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  1. #1
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    Aug 2011
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    Default 3 phase power to my Shed!

    Hi all,

    With a few financial goals ticked off in the last few months, I'm looking at options wrt supplying power to my shed. SWWMBO has even offered to make it my birthday present, including 3 phase if it's indeed doable. Until a couple of weeks ago, I had envisaged running single phase to the shed from the house. ATM we only have single phase at our house. Recent purchases and potential future purchases have made me look at the possibility of supplying 3 phase to the shed. I did have the option of connecting 3 phase to the house but the builders wanted an extra $2500 for that luxury and at the time I figured I would never need it!

    So far everything is looking promising. There is definitely 3 phase in the power pit. I have a couple of mates who are sparkys, and while they have not looked at the setup, they seem to think it is doable. There is one stumbling block that I can see however, from the power meter, the power needs to somehow get from one side of our (concrete) driveway to the other. There is a piece of 100mm sewer pipe that goes from one side of the driveway to the other side to facilitate running services without digging up the driveway. I have excavated and exposed it to find that the plumbers have used it to route the polypipe for water supply to the house through it. Where do I stand wrt now routing some orange conduit through there? Its about 3M in length and so the power will be running next to the water for about that length.

    I'm just trying to establish as many facts as possible before spending any money Also what sort of circuit should I consider to be sufficient for my needs? The shed is about 100M from the power meter. While I'm not qualified to make these decisions/calculations I have used an online calculator to work out some basics. 16 sqmm 3 phase cable should be able to provide about 40A (allowing a maximum of 5% voltage drop) maybe even 48A or so. I can't see that I will EVER draw that amount of current, since I never operate more than 1 or maybe 2 tools at any one time. Even if I was to purchase a machine tool that required say 5 HP, it would not go near that. Bearing in mind that I am not setting this up as a commercial venture, it's purely a hobby and will remain that.

    Will 40A do?

    Cheers,

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

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  3. #2
    Join Date
    Nov 2011
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    Sutherland Shire, Sydney
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    Default

    Being far from an expert in these things, I believe that your 48 Amps from 16mm cable is 'per phase'. Dunno how many horsepower that equates to on a lathe or mill, but would be absolutely heaps for a home workshop.
    I have 10mm 3 phase cable to my shed which is about 30 metres from the meter box, and have no problems with hobbiest sized lathe and tablesaw, dusty etc.
    As for running a conduit next to a water pipe, again speaking from a non expert point of view, there shouldn't be a problem.
    I'm sure someone with an electrical trade background will soon join in and enlighten us all.

    Good luck with your project,
    Alan...

  4. #3
    Join Date
    Feb 2013
    Location
    Laidley, SE Qld
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    368

    Default

    Where we are, the house is 70m back from the road and my shed is another 80m back from the house. When I went to extend the 240V from the house to my shed I was advised by the electrician that because of voltage drops over those distances I first had to upgrade the cables to the house.

    Given that I was going to have to trench from the road to the house to the shed and lay new cable from the road to the house to the shed, installing 3 phase while I was at it was a no brainer. The extra cost for 3 phase was 2k, which covered the 4 core cable, a 3 phase meter board at the house and a 3 phase sub-board in the shed.

    Well worth it I reckon.

  5. #4
    Join Date
    Dec 2007
    Location
    Brisbane
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    17

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    I agree with above comments. If you intend to run 3 phase to the shed your should also upgrade the house and meters at the house, then extend 3 phase from your main switchboard to the shed sub-board.

    Admittedly this is no cheap job, but well worthwhile. I have achieved the above over several stages including installation of a 12KW Grid Connect Solar System on my shed roof. The whole process included upgrading the street supply lines to 25mm2 so there should be no limitations on future additions. The Shed is supplied with 3 phase on 16mm2 underground cables.

    BTW in Queensland (probably Victoria too) all underground power must be a minimum 600mm below ground & marked above ground if longer than acertain dimension (sorry can't remember that bit from 3 years ago).

    OTO if you find the cost too great to do all the above. You can still send single phase to the shed subject to the limitations of the house load calcs and your street connection. Don't forget VFDs are now reasonably priced so as long as you have the single phase capacity 3 phase machines can be driven off single phase via VFD. I have just had a VFD installed to drive a 5HP DE. Due to the soft start capability of VFDs the max current draw is much lower. For my situation although I have 3 phase to the shed, single phase + VFD was a better solution.

  6. #5
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    Thanks Alan, Bob.

    The house is on a battle-axe block with the house about 60M from the street. Power cable to the house from the street is 35sqmm cable and so should not need upgrading. At the time of building I thought that 35 sq mm cable was a bit over the top but a sparky mate said that cable size was based on providing power to other parts of the block and not just to the house.

    The power meter is not at the house but at the entrance to our driveway in a pillar. The pillar is about 2M from the power pit. There is a sub panel or a distribution board on the house.

    What I propose is to run new 3 ph cable from the street to the pillar (about 2M in distance) and upgrade to 3 phase meters. The power for the shed will run direct from the pillar to the shed, bypassing the house. So, the shed will have 3 phase but not the house which may be an odd situation but not a big deal as far as I can see.

    Well, this is my cunning plan at this stage. If I run into a hurdle or it costs way more than I can justify then I will revert back to the original plan and run single phase from the house to the shed.

    Cheers,

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  7. #6
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    Aug 2011
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    Melbourne
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    Quote Originally Posted by Young Flyer View Post
    I agree with above comments. If you intend to run 3 phase to the shed your should also upgrade the house and meters at the house, then extend 3 phase from your main switchboard to the shed sub-board.

    Admittedly this is no cheap job, but well worthwhile. I have achieved the above over deveral stages including installation of a 12KW Grid Connect Solar System on my shed roof. The whole process included upgrading the street supply lines to 25mm2 so there should be no limitations on future additions. The Shed is supplied with 3 phase on 10mm2 underground cables.

    BTW in Queensland (probably Victoria too) all underground power must be a minimum 600mm below ground & marked above ground if longer than acertain dimension (sorry can't remember that bit from 3 years ago).

    OTO if you find the cost too great to do all the above. You can still send single phase to the shed subject to the limitations of the house load calcs and your street connection. Don't forget VFDs are now reasonably priced so as long as you have teh single phase capacity 3 phase machines can be driven off single phase via VFD. I have just had a VFD installed to drive a 5HP DE. Due to the soft start capability of VFDs the max current draw is much lower. For my situation although I have 3 phase to the shed, single phase + VFD was a better solution.
    Thanks, you posted this while I was typing. I have been informed that power must 500mm in ground (top of the conduit) and in fact if it is buried deeper then it's current carrying capability must be downgraded. Running new cable to the house is certainly not an option. There is an established garden, retaining wall and 400 sq M of concrete driveway over the top of it! In any case, given the above circumstances I think I have it covered without disturbing power to the house…….. I hope!

    VFD's certainly provide (some) options for people with single phase but it is certainly not a be all end all replacement to 3 phase. I am currently running 3 VFD's (soon to be 4) but 3 of the 4 are used for their variable speed properties. However, buying a 3 phase machine to run on single phase can get a lot more complex than simply using a VFD. Changing from star to delta is probably as simple as a conversion can get. The last few weeks I have been looking at SG. Some have been quite simple, manual machines but some I have looked at are hydraulic with auto feed. Try running that on single phase with VFD! I'm sure all the hydraulic valves and switchgear will all require 380/415 which is not going to happen without some major modification, least of all a VFD that will need to be rated to 4HP! It's not just a matter of setting the ramp up times to 5 seconds or so to reduce currents.

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  8. #7
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
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    Default

    Simon, IIRC in Tasmania the rules were and maybe still are that if you are adding a heat pump for home temperature control, the 3 phase connection was much cheaper. It was explained to me that all I had to do was say that I was going for a 3phase heat pump, and the connection would be made for say $1500, (I'm not sure of the correct amount now, but we'll say 1500). If however I had no plans for a heat pump, but just wanted to run a 3 phase sawbench or any other machine tool, compressor, welder etc. it would cost what ever it cost them to install it, which could be anything if they had to run the extra line a few kms for example, and I would have to pay for the transformer, with any subsequent customers connected to that transformer getting a free ride.
    From what I understand to be your situation, the 3 phases are available, but just ask your Sparky mates if you need to have some domestic 3 phase item in order to qualify for a cheaper connection cost, - it may still be cheaper to connect 3 phase to the house, even though you have no need for it, except to qualify for cheaper connections.
    Another route may be to build a rotary phase converter, and run all your 3 phase stuff off the one device with just a decent single phase incoming supply. Good luck whichever way you choose to go,
    Rob

  9. #8
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    Aug 2011
    Location
    Melbourne
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    Default

    Quote Originally Posted by Ropetangler View Post
    Simon, IIRC in Tasmania the rules were and maybe still are that if you are adding a heat pump for home temperature control, the 3 phase connection was much cheaper. It was explained to me that all I had to do was say that I was going for a 3phase heat pump, and the connection would be made for say $1500, (I'm not sure of the correct amount now, but we'll say 1500). If however I had no plans for a heat pump, but just wanted to run a 3 phase sawbench or any other machine tool, compressor, welder etc. it would cost what ever it cost them to install it, which could be anything if they had to run the extra line a few kms for example, and I would have to pay for the transformer, with any subsequent customers connected to that transformer getting a free ride.
    From what I understand to be your situation, the 3 phases are available, but just ask your Sparky mates if you need to have some domestic 3 phase item in order to qualify for a cheaper connection cost, - it may still be cheaper to connect 3 phase to the house, even though you have no need for it, except to qualify for cheaper connections.
    Another route may be to build a rotary phase converter, and run all your 3 phase stuff off the one device with just a decent single phase incoming supply. Good luck whichever way you choose to go,
    Rob
    Hi Rob,

    Thanks for the insight. Yes, a RPC is another option for me. One of the members here (Harty) showed me one that he has, made from a 3 ph motor and an old 3 ph arc welder. Connected to a 15A power supply, it could produce enough power for probably most, if not all my needs. That will definitely be my backup plan if I need to run a machine with switching/sequencing gear like a surface grinder with auto feed.

    Look, in all honesty I'm just happy to be getting power to my shed, instead of running 2 extension leads from the house. It's been quite restrictive TBH but I have until now worked around it. BUT, if I can have 3 phase for a bit of extra cost and maybe some hard work then I have a crack!

    Cheers,

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  10. #9
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    Oct 2008
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    N.W.Tasmania
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    I know what you mean with using an extension cord /s Simon and real 3 phase is the best if it is realistically possible, lets hope that it is no big drama in your case.
    Rob.

  11. #10
    Join Date
    Feb 2013
    Location
    Laidley, SE Qld
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    368

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    Quote Originally Posted by simonl View Post
    Look, in all honesty I'm just happy to be getting power to my shed, instead of running 2 extension leads from the house.......
    That sounds familiar. At the end of 80m of extension lead the air compressor could only start up when the tank was empty, and the welder was a bit feeble.

  12. #11
    Join Date
    Dec 2007
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    Brisbane
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    77
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    17

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    Simon,
    Undertand your more detailed description of your power connections.

    Yes you have an unusual situation, it all depends on the 3 phase equipent you want to connect and your projected maximum load in the shed.

    Like others have said,it was definitely cheaper for me to combine Solar Power install & the three phase upgrade; but still an expensive exercize. BTW the Solar system now contributes a total $9,000p.a. to our budget.

    As stated I have 3 phase to the shed, but for a 5HP DE (Delta) a 5KW Powtran VFD was definitely the easier and more efficient option. I'm currently converting my simple 100mm flex hose connected 3HP DE to fully ducted 150mm PVC, including a vent system. This will soon be ready for a custom BP Cyclone which will be vented outside.

    I was fortunate to have expert advice from both the Guru BobL and local cabinet maker WWF member John Samuel. Both have enthusiasticly contributed to this major project in my timber boat building workshop.

  13. #12
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    Aug 2011
    Location
    Melbourne
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    Quote Originally Posted by Young Flyer View Post
    Simon,
    Undertand your more detailed description of your power connections.

    Yes you have an unusual situation, it all depends on the 3 phase equipent you want to connect and your projected maximum load in the shed.

    Like others have said,it was definitely cheaper for me to combine Solar Power install & the three phase upgrade; but still an expensive exercize. BTW the Solar system now contributes a total $9,000p.a. to our budget.

    As stated I have 3 phase to the shed, but for a 5HP DE (Delta) a 5KW Powtran VFD was definitely the easier and more efficient option. I'm currently converting my simple 100mm flex hose connected 3HP DE to fully ducted 150mm PVC, including a vent system. This will soon be ready for a custom BP Cyclone which will be vented outside.

    I was fortunate to have expert advice from both the Guru BobL and local cabinet maker WWF member John Samuel. Both have enthusiasticly contributed to this major project in my timber boat building workshop.
    Thanks. Sounds like you have a great setup. Boat building always brings up bitter/sweet memories for me. My Dad spent 17 years building a yacht. Being the only son in the family, who do you think was expected to help him on my weekends?

    It was a Bruce Robberts Spray, 40 ft steel hull. Over-engineered and well built for ocean going. Biggest trip he did was from Mordialloc to refuge Cove and back. He was in his late 60's when he did that. I think he spent so much time building it that when it was launched and finished, he didn't know what to do with himself. Go figure!

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  14. #13
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    Feb 2006
    Location
    Perth
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    When I extended my shed in 2011 I decided to upgrade the shed power supply.

    Our house has only single phase and as at the time we were supposed to be getting underground power and meter upgrades in our street within 12 months I was going to wait for that to connect the house to 3P but decided, while the sparky was upgrading the shed power to run 3P wiring from the house to the shed (50m run).

    I already had a 20A SP line to he old part of the shed but the conduit was too small for the 3P wiring so I just left the 20A line in place and dug a new trench for the bigger 3P wiring/duct and ended up with a 40A SP connection in the new part of the shed.

    Now in 2014 the underground power upgrade in our area has been suspended. Meanwhile I've installed 5 single to 2 phase 240V VFDs on machines in my shed, 3 x 1.5kW, 1 x 2.2kW and 4kW. Only the latter, which drives a compressor, is not used for speed control.

    As my shed is small and full, the likelihood of shoehorning a big 3phase machine into it is looking vanishingly small and am now wondering whether I really need 3Phase. About the only reason I would like to have it now is to be able to test 3Phase motors on full 415V 3phase.

    In terms of power draw, my highest power draw at any one time is
    - while woodworking: using my 3HP table saw and 3HP DC and the 5HP compressor kicks in. I have the table saw running on the 20A circuit and the other 2 on the 40A line so its no problem.
    - while metal working: when using 15A welder / plasma cutter I use a 1/3rd HP squirrel cage ventilation fan and the compressor kicks in. this is all on the same (40A) line - also no problem

  15. #14
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    Apr 2007
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    I ran 3 phase to my shed then wired my house circuit off my shed when I built my house. I am not sure what the difference in cable cost was but I remember it was $500 more for the meter. I now find this state of the art meter (7 years ago) is one way and if I want to put solar on my house with return to grid counter I am up for a complete new meter which from emory was a few grand - so it didn't happen!!

    Back to 3 phase, I have not found the need for it but may one day so am not sorry I did it. I think if it is not a huge additional expense, it is a "nice to have option" so do it when you first wire up. After all, who wants to dig their trench as many times as Bob

  16. #15
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    Quote Originally Posted by Burnsy View Post
    . . . . . . who wants to dig their trench as many times as Bob
    In my next life I'll be considering a tunnel so then I can just run all the services through that.

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