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

[Guest112]

hi guys hoping you can settle a debate i had in work the other day a colleague of mine has been issuing minor works certs for the above explained situation but i asked him why he isnt issuing EICs when he does this he said its because its an existing circuit and hes just adding to it from the db???

seems wrong to me and rough tbh any input on this one?

thanks

 

[TaffyDuck]

Well if you take his argument to its logical conclusion as you can turn off the whole board via the 60947 main switch then the whole system is just one circuit, load of old rubbish. your right ,hes wrong

 

[Plonker 3]

Sounds like your colleague is correct, additions to a circuit can be covered with a MWC. If he were to change the protective device or install a RCD or RCBO then a EIC would be required.

 

[Plonker 3]

Well if you take his argument to its logical conclusion as you can turn off the whole board via the 60947 main switch then the whole system is just one circuit, load of old rubbish. your right ,hes wrong

So every job needs a EIC does it?

 

[TaffyDuck]

So every job needs a EIC does it?

Of course not but are you seriously saying that by adding another circuit to an MCB that its the same circuit as the one that was there before? Its a new circuit so it needs a EIC

 

[malcolmsanford]

If he was adding a singular unfused socket of a RFC or perhaps wiring a ground floor extension lights to the ground floor lighting circuit then yes a MEIWC is all that would be needed.

 

[telectrix]

nope. if the new work is supplied from existing MCB that already supplies a circuit, then the new work becomes part of the original circuit.

 

[GLENNSPARK]

Well if you take his argument to its logical conclusion as you can turn off the whole board via the 60947 main switch then the whole system is just one circuit, load of old rubbish. your right ,hes wrong

well as it`s still a new circuit..( ok ...yes, its cheeky to take it from an existing circuit at origin but theres nothing to say you cant do this)......but its STILL a new circuit and as such is subject to an EIC.......

 

[malcolmsanford]

Of course not but are you seriously saying that by adding another circuit to an MCB that its the same circuit as the one that was there before? Its a new circuit so it needs a EIC

You can't add another circuit to an existing circuits MCB that already as a circuit in it. Reg 314.4.

But if your using the MCB as a JB, and extending the circuit as in post 4 then your fine

 

[Engineer54]

nope. if the new work is supplied from existing MCB that already supplies a circuit, then the new work becomes part of the original circuit.

110% CORRECT!! Not by any means good practice, but none the less it remains as a single circuit!! It's not possible to have 2 or more circuits supplied by a single protective device!!!

 

[GLENNSPARK]

110% CORRECT!! Not by any means good practice, but none the less it remains as a single circuit!! It's not possible to have 2 or more circuits supplied by a single protective device!!!

allright...i get your drift eng mate.....time/current ....back to a single point at source and all that but.....lets say that the original/existing circuit served 5 points......typical for a small house down lighting circuit.....and the new feed consisted of.....lest say 8 or 9 points......

 

[Dave 85]

Does anyone here actually like filling out fekin certs? If I can get away with an MWC instead of an EIC-more power to me, the customer still gets the same job done at the end of the day. Having said this I would never use it as an excuse to NOT add an mcb, now that is rough.

 

[GLENNSPARK]

Does anyone here actually like filling out fekin certs? If I can get away with an MWC instead of an EIC-more power to me, the customer still gets the same job done at the end of the day. Having said this I would never use it as an excuse to NOT add an mcb, now that is rough.

well of course if you were to drop an MCB into the C/U for a NEW CIRCUIT......and run a circuit from that....as this would be clear...then it would be an EIC.....

 

[GLENNSPARK]

or what you could do is to take the line from one side of the C/U.....and the neutral from the other side.....a sort of shared responsibility if you like....half the circuit..half the cert...seemples....

 

[malcolmsanford]

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.

 

[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?

 

[telectrix]

if your new work requires RCD protection in order to comply ( e.g if you are burying cable in a wall < 50mm deep etc., etc.) then you must either fit RCD/RCBO to the circuit, or an RCD FCU to your new work.

 

[GT1]

interestingly the diagram on page 425 of BGB shows socket outlets wired downstream of an FCU wired in 1.5mm....
Makes perfect sense when thought about, but woulve triggered a trip to the van to check the book if i'd found it on PIR (ECR)..!