Head scratching lighting issue

[jibjob]

Hi Guys & Girls,

It's been a while, hope everything is good.

I have an issue that's proving to be a bit of a head scratcher. Please bear with me.
Recently carried out an EICR at a small empty basement flat. It's a TT, 100mA RCD at intake, dual split load at the board. Lots of issues identified, reverse polarity at sockets, no R2's at lights, non-fire rated downlights installed into lath & plaster ceilings that had been over boarded leaving a gap between the new ceiling & the old with wires fed down the gap rather than over the top, no access to existing lighting junction boxes/ceiling rose points, a junction box stuffed behind a KO box in order to extend the cable, spurs with multiple outlets off a 32a ring final without the appropriate over current protection & generally totally cack wiring throughout.
I won the quote to do the remedial works. One of the recommendations was to replace the existing Wickes specials for fire rated downlights. All the existing fittings had mains LED lamps in them, I changed the fittings for the integrated type, a brand I use all the time & have never had issues with.
I started with the kitchen, once finished I switched them on & they would start to intermittently flicker & pulse but finally settle down. Checked connections at lights & switch, no probs there. So I start to dig a bit deeper. I identified reverse polarity at the feed to the first light which I found strange as I didn't come across it previously, in fact I had a R1 + R2 when I carried out the EICR. Prior to identifying the reverse polarity I also found that if I plugged a load into any of the socket circuits (my Henry Hoover) the lights would pulse & the the RCDs would trip, one after the other (just the 30mA's in the board). After disconnection of the kitchen lights the circuit no longer tripped when I used the vacuum although there were other existing lights on the circuit that come on & were fine.
So I think, must be the reverse polarity at the kitchen lights. Despite not having access to the junction box above the ceiling (I can see it with my camera but can't reach it, but that's another story) I thought I had it cracked.
Been back there today & installed further replacement downlights on a different circuit. Lo & behold, same issue where it hadn't existed before, if I plugged my battery charger in the lights would flicker & pulse for a short time & then settle. If I plug the vacuum in it's the same as before, the RCDs trip. If the lights are switched off at the board everything else seems OK.
The thing that is baffling me is that this issue didn't appear to exist before I changed the lights over. The only thing I could think of is that GU10's can be fitted either way round but wondered whether the replacements I have used are polarity sensitive (for want of better expression). Thus, if there is an unidentified polarity issue between what would of been the existing lighting point & the more recently installed downlights (not mine, the ones I have removed) fitted with GU10's then this wouldn't happen.
I thought of maybe a borrowed neutral but this problem as far as I know didn't exist previously, the board is configured the same with the exception of the ring final which I have moved from the right hand RCD to the left following a tidy up of the rats nest inside the CU.
I'm a bit frazzled after a weekend of working & finding it a little difficult to get my head round.
Any thoughts would be most welcome.

 

[Vortigern]

What type of lights? And how are they switched? Led can't be operated in reverse polarity. I presume it is LED? Is the voltage at supply correct. Are the main supply cables loose? or even reversed polarity? Sorry you did say LED I see. Is there a loose connection. I guess that is the most likely cause from what I read.

 

[jibjob]

What type of lights? And how are they switched? Led can't be operated in reverse polarity. I presume it is LED? Is the voltage at supply correct. Are the main supply cables loose? or even reversed polarity?

Intergrated LED, polarity at CU main switch checks out. All terminals tight, haven't specifically checked the supply voltage but I didn't notice anything unusual when carrying out Ze or PFC.

 

[Vortigern]

What about the JB you mentioned? Often loose connections there. Just an ordinary switch?

 

[Strima]

IR test results?

 

[littlespark]

What’s the supply voltage and do you get the same at the fittings?
Old dimmer in circuit somewhere?
If someone’s cacked up a joint box, there could be a dimmer controlling the whole house.

 

[James]

How are you testing for reverse polarity?

Floating neutral or earth issues can fool simple testers.

When you say you have fixed a reversed polarity issue somewhere, did you actually identify a wrong connection somewhere or just swap ir over because a plug in tester told you too?

 

[Flanders]

You say all terminal are tight but the connection in the main head or meter could be loose. I've seen lost neutral show up as reverse polarity on some testers

 

[plugsandsparks]

I would start back at the incoming supply with the isolator off and do all the usual tests to make sure you have a good supply. Then start to introduce the circuits one, by one, testing each as you go. It does sound like something (or anything) is pulling the voltage down either by poor connections in the CU or upstream to service head or even beyond.

 

[Lucien Nunes]

Led can't be operated in reverse polarity

DC LED strings themselves no, but LED drivers and integrated LED fittings (and indeed anything AC that doesn't specifically monitor and warn about reverse polarity) will work fine with reverse polairty, albeit possibly with reduced safety due to SP switching being in the neutral.

If ordinary RCDs (without functional earth) are tripping, there are probably faults to earth. If RCBOs or devices with a functional earth are tripping, this could be due to a high-resistance neutral connection that is also causing the lights to malfunction and the tester to indicate an abnormal condition.

As above, check and report the voltages at the board, L-N, L-E, N-E with no load and with some significant load on (a few kW). Repeat at the end of a troublesome circuit, and report with Zs for the same circuit.

 

[Vortigern]

Is there actually a separate circuit for the lights or are some of them spurred off the socket circuit??

 

[jibjob]

What about the JB you mentioned? Often loose connections there. Just an ordinary switch?

Could be but I can't get to any, they're all either out of reach or out of site. No dimmers visible just standard switching
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IR test results?

With the exception of the ring final which I have rectified (it was 0.68 mohms) all circuits were high, > 299
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How are you testing for reverse polarity?

Floating neutral or earth issues can fool simple testers.

When you say you have fixed a reversed polarity issue somewhere, did you actually identify a wrong connection somewhere or just swap ir over because a plug in tester told you too?

I identified a couple of reverse polarity issues. I was alerted to both with a plug in tester while carrying out my functional testing prior to dropping socket fronts etc. Closer inspection revealed L-N reversal, one of the sockets is on it's own circuit the other is a spur from the ring.
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I would start back at the incoming supply with the isolator off and do all the usual tests to make sure you have a good supply. Then start to introduce the circuits one, by one, testing each as you go. It does sound like something (or anything) is pulling the voltage down either by poor connections in the CU or upstream to service head or even beyond.

Yep, as you say will start up stream & work my way back, thanks for the help
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Is there actually a separate circuit for the lights or are some of them spurred off the socket circuit??

2 light circuits feeding all lights both from CU