Power cable suitability for 240volts

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Ironsfan

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#311119 15-Dec-2023 19:20

Any help would be most appreciated.

Need to run power to a shed that is 35m from house. Now I have come across some 10mm 2core which I think after using my poor google search skills would be ok but not sure. It is tricab 2 x 10mm2 PV1*-Fi98 Pv cable 0.9/1.5kv DC as/nz35033 lszh 120. Hoping I can run this and put an earth rod in at the shed. Hopefully someone out there knows the answer.

tweake

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#3172179 15-Dec-2023 19:38

ask your sparky. as its going to require fuse board board work that home owners are not allowed to do.

Scott3

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#3172189 15-Dec-2023 20:38

You can find calculators online. I.e.

https://www.jcalc.net/cable-sizing-calculator-as3008

But the required sizing is going to be entirely depending on things you haven't listed, like required current, and conductor material.

Note that the nominal voltage in NZ is 230v.

And that any work inside the switchboard is required by law to be done by a registered electrician, who will need to do the calculation themselves anyway, so you might as well jump to that step.

SomeoneSomewhere

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#3172190 15-Dec-2023 20:52

That's PV cable, and rated for DC usage only. There appears to be a remarkable gap in our standards in that, as best I can see, there is no explicit requirement to have the cable rated for the voltage present on it.

It's only two cores. While it is in some circumstances permissible to use a two core cable with a separate earth stake and MEN link, this is only where there are no other conductive services or structures linking the two buildings - no ethernet, no copper water pipes, no metal fences, nothing. Generally, you should expect to use twin and earth (TPS, flat or circular) or two-core neutral screen. You could also use three sets of conduit wire, which would need to be in conduit for the whole length.

As single insulated cable, it must be enclosed in conduit for its entire length to provide a second layer of protection. You haven't said whether you intend to run it overhead, underground, or in some other way. Overhead cables have special requirements, underground generally needs conduit unless it's armoured cable or neutral screen in soft soil/sand.

Sizing is another matter altogether; you'll need to determine the expected loading and protection, and the actual cable length between the switchboards, not just the physical distance.

Consult your electrician.

larknz

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#3172198 15-Dec-2023 22:31

There is no standard as/nz35033. Tricab means that it is a flexible cable, which is not allowed for fixed wiring.

SomeoneSomewhere

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#3172199 15-Dec-2023 22:37

Heavy duty flexible cable is allowed for use in installations as fixed wiring. The intended purpose of that cable is for fixed PV arrays.

AS/NZS 5033 sets out the requirements for PV systems. Most likely the leading 3 is a miss-transcribed s.

Ironsfan

13 posts

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#3172312 16-Dec-2023 11:37

This was to give me some idea whether to buy this cable as it was at a good price. However after reading the reply's I think I'll leave it be.

Thank you everyone for your reply's.

SATTV

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#3172355 16-Dec-2023 14:55

Ironsfan:

Any help would be most appreciated.

Need to run power to a shed that is 35m from house. Now I have come across some 10mm 2core which I think after using my poor google search skills would be ok but not sure. It is tricab 2 x 10mm2 PV1*-Fi98 Pv cable 0.9/1.5kv DC as/nz35033 lszh 120. Hoping I can run this and put an earth rod in at the shed. Hopefully someone out there knows the answer.

No, this is not suitable, you can not put in a second earth rod.

There can be a potential difference between the earths and cause all sorts of issues.

If a separate earth cable was run then that May be suitable be suitable.

A quick google says this is for Photo Voltaic installs, so may not be suitable.

John

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larknz

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#3172360 16-Dec-2023 15:08

SATTV:

Ironsfan:

Any help would be most appreciated.

Need to run power to a shed that is 35m from house. Now I have come across some 10mm 2core which I think after using my poor google search skills would be ok but not sure. It is tricab 2 x 10mm2 PV1*-Fi98 Pv cable 0.9/1.5kv DC as/nz35033 lszh 120. Hoping I can run this and put an earth rod in at the shed. Hopefully someone out there knows the answer.

No, this is not suitable, you can not put in a second earth rod.

There can be a potential difference between the earths and cause all sorts of issues.

If a separate earth cable was run then that May be suitable be suitable.

A quick google says this is for Photo Voltaic installs, so may not be suitable.

John

Don't quote me on the latest rules, but previously you certainly could run a 2 wire sub-main and drive a separate earth rod.

SomeoneSomewhere

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#3172533 16-Dec-2023 21:37

Yeah, outbuildings clause, 5.5.3.1 (b) Separate MEN installation.

NOTE: Particular care is required where conductive pipes and such items as
telecommunication cable sheaths, covered walkways, etc may be continuous
between separate buildings and thus establish a parallel earth/neutral path.

Falls in the not recommended category, and there were suggestions that it wouldn't be OK to put e.g. EV chargers on them. Also, as it involves work on a main earthing system, it would arguably be subject to inspection.

Better to use 2C+E TPS or 2C NS, e.g.

https://express.ecsnz.com/en/lapp-8100679-olflex-power-ns-neutral-screen-cable-2x10

https://express.ecsnz.com/en/lapp-8100673-olflex-power-ns-neutral-screen-cable-2x6

https://express.ecsnz.com/en/lapp-3803844a-black-circular-tps-xple-3g10

Daynger

435 posts

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#3172679 17-Dec-2023 14:21

tweake:

ask your sparky. as its going to require fuse board board work that home owners are not allowed to do.

No, he should ask the Inspector that will be signing off the work any questions.

All homeowner work MUST be inspected by an electrical inspector who will do the connections at any switchboard as homeowners are not allowed to do any work on switchboards.

ECP51.

SomeoneSomewhere

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#3172766 17-Dec-2023 16:44

Yes, certain work done under homeowner exemptions including IIRC any new cable must be inspected by an inspector, not just an electrician.

However, some inspectors do not want to do actual electrical work for insurance/other reasons, so it's possible the homeowner would do some parts, an electrician would connect it, and an inspector would inspect it.

I think we were largely assuming that OP would supply the cable, and an electrician would do the rest, bypassing the requirement for an actual inspector unless a main earthing system was involved.

raytaylor

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#3173529 19-Dec-2023 22:32

I regularly ask my electrician this question.
We do work on secondary buildings with radio antennas and have to bond the antennas and mast both to a nearby earth rod at the secondary building, as well as to the electrical earth.

I get it explained to me each time by the electrician and I think i have remembered now... its okay as long as we have used TPS cable between the buildings and the neutral is only bonded to earth in the main fuse board, and not the remote fuse board.

Then the earth wire in the TPS cable (so 2 core wont work without an earth wire, hence TPS) is used to bond the two earth rods together so there isnt any potential earth voltage difference.

By only having neutral bonded to earth at the main fuse board, it stops the earth wire between the buildings from carrying current except in a fault condition where it causes (and encourages) the RCD to trip.

So yes to OP - you should just be using TPS cable and nothing else - unless its high current or three phase then talk to your electrician about options for neutral screen cable and the implications that creates.

Ray Taylor

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SomeoneSomewhere

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#3173534 19-Dec-2023 22:58

Neutral screen doesn't really change anything; it's just a more robust cable. It's still available with between two and five conductors, but the colour codes change a bit - two core NS will have red & white or red & blue inner cores, plus the unmarked screen that you would terminate and mark as an earth at both ends, and mark the second conductor (white or blue) as a black neutral.