Possible borrowed neutral ring mains

[TJC1]

Done a fuse board change on a propery, hasnt been touch since early 60s at a guess.

There is 2 ring mains, which i had split over the the 2 rcds. Each time i swithched on one, the other RCD tripped out, and vise versa.

Have no end to end on one ring main, and end to end on Line & Earth but not the neutral on the other ring.

To get it going for the weekend i put both rings on one RCD, but still tripped out.

Does this sound like a borrowed neutral problem, or a inter crossed ring main?

 

[westward10]

??? we are just having a bit if a titter? Well I was. I was, honest. I know Dave knows what interconnected things are, and I know he knows that I know what they are as well. That's it, really. Happy days. Bet that poor sod wishes he never had his fusebox replaced anyway......Oooerr I seem to have quoted the wrong bit now, apologies.

I was just thinking back to the op where he has "two" rings, it is likely to be one ring and the others radials. Yeah bet he ain't sleeping tonight.

 

[sparksburnout]

I was just thinking back to the op where he has "two" rings, it is likely to be one ring and the others radials. Yeah bet he ain't sleeping tonight.

Well the thing is, we can all bang on about testing beforehand, and obviously we should. But sometimes, things do go a bit squiffy, for one reason or another. Limited time, bit of an assumption made, or an oversight. But the thing is, it's Tuesday night now and this was a "tide you over" bodge from before the weekend? And the customer is paying good money, that's what I can never get my head round! Ah well. Your thinking about it, same here. But is matey??

 

[Toneyz]

I bet the op didn't sketch as layout of the property before he started to work out and confirm what is on what circuit.

BEST WAY

 

[Pete999]

Obviously not... Just after some advice.

Sorry TJC1 would have thought that on deciding to swap the Board fpr a new one you would have tested the wiring to find out if you had any problems, like the one you have now.

 

[dmxtothemax]

QUOTE-[Well, I have to be very careful here, as I can come over as a bit of a negative old git]

Too late !

 

[Midwest]

TJC1, looks as if you have a small problem. We all make mistakes, so hopefully you will learn by this one. I personally don't do an EICR before doing a CU change, but I do carry out some testing, like RFC continuity, IR, Zs. I also like others have suggested, inspect the state or condition of the wiring. Personally, I wouldn't do a CU change for an installation wired in the 60's. I'd decline. Incidentally, having just returned to the industry after a few years, I pretty much approached my first CU change like you have here. I was lucky and did not come across any faults. However, since being a member of this forum, and learning from the experience of other members, I sensibly do the former now.

Looking at your profile and posts, it seems you have recently entered the industry? And looking at some of your posts, I can't but help get the feeling you are running before you can walk. Perhaps driven by your fathers business.

I would advise, for what it's worth, to take stock of the type of work you are taking on. Don't be put off about the banter, it seems you have suitable qualifications, just lacking the experience, of which there's loads of here.

 

[Richard Burns]

Make sure that you do not have the neutral bars interconnected in the CU.
The fact that the circuits when all on the same RCD still trips the RCD either indicates linked neutral bars, a significant IR fault or that there is still another circuit that is powered across two RCDs.
Test continuity from one leg of the ring to other 2.5mm² cables in case they have been mixed up at some point and a circuit labelled immersion (for example) is actually the other leg of the ring.

 

[Dave OCD]

On a fairly recent board change I came across a ring with each leg on its own 15a rewirable fuse, had been like that for 40 odd years !

 

[Octopus]

On a fairly recent board change I came across a ring with each leg on its own 15a rewirable fuse, had been like that for 40 odd years !

Yup.... that's not unusual.

Also come across a CU with 2 x RFC's - both had 1 "live" in each of the 30A BS3036 fuses!

Thats why its ESSENTIAL to establish precisely what is doing what before you rip the old CU off the wall!

 

[Dave OCD]

Yup.... that's not unusual.

Also come across a CU with 2 x RFC's - both had 1 "live" in each of the 30A BS3036 fuses!

Thats why its ESSENTIAL to establish precisely what is doing what before you rip the old CU off the wall!

Yes I've had that on more than one occasion, even on an installation about 10 years old, strangely enough no certificate could be found for that one.