighter protects the ceiling where you cut the hole from spread of fire ,when you install down lighters if there is no ceiling then measure the joists mark on a piece of paper then when the ceilings are up transfer the measurments to the ceiling this way you dont hit the joists ,it a existing installation use a stud locator to identify the joists and mark the ceiling where they are , bungalow pop into the loft and measure the joists and transfer to the ceiling you should never cut out a ceiling joist or install to close to the joist ,and yes there have been fires caused by this have a look at the lnk PC electric put up very intresting