3 Phase Help

[Delaney]

Hi all,

I need to put 3 phase sockets into my new workshop. I should have this done by electricians but I cannot currently afford to do so, as I’ve had to pay out a lot of money.
What I’m going to try and do is install the board, sockets/isolators and cable myself, which should cut a two day job (for the electricians) down to a 1 day job.

Having a look around, it’s of course more complicated than I thought it would be, so need some help identifying the right parts and any deals that anyone might know of, that can help me save more money.

I have 5 machines that need 3 phase:

1 x Bandsaw 5kw (8amps)
1 x Planer 5 kw (8amps)
1 x Wide belt sander 10 kw (28 amps)
1 x Panel Saw 4kw (8 amps)
1 x Dust Extractor 4 kw (8amps) The extractor already has cable and isolators going into a controller so is not part of this equation.

All of the machines have cable and sockets on and are ready to be plugged in to a wall socket/isolator.
I’m going to go with 32 amp wall sockets/isolators (unless suggested otherwise)
What I’m struggling to identify is the start up amperage of each machine, which will dictate the thickness of cable and breaker, unless that is already given in the overall rating?

2.5mm core cable rated at 31 amps will be fine for the 8amp machines and potentially the 28 amp wide belt sander; unless start up amperage exceeds that?
4mm core cabal running into the board from the main board (3 phase inlet into the workshop) rated at 42 amps will give me enough power to have 2 machines running, (extractor + machine).
I could though bump this up to 6mm core and get 53 amps, in case I want to run 2 machines plus extractor?

I need breakers but not sure which ones. I know for example, the wrong breaker was fitted on the wide belt sander before, and the electrician changed it to one that although rated slgithly lower than the amperage, it was a ‘c’ cat one (or something), so it could deal with the load.

Components: (This is a list so far)

1 x 8 way board 125 amp TP+N Type B (not sure what TP + N and type B means) https://www.cef.co.uk/catalogue/products/4887747

4 x 32A 4 Pin 415V Wall Mounted Interlocking Socket https://quickbit.co.uk/32a-4-pin-415v-wall-mounted-interlocking-socket/

15 x mtr 2.5mm 4 core armoured cable https://quickbit.co.uk/swa-cable-4-core-2-5mm-per-metre/

15 x mtr 6mm core armoured cable https://quickbit.co.uk/swa-cable-4-core-6mm-per-metre/

Any help would be much appreciated.

 

[ChaiLatte]

Liaise with the electrician who you will use to do the one day's work and follow their recommendations. Even if you have to pay them £100 for a shopping list of items, it is money well spent.

In order to assist them in this, find documentation on the machines or take good, clear photos of the motor data plates and send as a package to the specifying electrician, as well as a rough layout which includes the incoming supply from the electricity company (so they know approximate cable lengths - if they calculate on the basis of 25m and you need 250m, voltage drop needs to be taken into account).

If you do the stuff off your own back and the first the electrician ever sees is you presenting it as a fait accompli, any legitimate one will run away. Bring them in early, explain that you will do the grunt work in the middle and that you want to pay them for the expertise up front and at the end.

TP&N is three phase and neutral, to accomodate five pin outlets. You may not need that if none of the machines use a neutral.

See:

https://www.tlc-direct.co.uk/Technical/DataSheets/Hager/Hager_Guide.pdf

for Type A/B disambiguation.

You probably know that SWA has a minimum bend radius, so factor that in, and any support needed for a bend (e.g. horizontal run on an internal corner) when planning cable routing.

Do you have the skills to terminate the wires of the SWA cable correctly?

 

[Delaney]

Liaise with the electrician who you will use to do the one day's work and follow their recommendations. Even if you have to pay them £100 for a shopping list of items, it is money well spent.

In order to assist them in this, find documentation on the machines or take good, clear photos of the motor data plates and send as a package to the specifying electrician, as well as a rough layout which includes the incoming supply from the electricity company (so they know approximate cable lengths - if they calculate on the basis of 25m and you need 250m, voltage drop needs to be taken into account).

If you do the stuff off your own back and the first the electrician ever sees is you presenting it as a fait accompli, any legitimate one will run away. Bring them in early, explain that you will do the grunt work in the middle and that you want to pay them for the expertise up front and at the end.

TP&N is three phase and neutral, to accomodate five pin outlets. You may not need that if none of the machines use a neutral.

See:

https://www.tlc-direct.co.uk/Technical/DataSheets/Hager/Hager_Guide.pdf

for Type A/B disambiguation.

You probably know that SWA has a minimum bend radius, so factor that in, and any support needed for a bend (e.g. horizontal run on an internal corner) when planning cable routing.

Do you have the skills to terminate the wires of the SWA cable correctly?

Thanks Chai, good advice re: electrcicians. I find though that many want to do all or nothing. If they’re busy, they wont entertain something that seems otherwise. Often they respond to someone asking them to certify something, as that's straight forward work and likely more pleasant on average than doing the grunt work.

I can terminate that type of 3 phase cable. I wired up my motors on the extractor and the isolators. I’ve not wired a breaker or board yet but seems straight forward.
All of my stuff was previously installed professionally, so I copied what was done when I need to add or make any changes. Was not aware of min cable direction but thanks for letting me know.

I can pull the plug shields on the existing machines to determine the cable type.

The thing I’m most interested in is the breakers and board and wiring that.

I’ll add the motor plate details here and the plan, although not sure where the machine will go yet. Kind of important but not more important than me discovering if I can work out the breakers and wiring the board (whilst not connected). Adding the switches/isolators is the part I feel confident in doing. Getting the right board and breakers is my number one priority at the mo.

 

[Spectric]

I need to put 3 phase sockets into my new workshop.

The starting point is the type of supply to your workshop, also you need a proper electrician involved to do the design work so you use the correct components, get this wrong and you will be wasting your money on stuff that is incorrect. Also remember that 400 volts will electrocute you much easier than 230 volts so needs to be done by the right person and not a domestic installer.

I’m going to go with 32 amp wall sockets/isolators (unless suggested otherwise)
What I’m struggling to identify is the start up amperage of each machine, which will dictate the thickness of cable and breaker, unless that is already given in the overall rating?

Each socket will be on it's own protective device in the main board which will protect the cable and the 32 amp socket, what you connect has no bearing providing it is within the rating of the socket and supply. Ie you do not want a 16 amp rated device fitted with a 32 amp plug and connected to a 32 amp supply because the cable between the plug and machine will not be able to handle the fault current needed for the 32 amp circuit. You always need a protective device where there is a change in cable CSA unless you derate the protective device.

There is as you have said a lot more in this than you thought so get the design right so every passes the final testing without issues.

 

[Delaney]

The starting point is the type of supply to your workshop, also you need a proper electrician involved to do the design work so you use the correct components, get this wrong and you will be wasting your money on stuff that is incorrect. Also remember that 400 volts will electrocute you much easier than 230 volts so needs to be done by the right person and not a domestic installer.


Each socket will be on it's own protective device in the main board which will protect the cable and the 32 amp socket, what you connect has no bearing providing it is within the rating of the socket and supply. Ie you do not want a 16 amp rated device fitted with a 32 amp plug and connected to a 32 amp supply because the cable between the plug and machine will not be able to handle the fault current needed for the 32 amp circuit. You always need a protective device where there is a change in cable CSA unless you derate the protective device.

There is as you have said a lot more in this than you thought so get the design right so every passes the final testing without issues.

Can you elaborate on the

'you do not want a 16 amp rated device fitted with a 32 amp plug and connected to a 32 amp supply’.

If for example, one machine is rated at 16 amps, what rated plug, cable and breaker would you use and why?

Cheers

 

[SDev]

I agree with what has been said so far. Just to add that when I did this it involved getting an upgraded 3 phase supply to the whole property which had to be done by UK power networks. As they charge per metre and are much more expensive than a regular electrician, we installed a glass fibre cabinet in the front garden, close to where the power comes into the property into which they put the meter. We could then do everything else at much lower cost than otherwise. I did the research on the options and produced a detailed written plan which I had approved by an electrical engineer before buying anything or starting work. The best option will depend on where your workshop is in relation to the house, the point of entry of your supply and what it currently is, as many uk properties are single phase. If you are doing the grunt work yourself make sure you lay the correct size ductwork underground for the size and length of the cable along with labelling tape before filling in the trench. There is an argument for using one size bigger duct so it’s easier for the sparks to pull the cable and gives you the option for upgrade in future. You may also want to include capacity for 3 phase EV charging and to run a separate duct for internet cable. Good luck!

 

[HOJ]

This is not specific technical advice, but personally I would use one cable size for all the 3 phase outlets, based on you largest demanding machine, lets say 4mm, and then use appropriately rated outlets and MCB's for the machine ultimately to be connected, once you have finalised their locations, this will be give you more flexibility and future proofing in the event you need to re-position any of them later.

Also will you not have any single phase machines, now or in the future that will need a 16A socket provision? again for future proofing buy a bigger board with spare ways, that will give you the capacity to add them as and when.

I would however, strongly advise communication with an industrial Electrician at an early stage.

 

[Delaney]

This is not specific technical advice, but personally I would use one cable size for all the 3 phase outlets, based on you largest demanding machine, lets say 4mm, and then use appropriately rated outlets and MCB's for the machine ultimately to be connected, once you have finalised their locations, this will be give you more flexibility and future proofing in the event you need to re-position any of them later.

Also will you not have any single phase machines, now or in the future that will need a 16A socket provision? again for future proofing buy a bigger board with spare ways, that will give you the capacity to add them as and when.

I would however, strongly advise communication with an industrial Electrician at an early stage.

Hi HOJ

Thanks for the advice.
I think you raise a good point re socket loads and cable. No doubt things will move around.

There is a 240 ring with sockets installed.
My cnc, drill and disc sander all run off that. I have no need yet for 16 or 33 amp single phase.

 

[Spectric]

'you do not want a 16 amp rated device fitted with a 32 amp plug and connected to a 32 amp supply’.

If you have a 32 amp socket that is on a 32 amp protective device and 4mm cable then you do not want to change a 16 amp plug on a machine so it can be connected to a 32 amp socket. The wiring on the machine will not be the same CSA so when cable size changes then a protective device is required to protect the smaller downstream cable.

If for example, one machine is rated at 16 amps, what rated plug, cable and breaker would you use and why?

You would have a 16 amp socket and the machine would have a 16 amp plug, the fixed wiring would be designed to provide a load of upto 16 amps and the protective device would protect the fixed wiring. Again your electrician would do the design and calcs to hopefully deliver a cost effective solution.

The design will be different depending on the usage, ie a one man band operation so you are in control of what machines are being used meaning you will not be operating multiple machines at the same time will be different compared to if you want to run all the machines, ie multiple operators.

 

[Sideways]

Personally, I would use 16A switched outlets for the smaller machines.
Breakers, type C is standard for induction motor machinery. I don't see anything in your list that shouts out to me that it needs a type D which tolerate an even greater startup surge.

I don't know your work environment to be able to advise between SWA cabling or put up some trunking and conduit and run "singles" inside this. In a barn I'd use SWA. In a nicer workshop I'd be inclined toward trunking and conduit.

The design sequence is essentially:
What are the full load amps of the machine ?
Choose the socket outlet that can deliver it. 8A load, that means a 16A as the smaller standard CE connector.
Choose the breaker that can deliver it - again you have to go up to the standard size above - breakers come in ... 6, 10, 16, 20, 25, 32 ... so you could use 10, but might prefer 16A to match the switched outlet and provide future versatility
Then do the cable calcs based on the chosen breaker. You need a size and type of cable that will deliver what a 16A type C breaker will supply, without getting too hot, taking account of how it's installed (in a conduit, underground, passing through insulation somewhere, bundled with other cables somewhere, fastened to a cable tray somewhere, etc), and without "dropping" too much voltage along the way.
This is the hard bit as it is relatively complicated and you're not going to learn it here. Domestic sparkies have simple overengineered rules of thumb they can rely on so they don't have to do this when they wire a house even though they have been shown where in the book to look up the calculations. Industrial commercial guys - this should be bread and butter.
Lastly, match the lead from the socket to the machine to the circuit rating. So fit a 16A rated flex into the DOL starter on the machine. This makes sure the flex won't be overloaded before the breaker trips.
The circuit breaker protects everything upto the starter, the starter protects the motor.

 

[Delaney]

I agree with what has been said so far. Just to add that when I did this it involved getting an upgraded 3 phase supply to the whole property which had to be done by UK power networks. As they charge per metre and are much more expensive than a regular electrician, we installed a glass fibre cabinet in the front garden, close to where the power comes into the property into which they put the meter. We could then do everything else at much lower cost than otherwise. I did the research on the options and produced a detailed written plan which I had approved by an electrical engineer before buying anything or starting work. The best option will depend on where your workshop is in relation to the house, the point of entry of your supply and what it currently is, as many uk properties are single phase. If you are doing the grunt work yourself make sure you lay the correct size ductwork underground for the size and length of the cable along with labelling tape before filling in the trench. There is an argument for using one size bigger duct so it’s easier for the sparks to pull the cable and gives you the option for upgrade in future. You may also want to include capacity for 3 phase EV charging and to run a separate duct for internet cable. Good luck!

Thanks for commenting.
This is an industrial unit on a farm that has other industrial units.
I could imagine getting 3 phase into a pvt residence would be very expensive and complicated.

 

[gmgmgm]

I've found trying to "help" sparkies is often counter-productive - they work to various regs and unless any prep work you do is spot-on (or incredibly elementary), they will need/want to do it again.

Is there an alternative approach - you're not going to be running all these machines at once. You'll be running 2 at a time (tool + extraction) - so perhaps you can, in one day, have the board and 2 sockets put in near your extractor. You can then plug in which ever machine you are using. You can buy 3ph extension leads online if you need them.

Then when funds allow you can put in more sockets in better locations etc.

As said, you'll need an industrial electrician who is familiar with 3ph. Perhaps use whoever did the neighbouring units, so they will have some familiarity with the local setup.

 

[Spectric]

This is an industrial unit on a farm that has other industrial units.

If you are renting the unit then you should consult the landlord and this sounds like a business rather than a home workshop so you need an electrician to design, install, test and certify the work. You need to get the electrician onboard, start the discussion and see if he will want you to do any work yourself, as said get it wrong and they will have to re do it and the cost goes up.

 

[HOJ]

I have no need yet for 16 or 33 amp single phase

That's my point, think ahead and build for the future, now... best thing I did was buy a bigger board in the first place, then when I moved shops it came with me and accommodated all my further needs.

 

[Delaney]

That's my point, think ahead and build for the future, now... best thing I did was buy a bigger board in the first place, then when I moved shops it came with me and accommodated all my further needs.

HOJ makes sense. I have 5 machines and wanted to by a 6 way or 8 way board wich would allow for growth down the line if needed.
That being said not sure if a 3ph board can also carry 240v 16 and 32 amp?

 

[Delaney]

I've taken pics of the motors and the results are.

Extractor = 7.6 Amp.
Wide Belt Sander = 21 amp
Panel Saw = 8.6 amp
Bandsaw = 9.1 amp
Planer = 8.6 amp

So aside from the WBS, all fall well under 16 amps. Again not sure what the amp surge is for the machines and still not able to find that information. I do know the WBS was on a cat C? rated braeker, to handle the initial start.
I also know the controller for the extractor is rated at 8 amps and the company said using it on a 7.6 amp would be fine, although that would be their limit.

I like the idea of putting extension leads on the machines,
putting 1 x 16 amp and 1 x 32 amp switch socket on the wall
and wiring the board accordingly.

That is a good idea and will save me money till I can pay more and know where the machines are going,

The trouble is that commercial electricians work in pairs (normally) and thus one day will cost me around £1,200 for their services. Given that I’ve just moved in and need to repair the floor and I've got £700 to my name, my requirements to get the costs down, aren't due to me being stingy. It’s just a simple matter of not having the funds.