Downlighters

[spiidey]

Do the downlighters in the below need a box around them, and if so, what material (plasterboard)?

Or is the square that's cut out of the rockwool sufficient?



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[Tjs]

They should have a heat hat on top of it or a fire rated fitting.

 

[securespark]

Bloody hell, you're not having much luck, are you?

Are these guys affiliated to a trade body?

 

[PrenticeBoyofDerry]

The light should have ventilation, the manufacturers instruction could offer recommendations on what this should be, I usually offer 150mm all way round, the problem then becomes it compromises the insulation you have fitted.
Dependant on what is above this area, could determine whether the fitting should have additional protection.

 

[Taylortwocities]

They should have a heat hat on top of it or a fire rated fitting.

Why do you think that?

 

[spiidey]

I should have added that the new ceiling (and therefore the light for the fitting itself) will sit flush along the timber battens that sit approx 3 inches below where the bottom of the insulation lies.

Does that give enough clearance from the insulation for the light, bearing in mind the other end (top) of the light will sit approx level with the insulation, and we've cut the hole that you can see out of the insulation (directly above where the light will sit)?

 

[PrenticeBoyofDerry]

Again "Downlights" must be given ventilation, you cannot encase them within thermal insulation. You should not either install them close to combustible materials such as timber.
Again, the manufacturers instructions that came with the product, should offer you guidance on the installation of these and clearances.

This may help you understand (included is leaflet link at the bottom of the report)
http://www.esc.org.uk/industry/product-safety/product-testing-screening/downlighters/
The other thing to consider is, that cables routed within thermal insulation also require a de-rating factor. Normally not an issue to lighting circuits rated at no more than 6A. But if there are any other power circuits such as sockets, cooker, shower, heating etc.. they will be effected.

 

[spiidey]

Again "Downlights" must be given ventilation, you cannot encase them within thermal insulation. You should not either install them close to combustible materials such as timber.
Again, the manufacturers instructions that came with the product, should offer you guidance on the installation of these and clearances.

This may help you understand (included is leaflet link at the bottom of the report)
http://www.esc.org.uk/industry/product-safety/product-testing-screening/downlighters/
The other thing to consider is, that cables routed within thermal insulation also require a de-rating factor. Normally not an issue to lighting circuits rated at no more than 6A. But if there are any other power circuits such as sockets, cooker, shower, heating etc.. they will be effected.

Thank you for your prompt replies.

Would you suggest building a plasterboard box around the downlighters? Or given that they will be installed with the light itself 3 inches below the bottom of the insulation (but the top of the light sitting level with the insulation) do we have enough ventilation already?

Also, we do have a number of electric cables running through the insulation (we're using rockwool RW5 acoustic insulation). What does the de-rating factor mean and what is required?

 

[riveralt]

Would you suggest building a plasterboard box around the downlighters? Or given that they will be installed with the light itself 3 inches below the bottom of the insulation (but the top of the light sitting level with the insulation) do we have enough ventilation already?

I know the rules are different in Scotland but seriously you need to get someone in who knows what they are doing electrically - because if this and your previous post is an example of their electrical competence then you are putting yourself and your family in danger.

For recessed downlights you must follow the manufacturers instructions - which in broad terms requires a minimum space of 100mm above and around the lamp. If you cannot achieve that then you can only fit surface mounted lights.
By the way if this is a flat roof you will probably be breaching other building regulations regarding insulation requirements.

Also, we do have a number of electric cables running through the insulation (we're using rockwool RW5 acoustic insulation). What does the de-rating factor mean and what is required?

Any competent electrician would know what de-rating means and how to apply it given that cables run through the insulation.
You can run cables through insulation but because of the potential heat generation your have to roughly half the cables current carrying capacity or double the size of the cable.
While standard cable sizes may be okay for most lighting circuits (although you appear to using Halogen lights) for socket or shower circuits this can cause significant problems.

 

[PrenticeBoyofDerry]

Would you suggest building a plasterboard box around the downlighters? Or given that they will be installed with the light itself 3 inches below the bottom of the insulation (but the top of the light sitting level with the insulation) do we have enough ventilation already?

They require ventilation all the way around them.
Building plasterboard shield will do to protect them from the insulation and create a gap, but ventilation is important.
There are number of hoods here, that may help you.
http://www.tlc-direct.co.uk/Main_Index/Fire_and_Smoke/Fire_Cover_Downlight/

Also, we do have a number of electric cables running through the insulation (we're using rockwool RW5 acoustic insulation). What does the de-rating factor mean and what is required?

There are number of different ways and methods that cables can be routed, the method of that route and the addition of thermal insulation, often means that a factor has to be applied to the cables current carrying capacity, as this is reduced as heat cannot be dissipated to the same effect, as it would if the cable was in free air or clipped direct.
Electrical cable is rated to a maximum current it can safely carry. This rating will depend on the type of cable or flex being used and it's CSA (circumference surface area) this is the maximum, if no de-rating factors apply.

There is a links here, that is worth browsing over:
http://www.tlc-direct.co.uk/Book/4.3.3.htm
Take a look at the - Thermal insulation correction factors
Also this
http://www.elecsa.co.uk/Technical-L...ting/Current-Carrying-Capacity-of-Cables.aspx

 

[spiidey]

There are number of different ways and methods that cables can be routed, the method of that route and the addition of thermal insulation, often means that a factor has to be applied to the cables current carrying capacity, as this is reduced as heat cannot be dissipated to the same effect, as it would if the cable was in free air or clipped direct.
Electrical cable is rated to a maximum current it can safely carry. This rating will depend on the type of cable or flex being used and it's CSA (circumference surface area) this is the maximum, if no de-rating factors apply.

There is a links here, that is worth browsing over:
http://www.tlc-direct.co.uk/Book/4.3.3.htm
Take a look at the - Thermal insulation correction factors

Does this basically mean that if the electric cables are re-routed through thermal insulation, we can use less appliances, less frequently, than before the thermal insulation was installed, to ensure we don't run the risk of the cable burning out / fire?

 

[PrenticeBoyofDerry]

delete

 

[PrenticeBoyofDerry]

Does this basically mean that if the electric cables are re-routed through thermal insulation, we can use less appliances, less frequently, than before the thermal insulation was installed, to ensure we don't run the risk of the cable burning out / fire?

It basically means, with the installation of thermal installation, that it is likely that this has compromised the current carrying capacity of the cables routed within this.
This could be considered a potential fire hazard, the only correct means of preventive action would be to, route cables away from thermal insulation or increase the CSA of cable.

 

[riveralt]

Does this basically mean that if the electric cables are re-routed through thermal insulation, we can use less appliances, less frequently, than before the thermal insulation was installed, to ensure we don't run the risk of the cable burning out / fire?

From this and your previous posts I take it you are installing this electrical installation - if so you really need to stop and get someone in who knows what they are doing about because from this reply you really have no idea what you are talking about electrically.
You have not mentioned what type of circuit(s) you are creating but clearly if appliances are involved you need to go right back to the beginning and properly and SAFELY design these circuits.

 

[spiidey]

Does this basically mean that if the electric cables are re-routed through thermal insulation, we can use less appliances, less frequently, than before the thermal insulation was installed, to ensure we don't run the risk of the cable burning out / fire?

From this and your previous posts I take it you are installing this electrical installation - if so you really need to stop and get someone in who knows what they are doing about because from this reply you really have no idea what you are talking about electrically.
You have not mentioned what type of circuit(s) you are creating but clearly if appliances are involved you need to go right back to the beginning and properly and SAFELY design these circuits.

We've got someone in to do the installation for us - I wouldn't go near electrics as, you have pointed out, I know nothing about them!

There are no "new" electrics - simply a re-routing of 2 electric sockets.

The contractor has installed rw5 rockwool:-

http://www.rockwool.co.uk/products/...(formerly known as RWA45, RW3, RW4, RW5, RW6)

And this is around a number of electric cables (the 2 sockets mentioned above and a number of other cables that come from the fuse box).

Is this rockwool different from thermal insulation in that it doesn't create the need for the cables to be de-rated, or does it in fact require a higher de-rating of the cables given its density?