split phase 240v INPUT to Quattro 230v

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mixman1 asked Apr 25, '21

split phase 240v INPUT to Quattro 230v

I have a 230v boat. with a Quattro 5K inverter charger. If I am in the us and have 240v split phase shore power, can it be safely connected to the Quattro using shore L1 (120v) and L2 (120v) which is 240v between them. Connected to Quattro input 1 L1 and Neutral?

I know that I can safely do this with all systems onboard using Shore L1 and L2 to Boat L1 and N without having the Quattro inline. What I am not clear on yet is if having the Quattro inline is an issue?

Theoretically, the Quattro shouldn't care.

I would appreciate a definitive answer on this. Would be an expensive experiment if it went wrong!

MultiPlus Quattro Inverter Charger Phoenix Inverter split phase

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mixman1 commented · Apr 25, 2021 at 12:50 PM

Just to add a little bit more... In straight pass through mode, it should be fine. L1 and N from shore power connections to L1 and N output to boat. So theoretically no matter what is on those 2 lines, it should simply pass through. The big concern might be in power assist mode where the inverter attempts to put 230v on L1 while there is already 120v there and 120v on N. I am very well versed in electricity and how it all interacts. The wild card is not knowing how the Quattro handles these things internally.

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mixman1 commented · Apr 28, 2021 at 01:31 PM

This is a modern boat built to EU standards. All branch circuits have circuit breakers on Line and Neutral. There is an RCD inline upstream of all. No load on board has a bonded neutral and ground. There is nothing unsafe about having +115v on Line and -115v on neutral Provided all lines are circuit protected and a continuous ground exists all the way back to the shore plug.

The question at hand is this, if the Quattro input sees +115v on L and -115v on N for a total voltage potential of 230v, will it cause any issues within the unit when in pass through mode?

The follow up and more advanced question is how will it act if it is put in power assist mode? Will the voltage on the neutral confuse the Quattro?

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Answer 1 · 2021-04-25T16:08:02Z

Kevin Windrem answered · Apr 25, 2021 at 04:08 PM

This is intrinsically unsafe. Incoming L2 would end up feeding the neutral bus of your distribution system. The neutral system has no circuit breakers so a fault in any device would route the full shore power current back to the safety ground.

You could use a split-phase distribution panel and use dual breakers for each branch circuit. The neutral bus would be unused.

The best solution is an isolation transformer on the shore power connection. This would also allow you to step down the 240 volt shore power to 230 volts.

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Answer 2 · 2021-04-28T14:55:56Z

Kevin Windrem answered · Apr 28, 2021 at 02:55 PM

Based on your description of the existing electrical system with breakers on the neutral conductor, your installation will be safe.

The Quatro will be perfectly happy with voltage on the neutral as well. The AC input voltage can be set to accept up to 270 volts so you should be OK there as well. Don't forget to accept wide frequency range.

The Quatro inverter is connected between line and neutral and in power assist there is no neutral to earth connection so there is no issue here either.

I'm fairly sure this has been addressed inside the Quatro, but you should verify that the ground relay and AC input relay are never closed at the same time, even for an instant. Normally, the ground relay closes when the inverter is running by itself (no shore power). Due to voltage on the neutral from the shore power connection, if they are both closed at the same time, the L2 side of shore power will short to safety ground which obviously would be bad.

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