SPLIT LOAD BOXES


Postby Suzan » Wed Aug 06, 2008 11:47 am

Hi
I'm looking at a rewiring project and would like some advise on these new split load fuse boxes, consumer units.

I understand the fuse box and an RCD either outside or inside the fuse box. But why have only some of the circuts protected by the RCD ??? It seems a backwards step to me.

Thanks Suzan
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Postby TheDoctor4 » Wed Aug 06, 2008 3:04 pm

Hi Suzan

Have you had a look at the DIY projects section of this site. There are several projects relating to electrical installations RCD's and Fuze boxes, they may be of some help to you: http://www.diydoctor.org.uk/projects.htm

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Postby ericmark » Wed Aug 06, 2008 4:32 pm

There are very few circuits which under current regulations can escape not having RCD protection.
For special circuits where special cable is used you can get away without RCD protection but in the main everything has RCD protection.
This makes me think you have been looking at a sale of obsolete stock?
I have just looked at projects and the page has not been up-dated most consumer units now have either no split or three way split. Those with no split are designed for use with RCBO's which combine the MCB and RCD together and those with three way split have two RCD's which protect most of the items in a house and 2 or 3 RCBO's to protect either vital equipment or equipment likely to trip RCD's so it does not affect the rest of the house.
Do remember consumer units come under Part P
ericmark

Postby TOPSPARK » Wed Aug 06, 2008 7:25 pm

Susan
As your knowledge o the consumer units is limited i would suggest you call in a local part p registered electrician and discuss the whole project with him and then he should be able to give you best advice on seeing the project and clear up any questions you may have
regards
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Postby Suzan » Thu Aug 07, 2008 7:10 am

Thanks for responding

I am quite happy to install a consumer unit (fuse Box) with MCB's a RCD and a Main switch.
The question I am researching is whats the advantage or disadvantage in these split load boxes ?
Half the circits are though the RCD which is fine. But why have half the circuts not protected by a RCD?
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Postby ericmark » Thu Aug 07, 2008 6:06 pm

Sorry not made it plain. The boxes are used in many places not just homes and they are made to be flexible so it can be configured as required. There are four standard versions.

Those with one neutral rail will be used with either MCB’s where no RCD is required or RCBO’s where earth leakage is required. But RCBO’s are both expensive and in most cases only switch the “Line” the “Neutral” being left connected so both for cost and in some cases regulations other options are used.

Before July the single split consumer unit was popular as not all items had to be protected by RCD’s and now these are being sold off cheap and special items like the lights, and smoke alarms are supplied through RCBO’s on non RCD side and less critical items through group RCD.

Again to reduce cost a duel RCD board is used this is to get around the requirement that the supply should be split into circuits to prevent inconvenient tripping and danger and it suggests lights and sockets should not be on the same RCD for same area.

Then a further progression where three neutral bars are used and two go through RCD’s and one is intended for use with RCBO’s.

An RBCO is a MCB and RCD combined but in most cases it does not switch neutral. Some specials clip on to existing MCB so you can use B, C, or D type but most come as one unit. The price can be from £13 to £40 for basic same unit according to make and one has to be careful when selecting what make to use. Now they are being used more the price is going down you must remember many of the regulations controlling their use have only been in force for a mouth or so and even electricians are not quite sure where what is required. As many have not yet studied the new regulations and sat the C&G2382 exam which shows they know how to read the book.

I hope I have explained this time and near everything has RCD protection but not all in the same way.

Eric
ericmark

Postby TOPSPARK » Thu Aug 07, 2008 9:22 pm

Susan as you still seem to have a lot of questions about consumer units and you still seem unsure I STRONGLY RECOMMEND you call in a local registered electrician and then you can discuss fully about rcds and mcbs and rcbo's and he can then best advise you the best way to go with regards to your upgrade.
all the best
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