Two electrical wiring questions

34degrees

I read on a ecssa newsletter that the maximum number of lighting points allowed on a circuit is ten. Points include each downlighter.
Is this not very unrealistic? I mean I would have thought that you could install as many as you like aslong as you didn't overload the 10 amp MCB.
10 x 50 watt downlighters seems like a huge waste of capacity on the circuit.
Is there any good reason for this rule.

Second I was under the impression that NYM-J was suitable for use outside, however I have seen manufacturers of this cable state in their catalogues that it can only be used outside if protected from direct sunlight. Can any sparks confirm that NYM is used outside as standard without special sunlight protection.

Any help appreciated.

2011

I mean I would have thought that you could install as many as you like aslong as you didn't overload the 10 amp MCB.

I would agree. For example some LED lights are rated at only 2 Watts, so clearly it would not make sense to apply such a rule in this case. I would never attempt to put 10 500W halogens on one circuit, but I would be happy with 30 2 Watt lights on one circuit. Common sense must prevail.

I was under the impression that NYM-J was suitable for use outside

It is.

I have seen manufacturers of this cable state in their catalogues that it can only be used outside if protected from direct sunlight

You are correct.

I found this:

"NYM-J is a VDE approved, solid conductor, 300/500v gray PVC insulated and jacketed installation cable. These cables are suitable for use in, on and under plaster, benton, brickwork and concrete. NYM-J cables should NOT be used in the direct laying of shaken, vibrated or compressed concrete. Outdoor usage is only possible as long as the cable is protected against direct sunlight. Usable in open air in dry, damp and wet environments."


I have never seen NYMJ cable damged from sunlight. I have seen it with PVC/PVC many times.

Stoner

34degrees wrote: »

I read on a ecssa newsletter that the maximum number of lighting points allowed on a circuit is ten. Points include each downlighter.

.

I agree, the max is 1000W/circuit, 10 lights per circuit is an old rule, unless things have changed in the last set of regs (i.e within the last few months) you can have for example 20 number 50Watt downlights on one circuit, but not more (20x50W=1000W=max load)

enmac

34degrees wrote: »

I read on a ecssa newsletter that the maximum number of lighting points allowed on a circuit is ten. Points include each downlighter.
Is this not very unrealistic? I mean I would have thought that you could install as many as you like aslong as you didn't overload the 10 amp MCB.
10 x 50 watt downlighters seems like a huge waste of capacity on the circuit.
Is there any good reason for this rule.

Second I was under the impression that NYM-J was suitable for use outside, however I have seen manufacturers of this cable state in their catalogues that it can only be used outside if protected from direct sunlight. Can any sparks confirm that NYM is used outside as standard without special sunlight protection.

Any help appreciated.

I haven't come across this requirement before and as far as i'm aware its not in the latest edition of wiring rules (or the previous edition)

When they refer to a circuit do they mean the wiring beyond the switch ?

- This would make more sense as most domestic switches are rated at 6 amps and this would also tie in with stoners comments about 1000w max.
(mind you I'm not too sure where stoners 1000W/circuit came from - I don't think this is specified in the rules either)

NYM should not be used in direct sunlight but even ETCI seem a bit confused with the issue.
They have stated the following in one of their guides:

'cables to outdoor luminaires should be NYM type where exposed to the weather. Sunlight damages PVC insulation'

This gives the impression that its OK to expose NYM cables to sunlight which is not correct.

2011

When they refer to a circuit do they mean the wiring beyond the switch ?

No, I do not think so. I would not think that this is would be the definition of a circuit.

This would make more sense as most domestic switches are rated at 6 amps

I would not think so. As we all know a light fitting could have a rating of anything from 1W to 1000W. That makes such a rule meaningless.

However Stoners approach is a far better one as it gives a guideline that ensures that the cable is not overloaded regardless of the number of light fittings.

'cables to outdoor luminaires should be NYM type where exposed to the weather. Sunlight damages PVC insulation'

This gives the impression that its OK to expose NYM cables to sunlight which is not correct.

You are right, this caused a lot of confusion for me.

davelerave

obviously 'the circuit' is from the protective device and rating of switches within the circuit is appropriate to load being switched.:D

2011

'the circuit' is from the protective device and rating of switches within the circuit is appropriate to load being switched.

That would be the way I would see it too.

enmac

OK so where does these requirements of 10 points per circuit or 1000watts per circuit come from ?

or is this just a guidline for domestic installations and from whom ?

davelerave

10 points /100watt standard light fitting=1kw was the old rule afaik.

2011

I think the 10 points per circuit was a guideline from the days that every light fitting was a 6" pendant and people could buy 150W bulbs for them. At this time there would normally be only 1 light per room too. I would guess it was felt then that 10 lights per circuit would be a good balance.

1000W per circuit is also just a recomendation that I have heard a few times. If you use it then nothing will be overloaded and there is room on a circuit for future expansion on the same circuit.

.G.

enmac wrote: »

OK so where does these requirements of 10 points per circuit or 1000watts per circuit come from ?

or is this just a guidline for domestic installations and from whom ?

Annex 43a of the third edition.

"Radial final circuits for lighting equipment in domestic or similar situations

Recommended maximum number of points per circuit:10"

enmac

thanks for clearing that up guys

I see they've dropped the 10 point recommendation from the latest edition

2011

I see they've dropped the 10 point recommendation from the latest edition

Really? It is good to see that they are moving with the times.

I would like to see them lift the ban on using the MK masterseal sockets as outside sockets. Only the commando type are allowed at present. The poblem with the commando type is that when used on a domestic premesis there are no appliences with a suitable plug!



The MK sockets are very well made and are rated IP65.

enmac

2011 wrote: »

Really? It is good to see that they are moving with the times.

I would like to see them lift the ban on using the MK masterseal sockets as outside sockets. Only the commando type are allowed at present. The poblem with the commando type is that when used on a domestic premesis there are no appliences with a suitable plug!



The MK sockets are very well made and are rated IP65.

They're allowed under the new rules for domestic premises- so long as the enclosure is IP54

2011

They're allowed under the new rules for domestic premises- so long as the enclosure is IP54

That is great to hear, and about time too.

Thanks enmac, I am not up to speed with the new regulations. I think they will be in force next September, is that correct??

Stoner

correct , new regs due in September.

SparKing

with regard to NYM-J being exposed to sunlight I have seen The sheath on the cable go hard and brittle with direct exposure to sunlight on shopfronts and when being ran to exterior air con and refrigeration units so its lifespan is reduced when exposed to UV. SWA would be better or just place them in a conduit/trunking still see it outside all the time, T+E outside is unforgiveable though

2011

SWA would be better or just place them in a conduit/trunking

You are correct, but if you are going to put NYMJ in conduit or trunking then you may as well save youself a fortune and put PVC or PVC/PCV in the trunking/conduit.

T+E outside is unforgiveable though

I agree, but I see it everywhere even on new builds.

Bruthal

enmac wrote: »

I haven't come across this requirement before and as far as i'm aware its not in the latest edition of wiring rules (or the previous edition)

When they refer to a circuit do they mean the wiring beyond the switch ?

- This would make more sense as most domestic switches are rated at 6 amps and this would also tie in with stoners comments about 1000w max.
(mind you I'm not too sure where stoners 1000W/circuit came from - I don't think this is specified in the rules either).

Well the circuit refers to the entire number of lights and switches connected to the 10 amp MCB. The 6 amp rating of the switch is not going to be subjected to the entire number of lights on the circuit usually, so if there was 1000 watts of lights, they might be divided over a number of switches, living room, kitchen, dining room, hall etc. So each switch would usually only have from 60 to 3 or 400 watts.

I thought i`d seen or heard something of the 1000 watt limit myself for lighting circuits. Its good practice anyway not to have large amount of lighting points on a circuit i`d say.

davelerave

robbie7730 wrote: »

Well the circuit refers to the entire number of lights and switches connected to the 10 amp MCB. The 6 amp rating of the switch is not going to be subjected to the entire number of lights on the circuit usually, so if there was 1000 watts of lights, they might be divided over a number of switches, living room, kitchen, dining room, hall etc. So each switch would usually only have from 60 to 3 or 400 watts.

I thought i`d seen or heard something of the 1000 watt limit myself for lighting circuits. Its good practice anyway not to have large amount of lighting points on a circuit i`d say.

i would divide a premises into zones where the lighting load is small,for ease of maintenance and avoidance of blackout.

Bruthal

davelerave wrote: »

i would divide a premises into zones where the lighting load is small,for ease of maintenance and avoidance of blackout.

yes 2 good reasons exactly why id say its bad practice to have lots of lights on one circuit even though they might be well within the circuit limit wattage wise.

homewardbound11

Hi,
I was looking for some multicore for future lighting in the attice space and purchased 7 core nymj.
Are these allowed as there are 6 numbered black and one earth.
I was told in CEF that they were for lighting circuits but read elsewhere their use are in 3 phase circuits.

Any thoughts there, regards,

michael999999

your probably safer to get a electrician to do it for you

M cebee

homewardbound11 wrote: »

Hi,
I was looking for some multicore for future lighting in the attice space and purchased 7 core nymj.
Are these allowed as there are 6 numbered black and one earth.
I was told in CEF that they were for lighting circuits but read elsewhere their use are in 3 phase circuits.

Any thoughts there, regards,

for up to 5-core -cables have to be correct colours

for 6-cores or more - cores can be numbered but 'neutral and earth' have to be marked at terminations by tape etc.


afraid i don't know too much but that's in the rules anyhow,covered by I.S. EN 60448