Query with a couple regs

[Short Circuit]

Hi - sorry, I haven't been on the forum for ages! Its that long I cant see how to attach photos now!


I have a couple of queries following some work carried out by another contractor and would appreciate a second opinion ( or as many as possible )

One of my customers has just purchased some porta-cabins / modular buildings. They were delivered to site and fitted out by the suppliers own contractors as part of the costs.
There has been 3 compartment dado trunking fitted to the perimeter of most of the building which will be used as offices and classrooms - within the centre compartment, both the cables for the socket circuit, and the data outlets have been ran together. Similarly, both cables have been ran through the same holes in the walls. I have always been led to believe that Reg 528.1 means that they can't be run together in the same compartment, or anywhere in parallel together without segregation. The counter argument given to me by them is that the CAT 5 data cable has a rating of 300 v which would comply with part 1 of 528.1. I have been provided a data sheet for the cables which shows a 'max operating voltage - UL' of 300 - would this be correct and allow them to run together? Not sure what the UL is! Before you ask, there is nothing in the other two compartments. This has also been brought up as an issue by an IT company who have installed additional data sockets


Also, they have not installed RCD additional protection for cables buried within the walls and have said that as they have followed the safe zones from the on-site guide - they do not need to be RCD protected - I pointed out Reg 522.6.202 which to me clearly states they are needed ( they are twin and earth cables in wooden partition walls with no mechanical protection such as conduit etc.). Am I right in thinking that all cables buried in the walls like this required additional protection by RCD


Can you clarify these for me


Thanks in advance

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[Pete999]

Might as well not use three compartment trunking if they are going to do it that way

 

[Short Circuit]

True - especially when single compartment like the 100 x 50 is half the price ( but looks naff!)

 

[Andy78]

So, no RCD protection for the socket outlets either ?

 

[Short Circuit]

Yeah, they have RCD for sockets - although they did 'miss' one circuit and had an MCB fitted instead of RCBO - apparently this was an oversight - despite the fact the certs had readings for the RCD times from that same MCB

 

[J.C.E]

the t&E cable and the cat5 should be separated like you say- if at any point they need to cross- you are meant to cross cables at 90degrees

 

[Andy-1960]

I think what they have done is bad practice, but if the insulation of the outer sheath is as they claim 300v I think they are just about ok as far as the regs go.
I would be concerned though if that CAT5 is not screened especially as they are running so close and in parallel to mains cabling, I think it has the potential for data corruption issues.
Also If the data cable is screened check that the they are all earthed.

 

[MisterE]

When using similar 3 compartment trunking we used to run the data in the top compartment (and drop down into the outlets)with the power in the middle and leave the bottom for the telephone (when not using the data cabling for the phones).

Here's a link to a .pdf file that gives further information (although 10 years old you'll get the gist...) :-
www.connectixcablingsystems.com/content/getFile.cfm?file=275

At the bottom of page 2 (right hand column), you'll see two relevant standards mentioned and a note that one standard's separation is more to do with electromagnetic interference than safety - but that safety must take precedence!

N.B. zooming into your photo you can see that it's UTP (unshielded) data cable.

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[The Ghost]

411.3.3 Additional protection
In a.c. systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:

1. (i) socket-outlets with a rated current not exceeding 20 A, and
2. (ii) mobile equipment with a current rating not exceeding 32 A for use outdoors.

An exception to (i) is permitted:

1. (a) where, other than for an installation in a dwelling, a documented risk assessment determines that the RCD protection is not necessary, or
2. (b) for a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment.
   
   415.1.1 The use of RCDs with a rated residual operating current (IΔn) not exceeding 30 mA and an operating time not exceeding 40 ms at a residual current of 5 IΔn is recognized in a.c. systems as additional protection in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users.
   

 

[Short Circuit]

Thanks for the replies so far
Andy - it isn't screened, or even LSF - just the cheap stuff
Mister E - i'll keep a copy of that PDF thanks - seems some handy info on there.
Vortigern - they have put RCD's for sockets - its the buried cables that are the issue for the other circuits

Cheers

 

[The Ghost]

Quite unequivocal there that RCD protection is needed. But your post #5 causes some confusion as you say they have RCD the RCBO so are the sockets protected with RCD or no? Personally I would have used the compartments for separation of data and cabling for sockets. However I see on a regular basis swathes of data cable laying over SWA trays for runs of 30 and more metres. Flopped over umpteen flourescent lights per office. And out of 60 tenants not one has ever complained of data corruption in the many years this has been in place. Of course you could be a party pooper and insist regards RCDs and data. However I might question the voltage rating as in here: Flame Retardant CAT5e Data Cables|EN50173|FIRE RESISTANT CABLES|Caledonian Cables - http://www.fireproof-cables.com/fire%20resistant%20cables(FIRETOX)/CAT5e-Data-Cables.htm which states 60v. Therefore should be screened from 230v cable.

 

[davesparks]

RCD protection formcables buried in the wall is not needed if the installation is under the supervision of a skilled or instructed person. I would think the caretaker (maintaimemece manager or whatever they're called now) would fall in to this category.

In one of those pictures it looks a lot like they've just cut a big hole in the top of the DB and pushed it up tight to the ceiling?
Is that a TP DB? If so then you might find there's a bit more than 300V present in the trunking anyway.

 

[Short Circuit]

There are no issues re the sockets - there was one circuit with no RCBO but that was changed. My questions were about the cables buried in the wall and the data within the containment. I have the print out for the cable ratings which does say 300
Are you saying that by wanting to follow the regs and insist on RCD protection that makes me a party pooper?

 

[Andy-1960]

RCD protection formcables buried in the wall is not needed if the installation is under the supervision of a skilled or instructed person. I would think the caretaker (maintaimemece manager or whatever they're called now) would fall in to this category.

In one of those pictures it looks a lot like they've just cut a big hole in the top of the DB and pushed it up tight to the ceiling?
Is that a TP DB? If so then you might find there's a bit more than 300V present in the trunking anyway.

I think the loophole regarding skilled or instructed persons and RCD's was closed off on the latest revision to the regs. The cables in the wall should be RCD protected unless a risk assessment is produced to prove that they should not be.

 

[Ian1981]

I think the loophole regarding skilled or instructed persons and RCD's was closed off on the latest revision to the regs. The cables in the wall should be RCD protected unless a risk assessment is produced to prove that they should not be.

The risk assessment only covers whether the socket outlet should be rcd protected or not.
Cables in walls needing additional protection by a 30ma rcd are not subject to a risk assessment it is required full stop unless protected by other means, mechanical protection or earthed metal conduit etc.