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'?