Inverter cable and breaker sizing

SwampYankee

Off grid 12V
600AH bank

I have a 2000W Wagan Elite that according to the manual the recommended fuse is an ANL 300A with #4 gauge cables. This doesn't sound right...a 300A fuse on 4 gauge wire??
I have a bunch of 0 gauge....can that be used with a 250A Breaker?. Is there a difference between a breaker and slow burn fuse? I always thought you fuse the system to protect the wire and thus 4 gauge does not rate a 300A fuse.

My run will be about 6ft. Can anyone tell me what size wire I would use with a 250A breaker for this inverter?

inverter specifications:

Overload protection: 2,000 W – 2,100 W
Reverse polarity protection: fuse
Short circuit protection: shutdown
High temperature protection
Working temperature: -10°C to 40°C
Input volt: 12 V DC
Output volt: 120 V AC
Output Waveform: Pure Sine Wave
TrueRated™ Power: 2,000 W
Surge power: 4,000 W
Maximum Efficiency: Approximate 90%
Frequency: 60 Hz
No load current draw: < 1.5 A
Total Harmonic Distortion: < 5%
Low battery alarm: 10.5 V ± 0.3 V
Low battery shut down: 9.5 V ± 0.3 V
High voltage protection: 15.5 V ± 0.5 V

Thanks
Swamp

BB.

Re: Inverter cable and breaker sizing

ABYC (American boating and yachting council) only allows around 130-160 Amps maximum for a 4 AWG cable (they allow 30-35 amps for a 14 AWG cable where NEC allows 15 amps--really 20 amps, another issue--maximum).

And 2/0 for 300 amp fuse.

If you want to run the inverter at 2,100 watts:

• 2,100 watts * 1/0.85 typical inverter eff * 1/10.5 volt cutoff * 1.25 NEC derating = 294 amp minimum branch circuit rating
• 2,100 watts * 1/0.85 typical inverter eff * 1/10.5 volt cutoff = 235 amp minimum branch circuit rating

And then there is voltage drop (simple calculator). For 235 amps and 0.5 volt maximum drop at 6 feet round trip for cable: 2 AWG for 0.5 volt drop.

Using the ABYC table, a minimum of 1 AWG cable.

Using NEC table 310-16 would be 300-350 circular mill cable minimum (plus even more deratings for temperature, conduit fill, etc.).

The reality is, most people will not run their inverter more than ~50% of capacity and only near rated capacity for a few seconds when starting motors (saws, well pump, etc.).

For a 600 AH flooded cell battery bank--The typical rule of thumb power support would be:

• 600 AH * 12 volts * 0.85 inverter eff * 1/20 Hour discharge rate= 306 Watts long term average power for cabin (2 days storage, 50% max discharge)
• 600 AH * 12 volts * 0.85 * 1/8 Hour = 765 Watts maximum continuous discharge
• 600 AH * 12 volts * 0.85 * 1/5 Hour = 1,224 Watts short term maximum discharge
• 600 AH * 12 volts * 0.85 * 1/2.5 Hour = 2,448 Watts maximum starting power

You could easily "dial back" the current rating to ~1,224 Watts as the maximum continuous power you would pull from that size battery bank--Save yourself lots of copper and expensive fuses/switches.

-Bill

SwampYankee

Re: Inverter cable and breaker sizing

Thank you Bill for the detailed answer.

Cariboocoot

Re: Inverter cable and breaker sizing

There is no chance 4 AWG will take 300 Amps.
Are you sure they didn't say 4/0?
2000 Watts on a 12 Volt system will come close to 200 Amps at maximum output/minimum input Voltage. 4 AWG would be at its limit around 1/2 that current.

If you want to use the 250 Amp breaker you need at least 2/0 (00) and 3/0 (000) would be better.

Depending on the distance involved and how close to maximum you run the inverter 4/0 may be preferable. It usually is on a 12 Volt system.

SwampYankee

Re: Inverter cable and breaker sizing

Cariboocoot wrote: »

There is no chance 4 AWG will take 300 Amps.
Are you sure they didn't say 4/0?
2000 Watts on a 12 Volt system will come close to 200 Amps at maximum output/minimum input Voltage. 4 AWG would be at its limit around 1/2 that current.

If you want to use the 250 Amp breaker you need at least 2/0 (00) and 3/0 (000) would be better.

Depending on the distance involved and how close to maximum you run the inverter 4/0 may be preferable. It usually is on a 12 Volt system.

I just checked again and it is 4AWG. Chinese manual probably.

zoneblue

Re: Inverter cable and breaker sizing

Its pretty common in the "cheap chinese" segment to find provided cables in that (lame) size range. Perhaps this is a good time to reevaluate whether you trust the health and wellbeing of your house and family to this product???

Blackcherry04

Re: Inverter cable and breaker sizing

If your inverter is 12 V use 4/0, you'll never regret it. The cost is very small in the scheme of things and you won't get as much of a voltage sag as you would with the other sizes. The Fuse /Breaker should be sized to the size cable your using.