# Forum Home Renovation Electrical  Easy to get a sparky to install a 15a powerpoint or not?

## LordBug

So, I picked up a goodly sized welder off an auction the other day, to find out it has a 15a plug. 
Sadly, I don't have any 15a points around the house or in the shed. Thus, time to get a sparky to come and install one. 
All I want to find out here is to basically get an idea of whether I'll be facing a larger charge and effort or a smaller one come that time, and also to save having to stuff around with getting someone out to look at stuff and then do some more umming and erring if it is to be a bigger job.  
So, the shed. The power runs from somewhere in the main switchboard (There isn't any obvious switch thingy in there to indicate a RCD/fuse to the shed, I should upload a photo to horrify people) into the shed, where it goes into a nice RCD setup, powerpoints on one circuit, lights on another, and there's a third for something else (I'll provide a photo later on if that helps). 
Quite pleasantly (or dodgily?) the cable from the main board to the shed sub-board is a three phase cable. The blue and the black wires are neatly terminated to the side, with the other three in use. Nice thick cables which give me hope. 
Does this mean that the sparky will just have to put in a 15a breaker and suitable cable to a 15a socket? Or is this an unfortunate case of "nope" and I'll need to consider digging a trench from the house to the shed (Doesn't look like there'd be very much room in the current conduit for much of anything else to fit through), which will heavily impact the decision. 
Also, whilst I'm asking, I'm going to assume that even though 3 phase cable was used, since it's currently being used for single phase I wouldn't be able to get 3 phase in the shed on that line as well? 
Cheers guys.

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## Master Splinter

> Does this mean that the sparky will just have to put in a 15a breaker and suitable cable to a 15a socket?

  Basically, yes, assuming there's nothing really disasterous about the existing installation!

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## Bedford

> Quite pleasantly (or dodgily?) the cable from the main board to the shed sub-board is a three phase cable. The blue and the black wires are neatly terminated to the side, with the other three in use.

   

> Basically, yes, assuming there's nothing really disasterous about the existing installation!

  I'd be curious as to what is used as a neutral.

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## chrisp

> The blue and the black wires are neatly terminated to the side, with the other three in use.

   

> I'd be curious as to what is used as a neutral.

  Good pick up, Bedford! 
I wonder what the colours are of the "other three" are?

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## Master Splinter

In a worst case the three phase cable makes a sturdy pull-through cord...but anything save the earth wire could be sleeved to an appropriate colour.

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## chalkyt

Hey Bedford... me too re the neutral! I am not sure that I want to see a picture, it might scare the children. 
Anyhow the short answer is provided that the cables are large enough (and they probably are), there should be no or little difference between installing a 10A and a 15A outlet.

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## LordBug

Haha, oh dear, at least it looks like my memory would stop me being a racist  :Tongue: 
I found an old photo taken by a friend legally entitled to unscrew the screws hiding the wires  :Whistling2:  and it appears I had the colours mixed up. It's the blue and the *white* wires that are neatly terminated to the side, as per the attached photo.
Though having a look in the main meter box, I suspect the lone RCD switch is for the shed circuit. 
Does this make it a lot less suspect? 
Also, the question about the three phase remains. I don't fully understand the workings of it (Trying to read up on it whilst my brain is in a mild flu shutdown mode is difficult), so can single phase be run off the first three wires and then the other two lines go towards completing the three phase, or does another cable need to be run for the single phase to remain?
This more applies to the off chance of me laying my hands on a three phase machine in the future, seeing as I won a 15a welder in an auction for $62, and I'd been jokingly bidding on some 3 phase machines at the same time. 
Anyway, thank you all greatly for the quick replies, now to think about where I'd want a 15a socket put and to chase up some quotes  :Smilie:  
Oh, and for the benefit of horrifying people with my meterbox in this day and age, a photo is also attached. I _really_ want to get it fixed up, but I'm shamefully afraid of having a sparky lay eyes on it and say "This is going to be a very big job". Until I change work, it's a plan on the backburner.

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## chrisp

> Does this make it a lot less suspect?

  Yes.  The colour code is correct.    

> Also, the question about the three phase remains. I don't fully  understand the workings of it (Trying to read up on it whilst my brain  is in a mild flu shutdown mode is difficult), so can single phase be run  off the first three wires and then the other two lines go towards  completing the three phase, or does another cable need to be run for the  single phase to remain?

  The remaining cables (blue and white) probably can be used to complete the 3-phase supply.  So, yes, the two other wires can be used to complete the 3-phase.   

> Oh, and for the benefit of horrifying people with my meterbox in this day and age, a photo is also attached. I _really_  want to get it fixed up, but I'm shamefully afraid of having a sparky  lay eyes on it and say "This is going to be a very big job". Until I  change work, it's a plan on the backburner.

  The switchboard looks "old as" but it still might be okay.  The promising thing is the three supply fuses above the meter - it does look like you may have a 3-phase supply.  However, at a casual glance, the rest of the board doesn't seem to have a lot on it and makes me wonder why there is a 3-phase supply.  Anyway, I think it is worthwhile getting a few quotes to see if it is practical to get 3-phase connected to the workshop.

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## Gaza

I didn't say this but you could just grind the earth pin down to fit, it may not trip the breaker if you have a 15amp circuit installed.

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## watson

:Rotfl: 
Eeewww!!  Naughty Gaza  :Hahaha:

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## chrisp

> I didn't say this but you could just grind the earth pin down to fit, it may not trip the breaker if you have a 15amp circuit installed.

  Just about any power circuit will be wired as a 16A or 20A (or greater) circuit.  As long as the current draw isn't consistently over 16A for the whole circuit, it won't trip.  The wiring is rated to 16A (plus). 
Personally, I wouldn't grind the earth pin down - I'd make a short 10A-plug-to-15A-socket adaptor cable.  :Smilie:

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## LordBug

Haha, the thought of grinding the pin and making a 15A->10A cable did cross my mind for split seconds each. But seeing as the shed is my cherished domain, I think I'd much prefer to be picky about obeying the requirements of my tools and just keep it proper without little bodgy in-betweens  :Smilie:  
If only we were more like NZ, I would so love to learn how to do it myself.

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## RustyNail

Two things come to mind about that sub-board - is the what appears to be lighting circuit coming in from the lower right have an earth? And does the conduit coming in from the top in the middle have anything connected to it?

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## LordBug

To give you a rundown on what's what:
Bottom right horizontal run - To the light switch 1 foot away
Bottom centre - Power in
Bottom left - To a solitary twin point outlet
Top left - To the light circuit (Three single batten fluros in some order)
Top centre - To two seperate twin point outlets 
I want the 15A outlet to be about 3~4 feet to the left of the sub-board along the stud that it's attached to, so overall it should be a relatively low hassle install for whoever I get in to do it  :Smilie:

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## RustyNail

Ahh, OK, that explains the tape-covered joiner in the top right - it's the actives for the light circuits. Not sure why they didn't run them straight into the top of the 8A breaker tho, maybe the cables were too short... 
I'd expect the sparky would want that 15A outlet to be on its own breaker/RCD, but there looks to be room on the rail for another MCB/RCD.

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## chalkyt

Just had a look to see how you are getting on. Not the worst old board I have ever seen, but it could do with a tidy up. You certainly appear to have 3 phase to the main board (3 sealed fuses are the give-away). AND it looks as though some kind sole has run 4 core to the shed but only connected one phase (red and black) as you only have a single phase main switch there. I suspect that the white and blue are not connected to the other two phases or may be connected and just terminated at the shed board. This all means that you should be able to get three phase connected to the shed easily if you want it. A slight show-stopper at the shed might be that you need more room at the board. Any smart electrician should only need about half an hour to tell you what is going on. 
Re the three phase supply. Without getting too technically messy, you will probably have a three phase supply and a neutral running down the street. The neutral "ends" of the three phase supply source (usually a transformer) are connected together and so there is 240V between each phase and the neutral. Different properties are connected to different phases so that the load on each phase is more or less equal. However, the trick is that each phase is "out of phase" with the other by what we call 120 degrees, given that there are 360 degrees in one cycle of AC. i.e in simple terms, in one rotation of the original source ( the generator at the power station) the phase windings are mechanically arranged so that one phase winding generates peak voltage at 0 degrees, another at 120 degrees, and the third at 240 degrees. Hence 3 phases. The clever thing is that you now have 415V between phases because they are generating AC and while one is generating +240V at the same instant the next one is generating -175V. Not strictly true but O.K for this explanation.  
So it suits the supply authority to supply power at 415V rather than 240V because you only need wire about half the size to transmit the same amount of power (half the current)... and that saves lots of $$$ in both copper wire cost and power loss through the wires. It also suits you for things like motors, with starting torque advantages, same power with smaller wires etc, etc. 
There, I hope that hasn't befuddled your flu ridden brain too much. Don't worry about how it works. Just accept that it does otherwise you will have to pull out your trigonometry books (sine of 120 degrees and all that)!!!!

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## bmcosta

Thanks for that now i'm having flash backs of tafe all over again

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