Porch downlights (with crummy diagram)

[tambourineman]

Hi there,

I'm wanting to install three downlights in the wooden ceiling of a fairly substantial front porch, controlled by a PIR detector. The lights and the PIR will be recessed into the ceiling. The interior of the porch roof shows no sign of moisture or leakage and has been vacuumed to remove 80 years of dust/muck.

The downlights I'm using are GU10's rated at 35 watts max, IP 65 and are F-marked for insertion into combustible material. The PIR has a switching capacity of 2000 watts, and is rated as IP 44.

I have chosen to take a spur off the ring main (from a junction box) to a switched fused connection unit. The FCU will provide functional switching. 2.5 T&E from junction box to the FCU, 1.0 T&E thereafter to the PIR, and from the PIR to the three lamps. The total length of 1.0 T&E cable from FCU to Lamp 3 will be about 5-6 meters.

I've installed single lamps off fused spurs before (security floodlights), but never more than a single lamp - and that's where I'm confused. Can someone take a look at the wiring diagram and give me an idea if the proposed wiring of the lamps is correct?

Also, am I right using 1.0 T&E for the load, or should I be using 1.5 T&E? I'm assuming three 35w lamps (total of 105w) at 240v will demand less than half an amp (105/240=0.43), making 1.0 T&E appropriate?

I'm also aware that technically this would be a notifiable installation.

Any advice would be appreciated.

Thanks,
W

Untitled

• tambourineman
• 17 Oct 2010
• 1

 

[sparkwright]

Looks ok.

 

[tambourineman]

Cheers pal.

Just to be clear... when using this daisychaining method of connecting the lamps, the final lamp has just a single T&E cable that connects it to the penultimate lamp? There is no T&E cable that 'returns' to the PIR detector?

 

[PrinceofDarkness]

You've evidently put some thought into this little project of yours. There's nothing wrong with your proposal, except: why do you think that this is Notifiable ?


Lucia

 

[sparkwright]

Cheers pal.

Just to be clear... when using this daisychaining method of connecting the lamps, the final lamp has just a single T&E cable that connects it to the penultimate lamp? There is no T&E cable that 'returns' to the PIR detector?

Last light has one T&E cable.

 

[PrinceofDarkness]

The PIR simply feeds your 'daisy chain' from the one end. There's no need for a return cable from the final light fitting to the PIR.....


Lucia

 

[tambourineman]

You've evidently put some thought into this little project of yours. There's nothing wrong with your proposal, except: why do you think that this is Notifiable ?

Lucia

Based on similar threads I've read on this and other forums, I'm led to believe that any electrical work done to the exterior of a house is notifiable/Part P covered (a porch technically is outside).

Am I wrong in that assumption?

 

[PrinceofDarkness]

Yes, you are mistaken in that belief. A covered porch attached to a dwelling is not considered by the B.Regs to be 'outside'.

Go ahead, throw your unnecessary notification fee away, if you must....


Lucia.

 

[tambourineman]

Ah, bless you.

Thanks for the info!

 

[tambourineman]

Went ahead and installed this design this morning, but I'm having a small problem.

Lamp 3 constantly blows immediately after switching the FCU. Sometimes it manages to survive until the FCU is switched for second or third time, but it eventually goes. I've gone through 3 cheapo GU10s and they're definitely blown (tried them in other spotlights in the house). Lamps 1 and 2 work fine and dandy.

The first time Lamp 3 blew, it actually blew the 3 Amp fuse as well. At the moment, a new 3 Amp fuse is managing to keep Lamps 1 and 2 functional.

Any ideas what might be causing this?

 

[ban-all-sheds]

The only thing I can think of that would cause one of the lamps to fail like that is a poor connection, probably with the lamp base, resulting in arcing.

Can you hear anything when you turn it on? Do the lamp pins look OK?

 

[riveralt]

What were your continuity and (after linking out the pir) the insulation resistance readings?

Have you snagged a cable somewhere causing a short circuit.

 

[ban-all-sheds]

Would that make a lamp fail?

 

[londonboy]

I would try one of the bulbs from fitting number 2 or 3, possibly you have a bad batch of bulbs?

 

[riveralt]

Would that make a lamp fail?

Not sure, but something is clearly wrong if both the lamp(s) and fuse have failed.

You have to be very unlucky to have a number of lamps go at the same point only.

Either there is a short circuit somewhere and/or the circuit has been wired incorrectly - possibly between lamp 2 and 3. The diagram shown only gives an outline of the wiring not the specifics - so is the fcu wired correctly, same for the pir and first light on the circuit - do the second and third lights take there power from the switch live on light 1?

Visual check first - then testing next.