# Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

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Registered Users Posts: 2
Please help a mechanical engineer out with this evil electricity stuff! I'm planning on installing a PV array on a utility building with three Magnum 120/240 sinewave inverters (model MS4448PAE) providing 13,200 watts. I'd like to run the output from these through underground conduit to a breaker panel in my house 200-500 feet away. When sizing the wire for the run to the house should I be using 240 volts and 50 amps or 120 volts and 100 amps? I only have one 230 volt load (well pump), everything else is 120.

Thanks for any help and even greater thanks for an explanation as to why that is.

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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

Welcome to the forum.

The inverter output is 240 Volt split-phase. The current rating is based on the power @ 240 Volts: 4400 Watts / 240 Volts = 18 Amps L1 to L2. The power available on either of these 'hots' to the neutral is 1/2 the total output or 2200 Watts. Divide by 120 Volts and you get 18 Amps again. The neutral line never carries more current than the difference between L1 and L2. Does that make sense? In other words on 120 Volts only half the total invert power is available; it is not 4400 Watts on L1-N and 4400 Watts on L2-N as well as 4400 Watts on L1-L2.

For three of these in parallel the total current would be 3 x 18 or roughly 60 Amps. The distance involved is quite a lot and fairly high range. At 200 feet you'd want 4 AWG to keep the V-drop below 3%. If it is 500 feet you're going to want 0 AWG. Pretty big wire for that distance (i.e. expensive).
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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

Thank you very much Cariboocoot. At 240 volts, 54 amps, and 500 feet it looks like I can get by with 2/0-2/0-2/0-1 aluminum SER at a bit under \$3 a foot. The trees that would otherwise have needed to come down to move things closer are quite happy with this result.
• Solar Expert Posts: 767 ✭✭✭✭
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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

Always transmit power at the highest possible voltage.
00ga aluminum is about the cheapest way to get that much power over distance.
My mechanical engineer friend also knows absolutely nothing about residential wiring and even less about industrial 480v 3 phase where he works.

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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

I converted every power tool to 240V that allows for rewiring the motor. Everything works better, stronger, cooler, more powerful. 240V availability is a given for me, in addition to the other reasons given.
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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?
CDN_VT wrote: »
If your only load of 220 V /60 hz is the well pump !! ?? Then maybe a change of pump to 120v with bigger pump drop wire & do just the 120 Volt single leg .. Im at the same crotch . 220 V deep well, power sucking drier , Table saw (that converts to 110 -120 volt) then there's the frigging shop non convertible !!! Hoists /plasma's / CNC's / every mans/boys toyz we dream of !! I'm leaning towards 220 V when NAWS has there next Sale I know .

VT

Under the circumstances changing to a 120 VAC pump would be entirely the wrong thing to do here.
He's got up to 13kW of power traveling hundreds of feet to the load center.
I should also warn about not trying to balance the 120 loads on the two halves of the split phase.
• Solar Expert Posts: 9,583 ✭✭✭✭✭
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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?

DO NOT change a working 240V well pump for a 120V . At 120V, you will double your amps, and will need even LARGER wire to run the well. And the depth of the well will also have to be considered if you change voltage, you still have maybe 200' of wire in the well that affects losses. Be sure your battery can supply the starting surge the well motor needs.
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• Solar Expert Posts: 492 ✭✭✭
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Re: Should I be using 240V or 120V when sizing a wiring run from inverter to load panel?
Under the circumstances changing to a 120 VAC pump would be entirely the wrong thing to do here.
He's got up to 13kW of power traveling hundreds of feet to the load center.
I should also warn about not trying to balance the 120 loads on the two halves of the split phase.

Agreed . Don't know what I was thinking or why it went that way !
Thanks for the reply . I'll clean .

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