Bridging AC-Out Neutral with Neutral/GND from Grid Supply when they meet in transfer switch?

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ee21 asked Sep 18, '19

Bridging AC-Out Neutral with Neutral/GND from Grid Supply when they meet in transfer switch?

Per a suggestion found in a Victron manual, I am looking at installing a manual transfer switch that will switch the Supply Feed going in to my "critical load" sub panel... between the AC-Out of my Victron MultiPlus, and the Grid Supply.

The Manual transfer switch has an isolated breaker that will allow only the Inverter Output L1 or the Grid L1 to be connected at one time to the Load L1. If the Inverters fail, or are being worked on, the "critical loads" can be cut over so they are supplied directly from grid.

The problem I am having, and the question I am asking is: The Transfer Switch has a common bus bar for the Neutral. Is it safe to bridge together the MultiPlus AC-Out Neutral, and what is essentially the AC-Input Neutral in this manor when using a transfer switch?

MultiPlus Quattro Inverter Charger wiring

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Daniël Boekel (Victron Energy Staff) answered · Sep 18, 2019 at 05:14 PM

Hi @ee21

No, you'll need another switch, that does break the neutral line.

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ee21 commented · Sep 18, 2019 at 06:43 PM

Thank you for the confirmation. I suspected as much from what I read, but I appreciate the clarification.

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Charlie ee21 commented · Jun 25, 2023 at 08:16 PM

Did you resolved this issue? If you did, please upload a picture of the installed transfer switch and the additional switch to break the neutral line. thxs

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sharpener Charlie commented · Jun 25, 2023 at 09:40 PM

You need a double pole switch. This one works fine IME

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brandon-copley commented · May 10, 2020 at 05:29 AM

Hello, I appreciate this answer, and just separated the neutrals in my 50amp 2 phase vehicle and made a manual transfer switch because I bought a 50amp multiplus, and probably should have purchased the Quattro, but I can’t return it, but I can’t figure out why bonding neutrals is incorrect. Why should we bond the neutrals? Other inverters bond input and output neutrals from what I can tell.

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Daniël Boekel (Victron Energy Staff) ♦♦ brandon-copley commented · May 10, 2020 at 06:15 PM

Hi @Brandon Copley

it partly has to do with grid code compliance etc, but it's also a safety thing to prevent voltage on input when in inverter mode.

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brandon-copley Daniël Boekel (Victron Energy Staff) ♦♦ commented · May 10, 2020 at 07:04 PM

Thanks!, yes it appears that there is a high risk of energizing the rv input neutral prong, this could zap ya if you touch the neutral prong and the rv chassis at the same tome, or potentially anyone else in the park. It was quite a bit of work to add, wish I bought the Quattro, but I wrongly assumed multiples could handle 50 amp 2 phase.

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Answer 1 · 2019-10-19T08:02:44Z

washington answered · Oct 19, 2019 at 08:02 AM

I suggest a minimum double pole ATS which breaks both live and neutral will be best to counter the neutral faults usually introduced by the power electronics transformerless inverter circuits as oppossed to the isolated neutrals in transformer type inverters. For near bumpless power transfer you can choose fast switching systems.

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Answer 2 · 2020-06-29T02:42:07Z

Eli Hunter answered · Jun 29, 2020 at 02:42 AM

Sorry to revive an old thread but I'm looking for a transfer switch that switches neutral and is UL listed. Has anybody run across any good options? The few I've found seem to have been discontinued.

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