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#1 02-09-2012 10:54:12

sucram
Rookie
Registered: 02-20-2010
Posts: 99

double cable

Quick question, I am about to buy cable to wire my workshop. We run 240 volts here and seen some cable that is 2.5mm2.
This is the size normally run for power points etc here which are normally rated at 10 amps. I thinking of putting 15 amp power points every where so when I get a 260 amp mig, I can plug it in any where. Will have a new supply ( mains power cable I found ) running from the main box to a separate fuse box in the shed all with circuit breakers. Question is that I often see 2.5 come up cheap but never the heavier which is 3.2 or 4 mm. With the 2.5 running at less than a quarter of the price, can I run double 2.5 cable instead?

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02-09-2012 10:54:12

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Re: double cable

#2 02-09-2012 11:13:02

lean
Enthusiast
Registered: 10-05-2008
Posts: 141

Re: double cable

i'm not familiar with how 2.5, 3.2, & 4mm translate (i guess that's a
diameter measurement?) into the common gauges or wire we have here; which
are 14 gauge, 12, and on down.  the smaller the gauge, the heavier the
wire..... go figure.
also, is the typical wire you have there stranded or solid?

i guess the real question is even if doubling up your wire runs will handle
the power, will it be acceptable by YOUR local electrical inspectors?  after
all, they're the ones you'll have to fool, not us.
;)

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#3 02-09-2012 11:16:51

reblam
Enthusiast
Registered: 10-05-2008
Posts: 106

Re: double cable

I don't know either, never heard it gaged in mm! I am on some groups that are spread out in Europe even and IIRC they always used gauge size.
Double runs will handle the load, but if something happens to one run your going to torch the other.
Are "ring" mains done there? A Ring main or circuit was/is common in kitchens etc, in England and some other areas.
They run the hot leg from the breaker to the outlets in a series as we do but instead of stopping as we do with ours they continue the hot legs back to the breaker! In this fashion the electric can travel either way.
Now, Does a ring circuit allow thinner wire as it is effectively two to the outlets? You got me.
I always shoot for overkill, I don't like the idea of overheated wiring anywhere! When I did my workshop I bought those expensive true 20amp rated 110v outlets at like $3.75 a piece as I knew I would be plugging my 110volt mig in and did not want any worries.

I'd ignore the temptation to save money on electrics at all costs!

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#4 02-09-2012 11:17:49

evad
Enthusiast
Registered: 10-05-2008
Posts: 239

Re: double cable

Could it be based on a fractional size?
So a '14' gauge is 1/14 of an inch
A '12' gauge is 1/12 of an inch
A '4' gauge is 1/4 of an inch
A '2' gauge is 1/2 of an inch
A '0' gauge is an inch

Now the above makes sense to me and I did not want to google it.  ;-)


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02-09-2012 11:17:49

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Re: double cable

#5 02-09-2012 11:26:10

laddie
Helper
Registered: 02-07-2009
Posts: 17

Re: double cable

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#6 02-09-2012 11:27:07

sucram
Rookie
Registered: 02-20-2010
Posts: 99

Re: double cable

For light which is usually 1.5 m2 it is solid. Multi strand for the larger
ones.
The question really is does running two small cables that equal, or exceed,
one large one in area squared, can it carry the same current?
As far as getting it passed, it wont be a worry as getting the workshop
passed for finial inspection before I run the wires and line the walls. I
deliberately left off any wiring and lining from the plans for that reason.

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#7 02-09-2012 11:29:28

sucram
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Registered: 02-20-2010
Posts: 99

Re: double cable

No ring circuits here at all.
I could just make the one huge cable I have ready down the wall just a point for the welder. It is right in the middle of the workshop as in the inside corner of the L shape I have.
I am looking at spending $400 for the heavier cable verses $100.

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#8 02-09-2012 11:32:36

lean
Enthusiast
Registered: 10-05-2008
Posts: 141

Re: double cable

good link!

one thing of note that i noticed.....
" Outside North America, wire sizes for electrical purposes are usually
given as the cross sectional area in square millimeters."
so the 2.5, 3.2, & 4 mm gauges you mentioned, Marcus, must be in square mm,
instead of diameter, as i had assumed.

in the end, it sounds like our standard gauge system came out of the
MANUFACTURING realm!

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#9 02-09-2012 11:34:08

lean
Enthusiast
Registered: 10-05-2008
Posts: 141

Re: double cable

sucram wrote:

As far as getting it passed, it wont be a worry as getting the workshop
passed for finial inspection before I run the wires and line the walls. I
deliberately left off any wiring and lining from the plans for that reason.

that's interesting.  they won't give a final inspection here until AFTER the
interior finishes and safety items (handrails, stair finishes, etc) are
done.  that means all electricals, plumbings, HVA/C, etc all have to be
installed in the walls and inspected BEFORE a framing inspection will be
approved.  then once the finishes are done, they come back for the final
inspections.

but, i guess if they're not expecting *any* interior finishes in your shop,
then a rough framing only should get you past, aye?
when do you expect to get the final framing inspection?

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#10 02-09-2012 11:35:46

lean
Enthusiast
Registered: 10-05-2008
Posts: 141

Re: double cable

another good reference chart....
http://upload.wikimedia.org/wikipedia/e … _Chart.pdf

looks like your #1.5 for lighting is similar to our #14.
but the but your 2.5 & 3.2 for outlets is pretty honkin' compared to our
#12.
your 3.2 is similar to our #8, which is usually used for larger appliances,
such as electric clothes dryers, ovens, and WELDERS!

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#11 02-09-2012 11:46:46

reblam
Enthusiast
Registered: 10-05-2008
Posts: 106

Re: double cable

Youch, that's a big jump in price!
Still have to take it in context of the safety aspect.
I surface mount my wiring in my shops, even if the area is studded.
With it on top in conduit, should anything go wrong it will be safer and more evident.

Yeah, I do it all myself too, but here in WV they have been fighting over codes etc, since the dawn of time...
Makes it easy to do as we please. We only need a true building permit if we are inside city limits or in a flood plan!
We have to file a plan to build notice, but nothing else! NOTHING!

You have to be real careful what you buy and from whom and have it inspected!

Yeah, with your shop you may be able to get by with mounting the welder outlet central to your main work area.
Do the other outlets on the lighter size wire.

Uh, Is your economy in the crapper? YOu could always go strip what you need out of a foreclosed house...
Just kidding, really :) LOL.

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#12 02-09-2012 12:06:15

miami
Helper
Registered: 10-05-2008
Posts: 25

Re: double cable

As long as the total current carrying capacity of the two wires exceeds the breaker size you will be OK.  I used this trick when I wired my garage and I had some surplus wire available.  I just doubled up the wires.  You have to make sure that the connections can handle multiple wires.  If one wire gets resistance and all the current tries to go to one wire it could overheat without the breaker tripping.

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#13 02-09-2012 13:52:36

sucram
Rookie
Registered: 02-20-2010
Posts: 99

Re: double cable

Will soon find out it my plans work or not that is for sure. They might just
come for the final inspection and say they wont sign off until all
electrical and lining is done?
I cant get them to come out until I have the final panel lift door in. Only
ordered it a few weeks ago as was just going to put in a old tilt door but
my wife liked my eBay special panel lift so much that we are getting a
custom one made at nearly 10X the cost of the other to match it! Least I
didn't have to pay full price for both. ;)
Now I am already getting ready to go through all this process again! I have
just removed two trees and dug the stumps out of the ground in that hot week
we just had! Putting up a single car garage to store my camper trailer in as
have had to remove it after all these years from the neighbors shed now
that the workshop is done. Don't want it in the workshop with all the
grinding and welding going on in there around it.

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#14 02-09-2012 14:09:02

evad
Enthusiast
Registered: 10-05-2008
Posts: 239

Re: double cable

Yeah right...........it ain't simple! lol
Now I need my scientific calculator to determine the actual sizes of the
wires! <:-)


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#15 02-09-2012 14:09:37

sucram
Rookie
Registered: 02-20-2010
Posts: 99

Re: double cable

Wow, wish we had it so easy getting something built!
My heavy cable I have to run from the main fuse box right to the other end of the house where my workshop is actually came from the portable class rooms my daughter had to you in primary school when the main school burnt down! When they removed the portables after the new school was built, I pulled all that heavy cable out of the mud and brought it home. ;)
My mate wreaks houses some times too so have picked up some power points and things. Never seen the 15 amp stuff though, just the 2.5 mm2 10 amp cable so far. Only see 15 amp if inside a workshop. Nothing in the house so far I have noticed unless a electric stove might but most are gas around here. Even my central heating only uses a 10 amp 240v power point.

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#16 02-09-2012 14:10:03

sucram
Rookie
Registered: 02-20-2010
Posts: 99

Re: double cable

Might be too tight anyway as I will be running in and out of each power point to the next one. If I double up it would be 4 wires in each hole.

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#17 02-09-2012 14:17:29

lean
Enthusiast
Registered: 10-05-2008
Posts: 141

Re: double cable

i hear ya, but don't you have different plug receptacles for different
purposes?
like one standard plug type for around the house schtuffs, and different
plugs for higher-current appliances?  then, you'd obviously run heavier wire
for the bigger applications.
if you *don't* do this, how do you safeguard against plugging high-draw
schtuffs into outlets that have lighter gauge wire going to them... thusly
causing problems?

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