Extending Lighting

[rantoftheday]

I want to extend a lighting circuit for an extension

The current system is loop in live

Can I take a feed from one of the ceiling roses to a junction box and run all wires to the three new rooms to there?

Compromising of 16 x 50watt downlights plus 1 extractor fan

 

[JamesBrownLive]

unless he goes for LEDs

So how do the building regs deal with situations like this ??

Whilst he is the owner of the property and would know that he needed to use LEDs in order for the circuit to fall within given current limits, if he ever sold it, the next owner might not know or might forget being told. You are then faced with the possibilty of the circuit being overloaded, if the LEDs were replaced by cheaper Halogens.

When making alterations like this, is it not best to base the number of lighting points on a worse case scenario? And if necessary, wire a new circuit?

Cheers

 

[Paul.M]

Back when we had 100w bulbs/luminaries the rule of thumb were applied and we only used to put 11 light fittings per circuit. Now with all the lower watt luminaries on the market, designing a lighting circuit is harder. In this case the op has told us he is installing 16 x 50w, for the fittings he using (im guessing mr16) this is fine. Here's an example for you. I were asked to fit 14 x 35w double bulb mr16 in a shop. Total watts = 980. What happens a couple of years down the line when bulbs need changing? If they replace them with 50w the circuit will be overloaded so I installed 2 circuits to share the load and also to make it idiot proof. These lights are going to be on 8 hours a day, 6 days a week. I a house situation, make it idiot proof. Anyone can change a bulb and overload a circuit but if it needs extending they would need an electrician who would look at the circuits loading and the intended use and make a decision on the facts. This is why I said install a new circuit in this circumstance.

 

[telectrix]

i agree with you paul on running a new circuit, but the argument of what if the customer......... in the future. suppose you install a 32A ring final, socket circuit and work on the basis of 27A for 2.5mm cable. then along comes a cold spell and mr. customer plugs in 4 or 5 3kW heaters???

 

[Paul.M]

i agree with you paul on running a new circuit, but the argument of what if the customer......... in the future. suppose you install a 32A ring final, socket circuit and work on the basis of 27A for 2.5mm cable. then along comes a cold spell and mr. customer plugs in 4 or 5 3kW heaters???

I knew someone would ask a question like that . Tel, I'm the type of guy that asks himself "what if?". This week I'm doing a kitchen rewire, the cooker is only 2kw but I'm using 6mm t&e just in case 5 years down the line they decide to up grade to a double range cooker (besides I've got an off cut just right for this cooker :). We can't protect the customer against their own stupidity all the time but a little bit of common sense in our part could save lifes.

 

[JamesBrownLive]

i agree with you paul on running a new circuit, but the argument of what if the customer......... in the future. suppose you install a 32A ring final, socket circuit and work on the basis of 27A for 2.5mm cable. then along comes a cold spell and mr. customer plugs in 4 or 5 3kW heaters???

That's an easy one to answer...
The way electricity prices are going, he won't be able to afford to plug one in, much less 4 or 5 :nonod:

Back to my original question...

I understand you could go on saying 'what if' ad infinitum, and that you can't regulate for 'user error', I just wondered what most people do when confronted with situations like this.

Cheers

 

[Adam W]

i agree with you paul on running a new circuit, but the argument of what if the customer......... in the future. suppose you install a 32A ring final, socket circuit and work on the basis of 27A for 2.5mm cable. then along comes a cold spell and mr. customer plugs in 4 or 5 3kW heaters???

The primary heat source would have been calculated separately to function properly without 'nuisance tripping'. OK if that broke down and there was a severely cold spell, severe enough to warrant firstly getting hold of (borrowing/buying) and secondly plugging in 4 or 5 3kW heaters in an area covered by one final circuit then there is a chance the breaker would operate if all the thermostats kicked in at the same time.
I would class this as fairly unlikely, in which case in a quick call to an electrician or long and meandering thread on a forum, the customer could be advised they should plug some of the heaters in elsewhere to avoid the protective device operating.

Lighting is a bit different though - you could expect the customer to have most of the lights on at the same time, and I think it's realistic to allow 50W per downlighter or 100W per pendant, partly to allow for modifications.

 

[Paul.M]

Back to my original question...I understand you could go on saying 'what if' ad infinitum, and that you can't regulate for 'user error', I just wondered what most people do when confronted with situations like this.Cheers

And its a great question, can't wait to read what others do. Jamesbrownlive (good name BTW) why don't you start a new thread with this question so the answers can be directed at your predicament and not the op's, he's got his answer tbh.

 

[rantoftheday]

Thanks for all replies.

I understand that a new circuit at the DB would have been the preferred option, but given that the dis board is at the other end of the house from the extension I decided that extending the upstairs lighting circuit, which only had 5 lights (60 watt each) on it.

I took a feed from one of the ceiling of the ceiling roses which was existing to a junction box in the loft, marked the junction box up as "extension lighting" and ran all my cables from there.

The existing wiring is all 1.5 mm T+E, covered by a 6A MCB at the split DB, which I moved over to the RCD protected side.

I think this was the best option in the circumstances.

For the sockets I extended the ring main, which I ensured the integrity of, added 4 dbl sockets and 2 x spurs. This is on a 32A MCB , again covered by a 30mA RCD at the DB

8 x 50 watt GU10's in the bedroom, 2 in a walk in cupboard and 4 in the en-suite bathroom.

I did push for the LED option but the customer almost fainted when I told them the price per unit, despite me advocating the long term energy saving benefits, not to mention the fact you dont singe your hair underneath the LED's

All the lights I installed were fire rated

 

[Paul.M]

Sounds like you've done your home work mate, that's what its all about. You've worked out the load on both circuits and believe that they won't be overloaded. Well done.

 

[rantoftheday]

Thanks Paul M