Wire gauge requirement for 24V 420AH battery bank and 1,500 Watt inverter?

[Silver_Is_Money]

Can I use #3 AWG THHN wire to series connect 4 x 6V and 420 AH batteries to achieve 24V and then connect the bank to my 24V x 1,500 Watt (3,000 Watt surge) inverter by also using #3 AWG THHN? Or will I need to use #2 AWG for this application? Asking because I already have #3 AWG, but I would need to purchase #2 AWG.

[Mike90250]

http://www.powerstream.com/Wire_Size.htm

3AWG is good for 75A, how far are the wire runs ?

3Kw @ 24V is going to end up being 150A. That's closer to O gauge for low losses. Maybe 2 ga if your batteries are fresh and it's only a surge AND just a short run, but the voltage loss in the wire and battery bank will both get you.

[inetdog]

If the area where the wire is installed is a wet or damp location, or the wire run is outside (even in conduit) wire which is ONLY labelled/listed as THHN will not be allowed. That wire type is for dry locations only.

However, most of the THHN that you see in supply houses or stores is also rated as THWN or THWN-2, giving it approval for wet areas as well.

[Silver_Is_Money]

I'm hoping to keep the wire runs down to 10 feet or less overall.

[Silver_Is_Money]

My inverter instructions recommend the use of #4 AWG, so by that measure wouldn't #3 AWG be offering a margin of safety and also a reduction in line loss?

[thastinger]

1008 watts is all you should pull from those batteries discharging them at a C10 rate so 3ga would be fine for a 10ft run of that.

[Silver_Is_Money]

1008 watts is all you should pull from those batteries discharging them at a C10 rate so 3ga would be fine for a 10ft run of that.

Thanks! Even C/8 is only 52.5 Amps (1,260 Watts).

Since it is only a budget 1,500 Watt inverter I figured that any pull of greater than 1,500 watts for more than a very brief "surge" time will shut down the inverter with an overload. And 1,500 Watts / 24 Volts = 62.5 Amps, which is below the maximum 75 Amps rating of the #3 AWG. Now I'm doubting this and wondering if I actually need #2 AWG.

[sensij]

Thanks! Even C/8 is only 52.5 Amps (1,260 Watts).

Since it is only a budget 1,500 Watt inverter I figured that any pull of greater than 1,500 watts for more than a very brief "surge" time will shut down the inverter with an overload. And 1,500 Watts / 24 Volts = 62.5 Amps, which is below the maximum 75 Amps rating of the #3 AWG. Now I'm doubting this and wondering if I actually need #2 AWG.

Is your wire aluminum? Copper #3 has an allowable ampacity of 100 A.

[Silver_Is_Money]

Is your wire aluminum? Copper #3 has an allowable ampacity of 100 A.

It is copper. It will be fused at 100 amps (per the inverter instructions). But what if I do get a momentary surge to 3,000 Watts, which is 125 Amps, and the inverter does as it claims and takes this brief surge without tripping? And if the surge lasts more than a brief moment, will the ANL type 100 amp fuse blow before the #3 wire burns? This is why I'm having second thoughts about the #3 wire vs. #2.

[Naptown]

Is your wire aluminum? Copper #3 has an allowable ampacity of 100 A.

with not more than three current carrying conductors in a cable or raceway Free air is much higher and depends on the insulation on the wire.

[sensij]

with not more than three current carrying conductors in a cable or raceway Free air is much higher and depends on the insulation on the wire.

Although the conductor rating may be higher in free air, the termination rating will always be limited to 100 A (if marked), or 85 A (if not marked). 3 AWG copper is never compliant for a circuit over 100 A.

[sensij]

It is copper. It will be fused at 100 amps (per the inverter instructions). But what if I do get a momentary surge to 3,000 Watts, which is 125 Amps, and the inverter does as it claims and takes this brief surge without tripping? And if the surge lasts more than a brief moment, will the ANL type 100 amp fuse blow before the #3 wire burns? This is why I'm having second thoughts about the #3 wire vs. #2.

The fuse will protect the conductor. That is what it is there for. With a 100 A fuse, as long as your 3 AWG is in free air and has insulation rated at 90 deg, you should be fine.

[Silver_Is_Money]

The fuse will protect the conductor. That is what it is there for. With a 100 A fuse, as long as your 3 AWG is in free air and has insulation rated at 90 deg, you should be fine.

It is THHN wire and it will be in free air. That is, if a battery box is considered to be free air. ???