Correct Metric Gauge Wire to Power Opus 150 Watt (Australia)

**long.1** · 03-22-2007, 08:40 AM

Hi All,

Whilst at my local "Super Cheap Auto" today (Australia), I thought I'd check out their wiring. To be honest, it only served to confuse me more, and I'm hoping someone can shed some light.

I have an Opus 150 Watt that will be powering my Via Epia based system, and in the User Guide for the Opus it says to use:

#12 AWG for power/ground
#18 AWG for ignition

Reading the very informative: FAQ: How to Wire an OPUS PSU, it quotes:

1) You can use 10 gauge wire for the connections; I believe Opus recommends 12 awg. Most people use 10 to be safe, especially when running longer lengths to the trunk.
2) Add the fuse to the fuse holder. You should use a fuse that is 15 – 20A, you don’t want to go higher then 20A

Now whilst I probably won't be wiring into the boot/trunk, I still want to be "safe", and make sure I use the right gauge wire. The problem is that we don't use the AWG in Australia - our wires are metric rated (in “mm” and/or “mm²”). So I've reviewed a number of AWG to Metric Conversion Tables such as:

My confusion deepens upon looking at the wires today. The thickest one they had there was sized at 5mm. Reviewing the charts, this would seem to put it between AWG 4 and AWG 5. However, the wire cable also says 2.90mm². Again reviewing the charts, this places it between AWG 12 and AWG 13, which sounds borderline at best. To confuse matters even further this cable also says "25 amp".

I've searched these forums for the answers and found threads such as this, but to be honest, I'm more confused than enlightened.

So finally getting to my questions, I'm hoping for advice on:

1) Which standard/gauge/rating should I be looking at - “mm” or “mm²” ?
2) Which size fuse should I use ? 15A, 20A, or 25A ?

Thanks in advance.

Cheers,

Long.1

**h3rk** · 03-22-2007, 08:57 AM

Originally Posted by long.1

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1) Which standard/gauge/rating should I be looking at - “mm” or “mm²” ?

They both should agree, it's simple geometry.
The chart you have shown is correct. I would get a measuring tool (micrometer or small, engineer's ruler) and measure for myself. Or find a more reliable source of wire.

Originally Posted by long.1

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2) Which size fuse should I use ? 15A, 20A, or 25A ?

If you find 10AWG equivalent, use 20A, if you go smaller, reduce the rating accordingly.

**v8 scimitar** · 03-22-2007, 10:08 AM

the metric is mm sq not diameter or thickness which is why it doesn't measure out properly. For 20A you want 4mm sq which is a standard metric size

**long.1** · 03-22-2007, 11:33 AM

Originally Posted by h3rk

They both should agree, it's simple geometry.........Or find a more reliable source of wire..........
If you find 10AWG equivalent, use 20A, if you go smaller, reduce the rating accordingly.

Originally Posted by v8 scimitar

the metric is mm sq not diameter or thickness which is why it doesn't measure out properly. For 20A you want 4mm sq which is a standard metric size

Thanks all - greatly appreciated.

I could definitely understand the maths for diameter/area, which was adding to the confusion.

In any case, armed with your thoughts and my research, I'll head down to an AutoBarn or a Strathfield store on the weekend. I reckon they're more into the Audio and In-Car Entertainment side of things, so I expect they'll have a more comprehensive range and available staff. In fairness to SuperCheapAuto, this stuff is probably not their specialty, and the store I went to was in the middle of a total renovation.

Thanks again.

Cheers,

Long.1

**h3rk** · 03-22-2007, 02:20 PM

I can't even visualize an australian starting off a sentence with the words 'I recon'. Funny.

**meddler** · 03-22-2007, 10:12 PM

Originally Posted by long.1

Thanks all - greatly appreciated.

I could definitely understand the maths for diameter/area, which was adding to the confusion.

In any case, armed with your thoughts and my research, I'll head down to an AutoBarn or a Strathfield store on the weekend. I reckon they're more into the Audio and In-Car Entertainment side of things, so I expect they'll have a more comprehensive range and available staff. In fairness to SuperCheapAuto, this stuff is probably not their specialty, and the store I went to was in the middle of a total renovation.

Thanks again.

Cheers,

Long.1

Definately go somewhere that has a better range of car audio stuff. Even try Dick Smith or Jaycar. They also have car audio gear.
Just a note, we do use Gauge sizes (AWG) in OZ for car audio. Auto electricial guys mainly use mm squared.

Originally Posted by h3rk

I can't even visualize an australian starting off a sentence with the words 'I recon'. Funny.

H3rk, You need to come here for a holiday. I can guarantee you'll leave saying it

**h3rk** · 03-22-2007, 10:21 PM

I intend to. In fact I thought I was going to when I joined the Navy, but I ended up locked up in a tube that may (or may not) have had several nuclear missles loaded in it, and not many foriegn ports wanted any part of that(nor our pentagon. Damn, I just got flagged.

Oh well, one day.
When I hear 'I recon', I picture Jeff Foxworthy or the like saying it, that's why I couldn't picture it.

**meddler** · 03-22-2007, 10:31 PM

I can understand some cities not wanting a nuke sub in their ports. I suppose that is just the way it goes.

**long.1** · 03-22-2007, 10:36 PM

Originally Posted by meddler

Definately go somewhere that has a better range of car audio stuff. Even try Dick Smith or Jaycar......

Will do - thanks !!

Originally Posted by h3rk

.........When I hear 'I recon', I picture Jeff Foxworthy or the like saying it, that's why I couldn't picture it.

Don't get much exposure to Jeff Foxworthy down here (apart from mates sending the odd video link via email). I do recall one "bit" though where he was a brain surgeon with a thick redneck accent - hilarious !!

**long.1** · 03-23-2007, 12:30 PM

Originally Posted by long.1

In any case, armed with your thoughts and my research, I'll head down to an AutoBarn or a Strathfield store on the weekend.

Originally Posted by meddler

....Even try Dick Smith or Jaycar. They also have car audio gear. Just a note, we do use Gauge sizes (AWG) in OZ for car audio........

OK, the Mrs was hosting some clothing party our place tonight so I took my 3 year old boy out for a fun filled evening of wiring and PC component shopping - wasn't he just pumped !!

Went to Dick Smith Superstore first - no joy. Then went to AutoBarn and wouldn't you know it, they had a choice of 8AWG or 12AWG. I chose 12AWG.

I got 3 metres of each wire (power/ground) as I plan to run both from the battery. My pc will most likely be going under the drivers seat (I know, I know - I'll be taking precautions), and my car battery is on the same side of the car. So given this distance, will I still be able to use the 20A fuse, or will a 15A be better ?

Cheers,

Long.1