# Sterling inverter cable size too small



## Techno100 (May 8, 2010)

Does anyone have any insight as to why sterling produce an 1800 watt inverter 12volt to 230 with ONLY 4AWG cable? Their recommended fuse on the DC side is 250 amps whilst the cable is barely adequate for 140
Mine is melting whilst still not blowing the fuse nor displaying any sign of overload. 
Surely DANGEROUS


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## Antonia (Apr 27, 2008)

Ah well

The resistance of a conductor is R =pL/A
So the area A is important but so to is the Length L, p is a constant for a particular conductor.

For a really short cable therefore, and it should be on the DC side, then the resistance will be low indeed and so the area ( diameter ) of the cable can be smaller.
Lower resistance less heating less wasted energy.

Regards

Antonia


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## listerdiesel (Aug 3, 2012)

Get hold of some decent double-sheath welding cable, look for 35sq mm or 50sq mm.

How much do you need? We've got some 35mm or 50mm welding.

Peter


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## Techno100 (May 8, 2010)

4awg is only just over 5mm
The minimum size for a 1 metre length at 1800watts is 10mm and a 250 amp fuse is ridiculous. This inverter also carries a peak rating of 3 kw


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## Techno100 (May 8, 2010)

Thanks Peter
I do have cable and will try to replace it but I'll have to modify the unit to accept adequate conductors and void the warranty too.
I cannot understand why they have manufactured it with clearly inadequate cable and at the same time recommended a 250amp fuse. A fire waiting to happen


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## listerdiesel (Aug 3, 2012)

4AWG is equivalent to 21sq mm?

Peter


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## clive1821 (Mar 27, 2010)

well Andy you should know what sizw you would need, you would need at least 35mm cable for that i would just change it and all will be better..... I would have no idea why they supply cable around 6mm far to small for 300 amps!!! as it is, would make a nice dim light at night


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## VanFlair (Nov 21, 2009)

I put our 2KW inverter on 50mm sq welder type cable for minimum volt drop, so the Sterling ones do seem very inadequate indeed.

Martin


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## Techno100 (May 8, 2010)

listerdiesel said:


> 4AWG is equivalent to 21sq mm?
> 
> Peter


Diameter
http://www.engineeringtoolbox.com/awg-wire-gauge-d_731.html


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## Techno100 (May 8, 2010)

20mm ought to be ok for 3000watts so I'm concerned at the heat and the insulation


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## erneboy (Feb 8, 2007)

Why not ask Charles Sterling, he is a good bloke and I am sure he will happily discuss it with you, Alan.


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## Antonia (Apr 27, 2008)

4 awg is 21mm squared

Thats should be ok for short lengths if thats what Stirling advise. Should be ok for up to 80Amp DC for lengths less than 1 metre.


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## Techno100 (May 8, 2010)

It's carrying up to 250 amp


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## Antonia (Apr 27, 2008)

Did you not say it was a 1800W inverter? at 12v thats about 150A.
Peak power may be greater, how long is your run? Did the inverter not come with DC cable attached?

Antonia


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## Techno100 (May 8, 2010)

It is 3000 watt peak rated with a recommended fuse of 250amps
Yes 4AWG cable is attached


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## Techno100 (May 8, 2010)

The insulation is 105deg C rated. Personally I don't think that is the solution to cable sizing so I'll be upgrading it ASAP


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## Antonia (Apr 27, 2008)

Yes that does seem then to be a little on the small side then.
Even though the peak output of these things is only ment to be for seconds, it does seem to be too small a cable.
An e-mail to Stirling power products will gain a quick response to this strange situation and should be interesting to hear. Please, if you do so, let us know what they say, I would be very interested.

Antonia


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## Pudsey_Bear (Sep 25, 2008)

It may have been fitted in error, they would want to know about it & I'm sure that they will want to send a new cable FOC and ensure it hasn't & doesn't happen again.


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## erneboy (Feb 8, 2007)

To illustrate what a good company Sterling are let me recount a story.

The charger/power supply on my boat failed at around five years old. It was a Sterling product. I rang them to find out if it was repairable. I spoke to Charles Sterling. He was concerned that it had failed and asked me to send it back so he could have it checked out.

A couple of days later he rang to tell me that it was beyond economic repair, but that it should not have failed and on that basis he was replacing it, free of charge, with a new model. 

They really do care about their products and I was mightily impressed by their attitude. Since then I have bought numerous Sterling Power products all of which have been excellent.

Ring them and discuss it, Alan.


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## olley (May 1, 2005)

I have an 1800watt Sterling inverter and its wired with 40mm cable and a 250amp fuse, never been any trouble.

Ian


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## Techno100 (May 8, 2010)

olley said:


> I have an 1800watt Sterling inverter and its wired with 40mm cable and a 250amp fuse, never been any trouble.
> 
> Ian


Clearly something isn't right then


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## Techno100 (May 8, 2010)

I'm still in France so I've emailed sterling UK


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## Pudsey_Bear (Sep 25, 2008)

I've only had the one experience with Sterling and it was a good one, I know they are proud of their products and make sure if there is a problem it isn't for long


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## olley (May 1, 2005)

Sorry Techno I have just pulled the cover off the inverter and its my wiring which is 40mm, I know this because its printed on the cable, the two short leads from the inverter as smaller, so I guess they are 25mm not 40mm as I stated. 25mm is rated at about 170amps so is just about ok for my 1800watt inverter on full chat.

The second picture shows it more clearly, the Red at the back is my 40mm, the Black next to it is as supplied by Sterling.

Apologise's for the duff info. 



























Ian


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## Techno100 (May 8, 2010)

I've got no where with this, despite requesting (4 times) to know what size cable this 1800watt unit should be supplied with in case it was sent out undersized by mistake. Jist of it was don't know but we've sold 15,000 without a problem the cable should be fine :roll: 
I've gone ahead and fitted 35mm


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## erneboy (Feb 8, 2007)

Techno100 said:


> I've got no where with this, despite requesting (4 times) to know what size cable this 1800watt unit should be supplied with in case it was sent out undersized by mistake. Jist of it was don't know but we've sold 15,000 without a problem the cable should be fine :roll:
> I've gone ahead and fitted 35mm


That's disappointing, Alan.


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## listerdiesel (Aug 3, 2012)

Seems odd that they cannot back up their products, although I suspect many are produced in the Far east for them.

35mm is a good solution.

Peter


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## Techno100 (May 8, 2010)

Ok time for an update
This is the effect on the supplied cable's insulation when running at or slightly over maximum continuous power.
2 KW caused this BUT the inverter made no complaints so to me the cable is simply not good enough.








Fitting 35mm cable has eliminated my worry of running at or over 1800 watts


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## Techno100 (May 8, 2010)

To explain the affected point above.
The insulation becomes floppy when it gets hot. The point in the picture is where the cable turned a corner around a battery (the batteries are NOT hot) While the insulation is floppy it has lost it's ability to stay in shape when pressure is applied. This is not a good thing to be going on out of sight so be alert and check frequently until you are happy that this is not occurring


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## Geriatricbackpacker (Aug 21, 2012)

Thanks for the update Techno, sobering pictures which has prompted me to make sure that I check mine as my unit is an Ebay import and I just fitted it with the supplied cables on face value.
Many thanks
Terry


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## listerdiesel (Aug 3, 2012)

That is verging on a safety issue that needs to be brought to someone's attention.

It's fine for us technicall-competent types to discuss it, but the guy in the street is clueless when it comes to this sort of thing.

Peter


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