minor works cert for new circuit doubled up from an existing mcb??

[TaffyDuck]

Well I`ll bow to superior knowledge. Seems amazing to me that, in theory, you can put a single socket outlet supplied via a new 2.5mm cable into a 32amp MCB supplying a ring, call it a junction box and issue a MWC but hey ho.

 

[GLENNSPARK]

Glenn as long as you comply with Regulation 433.1.1 regarding cable protection and disconnection times for the protective device you shouldn't have to many problems of how many actual lights are on the circuit.

Also of course you will have the 3% volt drop to consider.

yes Malcolm.....what you will have covered is all the norms.....and i would also assume that if not surface run and at a depth of less than 50mm...n all that lot.blah blah blah.....then the existing MCB is replaced with an RCBO....and earthing + bonding (both main and supplementary)...were checked first....and upgraded ..if necessary....

 

[Guest112]

thanks guys yes bonding was all checked prior to beginning the circuit was run in trunking throughout and was supplying additional fittings, access to existing fittings was the issue so the soulution for him was to run the feed from the db rather from another local fitting, bit of a funny situation i was leaning towards the eic side tbh but you live and learn, there was only one existing feed from the mcb and it supplies the lighting that couldnt be tapped off in the first place so not as bad as it could be, personally i dont like more than one conductor in a protective device unless its a ring but thats me thanks for the input

 

[Guitarist]

8.2.4 in the OSG specifically makes reference to taking a socket outlet as a spur from the origin of the circuit in the DB

 

[telectrix]

Well I`ll bow to superior knowledge. Seems amazing to me that, in theory, you can put a single socket outlet supplied via a new 2.5mm cable into a 32amp MCB supplying a ring, call it a junction box and issue a MWC but hey ho.

that would be adding a single socket outlet as a spur. just as if you spurred from a socket outlet remote from the CU.

 

[Engineer54]

Well I`ll bow to superior knowledge. Seems amazing to me that, in theory, you can put a single socket outlet supplied via a new 2.5mm cable into a 32amp MCB supplying a ring, call it a junction box and issue a MWC but hey ho.

NO Taffy, the 32A breaker wouldn't be able to protect the 2.5mm cable, in the same way as you would need to use a FCU to spur off a ring if you use a single 2.5mm cable.

You Can however connect another ring circuit to that single protective device, as then the 32A breaker will satisfy the circuits protection requirements, and as long as it satisfies the other circuit requirements, such as disconnection times etc, ...it complies!!!

As i've said, not the best of practices, and one that i would hope you rarely if indeed ever see, but it does comply!! lol!!!

EDIT.... Just realised that you can spur off a ring for a single socket!! Just shows you, how often i've allowed spurs off of ring circuits on my projects ...lol!! On the rare occasions i have, it's always been via FCU. I don't like seeing spurs on rings at the best of times....lol!!

 

[Guitarist]

Engineer54, have you never run a spur off a ring main as a single 2.5mm t&e cable? I feel like I'm missing something here...

 

[Guitarist]

Thanks for the edit Engineer54. Thought I was losing the plot for a minute there...

 

[TaffyDuck]

OK thank you guys. I fully understand the electrical aspect but I have to admit that through-out my time as a sparky I have never known this. Whenever I have come across arrangements like this in a CU during a PIR I`ve always flagged it up and I can honestly say I`ve always issued EICs for the work when Ive used an already used MCB
But I`m man enough to admit I dont know everything so thanks again, I`ve learned something new today.

 

[Guest112]

we learn new things every day clearde it up for me also thanks everybody

 

[telectrix]

think it's p21 of the brb. definition of a "circuit". ain't unwrapped the bgb yet, for what it co9st, think i'll display it at the tate.

 

[ample current]

I was told by my tutor that if you connect a new light circuit to the mcb of an existing lighting circuit it is deemed a new circuit.
I remember this because i was marked wrong in my assessment because i said it was altering an exixting circuit.

 

[Engineer54]

I was told by my tutor that if you connect a new light circuit to the mcb of an existing lighting circuit it is deemed a new circuit.
I remember this because i was marked wrong in my assessment because i said it was altering an exixting circuit.

Sounds like yet another lecturer/tutor that doesn't know too much about what he's teaching!! lol!!!

 

[telectrix]

I was told by my tutor that if you connect a new light circuit to the mcb of an existing lighting circuit it is deemed a new circuit.
I remember this because i was marked wrong in my assessment because i said it was altering an exixting circuit.

well, you were correct. your tutor was wrong. see post 26.

 

[TomTrundle]

When you alter an existing lighting circuit protected by an MCB, so long as your alteration is to BS 7671 there is no requirement to upgrade the MCB to RCBO. Is that right?