Ring Main Questions

[wiredworm]

Hi,

I'm looking to add a few additional sockets to an existing ring-main in a kitchen. I have a few questions that i'm hoping someone can assist me with.

1. Is this work notifiable under Part P? I know that certainly used to be the case but then I found an article on the NICEIC website which says amendments were made in April 2013 so that they're not notifiable unless a new circuit is required?

2. I need to obtain suitable cable. I understand that 2.5mm can be used for a ring main because the power draw is actually on both 'legs' of the circuit. I'm looking at ordering something like this (http://www.screwfix.com/p/prysmian-...ey/83956#product_additional_details_container), but the way they describe the technical spec has confused me a little. It says '1 strand per core. 18.5A rating. -15°C to 70°C' which would initially suggest it's no good for a 32A ringmain, but if that rating of 18.5A is per core then with the live and neutral cores added together you have a rating of over 36A. Am I reading that correct is that totally the wrong cable to go for?

Thanks for any pointers on this. My intention is to do the majority of the work myself but I will be getting a qualified electrician in to do the final check and cert for me.

Pete

 

[EFLImpudence]

1. Is this work notifiable under Part P? I know that certainly used to be the case but then I found an article on the NICEIC website which says amendments were made in April 2013 so that they're not notifiable unless a new circuit is required?

You are correct.

2. I need to obtain suitable cable. I understand that 2.5mm can be used for a ring main because the power draw is actually on both 'legs' of the circuit.

More than that; it is what IS used.

I'm looking at ordering something like this (http://www.screwfix.com/p/prysmian-...ey/83956#product_additional_details_container), but the way they describe the technical spec has confused me a little. It says '1 strand per core. 18.5A rating. -15°C to 70°C' which would initially suggest it's no good for a 32A ringmain,

They are wrong; it is 27A.
For some reason they do this quite often.
I may tell them.

but if that rating of 18.5A is per core then with the live and neutral cores added together you have a rating of over 36A.

It doesn't work like that.

Am I reading that correct is that totally the wrong cable to go for?

That is what is used for Ring Final Circuits.
It's not a ring main; they are in the road.

Thanks for any pointers on this. My intention is to do the majority of the work myself but I will be getting a qualified electrician in to do the final check and cert for me.

That may be alright for an inspection but not if the work were notifiable.

 

[ban-all-sheds]

1. Is this work notifiable

No, but the requirements of Part P still apply.



Arguably that requires you to be able to do testing.

http://www.tlc-direct.co.uk/Book/8.1.1.htm

if that rating of 18.5A is per core then with the live and neutral cores added together you have a rating of over 36A. Am I reading that correct is that totally the wrong cable to go for?

No - you are not reading that right - you don't add the currents flowing in the L & N to get a total like that.

http://www.google.co.uk/search?q=electrical+circuits+101


But it (almost certainly) is the right cable. I do wish sellers wouldn't quote "ratings" like that. 2.5mm² T/E can carry anything between 13.5A and 27A, depending on how it's installed.

But 18.5A is not the capacity for any of the reference methods in BS 7671.

http://www.batt.co.uk/products/view/624/Table-4D5A

You should read this, and consider how your cable is/will be installed.

http://electrical.theiet.org/wiring-matters/Pre 2004/bs7671-amd1-ring-circuits.cfm?type=pdf

My intention is to do the majority of the work myself but I will be getting a qualified electrician in to do the final check and cert for me.

It doesn't work like that.

If you want an electrician to issue a certificate you'll have to find one before you start and agree with her what you can DIY. She will not issue a certificate if you just get her along and present her with a fait accompli.

 

[wiredworm]

Thanks for the comments - much appreciated.

The person doing the certification and testing will most likely be a friend of a friend who works in the trade but of course i'll discuss with them before I start cabling things up. My main priority right now is to just chop the walls where cables are going to run because we're due to have the floor tiled shortly so ideally i'd like to get any messy work out of the way.

The installation will be predominantly surface mounted below the kitchen worktops with channels cut upwards for the five double sockets we want fitting flush over the worktops. The distribution of connected appliances isn't so bad. Washer and drier will be connected to a 2 gang under counter socket (fitted behind the cupboard that sits between them so accessible without removing either appliance). A seperate segment of the ring is routed in the roof void and this will be dropped down near the sink and again surface mounted before being boxed in with the pipes. Fridge freezer, hob and oven (13A) are all mounted close to the start of the ring. I took some time earlier today to plan the layout and i'll try to post some pictures of what I came up with later.

There's a few fuse spurs i've keyed off the main but i'm hearing that a lot of people frown on this. Given i'm channeling out the wall anyway it wouldn't be a huge problem to run two lengths of twin and earth and just make it a part of the ring. Any views on this? I presume the main benefit is it allows more flexibility in the future should it be required?

 

[ban-all-sheds]

The person doing the certification and testing will most likely be a friend of a friend who works in the trade

This is part of what "certification" entails - the signing of this declaration:

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2011 except for the departures, if any, detailed as follows:

So friend, or friend of a friend - how do you feel about expecting him to put his name to that if it isn't true?

 

[bernardgreen]

I being the person responsible for the design, :
So friend, or friend of a friend - how do you feel about expecting him to put his name to that if it isn't true?

Responsible means they accept responsibility for the design, it doesn't mean they have to be the person who does the design, if they consider the design is satisfactory and are willing to accept responsibility for it then they can sign that declaration

 

[wiredworm]

All understood - and part of the reason why i've already put a design on paper which i'll be showing to the person i'll be expecting to sign off on it.

I'm not demanding they allow me to do the work - if they don't feel comfortable doing it then i'll happily pay them to do the lot. Or alternatively we'll agree to a compromise where I perhaps channel and run in cables whilst they come and complete the final works.

I have no desire to cut corners or perform an unsafe installation but time is something of a factor hence why i'm looking for a compromise which will allow me to push ahead with some work until they're available to complete the final tasks.

I'll be calling the electrician this morning so hopefully he can get to me in the next 3/4 days.