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SantaUK
 
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Default Lghting Circuit Question

Yes. Its only using 11 watts so you can have 109 of those bulbs

--

SantaUK
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"Nearly Done!" wrote in message
om...
A lighting circuit is supposed to have a max of about 1200W or 12 x
100W bulbs. If you were to change all of the bulbs to the low
wattage(?) ones, eg 11W, would this mean you could have more bulbs on
the same circuit?

Cheers!



  #2   Report Post  
Andrew Gabriel
 
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In article ,
"James Salisbury" writes:
"SantaUK" Aye Right!! wrote in message
...
Yes. Its only using 11 watts so you can have 109 of those bulbs


Not quite so, some have poor power factor and what happens if somone puts
some normall bulbs in?


It is recommended you allow 100W min per lampholder, but you
have to use common sense. Certainly, you can't assume that
all lampholders will always hold only compact fluorescents.

--
Andrew Gabriel
  #3   Report Post  
The Natural Philosopher
 
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Andrew Gabriel wrote:

In article ,
"James Salisbury" writes:

"SantaUK" Aye Right!! wrote in message
et...

Yes. Its only using 11 watts so you can have 109 of those bulbs

Not quite so, some have poor power factor and what happens if somone puts
some normall bulbs in?


It is recommended you allow 100W min per lampholder, but you
have to use common sense. Certainly, you can't assume that
all lampholders will always hold only compact fluorescents.



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
reasonable.



  #4   Report Post  
Christian McArdle
 
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Default Lghting Circuit Question

A lighting circuit is supposed to have a max of about 1200W or
12 x 100W bulbs. If you were to change all of the bulbs to the
low wattage(?) ones, eg 11W, would this mean you could have more
bulbs on the same circuit?


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.

Christian.


  #5   Report Post  
The Natural Philosopher
 
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Default Lghting Circuit Question

Christian McArdle wrote:

A lighting circuit is supposed to have a max of about 1200W or
12 x 100W bulbs. If you were to change all of the bulbs to the
low wattage(?) ones, eg 11W, would this mean you could have more
bulbs on the same circuit?


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.



Yes, agreed.

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
lighting...


Christian.







  #6   Report Post  
Nearly Done!
 
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"James Salisbury" wrote in message ...
"SantaUK" Aye Right!! wrote in message
...
Yes. Its only using 11 watts so you can have 109 of those bulbs

--



Not quite so, some have poor power factor and what happens if somone puts
some normall bulbs in?


James,

What's poor power factor? Does this mean that an 11W bulb may be
higher than 11W? If so,how much by?

Cheers!
  #7   Report Post  
David W.E. Roberts
 
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Default Lghting Circuit Question


"Christian McArdle" wrote in message
. net...
A lighting circuit is supposed to have a max of about 1200W or
12 x 100W bulbs. If you were to change all of the bulbs to the
low wattage(?) ones, eg 11W, would this mean you could have more
bulbs on the same circuit?


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.

Christian.


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.
Dave R


  #8   Report Post  
Rick Hughes
 
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"Christian McArdle" wrote in message
. net...
What's poor power factor? Does this mean that an 11W bulb
may be higher than 11W? If so,how much by?


The current and voltage normally rise and fall etc



AFAIK - power factor does not have to be taken into account for domestic
lighting installation.





  #9   Report Post  
James Salisbury
 
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Default Lghting Circuit Question


"Rick Hughes" wrote in message
...

"Christian McArdle" wrote in message
. net...
What's poor power factor? Does this mean that an 11W bulb
may be higher than 11W? If so,how much by?


The current and voltage normally rise and fall etc



AFAIK - power factor does not have to be taken into account for domestic
lighting installation.

If you are going to push it to the margin then you do need to be aware of

the pitfalls I have a lamp in front of me, it is marked up as
20W 220-240V 175mA, that == 40VA max

the circuit would have to provide the 40VA




  #10   Report Post  
Frisket
 
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"Andrew Gabriel" wrote in message
...
Unfortunately in the case of a compact fluorescent (and many electronic
appliances), the low power factor is not due to inductive or capacitive
phase shift, which means it can't be corrected by simple addition of
capacitors or inductors.

--
Andrew Gabriel


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?
TIA, Richard.




  #11   Report Post  
N. Thornton
 
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"David W.E. Roberts" wrote in message news:bgdilv$nkj12$1

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.



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.


Regards, NT
  #12   Report Post  
Andrew Gabriel
 
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Default Lghting Circuit Question

In article ,
"Frisket" writes:

"Andrew Gabriel" wrote in message
...
Unfortunately in the case of a compact fluorescent (and many electronic
appliances), the low power factor is not due to inductive or capacitive
phase shift, which means it can't be corrected by simple addition of
capacitors or inductors.


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?
TIA, Richard.


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.

--
Andrew Gabriel
  #13   Report Post  
Frisket
 
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Default Lghting Circuit Question


"Andrew Gabriel" wrote in message
...
In article ,
"Frisket" writes:
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?
TIA, Richard.


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.

--
Andrew Gabriel

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,
regards, Richard.


  #14   Report Post  
Andrew Gabriel
 
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Default Lghting Circuit Question

In article ,
"Frisket" writes:

"Andrew Gabriel" wrote in message
...

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: http://www.cucumber.demon.co.uk/bagmains.jpg
which is clearly badly distorted from a perfect sine wave.

--
Andrew Gabriel
  #15   Report Post  
Frisket
 
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Default Lghting Circuit Question


"Andrew Gabriel" wrote in message
...
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.


Yeah, but many of them get round the pf by switching in and out large banks
of capacitors which only adds to the interesting shape of what used to be
sine-waves. Spikes of up to 30kv seem pretty common (although of short
duration) but even low-ish values of 3-500v sat on the peak for 5mS can
bugger up some expensive gear.


Just found a snapshot of the mains voltage waveform I took in our
office a couple of years ago:

http://www.cucumber.demon.co.uk/bagmains.jpg
which is clearly badly distorted from a perfect sine wave.

--
Andrew Gabriel


Nice! I suppose it'll be handy if you ever need a square wave for testing
purposes ;-)
Regards, Richard




  #16   Report Post  
Christian McArdle
 
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Minor nit -- that's actually a power factor of 1. PF = W / VA

Of course. That's what I said wasn't it? ;-)

Christian.



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The Natural Philosopher
 
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Rick Hughes wrote:

"Christian McArdle" wrote in message
. net...

What's poor power factor? Does this mean that an 11W bulb
may be higher than 11W? If so,how much by?

The current and voltage normally rise and fall etc



AFAIK - power factor does not have to be taken into account for domestic
lighting installation.



Thats because bulbs are essentially resistive loads.

Low energy ones probably are not, but they are so much less power
anyway...it doesn'tr matter.








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