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Topic Title: To what extent would a 12vDc power cable and coax be affected by the regs?
Topic Summary: Installing some CCTV
Created On: 17 July 2017 08:55 PM
Status: Read Only
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 17 July 2017 08:55 PM
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MWalker86

Posts: 56
Joined: 05 June 2017

I'm installing some CCTV and find it odd that I would need to take all the same precautions as I would for mains? For example 521.9 and 521.10. Hardly anyone supplies non-flexible sheathed cctv camera power cable (or am i not looking hard enough?) but in theory it then becomes part of a fixed installation?

But I'm struggling to find a regulation that excludes such a system from (at least some) of the regulations that protect against the really dangerous stuff.

Sorry if I'm being a bit lazy by not fancying a thorough read through of my copy of 17th at this time of night!
 17 July 2017 09:16 PM
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Fm

Posts: 1658
Joined: 24 August 2011

Appropriate Cabling methods for fire escape would spring to mind, other than and the usual segregation
 17 July 2017 09:22 PM
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MWalker86

Posts: 56
Joined: 05 June 2017

Originally posted by: Fm

Appropriate Cabling methods for fire escape would spring to mind, other than and the usual segregation


Stuff like that of course.

But does it really need enclosing in conduit, trunking etc and the other types of physical protection we would instinctively apply to 230vAC?

And then how does the fact you sort of have to transition between a fixed installation (socket) to an appliance (power supply in said socket) and back to fixed installation again (wiring run up to the camera) affect things?
 17 July 2017 09:32 PM
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Fm

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Joined: 24 August 2011

Containment depends on your cable choice/budget
What's the property?
Domestic?
Office Block?

Keep the socket accessible, better still use a spur better still use IP cameras??
 17 July 2017 09:44 PM
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MWalker86

Posts: 56
Joined: 05 June 2017

Originally posted by: Fm

Containment depends on your cable choice/budget

What's the property?

Domestic?

Office Block?



Keep the socket accessible, better still use a spur better still use IP cameras??


It's a small internal run from the socket to the outside of a converted container that will be used for storing tools in an aggregates yard.

It runs to the outside through buried black plastic circular conduit to the camera posts and up into 80mm box section steel and through 20mm galvanised steel conduit where it rises from the soil up into the box section camera posts.

The internal run doesn't go across any sort of walkway. Given the power levels involved I don't see why sensibly placing the run up high in the corner of the wall should really need the sort of protection outlined in the regs for mains power.
 17 July 2017 09:52 PM
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geoffsd

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Why do you want "non-flexible sheathed cable"?
 17 July 2017 09:57 PM
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MWalker86

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Originally posted by: geoffsd

Why do you want "non-flexible sheathed cable"?


Because if I read the regs right (and I fully accept I might not be) that is what I'm supposed to be using for a fixed wire installation, if I don't enclose in conduit etc.

Surely a CCTV system where I put the cables into place and secure against movement and leave in place for years counts as a fixed wire installation?
 17 July 2017 10:12 PM
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Fm

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Do you get shotgun cable designed for external use?
 17 July 2017 11:37 PM
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gkenyon

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Originally posted by: MWalker86

Originally posted by: geoffsd



Why do you want "non-flexible sheathed cable"?




Because if I read the regs right (and I fully accept I might not be) that is what I'm supposed to be using for a fixed wire installation, if I don't enclose in conduit etc.



Surely a CCTV system where I put the cables into place and secure against movement and leave in place for years counts as a fixed wire installation?
Yes.

But

Mechanical protection is not necessarily required for electric shock in this case - but it may be required for longevity of the installation, and performance.

It's just not true that every requirements of Chapter 1 to 6 inclusive applies to ALL cables, and perhaps as you said earlier you may be reading too much into it.

In particular with the Regs you quoted:

521.9.1 - begins "A flexible cable shall be used for fixed wiring only where the relevant provisions of the Regulations are met." ... what provisions do you think your cables do not meet? The standard quoted in the note to 521.9.1 (BS EN 50565-1) only applies to cables of the EN 50525-series of standards ... these are all power cables, so only applies to the DC 12 V cable (which the Reg implies should be "heavy duty" and perhaps nothing more) , and therefore for the coax you would be best looking at relevant parts of BS EN 50173 and BS EN 50174 series of standards for indoor and outdoor cabling installations as appropriate to the particular circumstances.

521.10.1 - pretty much all coax cables, as with other telecoms cables, are "sheathed" - therefore you could surely comply - and what's the interpretation of "sheathed" for the 12 V ... depending on the type of ELV, it may not need basic protection, only sheathing - depends on how you view it?



I'd be more concerned, given your explanation of the installation, to consider a number of other issues:

1. Whether you need to comply with relevant provisions of BS EN 50174-3 for parts of the cabling outdoors - along with SPDs if appropriate?

2. Whether the relevant structures in any part of the installation are protected against lightning in accordance with BS EN 62305 ... which may require additional measures such as SPDs for the coax cables leaving the main building, depending on the design of the LPS?

3. Whether you need metallic containment for electromagnetic compatibility, rather than safety?

4. Whether containment is required outdoors to protect against the effects of UV (and hence affect the continued operation of the CCTV installation)?

5. Method of support for escape routes etc (as has already been mentioned).

6. Whether there are any other provisions for acceptability of the installation to other industry standards (NACOSS/NSI etc - where applicable)?

7. Avoiding "earth loops" depending on how the remote equipment is powered, and whether it is locally bonded for any reason?

8. Whether the source of the 12 V supply is suitable for any overvoltage for supplying outdoors ... depending on what's around the places you're running to?

9. Where cables are buried, even in containment, or proper ducts, are they suitable for submersion ... in the event the containment gets wet, as it often does? In this case, probably more of a functionality issue than a safety one?

-------------------------
EUR ING Graham Kenyon CEng MIET TechIOSH
G Kenyon Technology Ltd

Web-Site: www.gkenyontech.com

Edited: 17 July 2017 at 11:53 PM by gkenyon
 18 July 2017 12:20 AM
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mapj1

Posts: 9049
Joined: 22 July 2004

I think common sense prevails
bellwire is fine for doorbells, unless the bell wire is for some reason routed inside a consumer unit or similar, with exposed live metal bits, whence it should be sleeved lest it touch them .
looking in and around section 414 - it only needs the basic insulation (to meet the selv/pelv test voltage, nothing higher ), unless it is in a box with exposed live parts from a higher voltage, in whcih case more insualtion is needed where it apporeached the live bits.

414.4 Requirements for SELV and PELV circuits
58
414.4.1 SELV and PELV circuits shall have:
(i) basic insulation between live parts and other SELV or PELV circuits, and
(ii) protective separation from live parts of circuits not being SELV or PELV provided by double or reinforced
insulation or by basic insulation and protective screening for the highest voltage present.
SELV circuits shall have basic insulation between live parts and Earth.
The PELV circuits and/or exposed-conductive-parts of equipment supplied by the PELV circuits may be earthed.
NOTE 1: [n particular, protective separation is necessary between the live parts of electrical equipment such as relays,
,~ontactors and auxiliary switches, and any part of a higher voltage circuit or a FELV circuit.
NOTE 2: The earthing of PELV circuits may be achieved by a connection to Earth or to an earthed protective conductor within
the source itself.
414.4.2 Protective separation of wiring systems of SELV or PELV circuits from the live parts of other
circuits, which have at least basic insulation, shall be achieved by one of the following arrangements:
(i) SELV and PELV circuit conductors enclosed in a non-metallic sheath or insulating enclosure in addition to
basic insulation
(ii) SELV and PELV circuit conductors separated from conductors of circuits at voltages higher than Band 1 by
an earthed metallic sheath or earthed metallic screen
(iii) Circuit conductors at voltages higher than Band I may be contained in a multi-conductor cable or other
grouping of conductors if the SELV and PELV conductors are insulated for the highest voltage present
(iv) The wiring systems of other circuits are in compliance with Regulation 412.2.4.1
(v) Physical separation.


No ?
(quoted from a pre yellow version, as that is what I have to hand here, but I'm sure the gist is not changed.)

-------------------------
regards Mike
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