3 phase wiring - cable advice Pls.

[Ratbag]

What sort of conduit are you using? Corrugated or rigid?

Rigid is a whole lot better, as it can be more elegantly and firmly fixed to your plaster/timber/whatever, with either half or full saddles: forget plastic saddles, steel are a whole lot better. You obviously will require the necessary angle and connectors to attach "seamlessly" to either end of your cable run.

Inside non-conductive conduit you don't actually require Double insulated cable at all: an infinitely cheaper alternative is to buy 100m rolls of 6mm square single insulated "builder's wire" in the appropriate colours. If you keep your cable run @ 6mm, you will be "future proofing" your installation, thus allowing for future installation of additional 3 phase equipment. You will still have the room and capacity to have an additional run of appropriately sized builder's wire for your 240v outlets in the same conduit, provided the current demand is sufficiently low. Given that you are currently only running a dust extractor, which is basically a low current draw fan, and <10A 240v appliances from this cable run it shouldn't be an issue.

Sure you'll have a lot of spare builder's wire, but if you buy from an elecrtical wholesaler rather than a retailer like Bunnings it will still be cheaper, and you will have spare cable for future projects, always a good thing in my opinion.

Yes, I'm a sparkie too.

[FenceFurniture]

I just purchased a few things for a sparky to fit to my installation from Sparky Direct (mail order in Brisbane). Pretty good service. Here's a link for 6mm single cable (which is extra for postage). Not sure how the price compares to elsewhere.

[Theberylbloke]

Hi Timless,

First up the disclaimer, I am a qualified sparky, what I mention here should be taken as general information only. I accept no liability for what you do with the information.

It may not be wise to use one conduit and expect to pull a second set of cables through it at a later date. To do so risks burning the insulation on both cables due to friction.

While you may get 4 core and earth cable through a 20mm conduit there is unlikely to be room for another cable to be pulled through in any case.

With regard to the number and position of earth stakes. Generally Australia uses the "Multiple Earthed Neutral" system (MEN) of earthing. This means that there is a connection between the main earth wire and the main neutral in your main switchboard.

The location of earth stakes relative to switchboards is determined by whether an earth wire has been run from, say, the main switchboard to a sub board. In your case, as your sparky has said there is no need to drive an earth stake at the shed, he would/should have run an earth wire from the main switchboard to your sub board. No connection between this earth and the neutral, at your shed, is required. If the earth wire were not run from the main switchboard to the shed then an earth stake would be required at the shed. The alternative of using the rio as an earth can be done, I am not totally up to speed with this, though. I recall there maybe some special requirements, though exactly what these are, I don't recall.

Your sparky should be doing a little more than just making the connections. There is an entire section of AS3000 (the sparkies bible) devoted to testing and it's there for good reason!

Cheers

The Beryl Bloke

[Timless Timber]

Thanks everyone.

I've run 32mm conduit with metal half saddles.

I've NOT yet glued the joints - i.e. the conduit can come down and be altered, different cable / cables run or removed if necessary etc.

Nothings connected yet.

I am waiting on a 20 and 10 amp 5 pin 3 phase switches and outlets to come in the mail.

In essence - when the sparky gets back from holidays (not long now I think) and he has the time - he will drop by - tale a look at what I have mocked up and either say yes - lets glue it all up or change the 4 core and earth cable if hes not happy or the single phase cable etc. HE will let me know where to fix the outlet switches to the frame of the shed, and then add the corrugated conduit on the short ends to the switches and the sub board and test - connect etc etc.

If he's not happy he will tell me what to do to change it & call back next time he has an hour spare between his solar panel install jobs...

Often if I have the wrong switch or RCD etc - her will supply me one and take the one I have to use elsewhere.

He's pretty good like that... I've had to move a mountain of stuff stored in my shed - to get the ladders into position to put the conduit and saddles up on the portal frames, and this takes a lot of time (that he doesn't want to have to charge me for while I do it and he stands around and waits).

This is why I try and get 'non critical stuff' done while hes off making a living with his core business (Solar Panels hook in) or in this case his trip to Germany on holidays.

Theres no problem getting the 2 cables thru the 32 mm conduit (I already have them in there with room to spare) and no friction problem coz i did them one straight length at a time and put it all together once the cable was in.

It took a bit of effort to open up the radiused bends to match the shed roof pitch over the portal frame at the ridge line and at the top wall purlin - because these arent 90 degrees, so I had to use a heat gun to soften the radius-ed bends before they were threaded with cables, and re-orient them to match the actual angles...(I made angle templates up out of bent welding rods and then made the elbows conform slightly to the templates while hot - and held them at the required angle, while pouring cold water on them to "set them" at the angle I needed.

It's seems to have worked OK, but again the sparky can decide if thats OK or not...(Likely he would have just used corrugated conduit for that bit).

See what he says when he gets back.

Theres some 20mm conduit and 2 core and earth cable that I could go buy for my lights & switches runs on gumtree....that I might grab that later if its still there when pay day rolls around.

I won't run that till sparky tells me how and where he wants it run... I want my power outlets ( 3 and single Phase) on the walls all in & operational first...then when I can manage it budget wise - the lights can be run later.

I will get there eventually - I can't insulate and line any of the walls internally until all the power is in....

Everything has to be done in its proper order...and cost / budget determines WHEN I can afford to get it done.

That's what happens when you build and run out of $ before its all finished... you have to scrimp & save to get it completed.

[Timless Timber]

& this is part of that scrimping and saving.

I am waiting on a 20 and 10 amp 5 pin 3 phase switches and outlets to come in the mail.

Well they never came.

So tonight I went and scored some off Gumtree.



$50.

This should be enough to finish my 3 phase outlets.

Next will be the single phase power points & then the lights!.

Slowly slowly - catchee monkey...

I love it when plans start to come together.