strange earthing problem (lighting)

[Neon Vagabond]

Right, so its been one of those long days.

swift breakdown:
top floor flat.
lighting cable is single cores in a conduit system.

was employed to install downlights in 2 rooms.

Really bizarre one for me, ive never encontered nything like this before.

So i tested the original fittings in these rooms to establish an earth path, all was well.
1.16 zs.

wired all my downlights and then crimped onto the switc and neutral at the original fitting.
zs was 1776.

disconected my wiring, still 1776 ohms.

this was the same for both rooms.

ran a new earth from the MET (10mm)
the done a zs with that new earth and across the switch/neutral at the light.
still getting 1776.

Really confused as the ze on the property is really low (0.25ohms)

this problem is only happening on this lighting circuit.

Any ideas on this?

i had plan to wrap up for the big quarantine but ill need to go back out tomorrow

 

[DPG]

Haha, surely the max zs applies wether you’ve got a dimmer or not

Yes but you cant test Zs through a resistor and expect sensible results!

 

[richy3333]

right I’ll just move it onto the rcd side of the board then.
This also might tell me more if it starts tripping out

I doubt a 3036 consumer unit will have an RCD side to it?

 

[westward10]

A dimmer switch isn't a resistor as such and under fault conditions the triac will close allowing fault current to flow.

 

[DPG]

A dimmer switch isn't a resistor as such and under fault conditions the triac will close allowing fault current to flow.

Ok, I simplified things, but you get my point. You certainly won't get a good Zs!!

 

[Timbo]

I doubt a 3036 consumer unit will have an RCD side to it?

Ah, but this is special - 3036 mcb's!!!! ???

 

[Neon Vagabond]

right ,I’ve been a bit of a silly boy,
I thought that if you have the dimmer turned up full then it behaves like a normal switch.

 

[DPG]

right ,I’ve been a bit of a silly boy,
I thought that if you have the dimmer turned up full then it behaves like a normal switch.

All sorted, that's the main thing.

 

[Neon Vagabond]

All sorted, that's the main thing.

onwards to Valhalla!

 

[richy3333]

So the circuit is now RCD protected?

 

[Neon Vagabond]

So the circuit is now RCD protected?

yes mate, completely righteous

 

[GBDamo]

right ,I’ve been a bit of a silly boy,
I thought that if you have the dimmer turned up full then it behaves like a normal switch.

Don't worry, I've learned something there also.

 

[Neon Vagabond]

Don't worry, I've learned something there also.

That’s it brother, always learning

 

[richy3333]

yes mate, completely righteous

Put up some pics please. I've never seen a 30306 CU with integral RCD protection. I'd like to learn...

 

[Neon Vagabond]

Put up some pics please. I've never seen a 30306 CU with integral RCD protection. I'd like to learn...

Never took any pics.
But I got the numbers confused it’s not 3036
I think they are 3871
Old wylex split

 

[davesparks]

Put up some pics please. I've never seen a 30306 CU with integral RCD protection. I'd like to learn...

They are rare but there was a wylex standard range CU with RCD protection.