Fault problem with up ring

[swaley]

got called out to a job yesterday. Upstairs ring Mcb not staying on. Done a quick visual took all sockets off didn’t notice anything out of sorts. All appliances unplugged only other thing on ring is boiler programmer off a fuse spur. So I split the ring did IR and one side was showing a low reading. I energised the good side and starting the tedious process of trying to find the culprit on the dead side. I came across 1 leg between 2 sockets which was giving me a reading of o.52 ohms IR. so I disconnected the link between and energised both sides. Voila mcb stays on. My concern now is I have a socket in hallway and boiler programmer with no power. Even though both legs are in board? And 2 sockets in another bedroom showing 60v output. I’m baffled didn’t have time to get boards up need to go back. Surely by disconnecting 1 faulty link I would in principle have 2 radials?? tenant just moved in recently new carpets fitted and it’s been intermittent tripping. Any ideas guys

 

[Dillb]

What do you mean “Voila MCB stays on” what was the IR of the 2 legs once you disconnected the faulty legs you found?

What meter did you use to get a IR of 0.52 ohms?

Did you leave both legs connected the same OCPd?

What size was the OCPD?

 

[Nigel]

Clearly there are joints somewhere that are either no accessible or you have missed checking everywhere.

 

[Octopus]

0.52 isn't low enough to trip a mcb imho...

Go back and confirm your findings, then investigate more

That's what I would do...

Edit. What was the IR of the disconnected part of the circuit?

And did the tripping start after the new carpets were fitted?

 

[swaley]

What do you mean “Voila MCB stays on” what was the IR of the 2 legs once you disconnected the faulty legs you found?
Because didn’t switch on prior
What meter did you use to get a IR of 0.52 ohms?
Fluke mft
Did you leave both legs connected the same OCPd?
Yes
What size was the OCPD?

Didn’t switch on prior. Fluke mft. Yes & 32a

 

[swaley]

Clearly there are joints somewhere that are either no accessible or you have missed checking everywhere.
I’m suspecting a JB or 2 I’m not a fan of fault finding.

 

[swaley]

I’m suspecting a JB OR 2 not a fan of fault finding

 

[Dillb]

Didn’t switch on prior. Fluke mft. Yes & 32a

So you have left 2 radials on a 32amp MCB? What size cable was it?
What range did you have your meter on to get that reading for the IR?

 

[swaley]

0.52 isn't low enough to trip a mcb imho...

Go back and confirm your findings, then investigate more

That's what I would do...

Edit. What was the IR of the disconnected part of the circuit?

And did the tripping start after the new carpets were fitted?

The IR was o.5 at disconnected part. I’m going back Saturday now so will update when I find out a little more. A nail from carpet gripper is always a possibility

 

[swaley]

So you have left 2 radials on a 32amp MCB? What size cable was it?
What range did you have your meter on to get that reading for the IR?

No spare ways on board also didn’t have a spare 16mcb on van. 2.5mm. Sorry should of mentioned 250v range on IR. didn’t test at 500v. I’m going back saturday

 

[Octopus]

No spare ways on board also didn’t have a spare 16mcb on van. 2.5mm. Sorry should of mentioned 250v range on IR. didn’t test at 500v. I’m going back saturday

Your 250v IR test .... Was between what?

 

[swaley]

Your 250v IR test .... Was between what?

The 2 sockets. Disconnected link. All other sockets previous to that were all over >200mohms

 

[Octopus]

Not quite what I meant

L&N to earth

Or between all 3 cores?

 

[swaley]

Not quite what I meant

L&N to earth

Or between all 3 cores?

L & N

 

[Octopus]

L & N

When fault finding between all 3 cores and 500 v is the only way to do it.