UK MCB screw won’t undo - what would you do?

[Mindgirl]

Curious what you would do

Screw holding ring final circuits live wires in MCB wont unscrew ,

it’s literally a ground out circle from what was originally a Philips head screw

Therefore couldn’t do end to end continuity
I did end to end from socket instead,

MCB probably needs to be changed, but I couldn’t find any new available.

probably needs whole board change unless there is an alternative compatible McB?
(Also RCD is on last legs as inconsistent results on functional testing)

 

[pc1966]

I’ve left it with client to see if they want board change, although not sure I want to inherit likely problems with house wiring

Is the EICR looking rather poorly for them then?

 

[suffolkspark]

Thanks all
I’ve left it with client to see if they want board change, although not sure I want to inherit likely problems with house wiring

that particular circuit:
r1 was 200 ohms.
r2 1.3 ohms
rn 0.6 ohms
R1+ R2 was not too bad considering (0.5 ohms)

Ah that's a C2 all day long then incomplete ring

 

[pc1966]

R1 = 200 ohms is a fire if you put any high load on it!

Doh, this is r1,r2,rn for ring end-end!

 

[Mindgirl]

I would probably say FI (as really needs further investigation)
Client wants to do investigating on their time but it may not be a problem in a socket (They have been warned but he’s a retired nuclear physicist)

I wonder if you do find problem between two sockets but don’t want to look for cable (to avoid making holes) you could disconnect neutral and earth, and have two radials instead (on separate breakers when board changed)

 

[pc1966]

If you can't find the cable route non-destructively to find a dodgy junction box, yes you could split the ring and change to 20A breakers to allow for the lower CCC of the system.

But you would need to be sure to disconnect both ends and check it is not spurred off to somewhere from a hidden junction box. If so one end would need to be kept joined leading to live ends at the other to be made safe and also to verify that you don't have any dodgy high-R connections on that spur route either.

But it might be better to run in another cable to replace the hard-to-find section as that might be a lot easier depending on the property and access to under floor/attic/etc.

 

[Wilko]

I’m such a pedant I’d decommission that mcb and make something out of what remained. “Where there is a doubt, there is no doubt” is the old saying I was taught.

 

[HappyHippyDad]

It’s denmans (a rebadged ge) - they don’t make that model and even used on eBay out of stock/no longer available

volex is a good shout, and might avoid whole unit change.
Only issue is RCD would also need changing

I keep all the old CU's I take out so I may well have a 32A steeple mcb, may have the RCD as well. Let me know if you get stuck and need them. No charge.
https://www.electriciansforums.net/attachments/all-jpg.60964/
At lunch now but managed to find this picture. See top left in the picture. Looks like your board, although not 100%

 

[Mindgirl]

I keep all the old CU's I take out so I may well have a 32A steeple mcb, may have the RCD as well. Let me know if you get stuck and need them. No charge.
https://www.electriciansforums.net/attachments/all-jpg.60964/
At lunch now but managed to find this picture. See top left in the picture. Looks like your board, although not 100%

Nice collection - thanks for offer - waiting on client