Multiplus Grounding and AC in and out wire size?

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pda1 asked Sep 16, '23

Multiplus Grounding and AC in and out wire size?

I have a Multiplus 24/2000 50-50 120v

My batteries are Battleborn 2 x 12-100 ah in series for a 24v output.

In reading the manual I'm trying to understand what wire sizes are needed for grounding and the AC input and AC output.

Batteries to the MP

- Battery supply to the Multiplus will be #2 copper welding wire

What size grounding wire do I use and where does it get connected?
(inside the MP is a what looks like a ground stud)

Is the MP ground wire secured to an earth ground rod?

The MP case....where does that get ground and what wire size is used? (I think the manual says it should be the same size as the AC input wire...but here I'm confused).

The manual says- " In a fixed installation, an uninterruptable grounding can be secured by means of the grounding wire of the AC input. Otherwise the casing must be grounded."

AC input

What size AC input wire should be used? Something that'll handle 15A- a 14/2 with ground? The manual says; Use a three-wire cable with a flexible core and a cross section of at least 6 mm² (something like 10A)

Does that mean the core should be stranded like found on extension cords?

AC output

The AC wires from the MP output I think should be able to handle 50A in the probability of Power Assist being used. So that would be the AC output breaker should handle a 50A. Is that correct?

There's mention in the manual of using GFCI's (earth leakage circuit breaker) on the AC output side. Is that really necessary?

Thanks

wiring

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Answer 1 · 2023-09-16T17:46:45Z

Alexandra answered · Sep 16, 2023 at 05:46 PM

@PDA1

6mm² fine strand. Do not use hard drawn.

The diameter of each wire is 6mm² the dimesioning is not referring to the whole of the 3 core with its outer sheath.

Yes, 6mm² fine strand can handle 50A and you should dimension for the full load of the inverter.

Grounding is a local regulations question. Are you offgrid or ongrid? Usually AC grounding would equal the cable diameter or larger if you are required to run a separate earth by regulations. And if grid connected is done naturally through the 6mm² incoming AC link.

GFCI is also a local regulation question and so is RCB and RCBOs.

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Answer 2 · 2023-09-16T18:56:29Z

pda1 answered · Sep 16, 2023 at 06:56 PM

The system is off-grid but the MP 24/2000 will have grid power as the AC input feed. There will be no back-feeding to the grid.

AC in

I understand the AC in to the MP must be stranded 6mm² and understand the 6mm² applies to each of the wires and not the total bundle.

MP grounding- the MP will be grounded to earth using a #2 stranded welding cable. Does that sound correct?

Thanks. Any other ideas are welcomed.

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Alexandra ♦ commented · Sep 17, 2023 at 05:58 AM

Since you will be wired permanently into grid, even if you are not using it, you will be grounded. Since switch gear does not usually disconnect those lines.

The block diagram is helpful. The ground input/output and case is usually common so would be permanently grounded just through the AC in. But again local regs apply the welding cable should be ok in dimension.

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