To RCD or NOT?

[telectrix]

A scenario for trainees to consider. Sub P.O. requirement is for 6 x double unswitched socket outlets fitted to the underside of the counter for tills, card reader and other IT/ electronic equipment. wiring will be surface in plastic containment. The supply for these is from al local 4 way CU, which is itself fed in SWA form a 40A MCB in the main DB, and the earthing ststem is TNC-S.

My questions are:

1. Would you fit RCD/RCBOs in the local CU?

2. Can you describe the earthing ( cpc ) arrangement for the circuit?

Reasons and reg. nos. for your answers.

 

[malcolmsanford]

Please sir me sir

 

[telectrix]

Please sir me sir

you retraining malc. or is it 2nd childhood? LOL.

 

[malcolmsanford]

Sitting here waitng for some kid with a laptop to interface into a BMS and bloody bored. Also laughably call an "engineer" not as long as my backside points south

 

[telectrix]

for engineer, substitute 2 days trained button pusher.

 

[malcolmsanford]

Wouldn't mind Tel but for some unkonown reason I've got involved and I'm only here to install lights lol
The client has a danfos chilled water system built in 1998. 4 pumps run off a single invertor. We have invertor starts and soft starts and every start known to man. The guy who designed this umpteen years ago is most likely dead and recently pumps have been changed and the invertot ramped down to 45hz because the new pumps are 20kw and the old ones 15kw.
So now we have tripping everywhere because the pump is off it's curve and I have a 20 yr old nost likly who has just master game of thrones on the x box to sort it out

 

[telectrix]

as long as you're getting paid, why worry.

 

[malcolmsanford]

I was getting paid for doing something simple lol right up my street that

 

[Simonslimline]

A scenario for trainees to consider. Sub P.O. requirement is for 6 x double unswitched socket outlets fitted to the underside of the counter for tills, card reader and other IT/ electronic equipment. wiring will be surface in plastic containment. The supply for these is from al local 4 way CU, which is itself fed in SWA form a 40A MCB in the main DB, and the earthing ststem is TNC-S.

My questions are:

1. Would you fit RCD/RCBOs in the local CU?

2. Can you describe the earthing ( cpc ) arrangement for the circuit?

Reasons and reg. nos. for your answers.

I would say from reading 411.3.3 that Additional protection by RCD could be omitted. (An exception is permitted for : socket outlets for use under supervision of skilled or instructed persons. A specific labelled or otherwise suitably identified socket outlet provided for connection of a particular item of equipment)

Regarding the CPC arrangement for this circuit then i guess a high integrity protective conductor should be provided as there will likely be leakage currents from the equipment, 543.7.2. socket outlet final circuits.


I am sure there is more to it than this but ill wait and see what others comments are on this.

 

[matt1386]

I agree with Simon :yesnod:

 

[Baker1988]

A scenario for trainees to consider. Sub P.O. requirement is for 6 x double unswitched socket outlets fitted to the underside of the counter for tills, card reader and other IT/ electronic equipment. wiring will be surface in plastic containment. The supply for these is from al local 4 way CU, which is itself fed in SWA form a 40A MCB in the main DB, and the earthing ststem is TNC-S.

My questions are:

1. Would you fit RCD/RCBOs in the local CU?

2. Can you describe the earthing ( cpc ) arrangement for the circuit?

Reasons and reg. nos. for your answers.

Just out of curiosity has the main db got a rcd?

 

[elliot123]

I was taught if a skilled compentant person is using the sockets it can be acceptable to not use an rcd also with computers they give off a lot of earth leakage which can lead to nuisance tripping which is not ideal in a business, depending on who's using the socket I'd probably not rcd the circuit maybe a rcd socket on the one to be used by employees.

as for earthing was taught if a circuit was used on multiple computers it needs to be high integrity earthing and also sockets need to have two seperate earth terminals with an earth in either one not the same terminal, I remember something about a 4mm seperate earth being pulled in for some reAson id look in my regs or osg but on route to work

 

[telectrix]

baker, no RCD in main DB. elliot, close. remember, the sockets are not for general use. as for the earthing, yes. hi integrity. if a radial circuit in 2.5mm, the cpc should be a ring ( or 2 parallel conductors) using separate terminals in both the sockets and the CU.

 

[Chrisuk]

No rcd in the board, labels required on all the said sockets saying IT Equipment Only, now if one would be used by the cleaner then I'd put an RCD socket on that one but not in the CU