Radial from ring main

[asthpsw]

I've recently had an electrician in to sort out why my RCCB kept triggering when I put the Ring Main CB on..............the exact cause was never found although a certain part of the Ring main was found to have a low Resistance reading (Less than 200MOhm ?) & when this part was included in the ring main it triggered the RCCB.

So when I asked for a 5 year Safety Check (prior to the above work) I was told that it couldn't have 5 year interval due to the Low Resistance on the ring main.................so wouldn't it of been the answer to cure both the above to "recable" the portion that had the Low resistance / Triggered the RCCB ?

Secondly & a bit more worrying is that the ring main is protected by a 32A CB but from this ring main is a Spur which is in effect a radial circuit.......this radial Circuit is in the kitchen with 7 sockets/ fused outlets from it.........

So am I right in saying that this number of sockets should not be a "Spur" which infact is a radial circuit ?............plus the fact that this is 2.5mm cable Radial in a kitchen........& with a Dishwasher, Washing Machine, Kettle, Toaster & a 2 KW Heater all possibly being run off this at one time this could exceed the 20A of the cabling & not trigger the 32A CB !!!

Paul

 

[rebuke]

The only way you should have a spur with multiple sockets off a ring final is via a FCU. Given the loads you describe could easily go over 13A however, this would be a bad idea in this situation - the best bet would be to make it part of the ring.

If there wasn't an FCU, then I would suspect the reason you might be getting a low insulation resistance reading is because due to the excess draw through the cable, the insulation has started to melt?

 

[Taylortwocities]

the best bet would be to make it part of the ring.

Or (better) a circuit in its own right. A 20A radial may still not be enough, given the loads....

 

[hairyben]

If there wasn't an FCU, then I would suspect the reason you might be getting a low insulation resistance reading is because due to the excess draw through the cable, the insulation has started to melt?

Although that is possible, I'd wager it's some kind of installation error, or possibly an unknown load/part of circuit. Once you start getting into kitchen fitter wiring.... ..you find the reason part P was introduced.

"sub 200M" shouldn't be a problem. A RCD will hold untill insulation falls well below 1M

 

[rebuke]

My thought was that if the cable is heating up as load gets used in the kitchen, then whatever fault is causing the low insulation reading might be getting worse, hence might be the cause of the trip. Although re-reading it if it happens as soon as you turn the breaker on then it seems less likely, as the cable wouldn't have had a chance to heat up...

 

[asthpsw]

Re the RCCB problem, The kitchen I talk of is infact an extension to the house when I had the RCCB I did infact "disconnect" the Kitchen from the circuit via a socket in the Original kitchen............however what surprised me as this socket was the closest to the new kitchen I was expecting to find this as part of the original ring main & 3 cable connections to this socket...............but I didn't I only found 2 cables one of which shot off to the new kitchen.

Anyway, even with the "New kitchen" disconnected I still got the RCCB tripping what I'm wondering if the cable from the consumer unit to this socket in the original kitchen has Overheated & deteriated in some way. This was the area that the "effected" cable was in.........because I disconnected this area out of the ring main & in effect for a short while it was one massive radial not quite getting back to the consumer unit the RCCB did not trigger.

As I said before I was never told what the cause of the RCCB triggering.

Whats annoying me even more is that the electrician gave me a 2 year NICEIC Safety Report with a Spur that has exessive number of sockets in the most highest power taking area of the kitchen, with a cabling taking up to 20A max.......protected by a 32A CB !!!!!.........How is that SAFE ?

Another thing if this spur is particularly close to the consumer unit & was drawing a heavy load would this load be balanced all around the ring or would more current actually be taken by the short distance from the consumer unit to the spur ? (If you see what I mean).........you can see what I'm thinking now by what some have said above......that the cable somewhere between the Consumer unit & the spur connection & the socket in the Original connection is damaged...

Paul