halogen light and lighting circuit

I would like to connect a halogen up lighter with a dimmer control to a lighting circuit. However, the up lighter has a 500W bulb (yes I know this is expensive to run!) and I am concerned about the load on the lighting circuit.
The rating info on the dimmer switch has two sets of figures with one set, I assume, referring to the min and max wattage of the bulb stated as 60-500W. The other set refers to 60-300W which I assume refers to the rating of the dimmer control itself.
If this is right this would explain why the light came with a 5A fused plug, because if the load of the whole light fitting was based just on the bulb rating then the max load would be 2.1A (500/240) and surely a 3A fuse would have been sufficient.
However, if the dimmer switch is rated at 300W then the max load of the light would increase to 800W (3.3A).
The lighting circuit currently has a max load of 400W (1.6A) and therefore installing the light still leave a total max load of under 5A. As this is protected by a 6A circuit breaker would this be OK.
If this is OK is there any problem with the light not having the protection of its own separate 5A fuse as I would cut off the plug and wire is directly into the circuit.
The switch for the light would be a standard wall switch and am I also correct in thinking that these switches are rated at 5A.
Any comment gratefully received.
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geoffr wrote:

I don't understand that.
Note that dimming halogen lights results in them becoming even more inefficient in terms of lumens per watt. If you need to dim it, why not just install smaller lamps?

The dimmer circuit itself will consume negligible current, however the light may have been supplied with a 5A fuse becase a 500W bulb will have a high switch-on surge current.

Is that actual load or calculated load? You must allow a minimum of 100W per point, so if you have 10 x 40W bulbs that must be considered to be 10 x 100W i.e. 1000W and the circuit is practically fully loaded.

Subject to the design load of 100W min per point.

Shouldn't be from that point of view. How will you be connecting the light to the permanent wiring?

Should be
Owain
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Thanks for your reply.
Owain wrote:

I understand what you are saying but its case of using what we already have. Also the light will only be used on an occassionally basis so hopefully it wont have too damaging effect on our electricity bills!

Its the actual load, so what you are saying that you should allow 100W for each lighting point in doing any calculation irrespective of what the actual load is?

There is an old lighting point that was used for lighting an alcove. The actual connection will be via a ceiling rose which I can hide behind some pannelling.
Thank again for your reply.
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geoffr wrote:

You must allow 100W or actual load if greater, yes.

If it's a screw connection it must remain accessible, and I'm not sure that ceiling roses are permitted other than ceilings, because they can give access to live parts without use of a tool. Also check that the "old" lighting point is earthed.
Owain
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Owain wrote:

Which if you are 6' or over, and live in a modern house, means all roses give access to live parts without a tool regardless of where they are! ;-)
--
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John.

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John Rumm wrote:

>> because they can give access to live parts without use of a tool.

But think of the childruuuuuun.
Owain
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So do (nearly) all BC and ES lampholders.
--
Andrew Gabriel

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geoffr wrote:

500w of halogen will be way too bright for any normal residence. Probably about right if you live in a castle.
Dimming it will reduce light output but not reduce power consumptoin much, and is simply not a smart move. Power consumptoin will be truly excessive.
Halogen uplighters are a fire risk, the bulbs run way hotter than any other type of domestic lightbulb, and theyre pointing upwards... not a good idea.
In short I'd drop the idea and think again. What size room are you trying to light? What ceiling height, single or double storey height? Why a freestanding uplighter, and why halogen?
NT
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On 31 Aug 2006 08:57:39 -0700, snipped-for-privacy@care2.com wrote:

I have 300W of halogen lighting in my tiny bathroom alone. Plus 60W or so of normal incandescent.
--
Frank Erskine
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On Thu, 31 Aug 2006 19:22:11 +0100 someone who may be Frank Erskine

That might well us a number of things. However, it does not tell us how sensible such a scheme is compared to a bathroom with a 21W energy saving bulb.
--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
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On 2006-08-31 19:54:46 +0100, David Hansen

Very sensible.
He has it because he likes it. It's called choice.
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Frank Erskine wrote:

That's not lighting. That's heating. Edgar
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Edgar Iredale wrote:

Which in a bathroom is perhaps quite a good idea!
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Frank Erskine wrote:

I do occasionally see lighting like this, and find it a truly unpleasant experience.
NT
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snipped-for-privacy@care2.com wrote:

The house is Victorian and the ceilings are 12' high so there is in excess of 6' clearance. I have used it in rooms with lower ceilings and it seemed OK or at least it didn't leave black scorch marks!
Its being used as its simply what I have available, although even if I was starting from scratch I would choose this type of light as it appears that the only downside is the electricity consumption. The quality of halogen light seems to me to be superior to any other as it does give a very good quality of light in high-ceilinged rooms. Having said that I am not too keen on the 50W halogen spot lights as they give too narrow a beam.
Andrew Gabriel wrote:

I'm interested in these energy saving versions. I assume they are available from B&Q etc?
Thanks for all the comments.
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They are not easy to find. B&Q do have them in stock occasionally, but I don't recall seeing them in other retail outlets. They were a General Electric invention, but you may find other manufacturers making them too now.
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geoffr wrote:

It doesnt much matter what you have available, as the electricity consumption will be many times the purchase cost of any reasonable fitting.
If youre determined to use halogen, at least omit the dimmer and get the right power bulb for the job.
NT
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500W halogen is probably a K9 lamp. These are available in 300W and (harder to find) 200W. They are also available in energy saving versions at 375W and 225W, with same light output as 500W and 300W respectively (internal infra-red reflective coating reflects the infra-red back onto the filament). So pick one of the lower powered versions so you don't need to use a dimmer.

This is wrong, but I don't know what the second set is for. It might the the max rating of halogen lamp.

Filament lamps have a significant switch-on surge. For these high power halogen lamps, the initial current is 17 times the running current, e.g. 35A for your 500W halogen. A 5A fuse will generally withstand this for long enough for the halogen lamp to warm up, but a lower current fuse may not.

This makes no sense.

Others already explained how you need to work out the loading.

If it's a portable lamp, it really needs a plug and socket. You could fit a 5A BS546 round pin socket to the lighting circuit. The loss of fuse doesn't matter in this case.

Yes, if not more, but it will be written on the back.
--
Andrew Gabriel

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Andrew Gabriel wrote:

The second set may be the derated capacity when used with an inductive load (i.e. a halogen!)
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John.

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Since when has a halogen lamp been an inductive load? Even if you mean a transormer driven low voltage halogen it won't be very inductive - nothing like a motor or solenoid.
--
Chris Green

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