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Topic Title: 110 volt sockets
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Created On: 10 July 2013 07:10 PM
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 10 July 2013 07:10 PM
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mrcornbeef

Posts: 248
Joined: 05 December 2005

Bit of advice on 110v sockets, client has supplied 5kva transformer i was planning on fitting a small double pole DB with 16 amp mcbs type b, fitting two twin sockets per mcb 2 circuits i think output is approx 46 amps , it is 400 v going in , using 6mm swa no longer than 50 metres , i wasn,t going to fit RCD in DB it will be centre tap earthed, it is a factory floor and will be for general power tools , with both cores live at socket will brown be correct for cores, any advice welcome
 10 July 2013 07:43 PM
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jcm256

Posts: 1893
Joined: 01 April 2006

mrcornbeef, this is common set up at quarries usually garages, where they use 110v portable hand tools. Your set up, parts of which are ok but I would turn it down. You must use double pole, two barred MCBs for each circuit, or looped circuits do not forget the earth from the centre tap to sockets
 10 July 2013 07:50 PM
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mrcornbeef

Posts: 248
Joined: 05 December 2005

thanks for reply jcm, i was aware of double pole mcbs and i did mention centre point to earth as well , what about the point of rcd and colours ?
 11 July 2013 07:38 PM
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jcm256

Posts: 1893
Joined: 01 April 2006

Cable colours- would depend on your installation methods, if encapsulation in trunking then conduit to the sockets, use PVC singles ( same size CPC) either 2.5mm or 4 mm as required and of the same colour. Two blacks (already imported into UK from other member states for 230 volt) i.e. lift 230v sockets, sockets on imported panels etc. Two greys (what is that person using to wire sockets telephone cable) no two browns is the colour used. Steel wire armoured Sometimes used. Alternatively, HI-tuff where the CPC is the same size, in both cases you are not going to get specialist coloured cores, no use over sleeving at terminations.

Have seen double pole RCD used as main switch on 110-volt distribution board. If we think about it the test button on a 230volt RCD is across live and neutral via a resistor only to test the tripping mechanism, what have we have with a 110-volt centre tapped transformer pole-to-pole is 110v single phase with an earthed centre tapped secondary winding the voltage to earth never exceeding 55v. (65v phase-to-phase with three phase transformer) Will it work, caution yes with the test button anyhow, (the normal RCD tester indicates get lost). An RCD could be fitted on the primary side of the transformer. (Building sites with a rating of 500mA)

I take it this is a reduced low voltage system your are doing, look at table 41.6 of BS7671 for maximum disconnection times. (Don't know if from said table they mean 110volt RCDs) Anyhow give you some food for thought , good luck with your easy to install project.
jcm
 15 July 2013 06:16 PM
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OldSparky

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Joined: 28 June 2011

why would you need an rcd on 110v system?
 15 July 2013 10:18 PM
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jcm256

Posts: 1893
Joined: 01 April 2006

Old sparkly, good question, I just pointed to the required regulation table 41.6 for maximum disconnection times. Contradictory that regulation for 5sec disconnection time when they also include RCBO (they may mean double pole RCBO) don't know.
Regulation 411.8.3 Fault protection shall be provided by means of overcurrent protective device in each line conductor (ok) or by an RCD?. Why do they write like this, does this make sense to the reader. Are the rules only rough guides and you have to put your own spin on them. (BTW where did he go). Sorry someone else may apply a common sense answer to your query.
(Yes have seen RCD mounted on yellow 110 v transformers for engineering students both the relevant lecturer and myself concluded it was overkill. However, all talk now about 50v touch voltage maybe.
What is this amendment:
AMD 16594 AMD 16594 is a Corrigendum. Amendment January 2010. Amendment May 2012. Amends and replaces BS EN 61009-1:2004 which remains current. Corrigendum January 2013.
 16 July 2013 08:45 AM
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Parsley

Posts: 1035
Joined: 04 November 2004

Originally posted by: OldSparky

why would you need an rcd on 110v system?



The link below is to an article from the voltimum website circa 2005 that you may be interested in.

http://www.voltimum.co.uk/news...rrent-protection.html

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