CU. How many 'ways'.

[peeky]

I'm getting there with my purchase of a new CU, but am finding some confusion with '8 way / 10 way' etc. descriptions. I don't want a pre-assembled split load unit as none of them have the combination of MCB's that I need. I have a requirement to connect to 8 'ways'. (4x32A, 3x6A, 1x45A). It seems to me, looking at various units on-line, that some of them seem to count the switches as 'ways', so that an "8 way" unit only has the capacity for 6 connections, and so on.
If I purchase, for instance, a Wylex 9 way split load unit and, separately, the 8 MCB's that I'll require, does that mean that I'll end up with one spare connection for future use, or will I in fact be one connection short?
I must say, this forum has been a fantastic help to me. I've learned more about household wiring than I ever thought I'd know.
(NB
Further to recent 'Scottish' comments; Yes, we now have the Electricity, piped straight in to the house in some cases. What next? Electric pumps for the bagpipes?)

 

[breezer]

What next? Electric pumps for the bagpipes?)

You can always buy bigger and use "blanking plates"

why do you not want rcd protection?

 

[securespark]

The code for Wylex units gives away the number of ways: NHRS 6604 is split 6 ways each.

That's 12 ways for breakers, the 2 module devices are pre-installed.

AFAICT, only MK number the total ways available as they sell some of their boards without incomers, RCD's etc. So in that case, if you wanted an MK 12 way split CU, you'd need a 16 way CU, plus DP iso & RCD and a split load busbar kit.

 

[peeky]

I only have a limited space for my new CU, so oversizing is not an option.
I understood that a split load unit (Wylex) included an RCD protection for up to half the connections and all I had to add were the MCB's. Don't tell me I've got that wrong?!
Just to be sure; If I purchase the '9 Way' Wylex split load CU, and purchase the 8 MCB's that I need, I'll have room for all 8 connections and one left over, and will have RCD protection for up to 4 of the connections?
That's what I'm after.

 

[Taylortwocities]

The Wylex boards come with two busbars that you can crop. You then have a reasonable amount of flexibility on how many ccts are RCD and non-RCD protected.

I am a bit worried that, from your questions, you may not have the knowledge needed to carry out this task properly. Changing the consumer unit is a heart & lung transplant operation and there are some things that need to be done regarding the arteries and other organs of the body.

For instance, have you considered the main bonding issues? What are your plans re this?

 

[peeky]

I'll be getting a fully qualified spark to do the work. All I'm doing is trying to have the appropriate CU unit for the job on site and ready to exchange for the old one. (I've only just ordered a Wylex 9 way unit plus the appropriate MCB's 5 mins ago, on-line). My electrician is coming next week, armed with a drum of 10mm cable, to exchange the CU units and connect my new electric (45A) shower.
I hope I've bought the right thing!

 

[Taylortwocities]

Sure, it'll be fine. I guess you dont have an overhead power feed with an earth spike in your garden do you?

 

[peeky]

Nope.
Just a standard "along the line" terraced house feed. It comes to me from my neighbour's house. Prior to that... who knows, but there's definitely no overhead feed.

 

[davy_owen_88]

I'll be getting a fully qualified spark to do the work. All I'm doing is trying to have the appropriate CU unit for the job on site and ready to exchange for the old one. (I've only just ordered a Wylex 9 way unit plus the appropriate MCB's 5 mins ago, on-line). My electrician is coming next week, armed with a drum of 10mm cable, to exchange the CU units and connect my new electric (45A) shower.
I hope I've bought the right thing!

Just out of curiosity, did your electrician tell you to buy the parts? Electricians can get parts cheaper than you can, they know what they need and they know what they like working with so why didn't you just let him get the things he needs to do his job?

 

[peeky]

I had already looked on-line and knew what I could get, and for how much. He couldn't get the CU for less, so gave me some specs to adhere to (number and Amp requirements of MCB connections / overall dimensions / split load requirements, and suggested I order it myself, to save some money. (He's a very decent chap, and is asking far too little for the work he's doing. Far from making himself some cash, he seems to be mostly concerned with saving me some. Assuming he does a good job, I'll be paying him double what he's quoted, and I'll still be getting a good deal. - He's a friend of a friend, and is giving me "mate's rates", but we've never met previously. I wouldn't take advantage of his decency).

 

[peeky]

As a general observance;
It's perhaps unfortunate that, with on-line purchases the general public can often buy products cheaper than retail outlets can buy wholesale (as in the case of my CU). Subsequently, longstanding retailers are struggling or going out of business. This applies across the board of products. Not just electrical. Where will it all lead? I don't know.

 

[davy_owen_88]

(He's a very decent chap, and is asking far too little for the work he's doing. Far from making himself some cash, he seems to be mostly concerned with saving me some. Assuming he does a good job, I'll be paying him double what he's quoted, and I'll still be getting a good deal. - He's a friend of a friend, and is giving me "mate's rates", but we've never met previously. I wouldn't take advantage of his decency).

*alarm bells ringing*

I hate to be the pessimist but are you sure this guy is a qualified, registered electrician?

 

[securespark]

Nope.
Just a standard "along the line" terraced house feed. It comes to me from my neighbour's house. Prior to that... who knows, but there's definitely no overhead feed.

So does the cut-out (where the main cable from outside is terminated) have an earth wire coming from it?

If so, you may have TT converted to TN-C-S. If not, you have TT and will require an earth rod & an S type RCD.

OR you can request a PME connection from the DNO.

 

[CallEdsFirst]

Nothing worse than a guy on the counter saying "My electrician said to get this!"

Tell your electrician if he's worth his salt and not doing a dodgy cash job on the side, he should source his own bloody materials!

Course, JohnD would advocate the use of RCBOs to save the 2 modules of an RCD!

Just out of curiosity, did your electrician tell you to buy the parts? Electricians can get parts cheaper than you can, they know what they need and they know what they like working with so why didn't you just let him get the things he needs to do his job?

and

*alarm bells ringing*

I hate to be the pessimist but are you sure this guy is a qualified, registered electrician?

both had me nodding my head in agreement!

 

[eyeofthebeholder]

Few questions on the consumer unit front:

1. What is the maximum size of a domestic consumer unit. I have seen them up to 21 way with 19MCB spaces (http://www.tlc-direct.co.uk/Products/MK5621.html). Reason I ask is that this may not be big enough.

2. I have draw up a consumer unit (no particular size) with all the CCTs going in and it comes to 22ways. This includes the RCDs as well as the MCBs. I do not want to limit the circuits I have, but am I going OTT with the RCDs? Is the Power and lighting RCDs at the correct rating?

3. You can see that I have the Front and back garden CCT under the 30mA RCD. I would ideally want to have a seperate enclosures for these, to make access easier when I get round to wiring up the front and back garden - eg one at the front and rear walls of the house (on the inside). It is possible to run a cable not protected by RCD (eg straight from the main isolator switch) to these enclosures and put a 30mA MCB in them? The reason I ask this is to reduce the size of the cosumer unit. What cable size will I probably need - or will it be best just to run 10mm to them?

4. I want two outside lights which are attached to the house. Can I leave them on the lighting circuit or is it best to run a seperate circuit for these also?

Thanks for all your help guys

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