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bigal avatar image
bigal asked

115v AC between Neutral & Earth on boat

I was going to add this to a existing post, but decided better here.

I have installed a Phoenix 12/375 on a boat.

DC in is polarity correct and 12.8v as measured with DMM. DC ground is a earth wiring which goes to the engine, also connected to the engine is the bonding wires and negative DC.

When I power on the inverter the status light indicates operation is normal.

When I plug AC devices into the inverter they function normally.

Measured with a DMM between neutral and phase is 230v AC - normal.

However measured between earth and neutral is 115v AC (exactly half of 230v AC). I do not think this is normal, can anyone please advise?

Thanks

Al


Phoenix Inverter
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6 Answers
boekel avatar image
boekel answered ·

This usually happens when the network is not grounded anywhere (housing of the Phoenix connected to the ships hull?)
some AC devices have a 'filter' at the input, with two capacitors to ground, if ground is floating it will get the midpoint voltage as you measure.

You might even feel a tingle when you touch it, and get horrible sounds when connecting audio devices.

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bigal avatar image bigal commented ·

Thanks for the prompt answer. The DC ground wire on the victron is connected to the AC breaker ground bus. The AC breaker ground bus in turn goes to a terminal on the motor.


Also connected to this terminal on the motor is bonding cable and DC battery negative.


Does that ground setup sound right?

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boekel avatar image boekel ♦ bigal commented ·

No you need to ground the housing of the inverter, there is a ground connector for that.
- edit -
I was wrong, after reading the manual I learned that you'll need to make the Neutral-ground connection yourself. So you both need to connect the ground connector to the ground (hull) of your boat / vehicle, -and- need to wire the inverter internally as per the manual.

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bigal avatar image
bigal answered ·

Also what else could I check to further fault find?

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JohnC avatar image
JohnC answered ·

Hi Al. I can't give good direct advice re this, as I'm neither a sparky nor can admit even having my head around all the nuances of earthing on a boat. Even though I live on a boat. :)

Have a look through this article: http://www.smartgauge.co.uk/earthing.html

Look particularly for mention of the Neutral-Earth bond (commonly called 'MEN link' in much of the world, you could Google it). You mustn't have that if you can measure a potential between them. Perhaps you should? Note this isn't advice from me, more so a question for you.

And for the experienced/qualified (like Boekel) to maybe expound upon. And wouldn't it be nice for Victron to 'explain it better' for their kit, especially the mobile/marine applications which are often diy'd. Yeh sorry guys, I know you're busy, but..

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boekel avatar image boekel ♦ commented ·

It's quite well described in the manual, see 3.3 - 3.5 and Appendix A

https://www.victronenergy.com/upload/documents/Manual-Phoenix-Inverter-250VA-1200VA-EN-NL-FR-DE-ES-IT.pdf

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JohnC avatar image JohnC ♦ boekel ♦ commented ·

Yeh, I'm sure it is for that model. What I was really suggesting was a general reference article in the manner of the link I posted. And sure all applications aren't the same, nor are regulations in all countries. I didn't suggest it would be easy either, ha..

I'm an 'inland mariner', and have found when I mention to a local sparky that I have kit that can switch MEN, I lose their interest- *eyes glaze over*. Something definitive would be good to show them, and for the odd diy ac job that will invariably take place in remote locations, could even save life.


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bigal avatar image
bigal answered ·

Hi Boekel,

Thank you very much for that information. I have found a few different Phoenix manuals but never one that one (which has pictures).

I do have a earth wire coming from the large metal lug that you are pointing to and it goes to the earth bus and then the engine (that's what I mean when I said DC earth - ie earth on DC side of the inverter).

Re the Netural-Earth link - I also googled this before I posted here and the first article that came up was this one https://www.proboat.com/2011/10/demystifying-the-neutral-to-ground-connection/ which I read that you should not link neutral and earth even though that is what the third photo in the article shows.

Then there is this article which says there should be a neutral - earth link at a "newly dervied" source : http://www.qualitymarineservices.net/Neutral-Ground%20Bond,%20Exchange%20Article,%2012-2005.pdf

I will try changing that jumper wire, but if it is meant to be that way, why does it not come from the factory like this?

Regards,

Al


PS: I had been looking at this manual which appears to be correct manual but is different to your link??? https://www.victronenergy.com/upload/documents/Manual-Phoenix-Inverter-180-350-EN-NL-FR-DE-ES.pdf (note no mention of the neutral connector)

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boekel avatar image boekel ♦ commented ·

you can also add an external neutral-earth connection, might be easier to do.

I don't know your local rules for this...so if you want the best answer ask a local electrician.

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bigal avatar image
bigal answered ·

Great support - thanks again @Boekel

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bigal avatar image
bigal answered ·

Hi @Boekel - I finally got around to taking the cover off my inverter today. It does not look like in the manual :



20190304-181527.jpg (372.6 KiB)
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boekel avatar image boekel ♦ commented ·

Ahhh great... :p

If you wire it to a board system, just make the neutral-earth binding as close to the unit as possible.

I'm not 100% sure about the rules, but I never use the units with these sockets in a hardwired installation, only for powering small devices directly plugged into the unit. I actually never gave it a thorough thought...


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bigal avatar image bigal boekel ♦ commented ·

Right ok.

I am still however a bit confused as to why neutral is carrying 115V AC? Is this how it should be?

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boekel avatar image boekel ♦ bigal commented ·

It is floating actually, due to the filter capacitors on the output board.

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