Author Topic: An electrical question regarding lighting  (Read 1028 times)

An electrical question regarding lighting
« on: December 21, 2020, 11:55:24 pm »


This is a plan view of the studio I am putting together.

Philips Hue lighting has already been purchased: 10 dimmable 9.5w white LED bulbs, shown as 6 pink and 4 orange Xs in the image and 4 dimmable 20w colour LED strips, as shown by the green stripe circling the room.

10 x 9.5w + 4 x 20w = 175w, or 0.76A on 230v mains. Our electrician says it is too much.

How much is the startup surge, if there is one? What is it that I am not understanding about lighting or electrics? I don't want to risk a fire but I am struggling to see how 0.76A is too much current.

Re: An electrical question regarding lighting
« Reply #1 on: December 22, 2020, 12:02:45 am »
If it were too much it would trip the breaker before it starts a fire. Which it won't because it isn't.

Maybe they're worried the next resident will proudly buy up some post-Brexit 100W freedom bulbs and put one in every fitting? But even that would still just trip the breaker.

Possibly they're worried about the switch, or is an actual mechanical dimmer involved? But even those tend to be rated far in excess or 0.75A.

I think you need to ask for a proper explanation or a proper electrician.

Kim

  • Timelord
Re: An electrical question regarding lighting
« Reply #2 on: December 22, 2020, 12:23:45 am »
The actual current is likely to be higher than the wattage would suggest, on account of the power factor.  But I'd expect it to be well within the 5A rating of a typical lighting circuit.

Inrush current may also be an issue, but it's hard to know what that might be without the circuit design of the lamps or empirical testing.


Maybe they're worried the next resident will proudly buy up some post-Brexit 100W freedom bulbs and put one in every fitting?

They're probably applying some electrician heuristic to that effect.  Or similar for inrush current.  Will the circuit be shared with lighting in other rooms?
Careful, Kim. Your sarcasm's showing...

Re: An electrical question regarding lighting
« Reply #3 on: December 22, 2020, 06:11:51 am »
https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=34806 Is a useful link.
Quote
I agree, the cpc can be an issue. I recently was testing an installation where 8 downlighters were connected in series from a junction box and found that R1+R2 was getting to the limit on the 8th. The terminal blocks supplied with the downlighters were small and cheap so that it was difficult to get two 1.5mm wires into each terminal. I thought of running another cable from the 8th downlighter back to the junction box - effectively creating a ring. Would that be a good solution?
above is pertinent. . Lights are usually daisy chained on a spur. Often connectors are a bodge.  I'm doing a similar plan with  eight 18 watt panel downlights and have found 'greenbrook lighting connectors' http://www.greenbrook.co.uk/ceiling-accessories-lcgn3p-852  (toolstation do a bulk pack) have yet to discuss details with my electrician so will be interested in outcome

Re: An electrical question regarding lighting
« Reply #4 on: December 22, 2020, 01:41:54 pm »
Quote
I agree, the cpc can be an issue.

Depending on what fittings you buy, they might not even have a CPC (earth) connection. And on LED drivers that do have an earth it's usually only connected to the surge suppression circuit.

In fact the Hue LED strip drivers come with an insulated earth pin:
https://www.currys.co.uk/gbuk/smart-tech/smart-tech/smart-home/smart-lighting/philips-hue-white-colour-ambiance-smart-led-lightstrip-plus-2-m-10214371-pdt.html

(not sure if this is the product the OP has)

Is this one of those times where following the letter of the regulations ties you in knots for no good reason?

Re: An electrical question regarding lighting
« Reply #5 on: December 22, 2020, 01:54:29 pm »
Without any real knowledge but having dipped a toe into the turgid world that is LED dimming sufficient to realise I have little understanding, could that be the issue?

Re: An electrical question regarding lighting
« Reply #6 on: December 22, 2020, 01:59:34 pm »
Without any real knowledge but having dipped a toe into the turgid world that is LED dimming sufficient to realise I have little understanding, could that be the issue?

The Hue bulbs are "smart" and all of the dimming happens internally in low voltage land under control of an app. There's no dimmer on the mains side, unless the electrician has got the wrong end of the galvanic isolation barrier stick.

Feanor

  • It's mostly downhill from here.
Re: An electrical question regarding lighting
« Reply #7 on: December 22, 2020, 02:08:43 pm »
It's certainly not a 'too much current' issue.

If the objection is the combined resistance by daisy-chaining 10 fittings ( with questionable quality connectors ) in one big long radial circuit, then surely that's easily overcome by only daisy-chaining 2 or 3 on a series of shorter individual radial circuits, tied back to one central junction box?

<ETA>Or daisy-chain the 1.5 T+E through a series of good quality ceiling roses, one in the vicinity of each fitting, and then a short tail of flex from the ceiling rose to the fitting. In this way, you don't daisy-chain through the poor connectors on the fittings themselves.

Kim

  • Timelord
Re: An electrical question regarding lighting
« Reply #8 on: December 22, 2020, 02:32:02 pm »
Quite.  Ideally, the solution to dubious connectors is to use better ones, not slightly fewer dubious connectors.
Careful, Kim. Your sarcasm's showing...

valkyrie

  • Look at the state of your face!
    • West Lothian Clarion
Re: An electrical question regarding lighting
« Reply #9 on: December 23, 2020, 08:23:20 pm »
What light level are you aiming for? Looks like a lot of lighting for one room, so if that’s what your electrician meant then he might have a point. If he’s worried about the load then get a better electrician.
World Class Excuses for Piss-Poor Performances

Kim

  • Timelord
Re: An electrical question regarding lighting
« Reply #10 on: December 23, 2020, 08:26:04 pm »
Presumably the idea with a setup like that is that it's adjustable (hence the use of Hue) to achieve different effects as the need/mood arises.  You'd only want it all on full when looking for pingfuckits.

Electrically it should work with everything at full brightness, for the same reason that chains should be long enough for big:big.
Careful, Kim. Your sarcasm's showing...

Cudzoziemiec

  • Eating all the pies and drinking all the tea.
Re: An electrical question regarding lighting
« Reply #11 on: December 23, 2020, 08:32:52 pm »
If it were too much it would trip the breaker before it starts a fire. Which it won't because it isn't.

Maybe they're worried the next resident will proudly buy up some post-Brexit 100W freedom bulbs and put one in every fitting? But even that would still just trip the breaker.

Possibly they're worried about the switch, or is an actual mechanical dimmer involved? But even those tend to be rated far in excess or 0.75A.

I think you need to ask for a proper explanation or a proper electrician.
Road-runner is that there Slovakia, free of Brexity freedoms.
Faster than a walk, slower than a train, often slightly higher than a person. (David Byrne)

Re: An electrical question regarding lighting
« Reply #12 on: December 31, 2020, 07:19:22 am »
I have been reading your links and have a better understanding but am not sure I know enough to tell an electrician their job. I called the electrician only to discover he had got out the right side of bed yesterday, saying that 14 lights would be no problem.

Thank you, everyone, for such help.

(not sure if this is the product the OP has)

Currys doesn't seem to sell the whole range. This is the one I have. If you click on the +11 photos, the first of those shows the black lead and transformer brick.

Presumably the idea with a setup like that is that it's adjustable (hence the use of Hue) to achieve different effects as the need/mood arises.  You'd only want it all on full when looking for pingfuckits.

As ever, Kim, you are spot on.

Maybe they're worried the next resident will proudly buy up some post-Brexit 100W freedom bulbs and put one in every fitting? But even that would still just trip the breaker.
Road-runner is in that there Slovakia, free of Brexity freedoms.

Here in Slovakia EU laws have been the same as in the UK; you can no longer buy incandescent bulbs but there are still a lot in use. Before I bought this space I rented an office which came fitted with three 150w bulbs, so anything is possible.