DC cabling in metal wireways

[Tradie]

Another topic causing a split in opinions.

I am yet to see a domestic installation with the DC cabling in metal wireways.

Please share a picture of 1 x 5 kw inverter with 1 x 5 kwh battery and 6 panels with the PV or battery cables in metal wireways.

I can share tens of thousands of installations with pretty pics of PVC conduit and trunking or bare double insulated wires cable tied to the rafters or conduits or cable trays in the roof space.

I have seen a few large domestic installations, with lots of inverters and batteries, but a single inverter with 1 battery, its like trying to get a pic of a dodo.

Some will argue that there are regulations indicating that single insulated and double insulated wires must be arranged in a certain manner, but like bus stops on Freeways (on the N2) , maybe the regulations dont apply here ?

I see this has been discussed on the platform in the past, but in reality, I am yet to see domestic installation with the DC cabling in metal wireways.

If it is is required then why haven't we adopted the UK regs and enforced metal enclosures ?

[Tradie]

It's like trying to tell a person that they can't mix the AC and DC wiring in the trunking below the inverter, suddenly split conduit becomes a topic of discussion, which some might say is not allowed, just smile

or that you should join all your earth wires from the solar and the grid to one common point, I cant believe that these kind of discussion are still not cleared up, you would think by now, someone will take the bull by the horns and get it right.

I started issuing 10 + page COC's, with single line diagrams and sketches and equipment lists and all that crazy time consuming junk, then realised all I am doing is adding ammo to an investigation, keep it short and simple, add a page of 2 with the absolute basic test results and move on.

One day when the real SSEG COC is released then we can start adjusting the COC accordingly.

[Tradie]

Just google typical inverter installation and see if you can find an inverter installation with DC cabling in metal wireways.

[GCE]

Just google typical inverter installation and see if you can find an inverter installation with DC cabling in metal wireways.

What regulation states it must be in a metal wire way ? I know of no such reg

[GCE]

or that you should join all your earth wires from the solar and the grid to one common point, I cant believe that these kind of discussion are still not cleared up, you would think by now, someone will take the bull by the horns and get it right.
.

There is only one earth , its the piece of ground you stand on , and it is round - Lets not go backwards and try convince people that there are 2 earths , an AC earth and a DC earth , no such thing exists

[Tradie]

I dont know of any either, hence the reason for this thread, I heard it being discussed again last week.

We install 25mm PVC conduit, from the roof down to the PVC trunking around the inverter and battery, if the panels are 460 watt, generally for domestic, we install 2 x 4 mm sq solaflex double insulated wire (red/black) in the same conduit with the earth wire all in the same pipe per string... 4 strings 4 x 25 mm pvc conduits.

I am starting to think it is such a waste to run 1 earth wire per string, all we are doing is bonding the rails and panel frames.

2 double insulated wires (which dont even need to be in a conduit) in a 25 mm PVC conduit, with 1 x separate 6 mm earth wire for the bonding (not lightning protection) strapped to the pvc conduit should be fine.

What regulation states it must be in a metal wire way ? I know of no such reg

[GCE]

2 double insulated wires (which dont even need to be in a conduit) in a 25 mm PVC conduit, with 1 x separate 6 mm earth wire for the bonding (not lightning protection) strapped to the pvc conduit should be fine.

Where do you get double insulated does not need to be in a conduit - Regs are pretty clear that single core will be in a wireway


6.4.6 Unarmoured cables
6.4.6.1 Unarmoured single-core cables without a metal sheath shall only be
used
a) in wireways (see 6.5),

6.5 Wireways

6.4.8 Wiring through building elements
6.4.8.1 If wiring has to pass right through a building element such as a floor,
a wall, a partition, or a ceiling, conductors and busbars shall be in a
non-flammable enclosure or wireway.

[GCE]

I dont know of any either, hence the reason for this thread, I heard it being discussed again last week.

.

When you hear the discussion ask them where in regs as SANS 60364-7-712 list the various scenarios

[Tradie]

Can we agree that the following would be considered a compliant method to wire from the panels on the roof to DC control box, to the inverter ?

Lets use a 460 watt panel (6 panel string)as an example within 15 m of the inverter:

1/ 4 mmsq double insulated red and black solaflex with a 4 mm earth pulled into a 25 mm PVc conduit inside the roof space, to the PVC trunking, down the wall to the DC control box, fitted with a double pole 32 amp DC isolator, 30 amp (1000VDC) fuse holders with 15/20 amp DC fuses and PVT2 20 ka (40 ka max) SPD.

Pretty much the standard configuration seen in 10's of thousands of installations. Personally I have never seen a domestic installation with metal wireways, I am sure there are.

If the conduit is on the roof exposed to the sun and subject to mechanical damage, then maybe you would consider using metal wireways, however then you need to consider the heat on the metal.

You would also need to consider damage to the wire if the installer has not deburred the wireway or used tex screws to attach components.

Because bonding is so critical, you would need to install earth jumpers between all the metal wireways and make sure the conduit has earth straps or clamps.

If you doing what 99 % of installers are doing with the earth wire, running it from the roof down to the DC control box then the inverter, then down to an earth spike, rather than directly from the roof to the earth spike then back to the DC control and inverter. As we all know if lightning hits the metal, it is going to take the ................................................ path of least resistance and boom, kiss you inverter and all the electronics devices goodbye. Thank goodness for insurance. Some might say the SPD will protect the equipment. I wish they had when it hit my house.

[Tradie]

On page 36 of IEC 60364-7-712:2017 © IEC 2017

The picture clearly indicates or should I say the way I read it, if you use a single core single insulated cable, you can keep it separated from the other single core single insulated wires using non insulated conduit or non insulated trunking, however, if you use a double insulated tinned multi strand wire, then you can install the wires without additional protection (strapped to a cable tray for example) as you will see on many industrial and commercial installations.

Installing double insulated tinned multi strand wire in the same 25mm non metallic conduit is compliant.

It might be a better to strap the earth wire on the outside the non metallic conduit to minimise the risk of leakage current to earth.

Considering some decent inverters have built in leakage current protection as you will experience when an F23 fault appears on the inverter.

When you hear the discussion ask them where in regs as SANS 60364-7-712 list the various scenarios

[Tradie]

This is a common question...

712.542.102 Separate earth electrode
If a separate earth electrode is provided for the PV array, this electrode shall be connected to
the main earthing terminal of the electrical installation by main equipotential bonding
conductors.

[Tradie]

This clears up the questions about where to install the earth wire.

PV array bonding conductors shall be run as close to the positive and negative PV array and
or sub-array conductors as possible to reduce induced voltages due to lightning. See also
712.521.103.

[Tradie]

Taking about insulation resistance, take note.

712.531.3.101.1 Array insulation resistance detection
The requirements in 712.531.3.101.1 regarding detection and response to abnormal array
insulation resistance to earth are intended to reduce hazards due to degradation of insulation.
A means shall be provided to measure the insulation resistance from the PV array to earth
before starting operation and at least once every 24 h. This can be done by an insulation
measuring device according to IEC 61557-2, or by an insulation monitoring device (IMD)
according to Annex C of IEC 61557-8:2014, to prevent a possible high risk of fire.