Advice/opinions on this setup

[leep82]

Not posted for a while so thought id pop on and see what opinions/advice people had the following situation.

Ive recently taken on a quite a large two storey extension consisting of kitche/diner and utility room downstairs and a bedroom and bathroom upstairs.

The existing setup is a 100a TT supply. The DNO’s fuse is mounted adjacent to a plastic 8 way consumer unit, which has a 30ma RCD acting as the main switch, all inside a small cupboard.

Needless to say this existing consumer unit is not big enough to accomodate the number of circuits i intend on installing in the new extension. Also the wiring run through the house is a nightmare so upgrading this to a consumer unit with more ways isnt really an option. Therefore my plan is to split the meter tails using a henley block and run a new supply to a new consumer unit situated in the utility room. This will be done in SWA clipped externally over a run of approx 20mtrs.

I intend on installing a switch fused isolator in the small cupboard after the henley block. One question i have is do i need to install a 100ma time delay RCD also? Im leaning towards yes as i remember a very similar setup i did when i worked direct for my last company where we did. The SWA will be installed as such that it will be very unlikely to ever get damaged and at no point is it hidden in any walls. The 100ma RCD is there just for fault protection yes? And subsequently offers discrimination to the dual 30ma RCD board i intend to install in the new extension. Would any enclosure i use for this RCD need to be of metal construction? Is there anything on the market that i can use to incorporate the sw fused isolator and RCD in the same enclosure?

The existing consumer unit is also going to replaced and given the lack of room afforded in the cupboard it has been agreed that this unit will comprise of RCBO’s.

Any thoughts on the setup described and questions would be most welcome

 

[Leesparkykent]

Lewden 100AMP SP&N SINGLE POLE AND NEUTRAL FUSED ISOLATOR SWITCH - https://www.superlecdirect.com/p-fs6380100-lewden-100amp-spandn-single-pole-and-neutral-fused-isolator-switch/

Lewden 80 AMP 100MA 2 POLE TIME DELAY RCCB / RCD - https://www.superlecdirect.com/p-801002s-lewden-80-amp-100ma-2-pole-time-delay-rccb-rcd?gclid=EAIaIQobChMImIec7vSz3QIVAZztCh0kbABUEAQYASABEgKhhfD_BwE

Replace the main switch in the switch fuse with the 100 mA s type RCD.

 

[bigspark17]

I dont like splitting the tails with henleys before a single point of isolation for the installation. Id prefer to keep the one consumer unit and run circuits back if possible,

 

[Wilko]

Hi - it's good that you are taking precautions to keep the new 20m cable safe, but we still need to provide protection against (an unlikely) L-E fault. I've used S type 100mA for this and never had issues with selectivity. As it's a house I would use a metal containment as per LSK.

 

[mhar]

I dont like splitting the tails with henleys before a single point of isolation for the installation. Id prefer to keep the one consumer unit and run circuits back if possible,

Use a Wylex REC2 (sub £15) as supplied by some dnos for isolation. Apparently doesn't require ammendment 3 metal enclosure.

 

[leep82]

I dont like splitting the tails with henleys before a single point of isolation for the installation. Id prefer to keep the one consumer unit and run circuits back if possible,

Keeping one consumer unit isnt really possible. Its an old cottage and the space below the floor above ceiling is limited as it it is, not your standard joists.