Consumer Unit 8m from cutout

[Andy™]

I agree and its perfectly feasable, however the chances are slimmer with T&E than a seperate Live. This is one of the reasons why those orrible single live and earth cables where designed.If I had to move any cu this distance from supply I would go with conc or armour as first choice, and doing so would not need to RCD, just provide isolation.

split con is treat the same as T&E... so if its chased into a wall, it needs RCD'd

 

[steptoe]

[quote name='Andy

 

[green-hornet]

[quote name='Andy

 

[Andy™]

but your gonna hit the earth before the line, so RCD will trip, not the case with singles, CPC can be a distance from the line

not always. split con is not fully surrounded by an earth. but if you dont hit the earth, your gonna hit the neutral, and take the fuse/MCB instead

 

[steptoe]

[quote name='Andy

 

[Andy™]

yes, point taken,but that is my general point about tails, you could in fact have an actual gap between conductors.

yes, you could have a gap between conductors. but the point is, tails, just like T&E, are possible to be damaged by hitting live only, and so not trip the MCB. RCD's are then used to disconnect if you get a shock. its not there to immediately detect the live has been hit, but if it does (like if you also hit earth), its a bit safer. within the RCD, its unlikely there would be enough current through you to trip an MCB.

with SWA etc, you must be in contact with the earth before you can hit a live, and so MCB will trip, and RCD's are not needed

 

[batty]

[quote name='Andy

 

[ianmacd]

[quote name='Andy

 

[TonyCE]

Bump:

DNOs always had their own ideas about tail length being protected by their equipment, hence all the numbers like 3m that people discuss, and use of switch-fuses so installation has its own fuse protection. However, on a new build in Salcombe I came across 30m tails and contacted local DNO - in short DNO lost court case for arbitary restriction on tail length. The courts considered the argument that cut-out fuse protects tails, a legitimate compliance with BS7671, without the use of switch-fuses etc. etc.

I found this piece of information on the Meter Operators website>

The meter tails should be as short as possible. Different distribution and metering companies have different policies but the length should always be less than 3 metres of cable from the cut-out through the metering equipment to the consumer unit. A example may be 1m of cable from the cut-out to the meter, then 1.5m from the meter to the consumer unit. The meter tail cable size must be consistent. BS7671 Reg 434.2.1 gives some guidance. If the consumer unit is required to be further away, then a switch-fuse unit should be installed close to the meter and a sub-main compliant with BS7671.

And the information in 434.2.1 does include the "3m in length" information.

 

[Megaohm7]

Do you have any details on the court case? I'd like to quote this at the NICEIC at some point. The only information I've seen on this previously is that in the OSG it says that the distributor sets the max length of the tails and the distributor I have discussed this with also quoted 3m max.

We could be seeing an amendment out soon regarding this to BS7671. Maybe !! :Salute

 

[binky]

Returning to Salcombe case, local DNO has been on site and given green light to 30m tails. Alas I wasn't there to be privy to the conversation so can't report exactly what was said.

 

[SPECIAL LOCATION]

And the information in 434.2.1 does include the "3m in length" information.

The 3m reference in 434.2.1 is relating to the position of protective devices where there is a reduction in C.S.A. or other change reducing the current carrying capacity of conductors.

(re-read 434.2 to put 434.2.1 into context...)

i.e. NOT where meter tails are just being extended..

That is longer meter tails are SAME size C.S.A. and SAME current capacity..

therefore regs 434.2, 434.2.1, 434.2.2 are not relevant...

If IMHO you read them all in context that is!

 

[Chr!s]

And the information in 434.2.1 does include the "3m in length" information.

As above

This allows us to install a protective device in the load side.

Think of a bus-bar and the reduced size of cable/conductor current capcity to the protective device

providing we install to 434.2.1 then it complies

 

[steptoe]

just as an aside to this,

just been to an LA property today where the meter is being moved and 5m of tails will be needed,

DNO have asked for a 63A switch fuse to be fitted (space on their board!), but will be available all day on the given date to terminate,

meter being moved from ground floor to upstairs and the guy talking to me seemed pretty decent actually,

I know sometimes we have probs with them, but TBH its a minority IMO.