Fused spur

[redman]

Hi all,

Got another written assignment to do for college & have a few querys.

The instruction sheets says :

"For a two bedroom terraced house,

Install a 300W exterior light with PIR sensor at approx 3.5 metres high, above kitchen window.

The client has just had the house decorated, & requests that there would be no disruption to the interior walls & decor.

Expain how you would approach this installation & what materials you would use."

I reckon I would lift a few floorboards in the bedroom & take a spur from the existing ring or radial circuit, using 2.5mm T&E & a switched FCU.

Then fix the FCU just above the skirting board, & feed the cable behind the skirting board & under the floorboards.

Then drill a hole through the exterior wall from outside into the space under the floorboards.

Then using 1.5mm flex, I would wire behind the skirting again, from the FCU, through the drilled hole, to the exterior light.

This way, it would all be consealed under floorboards apart from the FCU.

Does this sound acceptable ?

Would this be ok for functional switching & isolation ?

Also, as the light is rated at 300W, would it be ok to put a 5A fuse in the switched FCU ?

Hope this makes sense.

Cheers

 

[kme]

OK.

The FCU could go alongside an existing socket; with a 3A fuse. I`d personally probably drill down at an angle, straight through the rear of the FCU ( only feasible if you`re any good at "predictive drilling" i.e. knowing where the bit will exit for any given angle & thickness of wall.

Your idea sounds feasible, except for the fact that you`d need cable running up the wall to your FCU.

KME

 

[mikel]

Perhaps you could include that the building regs now state that outside lighting should not exceed 150 watts (I think it comes under energy efficency, just don't have my books to hand to give you the exact section). Might be worth a few extra marks!!

 

[redman]

Nice one mate,

At least I know im thinking along the right lines.

College keep giving us these installation situations to get us used to designing & using the regs books.

Cheers

 

[NozSpark]

Also dependant on where the cable comes out you may have to install conduit to go up the outside a little.

In which case end box, conduit, saddles, U box, gaskets, lids, screws, a female adaptor and a stuffing gland!

 

[SPECIAL LOCATION]

Functional switching can be confirmed with Table 53.2 on page 117 of Big red!

An FCU is ok for functional & isolation !

As Mikel said I would point out that 300watt halogen bulbs are about to be

or already have been phased out from sale at many typical outlets..

Lower wattage bulb will be more applicable for current wiring & building regs!

Guinness

 

[sparkytim]

Part L1

150 Watt max WITH AUTO CONTROL i.e. PIR, PEC

or Low energy type LAMP ONLY FITTING 40 lumens /watt i think it is

i.e. CFL, PL etc.

 

[spinlondon]

Why not come off the downstairs lighting circuit?

Have the collecge asked for any form of switching?

 

[redman]

Thanks for your help everyone,

Much appreiciated.

Why not come off the downstairs lighting circuit?Have the collecge asked for any form of switching?

College didnt specify which circuit & what switching should be used.

We was just told to refer to the regs books & try to plan the most suitable method.

I just thought id use the upstairs bedroom ring, as this seemed the easiest to access, & use a switched FCU as isolation for any maintenance at a later date.

 

[androiduk2002]

I might be way off the mark here but, should the FCU be at the recommended height of between 450mm and 1200mm after all thats part of BS7671.

3.5 mtrs is quite high up would it be better to take it from the upstairs lighting circuit and come down from the sofit to light fitting with conduit, being a PIR fitting i dont think a switch would be needed.

An FCU could be fitted in the loft with a note in CU would that comply with other regs ?

Not knowing all the regs yet Im just throwing ideas around :innocent

 

[spinlondon]

I think most people would expect a light to be on a lighting circuit. I know they don't have to be, but I think most people would expect it.

Installing an FCU off the upstairs ring would possibly cause distruption to the new decor.

As they've stipulated that the fitting should be above the kitchen window (I'm asuming the kitchen is on the ground floor), not above the bathroom or a bedroom window, then I'd lump it in with the ground floor.

As you intend lifting floor boards to access the upstairs ring, it wouldn't be that much harder to access the ground floor lighting circuit.

If they haven't stipulated any functional switching, then the MCB at the CU will be sufficient for maintenance switching.

If functional switching is required, could it not be outside perhaps with the cables run in conduit and the use of a waterproof switch? This would save there being any distruption to the decor.

 

[androiduk2002]

Some thing else to consider is the excisting installation at 17th regs and RCD protected if not I remeber reading somewhere the addition of an outside light would require the new installation for be RCD protected, but I could be wrong .

 

[redman]

If they haven't stipulated any functional switching, then the MCB at the CU will be sufficient for maintenance switching..

Good point that,

probably be better doing it that way.

If i were to use the downstairs lighting circuit, would it be best to break into the circuit using a junction box, or use the nearest ceiling rose ?

Cheers

 

[redman]

Some thing else to consider is the excisting installation at 17th regs and RCD protected if not I remeber reading somewhere the addition of an outside light would require the new installation for be RCD protected, but I could be wrong .

Not sure,

I`ll have to have a read up about that.

 

[androiduk2002]

Try measuring 3.5 metres up your own outside wall , I would be tempted to come from upstairs lighting circuit and down to light fitting this way no need to lift any floor boards.

 

[batty]

I think most people would expect a light to be on a lighting circuit. I know they don't have to be, but I think most people would expect it.Installing an FCU off the upstairs ring would possibly cause distruption to the new decor.

As they've stipulated that the fitting should be above the kitchen window (I'm asuming the kitchen is on the ground floor), not above the bathroom or a bedroom window, then I'd lump it in with the ground floor.

As you intend lifting floor boards to access the upstairs ring, it wouldn't be that much harder to access the ground floor lighting circuit.

If they haven't stipulated any functional switching, then the MCB at the CU will be sufficient for maintenance switching.

If functional switching is required, could it not be outside perhaps with the cables run in conduit and the use of a waterproof switch? This would save there being any distruption to the decor.

I would disagree with using MCB as functional switch because if light goes faulty which they do customer has no means of isolation apart from switching circuit off.

 

[M107]

Well I'd come off the upstairs lighting with T/E into adaptable box located in loft, then out of the box with FP200 or similar drop out of soffit down to light fitting.

Not for getting to fit rcd/rcbo to circuit.

The college are playing a crafty one with the question with regard to the property, think about the height of the pir (most advise max height of 2.5mtrs). Being a terrace property will the neighbours set the light off when they are in their garden, this then leads nicely onto light levels into next door from a 300watt lamp....advise a new 36watt security type fitting is used (new time guard ones are ok)

It's not just about the materials & installation method

 

[redman]

Well I'd come off the upstairs lighting with T/E into adaptable box located in loft, then out of the box with FP200 or similar drop out of soffit down to light fitting.Not for getting to fit rcd/rcbo to circuit.

The college are playing a crafty one with the question with regard to the property, think about the height of the pir (most advise max height of 2.5mtrs). Being a terrace property will the neighbours set the light off when they are in their garden, this then leads nicely onto light levels into next door from a 300watt lamp....advise a new 36watt security type fitting is used (new time guard ones are ok)

It's not just about the materials & installation method

You may right there,

Ive just been reading the spec for a PIR light on the screfix site,

that says 2.5 mtrs max height.

I reckon the college assignment may be looking for me to come up with a better alternative to comply with regs etc.

 

[spinlondon]

I would disagree with using MCB as functional switch because if light goes faulty which they do customer has no means of isolation apart from switching circuit off.

I agree not ideal. However this is a college question, and using the MCB for switching is allowed by the Regulations.

There is no requirement in BS7671 for outside lights to have RCD protection. There may be a requirement for notification under part P.

It might be, that you would have to use a separate PIR and light fitting, if the height of the light is too great.

 

[Risteard]

I might be way off the mark here but, should the FCU be at the recommended height of between 450mm and 1200mm after all thats part of BS7671.

Building Regulations not Wiring Regulations.