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Posted By Topic: Cable gauges

May 02 2018 13:31

Hi guys,
What is an adequate cable gauge from the switch board down to the grounding rod, and also from the switch board to heat pump (on its own circuit)

May 02 2018 17:09


May 02 2018 18:40

hmmm.... American talk....gauge....grounding rod

May 02 2018 19:47

Just looking at one here. 90mm cable to a earth mat of 25mm x 3mm copper strap with 4x 120 odd meter holes with16mm rods back filled with bentanite slurry. I think that is probably adequate.

May 02 2018 20:12

Tested one last week which gave a good result.
70mm Wricon welded to 25mm plate connecting 8 25mm vertical 10m D form steel reo
Other option, I agree with Mr Adams, I mean Apprentice

May 02 2018 21:30

Gauge 0000 would be adequate

May 02 2018 22:31

If there\'s a native tree close by then it\'s preferred to drive the grounding rod there. Much lower earth resistance that way. My rule of thumb is 0.1 gauge per meter for earth. My AC unit runs over bluetooth so no wires required.

May 03 2018 11:41

So to summarise... call your local electrician.

May 03 2018 12:09

👏👏 stoked I found such a bunch of helpful professionals.. cheers guys

May 03 2018 13:22

You haven\'t provided enough information to answer the question but you have provided enough to suggest this isn\'t something you should be doing yourself.

If you\'re in the US the short answer is that NZ electricians aren\'t familiar enough with US rules to advise you even if you gave more information. Call your local electrician.

If you\'re in NZ (and just using US terminology) and you\'re relying on the homeowner exemption then you\'re basically not allowed to do work on a switchboard, and the work you do needs to be checked by an inspector anyway. To avoid problems you\'re best to get them involved before you start so you don\'t make mistakes (like wrong cable sizes) that they could\'ve advised against in the first place. Call your local electrician or inspector.

Link to the work you can do below (assuming you\'re in NZ).

May 03 2018 14:24

Cheers for taking the time to give a proper answer Andrew. Yeah I am in NZ, the guy who\'s installing the heatpump reckons I\'d get away with 2.5mm tps, but just wanted to get a few opinions on that. Will not be working in the switch board. Cheers

May 03 2018 17:06

Your question, as posted probably made a few of the audience cringe as it asked things that should be second nature to a qualified person, as posted I didn\'t doubt the assumption you weren\'t. I suspect this is what enticed the responses given. If someone leads you through the process to size cable, protection etc they\'re potential helping you do something you should not be doing, it has numerous bad implications for both parties. I read it and wondered if it was a serious post or baiting to see who would bite.

May 03 2018 17:20

\"get away with 2.5\" hmmm, have you checked the instructions that came with the unit?

But you should still be getting an electrician to do the work.

May 03 2018 21:40

[quote]the guy who\'s installing the heatpump reckons I\'d get away with 2.5mm tps, but just wanted to get a few opinions on that. [/quote]
Why is that out of curiosity?

May 03 2018 23:08

I would be getting 3-4 quotes. I got 3 quotes and the unit I decided on as the most reliable and efficient for my location also ended up the cheapest. The cost for the sparky varied between about $250 for the company I went with up to $650. So for what the guy quoted I was quite happy letting someone else do all the work.
If you want a separate quote you need to let the sparky know the unit specs and what the manufacturer recommends. Also depends on how easy to run the cable, how long and the route of the cable

May 04 2018 09:50

i certainly don\'t tell my customers that \'i\'d get away with\' anything, if that\'s his attitude what\'s the rest of his workmanship like, we have rules, and standards, 2.5 is quite possibly very suitable, but there\'s a lot of factors to consider.


May 04 2018 10:27

mf51to1 suggests:

> Gauge 0000 would be adequate

Four aught? Adequate?? You, Sir, are an animal :)


May 06 2018 22:50

7/.044 should do for your grounding rod, and 7/.029 will be fine for your heatpump, but dont forget the de-rating factor for cables running in insulation, in which case you might need to up size to 7/.036.