Separation of AC and DC wiring in backup systems

[ians]

It seems there are rules with regards to AC and DC separation ... it seems the attitude is the same as my attitude to euro plugs in my house.

What are the facts with regards to installing AC and Dc wiring for backup systems ... in the same wireways ...

is there a specific distance

types of barriers required

crossing over of AC and DC wires in wireways.

What happens when you get to the inverter and you have a whole lots of AC and DC wires you need to now get into the inverter?

[Dylboy]

I have the exact same thoughts! It irritates me to no end! We need the definition of separation.

Is a single layer of PVC considered suitable separation... is it a 5mm gap... is it a PVC trunking plastic thickness fine like in those Dual power trunkings...

What about if they cross wires at 90° or run parallel....


What about having some 12V DC relays in a AC DB board... how far apart must they be to AC breakers, can the wires touch or just there be a 10mm gap or mist DC be 100% jn its own enclosure...? Smaft home stuff is real and there is DC components that will control AC so we need clarification.

There may be some somewhere but I can't find it yet


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[GCE]

Hi

I find the regulation clear with regards to separation
We tend to run a U shape trunking when it comes to inverters and DC cabling and use a split trunking if need be .
We have also run cable tray with a P8000 in the tray for Data cables to keep separate

Have attached reg below that I feel is relevant and a pic of the latest install.



6.1.7 If conductors that operate at different voltages run in the same wireway,
the insulation of each conductor shall be able to withstand the highest
conductor voltage in the wireway. Alternatively, the conductors shall be
separated by a continuous barrier of insulating material or earthed metal.

6.1.10 Conductors that form part of a d.c. installation shall not be run in the
same wireway as conductors that form part of an a.c. installation.

3.85
wireway
open or enclosed route or support such as a rack, tray, ladder, ducting,
trunking, sleeving or conduit that is intended to contain conductors or cables
NOTE A wireway can consist of one or more separate wireway channels, each of
which is intended for different services such as installation wiring and
telecommunication wiring.

[Dylboy]

That is well and good for wireways but I am more asking about in a DB, apologies i was not specific but that is more where my mind is.


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[BobZA]

Hi,

I think GCE covered it all pretty nicely from a regs point of view for wireways

For me the remainder is down to good practice and best effort. Wherever possible run AC and DC wires separately. Where paths cross ... try cross at 90 degrees.

In some panels/DB's it is virtually impossible ... but perhaps a strategically placed piece of trunking / tubing can help separate some of the "delicate" wires.

[ians]

When you run the P8000 ... do you put short pieces of earth wire with a lug or do you just use the pop rivetted joiner for the P8000 as the earth continuity.

[ians]

Hi,

I think GCE covered it all pretty nicely from a regs point of view for wireways

For me the remainder is down to good practice and best effort. Wherever possible run AC and DC wires separately. Where paths cross ... try cross at 90 degrees.

In some panels/DB's it is virtually impossible ... but perhaps a strategically placed piece of trunking / tubing can help separate some of the "delicate" wires.

The 90 % cross over is more for data applications ... when it comes to AC/DC and voltage variations ... its more about the highest voltage insulation protection.

[GCE]

When you run the P8000 ... do you put short pieces of earth wire with a lug or do you just use the pop rivetted joiner for the P8000 as the earth continuity.

use the pop rivet or tek screw for bonding and if not joined to the DB then an earth at the beginning
I have never seen any consultant insist on a bonding strap on each piece besides Transnet

[Weable]

GCE covered the answer perfectly. I would not recommend to any one at all to ever run DC and AC in the same wire ways. Always keep them separated and clearly marked. If in the same enclosure be it trunking or DB and if there had to be a problem and these currents mingle together for an evening drink. It will be a totally off the chat show

[GCE]

That is well and good for wireways but I am more asking about in a DB, apologies i was not specific but that is more where my mind is.


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Been thinking on this one and specifically to home automation type systems .

Technically a DB is not a wireway .
The home auto system use extremely low DC and generally with low current limiting capabilities to prevent damage to the components.
The home automation relays would generally be built into there own separate enclosure and I would term the "DB" as a motor control center or machine

I would say " each conductor shall be able to withstand the highest conductor voltage" as per 6.1.7 and as mentioned above , keep the control wiring in a separate trunking within the DB.
I would also use clause 5.1 note 2

5 Fundamental requirements
5.1 General
All commodities in an electrical installation shall be installed in accordance
with the requirements in this part of SANS 10142 and with the manufacturer's
instructions, where applicable.
NOTE 1 This clause contains the general safety principles applicable to electrical
installations.
NOTE 2 The manufacturer's instructions may contain more stringent requirements.

To me the regulations are written around DC wiring having a high short circuit ratings and the prevention of arching like experienced on PV , inverters ,Battery banks and telecommunication equipment.
I cannot think of anywhere that home automation systems would be mentioned in SANS 10142-1