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Topic Title: LV DC and AC cable on same cable tray?
Topic Summary: DC and AC on same cable tray
Created On: 24 February 2014 07:15 AM
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 24 February 2014 07:15 AM
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engineer29

Posts: 11
Joined: 12 November 2013

I am trying to find a regulation concerning the placing of DC and AC cables on the same cable tray. Generally DC control and AC cables are not placed on the same cable tray because of interference. In this case,both are LV and have sufficiently rated insulation. The DC cables have been laid inside of flexible conduits to provide segregation/barier between the cables
In fact, both have been laid on the same cable tray because of space limitations. Can someone please advise.
Thanks.
 24 February 2014 01:54 PM
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oneye

Posts: 164
Joined: 25 February 2008

The most obvious regulation is the 17th Edition (BS 7671).
What do you mean by AC and DC cables ?

Both AC and DC power cables are seen on the same tray with little segregation providing there is minimum interference.
'DC' can also be read as Analogue, where segregation is more important to both the above.
For the above I had in mind 120vDC / 230vAC power..
 24 February 2014 06:02 PM
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engineer29

Posts: 11
Joined: 12 November 2013

In fact this is for an installation of a PV system for a building. The DC cables from the PV strings have been laid on the same distribution cable tray but in conduit when routed from the roof to the inverters. The voltages we are talking about is 600V DC and 230 V/400 V AC.

I have looked into the BS but haven found anything yet. I am still looking. Are there any other relevant regulations that i cannot think of?
 25 February 2014 07:48 AM
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phantom9

Posts: 673
Joined: 16 December 2002

I think the relevant Reg. is the one about the both cables having insulation relevant to the highest voltage. A cable tray is just a convenient way of supporting cables. I really wouldn't worry yourself over it I cannot see any reason why DC and AC cables cannot lie side-by-side on a cable tray. What in particular concerns you?

@oneye The most obvious regulation is the 17th edition. Really? BS7671 is not 'a' Reg it contains ALL the Regs.. Which Reg. in particular out of the Regs. The most irritating response you can give to anyone asking a question is 'read the regs'. "What do you mean by AC and DC cables." Erm, er, erm...hmm.

Edited: 25 February 2014 at 07:56 AM by phantom9
 25 February 2014 02:15 PM
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Avatar for OMS.
OMS

Posts: 19668
Joined: 23 March 2004

Are the cables (DC ) single core - are they insulated and sheathed as a minimum - is the DC system clearly labelled along the conductor length.

What is the voltage grading of the adjacent LV AC Cables - or is a claim being made on the conduit system (presumably earthed)

In principle, there isn't usually a problem - but it does require there to have been a bit of thought put into the design to achieve a safe system

Regards

OMS

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