Thread: What sort of three phase do I need

What he's trying to work out is the number and layout of the various circuits and breakers in the house so he can determine the electrical load on each circuit - he just needs to know what you are planning to hook up to the 3P power

Maybe let's take a step back.
Are you setting up a workshop at the same time as building the house and if so where is it and what size workshop are you setting up.

If your workshop is attached to your house then all you need is standard 3Phase power to your house and perhaps a single 3P line to the workshop terminating in a 20A 3P socket. Make sure you ask for a couple of individually breakers 10A and 15A circuits as well.

For Wood working machines I doubt you will need anything bigger than 20A and you won't need anything hardwired because that becomes a PITA. Don't tell him you need 3 x 3P power points as this will cost and arm and a leg and sure as eggs the location of the points won't be where you eventually really need them. If you wish you can plug/unplug each machine into that one socket (boy does that get tiresome) but you can eventually when things setting add 3P lines, sockets and breakers as you need them (+$$$$).

If your workshop is separated from the house I recommend getting the 3P run to the workshop and a separate breaker box installed in the workshop. This will make adding on extra 10A/15A SP circuits much cheaper than running separate 3P lines (this is a legal requirement) for every machine from the house to the workshop.

Sparkies making up quotes etc like to know what they are connecting to so if you don't know what you will be buying you can look up a 3P machine on a website that is close to what you will be getting and tell him you are going to connect this machine but you want a socket - not hard wired.

I'd still get 3P Power but don't forget that VFDs can easily allow many lower power 3P machines to run from 10A GPOs and you will need an abundance of these in any workshop. I have 10 (MW and WW lathes, MW mill, DP, Grinders, BSaw, BSander, DC, ventilator fans) 3 phase machines in my shed all running from 10 or 15A GPOs. On smaller 3P machines the cost of a VFD can be cheaper than getting a sparky in to install an extra 3P socket/line and breaker and you can move it anywhere there are 10A or 15A GPOs - its a lot safe than having 3P cables all over the floor.

Just ask him for a 3 phase sub board in the shed/workshop. 1x 20A 3 phase 5 pin outlet should handle pretty much anything you might acquire. Ask for some spare modules in the sub board so you can add extra circuits in the future. Get the biggest submains that your main board can handle to cater for future expansion in the shed.

Thanks Bob.
For the foreseeable future, any 3 phase machine will be located in the carport, which is attached to the house. In fact the house is double storey and the top floor extends about 4 metres beyond the bottom, and this will be the carport. In fact it is unusable as a carport due to the compromises we made to get the house design approved and the neighbours on side. There are two solid walls and I will probably put some screening around the rest. The 3phase point(s) will therefore be on the rear wall of the house, which is a side wall of the carport.

There is also a rather large garage which will be renovated one day, and the workshop will perhaps be moved to that. I don’t want to make any plans around it at his stage as there is too much life to get in the way.

So it looks like I should ask for either one or two 20amp 3phase sockets on the back wall. One will probably do the job but I’ll see if another one is that much extra cost. I’m not trying to accomodate every eventuality of machine type, just the average sort, and it seems 20amp can do that.

The one thing I don’t understand though is the meaning of the sentence “ Make sure you ask for a couple of individually breakers 10A and 15A circuits as well.” Does this mean if I purchased a 15A machine I could not run it off a 20A circuit?

Cheers
Arron

if you want to do it properly, get an electrical engineer to design the circuit and give you the drawing - future electrician who will be working on your shed can use it as well.

just remember when machines in your shop is working, often its not just one machine, for me, the worst case is wide belt sander(25hp) + compressor (10hp)+ dust extractor (4hp). will you add other machines when its all complete? probably not at this stage but once you have 3 phase you will want to add machines to your shop. My shop is 63amp and I wish I have gone for 100amp.

only machine in my shop that is hardwired is the sander.

Originally Posted by Arron

The one thing I don’t understand though is the meaning of the sentence “ Make sure you ask for a couple of individually breakers 10A and 15A circuits as well.” Does this mean if I purchased a 15A machine I could not run it off a 20A circuit?

You won't be able to run a 15A Machine off a 20A 3P circuits they will need a dedicated 15A Single Phase GPO - but 15A circuits usually have 20A breakers. 10A circuits refer to an individual GPO, usually have 16A breakers.

As a the workshop is part of the house the sparky will assume you will be running 1 x 10A device in the workshop at a time (this is not unreasonable - its how most people operate) so the sparky may just put the 10A GPOs on the same 10A circuit as one of the house 10A circuits which is not ideal especially as you might have other stuff running at a time in the shed. eg a 10A compressor.

AS NCArchr says Sub board is good idea

All 15A GPOs have to be on independent circuits/breakers anyway (I have 5, DC, Welder/plasma, Bandsaw, Table saw, spare ). You really need at least 2 of these eg a DC and enough for a 15A machine running at the same time. What have you thought of regarding dust extraction?

If you want to be all out cautions I would allow for 3 x 15A as you might end up with a 15A compressor. But you will need to tell the sparky what you want - again if you don't have the specific machine look up a comparable machine. I helped out a mens shed with setting up their electrical requirements and as it was a City council building their electrical planners had to know exactly what machine was available so we just pulled details of machines from the Hare and Fornes website and they were very happy with this,.

Ok, so when you mentioned the 10 an 15amp circuits you were talking about single phase. That was my confusion.

Thanks for the help - all.
Cheers
Arron

Originally Posted by Arron

Ok, so when you mentioned the 10 an 15amp circuits you were talking about single phase. That was my confusion.

The smallest 3P socket you will see prof installed these days is a 20A.

Originally Posted by Arron

Ok, so when you mentioned the 10 an 15amp circuits you were talking about single phase. That was my confusion.

Thanks for the help - all.
Cheers
Arron

also if you are going to have more than 1 power point/plug/machines, use the largest capacity plug/point so you can always swap them out.

3 Phase plug has 4-5 pins plug depends on your machine (My thicknesser has 5 pins - and they are all required.). different amp use different plug, you cant use a 32amp plug on a 20amp socket. because of this I made all my cables, socket and plug the same - 32amp. it cost more but its easier to use when you have a lot of machines. but not a lot of power point.

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