Spur off Main Tails

[mamba]

Can one - providing Max demand is within limits. Cut / break into 25mm Main Tails between Meter and CU. Then Henley block at said join then spur off HBlock and install another Small RCD Garage DB. So effectivley x2 boards in one property are feed off one head/meter. Client has a garage which is attached to the house and he has really done up well new floors etc for a new Gym for his missus. and wants me to install power and lights in new gym. The service head and meter are in the garage. The DB "Old Re wireable" is situated in the house which he has recently had redecorated at a large expense and looks the "Dogs Genitals" My advise when surveying was to replace DB and move it adjacent to Service head he was in aggreement. However he has since come back and said after talks with the missus they want to leave the DB in situ and not have it moved or upgraded on account of wrecking the new decor. I said there will be damage in any case as I still have to get a feed off present DB into garage, he looked gobsmacked and as with all clients they think we either have Blu Tooth Wi Fi electrics or we somehow manage to just push cables through walls ceilings and floors like magic. This is my only solution I dont think there is anything in the regs to say it cannot be done as we are spuring off the consumer side. although I will say it is proberly not good practise.

 

[Sintra]

How far from original cu to garage. I would say you would need overcurrent protection at the original cu after you spur of the existing tails.

 

[telectrix]

from meter, 25mm tails into 80A fused 2 pole switch/ isolator ( this will give you a single isolation point for the whole installation and overcurrent protection for the tails.) then to henleys. then from henleys to each CU.

 

[mamba]

why?? do not understand why present original CU must now be all of a suddern be protected ??/ tails are +/- 2 meters long

 

[Octopus]

why?? do not understand why present original CU must now be all of a suddern be protected ??/ tails are +/- 2 meters long

Think single point of isolation for the installation. And a good read of the BGB is in order.

 

[mamba]

Bit over engineered!! Other than offering additional protection why a fused isolator??. Why not a bolt standard 60947/3 DP 100amp isoloator as all the isolator is doing is to enable and provide one to isolate the CU's for maintanance rather than breaking the seal and pulling the supply fuse out everytime to work on CU's. The 25mm tails are already protected by the BS1361 100a fuse. The new mini additional CU will have an RCD main Switch to protect all final circuits from it.

 

[Octopus]

Bit over engineered!! Other than offering additional protection why a fused isolator??. Why not a bolt standard 60947/3 DP 100amp isoloator as all the isolator is doing is to enable and provide one to isolate the CU's for maintanance rather than breaking the seal and pulling the supply fuse out everytime to work on CU's. The 25mm tails are already protected by the BS1361 100a fuse. The new mini additional CU will have an RCD main Switch to protect all final circuits from it.

Yes that would be OK too.

 

[mamba]

Understand single isolation but my question is why fused??

 

[Octopus]

Understand single isolation but my question is why fused??

Only necessary, IMHO, if over 3m from DNO to CU's

 

[mamba]

Have had a read of the BGB its my favourite bedtime read every night as it gets me off to a good nights sleep, works every time. Isolators between meters and CU is still appears a very grey area in domestics. Only speaking to my NIC field Eng about it recently. The issue on old installations is the old on going one about the tails out the meter on the consumer side of the install ARE the resosposibilty of consumer yet they are sealed by the supply co???? Yep going forward new installs and any CU changes where the main fuse is pulled by the Supply Co or with their approval {ha ha :33:} and subject to client willing to pay for the extra gear and labour on CU changes a DP switch should be installed as standard for good practice only not a regulation. Also in the BGB there is nothing to say this is a requirement. The mini GB page 17 Sec 2.2.4 Electricity Isolator Switch It says THE SUPPLIER MAY provide .... The supplier.... not consumer.
Any views on this

 

[mamba]

Murdoch ..Always appreciate your wisdom experiance and honesty mate.