consumer units

alan rose · Posted: Fri Nov 23, 2007 9:28 pm Post Subject: consumer units

for a domestic dwelling, which is more suitable, a consumer unit protected by an rcd or one with a double pole isolator ?

ricicle · Posted: Fri Nov 23, 2007 9:30 pm Post Subject:

Why do you ask?

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big_vic · Posted: Fri Nov 23, 2007 9:42 pm Post Subject:

>>Its a perfectly legitamate question

No its not. If you are even considering changing a consumer unit yourself you should know what is required.

Sorry to be so blunt but its a fact

comms · Posted: Fri Nov 23, 2007 9:44 pm Post Subject:

depends on what earthing arrangement you have.
But remember with a 30mA rcd as a mainswitch you will loose all circuits in the event of the rcd tripping, this isnt good if you are in the shower & its during the hours of darkness, wet hands in the dark trying to reset the rcd.

You decide.

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alan rose · Posted: Fri Nov 23, 2007 9:57 pm Post Subject:

comms wrote:

depends on what earthing arrangement you have.
But remember with a 30mA rcd as a mainswitch you will loose all circuits in the event of the rcd tripping, this isnt good if you are in the shower & its during the hours of darkness, wet hands in the dark trying to reset the rcd.

You decide.

thank you for taking the time to explain the answer. I'm glad some people still have manners out there

big_vic · Posted: Fri Nov 23, 2007 10:02 pm Post Subject:

Did Part P get cancelled or something?

comms · Posted: Fri Nov 23, 2007 10:02 pm Post Subject:

I dont mind giving advice but please be aware if you are planning on doing a consumer unit change yourself, there is a little more involved in this type of work than people realise.

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prior planning & preparation prevents p*** poor performance.

Taylortwocities · Posted: Fri Nov 23, 2007 11:30 pm Post Subject:

Absolutely, and much more next year when the 17th edition arrives!

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alan rose · Posted: Sat Nov 24, 2007 11:44 am Post Subject:

comms wrote:

I dont mind giving advice but please be aware if you are planning on doing a consumer unit change yourself, there is a little more involved in this type of work than people realise.

I think it only fair to let you know that I served as an apprentice electrician and was jib approved but that was 25 or so years ago, back as far as the 14th edition, so it's ok to go into this topic a little more deeply if you so wish

Chivers7 · Posted: Sat Nov 24, 2007 12:00 pm Post Subject:

Alan,

Personally i'd have one with a 100 mA RCD which would offer fire protection and is normally double poled anyway. I'd have a split load; 30mA rcd for ring/radial and lighting and circuits serving fridge freezers and cookers on the other side. Hope that's a polite enough response

somethingl ik this http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_NHRS/index.html

bernardgreen · Posted: Sat Nov 24, 2007 12:05 pm Post Subject:

The isolator is very useful if you need to change the RCD if it fails to operate when tested or when needed to operate.

The RCD is extremely useful to prevent ( or just reduce the chance of ) death by electrocution, fire and other disasters caused by faults or damage in wiring and/or equipment.

The RCD is also useful to prevent expensive but safe ( the meter spins but no one gets hurt ) loss of electricity to ground through leaky cabling.

securespark · Posted: Wed Nov 28, 2007 12:21 am Post Subject:

Chivers7 wrote:

Personally i'd have one with a 100 mA RCD.........30mA rcd for ring/radial and lighting

But the incomer needs to be TD...

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JohnD · Posted: Wed Nov 28, 2007 12:56 am Post Subject:

option 2 above

plugwash · Posted: Wed Nov 28, 2007 1:21 am Post Subject:

alan rose wrote:

I think it only fair to let you know that I served as an apprentice electrician and was jib approved but that was 25 or so years ago, back as far as the 14th edition, so it's ok to go into this topic a little more deeply if you so wish

It is considered very bad practice to put lights on a 30ma RCD especially one that is shared with other kit and afaict smoke alarms must not be on a 30ma RCD.

However certain loads are required to be on one (primerally sockets that can reasonablly be expected to supply equipment outside the equipotential zone) and for some other loads (showers, other general use sockets etc) it is considered a very good idea by most electricans to put them on one.

On a TT install you also need a main RCD as the EFLI is too high for MCBs to protect properly against earth faults. typically a 100ma or 300ma time delay RCD is used for this. Some like to use them on TN installations as well but most don't bother.

The cheap and nasty soloution to RCD protection is to use a split load board where some ways are covered just by the mainswitch and the rest are covered by a single RCD. The downside is with one RCD covering a lot of stuff when it does get tripped it can be very annoying (especially if computers are on the RCD).

RCBOs are a better soloution because they let you split the RCD proection by circuit but cost more, RCD sockets are even better because they let you split the protection by the outlet but are even more expensive.