overcurrent protection

[paddyscouse]

hi can any one give me there view on what would be recorded in; the overcurrent protective device for the modified circuit on a domestic minor works cert ,for additional lights fed from a fused spur 3a witch is fed from the ring circuit ? would it be the 1362 fuse in the f sp or the 32 mcb at the c u..........

 

[leep82]

ocercurrent protection

when ive done anything similar in the past ive recorde the 1362 fuse

 

[davesparks]

Re: ocercurrent protection

If it is a new lighting circuit fed from the fused spur then it is a new circuit with the 3A fuse as it's OCPD.
If you added the fused spur to the ring circuit then that is a modification to the existing circuit.

 

[paddyscouse]

Re: ocercurrent protection

yes its a fuse spur added to r c that feeds the lights
thaks for that ill record it as the 1362 fuse ..........should i record the 80% zs values or normal value

 

[davesparks]

Then you have modified one existing circuit and created another new circuit. Not a minor works job really is it?

 

[D Skelton]

It is a minor works job Dave as it doesn't involve the provision of a new circuit. It's an alteration to an existing circuit. And yes Paddy, it's the fuse which offers the overcurrent protection to the new part of the circuit, so that is what goes in the box.

As for the 80% value Paddy, what do you think you should record and why?

 

[paddyscouse]

It is a minor works job Dave as it doesn't involve the provision of a new circuit. It's an alteration to an existing circuit. And yes Paddy, it's the fuse which offers the overcurrent protection to the new part of the circuit, so that is what goes in the box.

As for the 80% value Paddy, what do you think you should record and why?

i think it should be the normal values as said in the bs7671 requirements for elec instal as this is what the cert asks for as oposed to the osg values..... am not sure to be honest

 

[paddyscouse]

i think its the values in the 7671 as this is what the cert asks for as oposed to the 80% in the osg

reasons for the 80% apart from the obvious the "lower the zs safer" im not sure.... what is correct

 

[D Skelton]

i think it should be the normal values as said in the bs7671 requirements for elec instal as this is what the cert asks for as oposed to the osg values..... am not sure to be honest

Those values are for when that cable is operating at 20°C. Under fault conditions that temperature is going to rise considerably increasing the resistance of the cable. The maximum permitted Zs values need to be corrected to take account of this rise in resistance.

I'll ask you that question again

 

[paddyscouse]

ok so your recording 80% values thus allowing for any rise in resistance ? the normal ambient temp is 30 c

 

[D Skelton]

ok so your recording 80% values thus allowing for any rise in resistance ? the normal ambient temp is 30 c

Bingo

 

[davesparks]

It is a minor works job Dave as it doesn't involve the provision of a new circuit.

Circuit: An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device (quote from the ever so holy and never wrong BGB)

We've already established that the overcurrent protective device is the 1362 fuse, so the assembly of electrical equipment connected to it is a circuit is it not?

If you connect a switchfuse with a 6A BS88 to a busbar and feed a dditional lights from it, is the lighting circuit a new circuit, or is it an alteration to the existing circuit feeding the busbar?

 

[D Skelton]

Circuit: An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device (quote from the ever so holy and never wrong BGB)

We've already established that the overcurrent protective device is the 1362 fuse, so the assembly of electrical equipment connected to it is a circuit is it not?

If you connect a switchfuse with a 6A BS88 to a busbar and feed a dditional lights from it, is the lighting circuit a new circuit, or is it an alteration to the existing circuit feeding the busbar?

So what about when you spur off an existing ring final circuit for a single socket outlet? By your definition, is that not connecting an assembly of electrical equipment to the existing circuit, thus making the addition a 'new' circuit? We can argue the ---- over the definitions of the words 'new', 'circuit', 'addition', 'alteration' and 'assembly' all night long and no one will have an answer. That's because their definitions as prescribed by BS 7671 are about as clear as mud.

The fact still remains however, that you don't need to fill in an EIC if all you're doing is spurring off a ring final circuit to supply a light or two. The suggestion that this is a must would be nothing short of bonkers. A MWC is all that is required.

 

[davesparks]

Taking a spur from an existing ring wouldn't involve another OCPD, it would still be the OCPD for the ring.

My point is that by installing a new OCPD and wiring from that you are creating a new circuit.

How would you define a new circuit?

What if it's 3 lights, or 4 or.....

 

[D Skelton]

Taking a spur from an existing ring wouldn't involve another OCPD, it would still be the OCPD for the ring.

My point is that by installing a new OCPD and wiring from that you are creating a new circuit.

How would you define a new circuit?

What if it's 3 lights, or 4 or.....

I'm not going to argue with you mate, if you want to define it like that then you crack on.

You better make sure however that if you want to do it your way properly, that for every fused connection unit you install within an installation you use a separate schedule of test results within your EIC. Each fused connection unit would after all be it's own sub-distribution board.

Now, what was I saying earlier? Something about 'bonkers'?

 

[Pete999]

Dave, got to agree with Mr Skelton it's a modification to an existing circuit, just the sams as if you had installed a couple of extra sockets to an already existing RFC, MNWs cert for me

 

[Badged01]

I've always taken it that the MEIWC is for work not encompassing a "new circuit" --- for me a "new circuit" would be a circuit being directly connected to the consumer unit.

If I'm modifying an "existing circuit" I would use the MEIWC with the "new" OCPD being recorded as the protective device for the modified circuit -- in this case the 3A FCU.

But as ever with the BGB, you can interpret it to read either way so pays your money and takes your choice ...............

 

[davesparks]

I'm not going to argue with you mate, if you want to define it like that then you crack on.

You better make sure however that if you want to do it your way properly, that for every fused connection unit you install within an installation you use a separate schedule of test results within your EIC. Each fused connection unit would after all be it's own sub-distribution board.

Now, what was I saying earlier? Something about 'bonkers'?

No worries, I'm not looking for an argument but I do think it's an interesting point of debate.

For the record I personally do use a minor works too, but am interested to see other peoples thoughts. But also I very rarely, if ever use a SFCU or FCU in this way, and if I do it's usually patching up some DIY efforts rather than new works.

What irritates the hell out of me is people who use this as a way to dodge out of doing proper testing and part P. I've seen a few small extensions where the existing ring has been extended and FCU's put in each room to feed the light, thus they have only altered one circuit and so part P doesn't apply.

'There you go madam I've used a trick that means you save money and don't have to have all that testing nonsense done and I don't have to worry about all that bonding etc the other guys quoted for'

 

[Richard Burns]

If you have an overcurrent protection device near the origin of the circuit and then add additional lower (or even higher!) overcurrent protection devices further downstream, the wiring is still protected by the original overcurrent protective device (even if the later one would go first) so would be part of the same circuit.

 

[D Skelton]

I think you'll find Dave that people who dodge proper testing will behave that way regardless. Carrying out minor works is no excuse for dodging testing. The same tests are required after minor works such as the alteration of a circuit as would be required with the installation of a new circuit. The same results would be recorded on the MWC; continuity of protective conductors of the modified circuit (including bonding and main earthing conductors), continuity of ring final circuit conductors (if applicable), IR, polarity, Zs, RCD etc... as would be recorded for a single new circuit on an EIC.

I have spurred of power circuits to feed lights plenty of times in all manner of installations. This isn't somehow in order to dodge testing or to dodge the part pee police in circumstances where notification would be applicable, but simply because it has been the best solution in the cases where it has been done. Remember also that you can alter as many circuits as you like without it being notifiable (disregarding alterations in special locations or certain alterations outside). You may in such a situation be required to fill out many separate MWCs, in which case it may just be more practical from a paperwork point of view to just fill out an EIC instead.