Three phase power / garage wiring

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mdf

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#223916 24-Oct-2017 13:02

Our house had three phase power when we moved in - it was separate flats upstairs and down so had two ovens. We've since had the meters merged (maybe "amalgamated") and second oven removed. When finishing off the meter merging, the network line guy removed a "pole fuse" (I think?), as he said we had no need for three phase power. I didn't think much of this at the time.

I am now refitting the garage and the (professionally qualified and suitably licensed/certified) electrician is coming in a couple of weeks to do the wiring. I've seen a couple of tools that use three phase power that I am currently lusting after and one day may actually be able to afford (once I've paid for the garage) - a big table saw induction motor and a welder.

So I can talk to the (professionally qualified and suitably licensed/certified) electrician on a somewhat informed basis, I have a few queries:

- Is three phase wiring different to ordinary wiring? Oven sockets are often different to ordinary sockets, but thought that was a 15 amp circuit?

- Does three phase power cost any more than single phase power? I assume you typically use more power if you're using bigger tools, but do you need to go on a commercial plan or similar to get it?

- A separate set of breakers in the garage seems like a passably good idea, but no idea if that is actually worthwhile or not. Thoughts?

- Anything else you wish you had done when you were wiring your garage?

I'm planning on lining the garage once the wiring is in, but will be using ply and screws so I can remove the linings if/when necessary. It's not the end of the world if I miss something now, but would obviously prefer to do it once, properly.

Hopefully it is clear that my knowledge of mains electricity is limited, though sufficient to be afraid of it (voiding insurance if nothing else). I do enjoy electroBOOM's antics (that I am pretty sure are staged anyway), but I have zero desire to emulate them and all work will actually be done by professionally qualified and suitably licensed/certified electricians. Really just after some base knowledge so that I don't ask them to do (or not do) something I will regret later.

Mattmannz

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#1888634 24-Oct-2017 14:43

Three phase outlets have a different physical plug and use heavier gauge cable as they are designed to handle more current.

From an appliance point of view, you can go up to 15 amps on single phase which is around 3000W so unless you are doing something fairly industrial you can usually get away with single phase power. I run a 200amp mig welder and a bunch of other large tools with no issues on single phase.

All garages I have been involved in have had separate breakers located in a panel in the garage. Always put in more lights and outlets than you need. Also run UTP out to the garage so you can have IP access.

frankv

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#1888643 24-Oct-2017 15:00

Breakers, RCDs, etc are a good idea in your garage panel so that if you blow a fuse or whatever, you don't have to run back to the main panel to reset it.

I would have run UTP if I'd thought of it. But there are alternatives. Use powerline modems, although they're a bit limited in speed. Or, depending on your layout and materials, your house WiFi might be good enough to the garage.

Plumb in a water supply?

blakamin

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#1888662 24-Oct-2017 15:12

I'd love 3-phase. Heaps of people around here have it.

Welders are sooo cheap second-hand when companies go bust or upgrade, and you could build your own industrial shed with a 3-phase welder!

I don't think you need a different plan.

Definitely have a switchboard in your garage.

And comparing socket and plug size (this is actually an adapter).

Aredwood

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#1888788 24-Oct-2017 16:52

A big advantage of 3 phase power is less voltage drop over long distances. Depending on the total distance from the point of supply to the garage. 3 phase might even be cheaper than single phase, solely from being able to use a cheaper cable for the same capacity.

As for ongoing costs, it depends on the lines company if they have any extra charges for 3 phase. Hopefully they won't charge you massive fees to have the 3rd phase reconnected.

richms

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#1888875 24-Oct-2017 18:13

You should be ok since you had it in the past but when I asked about upgrading to it as I was hitting the limit of the single phase supply often I was going to be up for whole new panel inside with rcd on everything since I have breakers that don't have enough amps on the big number (4500a comes to mind)

Check that out before proceeding. Also EVs only need single phase to charge on their inbuilt charger so that isn't a reason to jump for 3 phase in a garage.

Richard rich.ms

mdf

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#1888942 24-Oct-2017 20:26

Superb, thanks all. Ethernet is an excellent point. I had it on my initial specs but had completely forgotten about it until now. I've even got a hole in the ground at the moment to run some conduit out there!

I'd love a sink in the garage, and the water main is right there. Unfortunately the waste water drains are miles off so I can't see that working easily. I'll have to make do with a hose :(

Dyson

Shop now for Dyson appliances (affiliate link).

hyperman

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#1888967 24-Oct-2017 21:04

blakamin:

And comparing socket and plug size (this is actually and adapter).

off topic but is is just me or does that seem like a REALLY stupid adapter......

The views expressed by me are not necessarily those of my employer

richms

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#1889015 24-Oct-2017 22:34

hyperman:

off topic but is is just me or does that seem like a REALLY stupid adapter......

Used for test and tagging. Saw the guy doing that at prior job had one for just that reason.

Richard rich.ms

mattwnz

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#1889035 25-Oct-2017 00:10

We have 3 phase power and I don't think we get charged anything extra for the 3 phase connection, it is a residential connection too. BUt pays to check the power company.

mclean

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#1889148 25-Oct-2017 09:35

If you're going to have a decent workshop then a separate sub-board in the garage is a good idea, ie run a single 3-phase submain from your main switchboard to the garage sub-board and distribute the garage circuits from there. You then isolate the garage at a single switch in the garage.

3-phase circuit breakers are bigger (3 modules wide instead of 1, duh!) so 3-phase boards are bigger and more expensive.

The cabling in a 3-phase circuit is different, 4 conductors + earth instead of 2 conductors + earth, but for the same kW rating the conductors are much smaller.

IMHO 3-phase motors are more rugged, reliable and simpler then single phase motors.

There's a lot to be said for surface-run wiring in a garage/workshop - practical rather than beautiful.