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Question re Inverter cabling

iamgigglz

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I have an inverter/charger that just says it’s rated to “1000W output” (and 10A charging).
Let’s ignore efficiency losses for now.

The 12v cables coming out of it say 16 square millimetres, which google tells me is 6AWG.
Google also tells me 6AWG copper wire is rated to 55~65A which equates to 660~780W, not 1000W.

The 12v cables are wired into the inverter internally so changing them for beefier ones isn’t really an option.

Am I right in my calculations? Does this mean I’m limited to 660W (to be safe)?
 
Your draw is 1000W at 220VAC not DC...

1000WAC converted from DC will be less than 60A on battery side (if you running 24VDC).
 
SANS 10142-1 PVC single core copper table:
16mm² will handle 86A assuming DC power and using the clipped direct method and not running an a thermal isolating wall or conduit.

86A at 12V nominal (10.3V when low and 13.6V when high, thumbsuck typical values) = 1032W or close to a kilowatt.
As long as you add an 80A fuse you should be golden.
And yes, adding a fuse is a legal requirement as per section 7.15.1.2

Also my above calculations is for regular PVC cables. Mylar, Kevlar, Silicone, Rubber (HO) are all used and have different characteristics.
PVC is the most common cables though.
 
Your draw is 1000W at 220VAC not DC...
Umm. 1000W is 1000W. AC or DC makes no difference. The voltage is part of the equation. P = V x A

1000WAC converted from DC will be less than 60A on battery side (if you running 24VDC).
OP stated that he is using 12V.

Some 6AWG cables are rated higher, depends on the no of strands, metal purity etc.

That 1000W may also be a peak value, not sustained...
Thumbsup. Agree with this statement.
Most of these smaller 1000W inverter have some form of peak rating and not sustained.
Even the larger companies like Victron and SMA love to cheat on their ratings.

Victron fine-print:
All their inverters are rated for Non-linear load, crest factor 3:1 and they do a temperature de-rating. So their 1200W inverter at 25° become a 600W inverter at 65°. And remember that is the inverter temperature, not the ambient.

SMA:
All their inverter are rated at H ratings. Half hour ratings.
So their 8000W inverter can run for 30min with an ambient or 25°. After that it is de-rated to 5500W for continuous operation.

Full disclaimer:
I work for a inverter/solar installation company.
 
SANS 10142-1 PVC single core copper table:
16mm² will handle 86A assuming DC power and using the clipped direct method and not running an a thermal isolating wall or conduit.

86A at 12V nominal (10.3V when low and 13.6V when high, thumbsuck typical values) = 1032W or close to a kilowatt.
As long as you add an 80A fuse you should be golden.
And yes, adding a fuse is a legal requirement as per section 7.15.1.2

Also my above calculations is for regular PVC cables. Mylar, Kevlar, Silicone, Rubber (HO) are all used and have different characteristics.
PVC is the most common cables though.
@iamgigglz just remember that SANS 10142-1 is for connecting to the premises wiring. If the device is meant to be a stand alone "plug in" type of setup (the pre-installed cables seem to indicate that) then it is not strictly applicable (but is still a good guideline).

Since the wiring is pre-installed, it might also have a built in fuse on the 12V side. If not, for your own safety, follow eleventh's advice and add a fuse, preferably as close as possible to the battery to protect against cable short circuits.
 
Umm. 1000W is 1000W. AC or DC makes no difference. The voltage is part of the equation. P = V x A


OP stated that he is using 12V.


Thumbsup. Agree with this statement.
Most of these smaller 1000W inverter have some form of peak rating and not sustained.
Even the larger companies like Victron and SMA love to cheat on their ratings.

Victron fine-print:
All their inverters are rated for Non-linear load, crest factor 3:1 and they do a temperature de-rating. So their 1200W inverter at 25° become a 600W inverter at 65°. And remember that is the inverter temperature, not the ambient.

SMA:
All their inverter are rated at H ratings. Half hour ratings.
So their 8000W inverter can run for 30min with an ambient or 25°. After that it is de-rated to 5500W for continuous operation.

Full disclaimer:
I work for a inverter/solar installation company.
Edit: I understand your side. I could have worded my initial response differently.
 
Last edited:
Edit: I understand your side. I could have worded my initial response differently.
I understand. I had an asshat of a lecturer at 'varsity that would easily flunk you if you used terms or symbols incorrect.
If you did all your calculations, and did not include a V for voltage you get a zero. No symbol = no answer.

He was horrible, but he drilled into me a way of thought that has come in very handy.
 
Umm. 1000W is 1000W. AC or DC makes no difference. The voltage is part of the equation. P = V x A


OP stated that he is using 12V.


Thumbsup. Agree with this statement.
Most of these smaller 1000W inverter have some form of peak rating and not sustained.
Even the larger companies like Victron and SMA love to cheat on their ratings.

Victron fine-print:
All their inverters are rated for Non-linear load, crest factor 3:1 and they do a temperature de-rating. So their 1200W inverter at 25° become a 600W inverter at 65°. And remember that is the inverter temperature, not the ambient.

SMA:
All their inverter are rated at H ratings. Half hour ratings.
So their 8000W inverter can run for 30min with an ambient or 25°. After that it is de-rated to 5500W for continuous operation.

Full disclaimer:
I work for a inverter/solar installation company.

How much are the Deye/Sunsynk inverters derated?
 
How much are the Deye/Sunsynk inverters derated?

The spec sheet claims 5000W from on the 5000W model, which is great.
And then you do the math.
It has a max of 20.8A on the 230V side, so 4750W. Hmmm.
And then they have a clause which reads ">45 Derating." With no indication of what the de-rating is.

Well, that is the difference between European cheating and Asian cheating.
The one spells out how they are cheating and the other is a little more vague.
 
Yeah this is a fong-kong thing - the brand is "Intelligent" :ROFLMAO:
On the side of the box it says it can run a "1000W Heater or 1000W light" which implies it can handle a constant 1000W draw but I'm not testing that.

Thanks for the input everyone - I feel a lot more confident about it now. I just need a battery, various connectors, some kind of clever way to control a few 12v cooling fans and about a million fuses & breakers and I can build myself a load-shedding box.
 

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