Discuss LED lighting dropping out under circuit load in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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Rockingit

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I have a complex domestic - incomer is to a primary board in a pump house, main house is fed from a sub board via a 50m 35/3 SWA on a DP B63 (+ shunt). Two other sub boards, plus a load of dedicated radials all doing various 'heavy' services like water plant, ground source etc.

Being a new build it's full of LED downlights, and whenever something 'chunky' (take your pick out of various pumps, motors etc around the place) elsewhere starts up they all flicker. Paper calculations say I'm well within VD limits on all circuits (1.8% on the house), and all connections are tight. I'd originally thought it was an inductance issue until I also noticed today that the oven firing will also produce the same effect.

The problem is cross-boards (so a load on DB3 will affect DB2, for example) so it's a site wide issue.

My thoughts are either that the electronics in these LED's (Robus) are particularly sensitive or that they're somehow being affected by the pole transformer that feeds the place.

Given the practical/cost restraints of this being a domestic, if I fit surge protection to the three lighting circuits am I likely to see anything of any real value with this problem or can anyone see another obvious thing that I've overlooked?
 

snowhead

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You say the paper Volt drop is within limits, what's the actual volt drop when the LED's are dimming?
You'll need an analogue meter to see it, not a pseudo LCD one, a real moving needle.
 
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I'll give that a go, good shout. Although, when you work the maths out it just doesn't make sense, so not sure where it will lead.... To flesh the cable calcs out : 35/3 SWA 70deg buried has a 7671 tabulated rating of 1.25 : Let's assume 100w of LED lights gets us to .43A : 50m = 0.02v Not exactly borderline, is it?!

AND.... in writing this just now, I've just realised/remembered that a HF striplight which is on a direct radial from DB1 also dips when you apply a circuit load elsewhere downstream. So therefore the VD is occuring right at the start - cable calcs on distribution circuits are irrelevant.

Now I'm really confused!!
 
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And I agree with Farm, too!! It's gonna be a right barrel of laughs to get them to come out to this one.........
 

snowhead

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Although, when you work the maths out it just doesn't make sense, so not sure where it will lead....



So therefore the VD is occuring right at the start

You're just trying to see if it's a straight forward volt drop caused as suggested by a loose DNO or whether you've got some wierd harmonic/ frequency or other fault.

Looks like DNO fault, maybe undersized / faulty transformer or your primary connection or switch / isolator faulty.
 

darkwood

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Have you got dimmers on the LED's if so how many lights per dimmer, as others have said loose connection is a possibility and id be inspecting that any of the busbar or tails have been located correctly in the mcb/switch clamps and are not sitting on the rear of the clamp, the electronic flourescent should be compensated to allow for voltage fluctuations, a surge protector does what it says on the tin and protect from damaging spikes but other than that it wont stabilise VD when heavy loads are applied.

Other possible area's are load sharing of transformer with neighbours, size of transformer as a borderline transformer with struggle when heavy loads are switched on or high inductive loads thus effecting voltage but these issues with have to be taken up with the DNO
 
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Rockingit

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Have you got dimmers on the LED's if so how many lights per dimmer, as others have said loose connection is a possibility, the electronic flourescent should be compensated to allow for voltage fluctuations, a surge protector does what it says on the tin and protect from damaging spikes but other than that it wont stabilise VD when heavy loads are applied.
Only have one dimmer on some of them, not all by a long way and they're spread all over the site and different parts of the distribution network.

Harmonics just got a mention - it's a 1ph install, granted there's a potential FLICKER influence via the ground source unit but at the moment it's turned off, so not there, and I'm scratching my head trying to think of anything more disturbing than a HF fluorescent.
 

darkwood

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I did an edit to add a few more ideas .... if you re-check my post.

The LED dimmer thing was a thought because they make the lamps more suseptable to undervoltage and also too many lamps on one dimmer can effect powerfactor making them more sensitive but as you said the issue isn't localised to a few lighting circuits, you say it does it with the flourescent light, what id be inclined to do is switch all the LED's off and see if this flourescent still is effected.... where im aiming at with this is a large Power Factor issue with all the electronic lights in the circuit but this is a shot in the dark and il even have to read up on LED's electronics myself to see if this is the case.
 
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Rockingit

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Cheers all for the ideas, I'm onsite at the moment (joys of smart phones!) so when it next stops cacking down I'll have some combination play and see what I can make happen. There IS a possibility it might be transformer based as the site has its own dedicated pole and I know its only a 16kw and seen a few years on it! Or could just as easily be a loose joint on the incomer/meter/isolator. Pretty sure all bus bars consumer side are 100%.
 

Richard Burns

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I would tend to the loose connection near or before the origin.
If you did a low resistance test of the live and neutral from the top of either an initial breaker or the main switch back to the origin (if accessible) and see if the readings are higher than expected this may help narrow down the fault to internal or external to the installation.
 

UKMeterman

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Hi,
Check the voltage at the supply when under load as others have said, also check the the PSCC and is it normal in your experiance?
 
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Not sure whether this is relevant or not (probably isn't!) but I noticed today when on site on my own that the Robus LED's that are fitted are really noisy as far as interference goes - I noticed it when trying to tune in my radio, as soon as I turned them off I got crystal clear reception but loads of noise with them on. Admittedly these are fixed in joist space where above them are loads of underfloor heating tray, so I guess acting as a big aerial.
 
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UPDATE -

After measuring voltages both by analogue and digital tracking across the main incoming bus bars and seeing as much as a 20v drop from only 4 or 5 amps of load, flagged it to the DNO who came out last week, looked at their connections, HV fuses etc and went away to arrange for an engineer to fit a quality analyser for a week so that they could look at it.

Today though, an inspection team arrived to do a pre-visit for changing the pole transformer at their cost - hurrah! I'd been under the impression that it was a 16Kva set, but they told me it was only a 5! So that explains a lot, and the calculated diversity on the installation is something like 220A due to a heat pump and private water treatment works. Anyway, they're going to fit a 25Kva at no charge (and change the 80A to 100A). Have to say, I like Western Power as my area DNO, they're really great to work with.
 

darkwood

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Other possible area's are load sharing of transformer with neighbours, size of transformer as a borderline transformer with struggle when heavy loads are switched on or high inductive loads thus effecting voltage but these issues with have to be taken up with the DNO
Glad you sorted it at no expense but hey! brownie point my way it was on my list :wink5:
 
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