I believe the spirit of the regulation is that at any given time in the
future, there is no combination of light bulbs and or fittings which
could reasonably overload the wiring in the future.
6A is 1500W, or ten 150W bulbs, or 35 odd 40W bulbs. The gibbons who
wired my house reckoned on at best two big rooms per circuit. But I have
standard lamp sockets as well as wall lights and so on, so it was
No. You must allow 100W per fitting so that the cretin that buys your house
doesn't take out the electrics when he decides he prefers that warm glow
(i.e. global warming). If the fittings are only capable of taking low energy
bulbs, then you may allow for the likely output of the fitting. (i.e. an 18W
fluorescent strip fitting could be assumed to draw 18W, not 100W because you
can't shoehorn a 100W GLS into it).
12 fittings is pretty excessive for a lighting circuit anyway. You should
divide into several circuits so that a fault on one doesn't take out all
your lights. Traditionally, one lighting circuit per floor is used. I prefer
a random pattern, so that in the event of a lighting fault, several lights
on each floor, and every other hallway still works. I think it is safer.
Additional point, tiou alos need to guard aghainst the retrofitting of
e.g. 8 2x40W wall lights where a single central 150W bulb used to do the
same job :-)
An increase in ten of the current requirements.
I often wonder how Lawrence and Handy Andy manage all their fancy
Food for thought!
We have upstairs lighting, downstairs lighting.
Just went round and totalled up all the light fittings and came to 1194W,
which is slightly scary.
The uplift of those nice Ring fittings which have 4 * 40w reflector lights
on a single fitting is fortunately balanced by some low wattage bulbs, but I
must be pushing the boundaries of safe lighting.
I am fitting a new ring main anyway, and have spare real estate on my
consumer unit, so I think I will split off one half of this lighting onto
its own circuit.
Shows that you should total up your light fittings each time you make what
seems to be a minor change!
A slightly embarrassed.
Well, not in this universe. 1.2kW on a lighting ring is not a problem.
When you've got 11 light fittings plus all the power sockets in 5
rooms including the kitchen ALL on ONE 5A lighting ring, then you may
well have a problem. It has been known.
Forgive my ignorance but what causes the phase shift then? Even if the shift
isn't caused by these factors surely it can be offset by them. Capacitive /
Inductive effects will still push the current around WRT voltage won't they?
These appliances have negligable phase shift, and are neither capacitive
nor inductive in nature. The low power factor is caused by them only
drawing current at the peaks of the sine wave, so they are powered
entirely from only a small part of the voltage waveform.
Actually, this is such a significant problem because of the number of
such appliances, that the mains sine wave is noticably flattened at
the peaks if you look at it on a scope nowadays.
Ah, things become clearer! So many new devices seem to run using "pretend"
ac (for want of a better phrase). Makes you wonder what kind of trouble
we're heading for. The 3 phase supplies in some factories where I've worked
have looked scary on a scope due to the effects of inverters and dc drives
on the larger machinery.Then they take this crap to run computers and office
equipment. Adding filtering on the input helps but surely they should try to
stop the wave deformation in the first place. Thanks for the info Andy,
New EU regulations limit the harmonic Current distortion allowed
by appliances. Low power appliances are still allowed to be low
power factor, but higher powered appliances aren't. This is relatively
new though, and lots of existing appliances don't conform. Large
industrial users get charged a penalty for low power factor.
Just found a snapshot of the mains voltage waveform I took in our
office a couple of years ago:
which is clearly badly distorted from a perfect sine wave.
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