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  1. #1
    Join Date
    Jul 2013
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    Default 3 phase wiring - cable advice Pls.

    I have 3 phase power on in my shed, a sub board, 1 x 32 amp outlet and switch (plus a single x 2 outlet single phase power point).

    No lights etc yet.

    This 3 phase outlet runs my Robland X31 combination machine.

    Since then I bought a 5 hp, 3 phase H & F style twin bag dust extractor!

    It has a very short 3 phase lead with a 20 amp plug on it, and it is on the opposite side of my 6 meter wide shed to my power sub board and existing 1 and only 32 amp outlet!

    So in essence while I have a dust collector, I can't use it yet, at the same time as my machine that's making the dust!

    I managed to find a 20 amp outlet and switch second hand on gumtree for $20, that would suit the dusty - so grabbed it.

    Now I intend tomorrow to go to Bunnings and BUY the cabling & corrugated grey conduit & 32mm saddles necessary to run the 3 phase wire...from the sub board across the portal frame to the other side of the shed where the dusty is and where I will mount the outlet, when it arrives in the mail.

    The run in from the street has 3 x 60 amp fuses from memory - the mains board has 40 amp rcd for the shed 3 phase?...(I think)...

    The cable to the shed is 6mm^2, 4 core and earth and distance turned out to be a little under 30 meters from meter box on house into sub board.

    Obviously I'm not going to hook this cable up myself... I will get a sparky in to do it - BUT, I want to save cost by sourcing my own cable conduit saddles and run it there myself to save labor and time and just get the sparky to connect the wires into the sub board when I can afford it. The sparky who put my power on - is away in Germany on holidays another couple weeks before he comes back and I want to have this done before he does if I can, so his time & effort to assist me is minimal.

    So.. the distance is about 15 meters of cable required.

    Questions

    1. What spec cable (mm^2) do I buy for this 15 meter run across the portal frame from one side of the shed to the other?. (More 6Mm^2 - yikes that stuffs about $6+ a meter).

    2. Do I need another 3 phase rcd thingy in the sub board (there's room for another 1 or 2 bye the looks) - or does he splice the wires into the existing one and it protects both outlets?. (If i need another, how many amps rating do I buy for this 2nd one)?

    3. Is there anything different I need to know about pulling the wire thru the flexible grey conduit and affixing it with saddles and tek screws to the portal frame..or do I just copy what he's already done running it into the sub board and to existing outlet?

    4. If I wish to have single phase power points on that opposite wall eventually as well, - do I need to buy that white 2 core and earth single phase power wire of a size capable of running say a 20 amp outlet, and run a length of that thru the same conduit at the same time... before I saddle it all to the portal frame...or just install a pull chord for now and pull some single phase wire thru later?

    5. If I should run the single phase power wire now with the 3 phase one - what sort (specification) wire do I get and is it Ok to run it in the same conduit as the 3 phase wire or should it have it's own separate smaller dia corrugated conduit like the 1 only double power point outlet I have now next to the sub board has?

    Just don't want to do anything the sparkys gonna larf at and make me pull it all down...and re do, coz I did it wrong.

    It would be nice when he gets back, if he can check it over - connect one end into the sub board, and other end to the outlet and I'm good to go... so I am trying to save $ obviously... Coz he values his time about 10 times what he values mine at, when we do "swap labor" coz lectricians are so much smarter than other trades you know - so I have to minimize his time here, to be able to afford his genius skill set.

    Later, I want to add a 3rd x 3 phase outlet @ 10 amps to run my little compressor....... but that's right next to my existing 32 amp outlet and the sub meter so not a big job like this run across the shed.

    Also I still have to get him back at some point, to connect all my 8 double batten flouro lights up.

    The costs seem never ending with this shed. (But at least I can bite it off in small chunks as i can afford it & I get time to think about where I REALLY want stuff) rather than pay out big and get it all done and then later regret not planning it better at the outset.

    TIA.

    ADDED BY ADMIN


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    or moderators for advice offered by members posting replies
    or asking questions regarding electrical work.
    We strongly advise contacting a Licensed Tradeperson for all electrical work.



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  3. #2
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    Jul 2006
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    Port Huon
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    Default

    Correct me if I'm wrong but doesn't the various legislation state that you have to be a suitably qualified person to do ANY work involving electrical installation? This includes running cable, conduit etc.
    I'm surprised that a licensed electrician would sign off on any such work.

  4. #3
    Join Date
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    Perth
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    Default I

    I ran the conduit to my shed and helped the sparky pull the 6 mm cable thru... he had no issues signing off at all (Have the certificate here).

    It's not like this is my first rodeo...

    I ran a lot of the cabling and conduit inside the shed for his install...albeit this time he was there to watch me... but hey.. if he tests it before he couples it up - wheres the big deal.

    So - what sized cable do I need?

  5. #4
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    Jul 2006
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    Port Huon
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    Default

    I wasn't questioning your ability, just the legality.
    Perhaps you should wait until your sparky returns and address the questions to him.

  6. #5
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    Default Perhaps not

    yeah and perhaps not, too!


  7. #6
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    May 2013
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    dondemn
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    Default

    maybe there is a reason - "he values his time about 10 times what he values mine at, when we do "swap labor" coz lectricians are so much smarter than other trades you know - so I have to minimize his time here, to be able to afford his genius skill set. ????? yes i'm an electrician also.

  8. #7
    Join Date
    Dec 2005
    Location
    Canberra
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    Default

    There's a range of issues to be aware of for three-phase, as the capacity for something nasty happening is considerably greater due to the bigger power draw.

    Cable size is determined by how much power is needed, the distance (for voltage drop...as an industrial motor expecting 230 volts may not be happy at 190) and how the cable is run (in conduit, in free air, attached to the wall, fully covered in thermal insulation and so on)

    6mm three phase cable is good for anywhere between 19 to 42 amps (depending on how it is run) and 4mm is 15-33 amps.
    You should also have it connected by an RCD/MCB to protect you/the wire BUT depending on the inrush current you'll need to get the right one - A C curve MCB will handle five to ten times inrush, a D curve 10-20 times inrush)


    The Olex handbook is here - http://www.olex.com.au/Australasia/2...andbook_FA.pdf

    Oh, and as for adding extra wire for standard power points - that'll depend on the size of your conduit and the wire that's already in it. (I think there are tables for that in the Olex handbook, otherwise AS3008 and AS3000)

    If it's going to have a 15 amp power point then (from memory, check AS3000) you can only have one other 10 amp power point on that run, but if it's just going to have 10 amp sockets, you can go wild as there's no limit to the number you can have. Cable is minimum 2.5mm, typical RCD/MCB size is 16 amps.

    Another useful resource:

    http://www.schneider-electric.com.au...conductors.pdf

  9. #8
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    Perth
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    Default Uh huh!

    Uh Huh,

    Yes 4mm^2 & 20mm conduit.

    Thing is, I already have on hand 32mm orange conduit, BUT thats for underground use (i.e. not UV stable) however this is inside a shed and no skylights so - if I paint the orange conduit I have on hand, to protect it from the UV rays it will never see inside the shed, it should be big enough dia to carry both the 4mm^2, 3 phase, 4 core and earth cable I need to run my dusty, as well as single phase 2.5 tps for any future power points on that side of the shed!.

    Least that's my plan at this stage.

    It's subject to change if there's good reason to do so.

    Thanks for those who assisted, the rest...

  10. #9
    Join Date
    Jun 2013
    Location
    Geelong
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    Default

    A wiseman once said

    "I went all over buying 2nd hand switches and outlets only to find that some of what I bought was the wrong outlet (4 pin outlet and my machine had a 5 pin plug.... so we had to supply and fit a new plug to the machine).


    Unless you know what your buying - its best left to the sparky probably - a LOT of what I bought couldn't be used...and the time effort and Distance to collect it all adds up (fuel along with the multinova speeding fine I got) "

    "Hopefully you can benefit from my recent experience and mistakes! "


    Better to wait for your sparky to comeback and advise as he knows your particular setup

  11. #10
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    Perth
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    Default I am

    I am waiting for the sparky to come back from holidays, and while I am waiting, I'm installing conduit, and cable, to keep me outta trouble!

    I could spend half my life waiting or I could even die waiting!

    Victory favors the brave....(While failure favors the fool).

    Only time will tell (which i turn out to be) - but - at least I won't have wasted my time waiting!

    2 steps forward, and one step back, is still making progress - while waiting is making nothing!

    As Bob is want to remind me on occasion - this is all part of my Karmic Zen journey....while sitting still waiting, is no journey at all!.

    The longest of all journeys starts with the first step, - after that it's just a matter of keep placing one foot in front of the other until you get there.

    I am making steps - albeit small ones... and niggling the forums sparky's along the way?... well that's called 'light entertainment'!

    Either way i will get there... dead or alive is the only bit yet to be determined!

  12. #11
    Join Date
    Aug 2008
    Location
    Adelaide, South Awstraylia.
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    Default

    Quote Originally Posted by Timless Timber View Post
    ... well that's called 'light entertainment'!
    Sounds to me you are on a "Power trip" .............
    Try to look unimportant, they may be low on ammo.

  13. #12
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    Default Yup

    Yeah I find it hard to understand the negative nellies...
    The conduits are held up with metal saddles with teks... I can always take them out again if it proves necessary.
    Similarly the joints aren't glued (yet) just friction fit - I wait for the sparky's 'go ahead' before doing that, in case for any reason he wants to change anything - it's a easy disassemble.
    If he is good with my conduit and positioning and cable selection then it's an easy 5 minute, slip each joint, glue up and re tighten teks.
    A drawstring run with the 3 phase cable - means we can run anything else like extra cable in there if needed at any point, including before I glue up the joints.
    All that time saved - measuring up the lengths of conduit and cutting, de-buring them, feeding the cable and drawstring thru etc. Also with the pitched roof - normal 90 degree elbows - have to be heated and opened up slightly to make the correct angles to match the roof pitch - and that also takes time.
    It's all time saved for the sparky...if he takes a look and is happy - he can test and connect etc, if not - well I can tear it back in 5 mins and re do - but again a LOT of the time consuming stuff like measuring and cutting to length is already done. Obviously I leave a coil of spare length on my cable ends...so he has more than plenty to run into the sub board and can slip on a short piece of corrugated flexible conduit cut to length to neaten up the end bends. It should come out alright.
    I should really buy a taller step ladder -I don't like standing 2 feet on top step of the short one I have, to reach the pitch of the roof!. Well not to work with drills and tek screws etc - different if I can hang on with one hand!
    Good excuse for cleaning out more of my shed while I'm up there, making more space every day! (And the pile down the front waiting for a skip bin is likewise growing every day)! At least I am doing something and making slow progress.

  14. #13
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    Aug 2008
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    Adelaide, South Awstraylia.
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    Default

    I wired up my shed IAW the AUS/NZ Standard, I think I have a copy if you want? Then I started to ring around the sparkies until I found one willing to inspect my work and sign it off. I had a separate power box in my shed with all the various circuit breakers for power, lights, 15A circuits etc, all wired up, but the main wire from the shed box to the house box was not connected. The first sparkie I rang had no problem with the concept, came around and the only thing I hadn't done was install an earth stake for the shed. I assumed the one from the house was enough, everything else - the power, lights - he was more than happy with and he connected and issued a certificate.
    Try to look unimportant, they may be low on ammo.

  15. #14
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    Default Thanks Ric

    Thanks Ric,

    Anything you have would be good please.

    When the sparky was doing the sub board I asked if we needed to ground spike it, and he said "no" coz the one at the meter box on the house was sufficient (Also that the metal shed which the sub board is earthed too - is bolted into concrete with steel reo in mine down 4 feet into the ground anyway.

    I was surprised... I guess it depends on the sparky.

    I already have the power on the sub board in the shed from the meter box on the house - so even tho i could knock it out at the house meter box - I draw the line at messing with connections... the "right" thing to do is let the sparky do it.

    I figure it this way...

    I MIGHT work out enough - to "make it work", but what I pay the Sparky for his knowledge and expertise is - to know 100% that if / when something goes wrong... it will definitely "not work" (earth trip) when it is s'posed too - in order to protect user/s (including me).

    Many years back I bought a old farm house - where unbeknown to me, the previous original owner 2twice removed from me had done work himself connecting lights outside under the eves!.

    One night in a massive storm the gutters overflowed and water ran all thru these lights.

    Instead of blowing a fuse... it fused "open circuit" and electrified the tin roof of the house and lots else besides.

    I came out of the bedroom in the dark... half asleep, to see "little blue fireflies" buzzing around all over the wet copper flyscreen on the kitchen window!

    I almost reached out to touch one before I stopped myself.... thinking - I wonder if thats live current?

    Turned out after we got SECWA (Western Power) out in the middle of the night - the confirmed the wet house was live all over and knocked out a pole fuse for me...

    Next day a sparky came and started fixing everything - and traced it back to these eaves lights... the polarity was reversed or something & that's why the lights worked but fused open circuit - electrifying most of the house.

    If one of the kids had woken up before me and touched anything metal like the flyscreen doors etc (heck even the metal lid on the meter box was live) - theycould have been killed.

    After this "lesson" in life - I don't mess with lectrickery... I will dig a trench and put in conduit with a pull thru.... or run conduit in my shed and again put the cable in or a pull thru...

    But connecting stuff up... I draw the line there.

    I don't begrudge the guy his pound of flesh for his qualification, knowledge, and experience,...when it comes to hooking it up.

    After all even sparky's have to eat, put a roof over their head, and pay their bills - BUT, mine and his missus drive 2 brand spanking new BMW's, he has 2 new BMW Motorbikes in his garage, and his double story house on the hill in the swanky suburb, with in ground pool and everything that opens and shuts, is worth well over the $Mil.... so - as a one man band sparky, he sure knows how to charge! (Which is how he and her are away in Germany for 3 weeks on holiday, while I am at home running conduit in my shed)!

    I don't mind paying him - but I can't afford to pay him to do grunt work like digging trenches etc...which I am more than capable of.

    I know that might annoy a few sparky's on the forums - but hey - its is what it is... I didn't win lotto last week or this one so, - for now I have to do what I can...to make the $ stretch.

    Maybe if I had I wouldn't be worrying about trying to do stuff myself to save a $! (and copping flak for it).

  16. #15
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    Canberra
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    Default

    The majority of supply authorities prefer outbuildings to be earthed at the same stake as the main connection.

    I think the reasoning is that if you have more than one main earthing point it can lead to different levels of earth potential (the earth at your main switchboard is connected to the neutral side of your mains connection so it has less resistance than an 'earth-only' connection) which can lead to fault currents that are not high enough to quickly trip protective devices.

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