question

hydroplosion avatar image

Multiplus 12|3000|120 AC-Out-1 wire size

Multiplus 12|3000|120 AC-Out-1: 75A possible. AWG 6 recommended.

AC-In says to use three-wire cable, AWG 6 gauge. Rated for 50A.

I've seen 6/3 cable say 55A per conductor, so is 6/3 cable sufficient for AC-Out-1? Or use three AWG 6 wires, or a lower gauge like 4/3?

Thanks!

wiringpowerassist
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Seems like an easy question for Victron... anyone set one of these up for PowerAssist 75A @ 120VAC?

3 Answers
rickp avatar image
rickp answered ·

I think the 6/3 would cover it. 120V at 50A is going to be 6000 watts. At that wattage, the duration won’t be long enough to stress the cabling.

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It can run at 75A with PowerAssist though.

If you are actually planning on drawing 9000 watts continuous from it, you should use cable appropriate for that load. It will only enlist Power Assist mode if the loads you have connected while on grid power are unable to run on the current provided. Only you can say what you plan to connect.

In my case, Power Assist would be available if the only AC grid power available was a 15 amp plug, for example, so I had to limit grid power to that, but my connected loads under battery power were, say, 22 amps. It would make up the difference when needed, and charge when not, up to the 15 amp limit I set.

If you’re not sure of what you might do, then it’s best to cable for the max, and select fuses/breakers accordingly.

Kevin Windrem avatar image
Kevin Windrem answered ·

The spec sheet for the 120/3000 Multi indicates 6 AWG is the largest wire size it can accommodate for the AC inputs and outputs.

While the transfer switch is rated at 50 amps and you can theoretically get 25 more amps out of the inverter totaling 75 amps I would not design a system based on that maximum to a single output from the Multi. The input to the Multi may disconnect for a number of reasons leaving you with only the inverter's output at least for a while. This could quickly cause an overload and shutdown the inverter. For this reason, I would not design a system with more than 25 amps load on AC 1 output. Additional loads totaling 50 amps could be connected to AC 2 output. These are shed when the AC input drops out so there's significantly less chance of inverter overload. There is still a potential for overload with AC input present but the inverter off. This condition would trip the 50 amp input breaker. To avoid tripping the input breaker, the total of all loads should probably be less than 50 amps, so 25 amps max on AC 1 out and the remainder on AC 2 out.

This approach also reduces current in the AC output conductors. AC 1 out could use 10 AWG wire (30 amps max at 60 C). AC 1 out could use 6 AWG (55 amps max at 60 C).

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solardude avatar image
solardude answered ·

If you are worried about ampacity, use 6AWG boat cable rated BC-5W2. 6AWG is rated for 120A in single wire runs, or 84A in 3 wire bundles. Most quality marine wire has this rating.

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How do you get 6AWG into the 3/4" waterproof strain-relief? I found it difficult to get 10/3 into the strain-relief.

Thanks

I had to strip the outer cover off the 6/3 bundle, leaving only the colored sheathing. For both AC-In and AC-Out-1. Certainly not ideal, and the wires were still a pain to shove into the terminal, even with ferrules. Not a fan at all of the installation process for this inverter.