Workshop Lighting

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Mawson on 23/05/2023 19:24:35:

The only meter that is relevant here is the one by which you are charged by your electricity supplier.

If IT shows excess power consumed by ballasts and capacitors left in fittings upgraded to LED then you need to be concerned as it will hit you in the pocket.

This was the case for me any other theoretical arguments are just hot air.

Lots of posts on three different fora on this subject with no mention of what the supplier meter said! The forum posts all rely on OWL and Fluke measurements and some simple maths. I see I was not the first to mention Power Factor as a likely cause.

Domestic and Industrial power are metered differently. At the moment, UK domestic meters measure real power, so the consumer doesn't pay for apparent power. Therefore LED tubes will make the claimed power savings even if the ballast is left in place. (It will waste a small amount of real-power.)

Unlike ordinary consumers, Industrial users do pay for apparent power. As their devices often put heavy inductive loads on the network, industry are encouraged to correct power factor before they connect. Could get big bills if they don't, but it depends on the nature of the load! Power factor correction involves fitting a cabinet full of capacitors, which could be static for a fixed reactive load, or dynamic if the load varies. In older installations, a man monitored power factor meters and threw switches as necessary to improve it. A modern system would probably do it automatically.

As Andrew's installation is Industrial he might well be paying for apparent power, and should be worried about the possibility. The lighting upgrade has been approached as a domestic upgrade: substitute 24W lamps for 70W units, job done. Fair enough, but there's a booby trap if the meter registers apparent power/.

Maybe saving money by not consulting an industrial electrical engineer who understands power factor was a missed opportunity? I suggest it because the whole installation could be running up bills because it's not been power factor corrected. There's a hint of this in Andrew's other posts. In addition to the LEDs, Andrew also got unexpectedly high power consumption measurements from a 30HP motor and a Beaver lathe. He also noticed measurements varied at different times; this could be because the power factor of his installation depends on what else is switched on or off.

Andrew believes he was mis-sold tubes, and the manufacturer has taken note, even though industrial purchasers aren't protected by consumer legislation. I don't think Andrew as an industrial user has a case against the retailer, and guess the manufacturer wanted to avoid messy bad publicity. I'm glad it's been resolved in Andrew's favour, even though Industry are expected to be an "intelligent customer."

Sorry to say the notion that "any other theoretical arguments are just hot air" is flawed. Ignoring engineering evidence rarely ends well! Power factor correction needs an electrician familiar with the subject, and an 'independent engineer' using a Fluke to measure amps and volts suggests he wasn't qualified in this particular subject. If the OWL or Fluke show high power on anything else, I'd send for a specialist. Power factor could be still costing more money than the fluorescents wasted!

Dave

[Robert Atkinson 2Participant @robertatkinson2]

It should be noted that it is the power factor correction capacitors that are causing the issue, not the inductive ballast chokes. Depending on the type of circuit in the replacement LED "tube" leaving them in may actually improve the overall efficency. At the lower currrent of the LEDs the affect on power factor is minimal.

Some years ago some dodgy companies were selling "energy saving" devices that were just a capacitor in a plug. Their claims were based on a small power factor correction. This ignored A. Most domestic uses have little fixed inductive load and B. Domestic meters are real power so it makes no difference to the bill.
Correcting power factor does save energy overall because the reactive current does increase the power lost as heat in the resistance of the power distribution system. Power companies don't like this because it causes heating in their transformers.

Robert.

Edited By Robert Atkinson 2 on 24/05/2023 12:52:03

[john fletcher 1Participant @johnfletcher1]

I have a cheap meter similar to what Dave above has, mine does indicate Power factor and is accurate enough for domestic/ workshop use. I have an ex university Wattmeter and I've checked my el cheepo against it out of interest, good enough. Regarding Power factor in industry some machine have the capacitor wired across the inductive load direct, so the capacitors are only in operation when the load requires them, but in that arrangement they cannot adjust to a varying load, so power factor is near enough, .8 or so. The other idea as Dave mention, such injection moulding machines, with a varying load, then a bank of capacitors in a steel cabinet is used, and VAR sensing equipment fitted, one can hear the contactor switching in and out, keeping the Pf near .9. Maybe things have moved on and some electronic device does the same job in a quiet manner now days. On the C&G Electrical Installation course, power factor was part of the syllabus back in the 60's, 70's & 80's. John

[Rod RenshawParticipant @rodrenshaw28584]

Dave

Thanks for the suggested type of wattmeter. For some reason, perhaps influenced by the posts above, I had thought it would be more complicated and expensive than that. I will get one and see how much power things actually use.

Rod

[Andrew MawsonParticipant @andrewmawson48459]

Replying to "Dave":

You are working on a fundamental misunderstanding. Despite the scale of my workshops I am NOT an industrial customer – I am a retired private individual and metered accordingly.

It was I that brought up the power factor issue with TLC thinking that it might have a bearing not them. Their representative used his own instrumentation and sadly I wasn't able to note what it was – in fact he had two sets to compare results (which they did)

[Robert Atkinson 2Participant @robertatkinson2]

Andrew,
What meter did you use to identify the issue initally?

Robert.

[Andrew SkinnerParticipant @andrewskinner94774]

I did chip in to the original thread, but realised I was starting to bang on a bit about power factor, and such.

In the interests of getting to the bottom of the issue, I’d still like to know if Andy Mawson’s leccy meter measures in kVArH or kWH. That’s absolutely key.

All the reps/technicians sent there to investigate did no more than clamp the supply cable, using P=IV (the ‘DC formula’ ), rather than addressing phase, ie P=IVcos[phi].

For example, if I powered up a fluo light fitting with no tube in it, I would see the full leading VARs supplied by the capacitor, shown as a significant current on my clamp meter. There would be, however, pretty much no charge for this on a domestic kWH tariff.

He got a great result from the supplier, but it still gnaws at me now and again that we haven’t fully ‘bottomed out’ the technicalities of this.

 

 

Edited By Andrew Skinner on 02/06/2023 12:26:30

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Mawson on 24/05/2023 19:13:54:

Replying to "Dave":

You are working on a fundamental misunderstanding. Despite the scale of my workshops I am NOT an industrial customer – I am a retired private individual and metered accordingly.

…

I suggest it's the installation that's industrial: 3-phase and many kilowatts. It's electrically nothing like a bungalow in Penge! In my book if it looks like a duck, walks like a duck and quacks like a duck, it is a duck. Could be wrong, but I wouldn't expect the meter on something like that to be domestic.

I think the dispute is because a domestic customer wandered into in industrial territory. Installations on this scale are rarely operated by retired private individuals. Most of us, me included, have bog-standard household electrics with domestic meters that measure real, not apparent, power. In our homes those LED lights would save us money exactly as advertised.

As industrial meters typically measure apparent power it's possible that these lights didn't save money in this installation. 'The only meter that is relevant here is the one by which you are charged by your electricity supplier'. Spot on, but I don't think it's a domestic meter: worth checking I suggest!

I'm fairly sure the issue is due to Power Factor and that the LEDs weren't really consuming lots of energy. Industrial customers are familiar with Power Factor considerations, most domestic users have never heard of it and don't need to care, lucky them. Here's what the NTOC has to say about Power Factor in what I call industrial circumstances:

Heavy responsibilities are placed on industrial customers because they often have unusual electrical requirements likely to mess up the power factor, making it necessary for them to design an installation that satisfies the rules. Money is a strong incentive – if an industrial customer fails to correct his Power Factor, the meter charges for apparent power and his electricity bill shoots up. The meter charges for real power only when the PF is within limits. The point is Power Factor would explain why the LED lamps were apparent power hogs.

Simpler rules apply to domestic consumers because we're all much the same electrically. As most home and office devices come with a 13A plug, we're predictable!

No point in arguing about it on the internet; it's the suppliers Terms and Conditions and his meter that decide.

Dave

[not done it yetParticipant @notdoneityet]

I do recall a video about wattless power, and smart meters that are able to and could/will soon measure our domestic usage including it. Bigclivedotcom I think?

[EmgeeParticipant @emgee]

One updating fluorescents in a factory job I did many years ago was designed by Thorn Lighting who provided an equal mix of leading and lagging PF fittings which they claimed gave unity PF if used in equal numbers of course.
So PF was taken into account by that consumer.

Emgee

[duncan webster 1Participant @duncanwebster1]

I've just replaced a very old 4ft fluorescent with a 5ft LED tube. Reduced my power consumption by a whole 10W, but you now need sunglasses compared to what it was before. A dark corner of the workshop is now well lit. OK the tube was pretty old, but the fitting was at least 50 years old, so I splashed out on anew one rather than messing about converting it.

[not done it yetParticipant @notdoneityet]

Posted by duncan webster on 03/06/2023 00:16:40:

I've just replaced a very old 4ft fluorescent with a 5ft LED tube. Reduced my power consumption by a whole 10W, but you now need sunglasses compared to what it was before. A dark corner of the workshop is now well lit. OK the tube was pretty old, but the fitting was at least 50 years old, so I splashed out on anew one rather than messing about converting it.

Same here. I replaced a 5’ fluorescent, with a 4’ LED, in the kitchen about 3 or 4 years ago (time flies!). Lower power (tube was 60W) and light far brighter. No problem with striking or warming up, no excuse for not turning off the light when not in the kitchen. Generally a good job done with mostly lots of brownie points from SWMBO (apart from there now being no excuse for leaving on the light all the time!).

The original fluorescent, fitted in the original kitchen (now the utility room) is still good – far better than the one fitted about 30 years ago in the extension. I’ve no idea of the relevant efficiencies of the older and newer tube fittings but the original is still bright and has only had one (or perhaps two) tubes in 50 years. The newer one ate starters and tubes. But the facts remain that the LED fitting is far superior to the fluorescents in every way.

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