Supply type

[sh]

Can somebody tell me (in laymans terms) why I cant use a 100A main switch with a 30 mA rcd split unit and why on a TT system it has to have RCD coverage on both sides of split board (I cant find this information anywhere)
Looking at the 16th edition regs it says that on a TT system only the socket outlets have to be covered bo RCD.Have I read this correctly.
Is another option to have single RCD coverage using 1oo mA

 

[plugwash]

on a TT you must have a 30ma non delayed rcd on all sockets

additionally because of the high earth fault loop in most cases you need some form of rcd on everything else

in a domestic situation this is normally done with a 100ma type S (time delay) though higher trip point rcds can be used.

another option is to use 30ma rcbos on the non-rcd side of a normal split board (or even just using them for everything and not bothering with the split)

putting everything on the same 30ma rcd is not explicitly prohibited but means you lose lighting if any appliance develops a fault that trips the rcd and so is not generally reccomended.

 

[sh]

Is this the type S you are referring to
www.tlc-direct.co.uk/Products/BH80slash2slash100.html
What do refer to as HIGH earth fault loop.
If I have the correct earth loop impedence can I still not use a standard douple pole main switch,does it definately have to be rcd.

 

[ban-all-sheds]

Is this the type S you are referring to
www.tlc-direct.co.uk/Products/BH80slash2slash100.html

That does not appear to be a time-delayed one. The incomer should be time delayed or you won't get proper discrimination against the 30mA socket one.

What do refer to as HIGH earth fault loop.
If I have the correct earth loop impedence can I still not use a standard douple pole main switch,

A TT supply will always have a high earth loop impedance compared to TN systems, which should be well under 1 ohm.

does it definately have to be rcd.

Y E S ! !

 

[sh]

Could you point me in the right direction for one that has the necessary time delay.
Thanks

 

[timmyquick]

Could you point me in the right direction for one that has the necessary time delay.
Thanks

http://rswww.com/cgi-bin/bv/browse/...dddjgkjkehcfngcfkmdgkldfil.0&catoid=-84178471

Think you maybe have to be a member to purchase, not sure

 

[sh]

Does anybody know who else apart from MK make the 100mA time delayed rcd Incomer for a split board
Thanks

 

[ban-all-sheds]

I imagine they all do - Crabtree, Merlin-Gerin, Hager, Siemens, Wylex...

If you've not chosen your new CU yet, then I guess you should check beforehand that they do make such a device, but I doubt if it'll limit your choice.

Don't forget it must be a plastic CU. If you want a metal one, or for some reason don't want or can't get a time-delayed incomer, then there is always the option of a standalone RCD in a separate (plastic) enclosure.

 

[AliasOmega]

Crabtree, Merlin-Gerin, Hager, Siemens, Wylex...

These are the more expensive of the range.

There are many cheaper versions that require more input from the person fitting it (elbow grease)..but its far far cheaper. I think its down too £6 a mcb..

Some of the cheaper ones are like..

Contactum
Square D
& many many more..

 

[ban-all-sheds]

One of the great things about DIY is that you don't have to compete on price, you don't have to make savings on everything you buy, as often they are just one-offs, and so you can afford the better stuff.

 

[AliasOmega]

I do admit, the more expensive items are easier to work on and do look pretty, tho if im saving £2-3 per mcb, and ive got a 14 way split board with type B and C's fitted, id rather have the cheaper.

Personally i dont like MK as i think they are poor for the price you pay, but for some of the mid range items...(Newy & eyer own brand sockets) they are not bad. If you look in B&Q and wilkinson..

A double socket..£1.49
A MK double socket £7.99

The examples are there..and if you kitting the whole house in it, then your going to be paying more. The cheaper items tend to be last years items, i remember when MK were square, then Tenby were the old MK, then they come down the ranges as years go on. Many makes make other makes..

 

[Adam_151]

please delete

 

[sh]

I have already chosen a contactum split board from tlc http://www.tlc-direct.co.uk/Products/CMPS14slash80N.html
Can I replace the standard 100A Incoming isolator with the 80A 100mA rcd incomer.
Would this not be the same as in a seperate enclosure.

 

[ban-all-sheds]

I have already chosen a contactum split board from tlc http://www.tlc-direct.co.uk/Products/CMPS14slash80N.html

Why that make?

I don't know what they are like inside, or how easy to wire, but the impression they give from the outside is that they are cheap'n'nasty.

Can I replace the standard 100A Incoming isolator with the 80A 100mA rcd incomer.

No - as I said, that Contactum one is not time-delayed.

Would this not be the same as in a seperate enclosure.

If Contactum don't make a 100ma time-delayed, then you'll have to have one in a separate enclosure.

 

[AliasOmega]

Can I replace the standard 100A Incoming isolator with the 80A 100mA rcd incomer

I would say yes...

In the past we have replaced these, but not with contactum ones, look out for single way RCD board of the tyre you require, and check the size of the RCD, and if it fits on the mounting rail.

Ive seen some others fit into these boards, just have a look round. You need a kind warming counter salesman that is willing to assist you in your task.

I use to work for a boss, who was always on a budget, so we had to deal with the cheap items he bought, they may be hard, and you have to work with them..but im up for contactum...

Ill even come do it for you..as i love them so much...