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Topic Title: RDC Protection for 3 Phase socket outlets
Topic Summary: Needed?
Created On: 23 April 2014 09:39 PM
Status: Post and Reply
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 23 April 2014 09:39 PM
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DMHeywood

Posts: 3
Joined: 23 April 2014

Hello Lad's & Ladies bit new here but hoping somone could shed light on a query i have.

I have just been asked to do and install on a small industrial unit, with this i have been asked to install 3 x 3 phase socket outlets.

Do these circuits need to be protected by an RCD?

Thanks.

Dan.

Edited: 23 April 2014 at 10:08 PM by DMHeywood
 23 April 2014 09:54 PM
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jcm256

Posts: 1866
Joined: 01 April 2006

Sockets could be used for anything, even outdoor equipment. If I were inspecting there, leads across the floor etc, would be asking for RCD protection. Cover your own back as well at all times.
jcm
 23 April 2014 10:13 PM
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DMHeywood

Posts: 3
Joined: 23 April 2014

Yeah was thinking that, ideally i would use a RCD incommer but the current demand is 140A the only TP RCD's i have managed to find are rated @ 100A.

Was thinking possibly RCD protected socket outlets?

Dan.
 23 April 2014 10:21 PM
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slittle

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Joined: 22 November 2007

Look at the schineder acti9 range, they do an "rcbo pod" for tp mcbs.

I've not had the chance to try any yet but could be worth a look.

Also if you've really got a 140A demand. You need to consider what sort of board you are using. I think hager and mem3 are only rated to 125A.

Stu
 23 April 2014 10:22 PM
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AJJewsbury

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Regs generally only require 30mA RCD protection for sockets rated <=20A or <=32A if used to feed equipment outdoors - regardless of the number of phases involved. What rating sockets are you proposing? and what are they intended to be used for?

- Andy.
 23 April 2014 10:39 PM
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DMHeywood

Posts: 3
Joined: 23 April 2014

My bad just added diversity and it comes to 108A

It's typically a car body work shop, so the sockets would be fro 1. spray booth, 2. sprayer. 3 welder. unlikely they will be going outdoors.
 24 April 2014 02:49 PM
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AJJewsbury

Posts: 11462
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ideally i would use a RCD incommer

Would it be ideal for the place to be plunged into darkness if there was a minor fault on an hand-held appliance? (I usually use the example of a circular saw in a workshop, but that's maybe not applicable to this case, but you get my drift I'm sure).
- Andy.
 24 April 2014 08:38 PM
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spinlondon

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There is no requirement to provide RCD protection to circuits other than in some instances relating to special locations.
For instance locations containing a bath or shower, Agricultural/horticultural installations, etc.
Some socket-outlets intended for unsupervised general use by ordinary persons must be RCD protected.
Mobile equipment intended to be used outdoors must be RCD protected.
 26 April 2014 10:28 AM
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davezawadi

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RCD incomer unwise unless the whole is TT?

Your current requirements appear to me to be wildly high! Bodyshop welders are small (unless they have a fixed spot welder), say 6kVA max, the spray booth fans and lights perhaps 3kVA, The compressor perhaps 15kVA (20hp) or less.

I would not attempt to fit RCDs to either the compressor or spray booth, both are likely to give you problems and don't need additional protection, In fact I wouldn't fit plugs either as they are fixed appliances and need to have reliable static earthing against sparks.
So workshop sockets of 16A, with an RCD, individual if you wish.

Welders and hand tools (grinders etc) are usually single phase, so fit single phase 16A sockets for these, simply so that new tools do not need to have the plugs changed, which is liable to error and a nuisance.

Don't forget the spray booth gas / oil bonding and water too if its a wet one! Perhaps its an electricly heated spray booth (unusual), same comments apply to fixed loads as above.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 26 April 2014 03:31 PM
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spinlondon

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I would not say that welders are usually single phase, not at all.
 26 April 2014 09:00 PM
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davezawadi

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The ones used for car bodywork are spin, not 500A MIGS!

-------------------------
David
CEng etc, don't ask, its a result not a question!
 27 April 2014 06:19 AM
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Jaymack

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Joined: 07 April 2004

Originally posted by: davezawadi
Don't forget the spray booth gas / oil bonding and water too if its a wet one!

"Don't forget" that a spray booth orobably requires ATEX hazardous area protection!

Regards

Just a poor country boy
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