Hi all
I've got a 2 gang light switch (if gang is the right word), one switch controls one light the 2nd the other light.
The wiring is normal (Common to L1) but there's a small piece of wide 3" which connects from one common to the other common. Is this some sort of loop in wiring but done at the switch?
I'm not sure what it can do but to provide power to another light.
Any comments?
The light fittings have a common neutral already inside them and the switching only makes and breaks the live feed to them for control of the lights. You are correct in thinking that the looped over switches (common to common) are only being used to supply a live feed to both light fittings from the one live supply.
Could this be a competent person? (Part P and all that)
"John" wrote in news:A2AId.655$ snipped-for-privacy@newsfe1-gui.ntli.net:
Knows enough to think and ask - should pass applied darwinism
mike
But does he understand, a three year old can ask....
Bzzzzzzt! "Part P"?
Who said anything about this being a dwelling?
I would agree about competency, but surely we all have to learn to become competent. Asking on here is one way of doing this.
Is the cable a triple and earth? If running a switch drop for say the sort of fitting than has two settings - say three bulbs where you can have one, two, or all three with both switches, this would save running two TW&E cables. But you'd need to share the live with both switches.
It's unlikely to save cable for two separate lights, though.
This was done by a certified electrician. we had the switched changed from one wide of the wall to the other (easy work but I was away), he basically copied what was already there.
There are 3 cables, all TW&E, all the reds go into the switch, all the blacs go into a terminal block, ditto for earth. Wire is also 1.5mm2 not 1.0mm2.
I was only examing the switches to check the wiring for a new outside light I'm putting in.
What I also found out is that the downstairs light circuit, is -
1) all using 1.5mm2 wire 2) more spurs running than the cast of Rawhide - ie. light understairs is a spur, which feeds a FCU spur which powers the alarm (low wattage (it's a wireless system) but doesn't sound too clever. 3) The downstairs light ring is in 'theory' overloaded, so the outside light will have to powered by the upstairs light circuit but with the switch downstairs! Is this a problem?
Apologies to anyone who's read this under another thread.
-- The downstairs light ring is in 'theory' overloaded, so the outside light will have to powered by the upstairs light circuit ring but with the switch downstairs! Is this a problem?
Also I noticed a lot of 30amp juction boxes on my 5 amp light circuit - is this also a problem? (they were done before we moved as part of a garage conversion and have been working fine for 10 years or so).
Thank you
Apologies to anyone who's read this under another thread.
On Sun, 23 Jan 2005 11:08:58 -0000, "MP" strung together this:
You'd be better off apologising for sticking a sig seperator in the middle of your post.
The lighting circuit will be a radial, not a ring so there aren't tecnically any spurs on the circuit, as such, IYSWIM.
There's also the thing of diversity, which says you won't have all the lights on at once so you can effectively go 33% over what you think your maximum circuit current is limted to.
No, unless they're all badly terminated.
"Lurch" wrote | There's also the thing of diversity, which says you won't have all the | lights on at once so you can effectively go 33% over what you think | your maximum circuit current is limted to.
Surely there is *no* diversity allowed on a lighting circuit - precisely because it is quite likely that all lights will be on at once - especially in the bog-standard one-light-in-the-middle-of-the-ceiling per room types of installation?
Owain
No problem.
All sounds fine.
No. Personally, I prefer rooms to be randomly assigned to circuits, so that in the event of a fault, a nearby room will have light. There is an alternative, though. If all the light fittings are happy with it (standard pendant fittings are fine, but SES/SBS are not), then you can usually replace the MCB with a 10A.
Christian.
On Sun, 23 Jan 2005 23:38:38 -0000, "Owain" strung together this:
There is, it was 66%, I don't think it's changed.
Well, can't say as I've ever overloaded a lighting circuit personally, even with going over 6A on a few occasions. In an ideal situation you would leave the diversity out of it rather than loading all the circuits up to the max.
AFAICU from a quick read of the OSG, there's no 'diversity' allowed in the design of the lighting circuit itself: its Table 1A shows 'current demand to be assumed' as 'current equivalent to the connected load, with a minimum of 100W per lampholder' (the latter methinks will get updated Real Soon Now to take account of non-BC low-energy fittings - 2D, 4-pin, and the like, where it's pretty reasonable to claim that there's little likelihood of the 10-25W loomin' air being replaced with a
100W-tungsten-capable BC lampholder). So 14 lampholders is your lot, roughly speaking...However, you *are* then OK to assume diversity in calculating the load each lighting circuit contributes to the whole installation - and that's where you remember the 66% figure from (that's for an individual household install, with higher proportions for commercial (90%) and small-hotels-boarding-houses-and-similar (75%)). As with all applications of diversity, it's not always a get-out-of-jail-free card - if there are particular circumstances on a given circuit, e.g. 500W of kitchen downlighters switched as one, that's already half of the 960W with 66% of the 6A nominal represents...
I just got lost here :-( Surely diversity allows an increase in the total loading as it assumes not all will be turned on ? So a 6A nominal current gives about 1500W which is then multiplied by 1/0.66 to give 2250 as the maximum lighting on the circuit.
The circuit itself should be designed for running under full load, and the protective device must be chosen so its nominal rating is greater than that full load will draw, while being less than the rating for the cable selected (derated by all relevant factors). You do *not* design in an 'overload' on the individual lighting (or other) circuit.
You *do*, though, get to recognise that full load on the lighting circuit will be 'rare' - so although the circuit itself must be safe under its full load, the contribution to the total *installation* load which this circuit makes is taken, in normal circumstances, to be a mere
66% of its total current demand.
. ^^^^^^^^
Delete "or other". Diversity /is/ allowed within many other types of circuit - e.g. the standard (OSG Appendix 8) circuits are based on a maximum floor area served, not on a full 13 A at each socket! The 'rules' for diversity within individual circuits are set out in Table 1A of the OSG, together with its footnotes. Another example is that that a domestic cooker circuit does not have to be designed for the full load current (FLC) of the appliance(s) connected - a design current of 10 A plus 30% of the remaining FLC[*] is allowed.
[*] FAOD this means Ib = 10 + 0.3 * (FLC - 10) amps, where Ib is the design current.The point is not so much that full load on the lighting circuit will be rare, but that it will rarely coincide with simultaneous full load on several other circuits. The 66%, BTW only applies for domestic installations, higher figures are stipulated for non-domestic situations. Diversity /between/ circuits at a consumer unit or dis-board is dealt with by Table 1B in the OSG.
It's a common mistake to confuse the two diversity tables, and the cause of similar thread topics here in the past.
Thanks for the correction, Andy!
Aye - off to wrap head in cold wet towel (and turn on the Golf's sidelights just to watch *both* numberplate lights being on - today's d-i-y 'triumph'!)...
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