200amp isolator at cutout position.

rattlehead85 · Oct 31, 2012

I am currently working on a contract replacing lateral main cables to a block of flats including installing a new 3 phase Ryefield with BS88 63A fuses. Is there any requirement to provide a 200amp 3 phase isolation switch between the DLO 200amp service head and my Ryefield board. If so what reg/regs from bs7671 confirm this.

DHES · Oct 31, 2012

Working for a local authority at the moment doing the design side for these type of jobs ie lateral mains and we have an agreement from the DNO saying no to install an isolator or switch fuse before a ryefield because it will be possible for a remnant to isolate and run a in metered supply to the flats. I think this makes sense

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DHES · Oct 31, 2012

Remnant should be tennant

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rattlehead85 · Oct 31, 2012

Cant say i get that theory. The intake room is locked and not accessible by (Tenants)
and secondly both the Ryefield and Isolator are locked. How would a meter be installed by a tenant in this case without shutting the block off?

DHES · Oct 31, 2012

We have had loads of issues in the past the undesirable tennants who think that they should not pay for the electricity for growing herbs have shut off the isolators in the middle of the night and run there own cables to the flats then just switched back on and all other residents think it was a power cut

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DHES · Oct 31, 2012

1st post should have said un metered supply (bloody predictive text)

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Guest55 · Oct 31, 2012

does the ryefield board have a main switch switch rated at 200 a ?
if yes , then no isolator required
if no , then you need a 200a isolator.
dont have a reg but single point of switching is required whether the mains room is secure or not.

DHES · Oct 31, 2012

As I said the local authority have approval from UKPN in this case but the authority you are working for may be different. Ask the design engineer the question and see what he comes back with

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Guest55 · Oct 31, 2012

if someone with a bit of skill wants to tap off some free power they can do it regardless of whether theres an isolator fitted or not.
that is a building security issue and shouldnt impede on the requirement to have a single point of isolation for the entire installation.

rattlehead85 · Oct 31, 2012

biff55 said:
does the ryefield board have a main switch switch rated at 200 a ?
if yes , then no isolator required
if no , then you need a 200a isolator.
dont have a reg but single point of switching is required whether the mains room is secure or not.

The ryefield has no main switch. Tails terminate into busbars at bottom of fuses. Therefore the only point of isolation would be to pull the main service head fuses which are sealed to prevent unauthorised removal. Therefore how the hell do you turn off in case of emergency?
Also all this agreement carry on.., where does that leave me when it comes to completing an NICEIC cert.

rattlehead85 · Oct 31, 2012

A non skilled person could still bypass their meter by pulling the associated flat fuse out of the ryefield anyway regardless of an isolator being there or not. So the theory of an isolator permitting an unskilled person to switch off to bypass a meter doesn't really stand up.

Guest55 · Oct 31, 2012

well youve answered your own question , no its not right.
as for the cert , well i'd point out this flaw to the client before you start tbh.

thinking some more about it , i'd want it in writing no isolator is to be fitted then record the deviation on the general comments part of the EIC

rattlehead85 · Oct 31, 2012

biff55 said:
well youve answered your own question , no its not right.
as for the cert , well i'd point out this flaw to the client before you start tbh.

Thanks mate. The local authority say they dont want it put in so i guess when the work is completed this will be recorded as a departure on page 1 of the installation certificate. At least i assume this covers me if the departure highlights the fact the client has refused this.

Engineer54 · Nov 1, 2012

DHES said:
Working for a local authority at the moment doing the design side for these type of jobs ie lateral mains and we have an agreement from the DNO saying no to install an isolator or switch fuse before a ryefield because it will be possible for a remnant to isolate and run a in metered supply to the flats. I think this makes sense 

I hope that your local Authority has this foolish waiver in black and white on official company paper!! Since when does the DNO hold sway over fundamental safety, emergency, switching arrangements??

rattlehead85 said:
Thanks mate. The local authority say they dont want it put in so i guess when the work is completed this will be recorded as a departure on page 1 of the installation certificate. At least i assume this covers me if the departure highlights the fact the client has refused this.

No, not unless you can provide proof!!!

Again, who is the person responsible actually instructing you to depart from BS7671?? Is he, or the authority taking the full legal and/or civil responsibility for this safety omission instruction, or are they going to pass the buck on to you, if or when that safety omission contributed say, to the loss of life and or the building??

To both of you, ....get an official written instruction my friends, and keep it in a long term safe place!!! lol!!

I still have around 12 to 14 written instructions, which i have insisted on, for work carried out against contract specifications over the years. One of which, came in very handy long before any court proceedings ensued!!!