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Inverter


weldon

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I am looking at two inverters from HF one is 1500 watt continuous/3000 watt peak and the other one is 2000 watt continuous/4000 watt peak. I have three 12 vote batt. in parallel. What size wire would I need going to the batts. Thank you for input.

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Absolute minimum (30amp) would be 6 gauge... 4 gauge for 40amp and 2 gauge for 60amp. Personally, I wouldn't go anything smaller than 2 gauge for that distance, and would prefer 1/0 if I could afford it. With the 2000 watt, my preference would be for 2/0.

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4000 watts at 12 volts gives you 334 amps (4000 / 12) and 3000 gives you 250 amps. Using peak amps and 12 volts is kind of a fudge factor since you'll rarely be using the full surge rating but you will also often be seeing less than 12 volts.

 

The chart here, using the 4000 watt draw shows about a 3.37% voltage drop using 4/0 cable and that is well over the 2% recommended value. For the smaller one you are looking at 2.52% which is marginal.

 

http://www.powerstream.com/Wire_Size.htm (near the bottom of the page)

 

I'd really rethink the inverter location at this point and see if the high current 12 volt DC wiring can be made shorter. If you can't move things go with the copper 4/0 and live with the voltage drop.

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The fact is that while you can go too small in wire gauge you can't go too big. Just use the biggest gauge that will fit in the connectors on the inverter, assuming that cost isn't a problem, and you will have the lowest voltage drop possible. I found that going to a local welding supply store gave the cheapest wire prices especially since shipping can add up on heavy wire.

 

Rich

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Very true, Stan. I was gauging for existing panel capacity rather than controller capacity.. which really is the better approach.

 

Rich is correct too. You can NEVER go too big. Personally, I have a 45 amp controller and use 2/0 for an 18" run. The inverters you're looking at, it might be difficult to run anything larger than 1/0 with the provided connectors.

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