Re: [Amel Yacht Owners] Re: FW: inverters/chargers


Andrew & Kate Lamb
 

Hi Gary

 

Many thanks for taking the time to answer my queries so thoroughly  - for me and I hope for others this has been a very useful discussion – it sounds like the key here is trust (or lack of) in the wiring in the pedestal and how that may influence safety, and I can well understand the lack of trust in the pedestal even from my relative narrow experience of these in Europe.

 

I suppose designing these systems is about balancing the relative risks, and perhaps therefore Amel’s decision not to connect the boat’s bonding to the AC ground, particularly for a boat that is designed to travel around the world and plug into all sorts of systems.

 

In my reading around this it became apparently that there is also a not insignificant risk of GFCI (RCD) failure - I suppose therefore one of the most important things - as with many systems on the boat - is regular maintenance and testing and this also includes the electrical systems.

 

Thanks!

 

Andrew

 

Ronpische

SM2k 472

Canet en Roussillion, France

 

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Sunday, February 01, 2015 9:11 PM
To: amelyachtowners@...
Subject: Re: RE: [Amel Yacht Owners] Re: FW: inverters/chargers

 

 

Gary,

 I completely agree with Amels philosophy about bonding and totally disagree with ABYC regulations.

I believe that the floating ground on the DC side of the boat and the lack of a connection of the boats bonding and the Ac earth is the way to go.

You just never know what you are plugging into. ABYC standards are written for mostly coastal USA sailors who never plug into a foreign pedestal/

On the last two boats which i personally stripped to the hull and replaced everything, I gained a lot of knowledge how boats were built.

On my other boats I always took a voltmeter/ohm meter to the dock and measured the pedestal socket.

My tartan 37 was 110 volts. when I went to the pedestal at the St Georges dinghy club I encountered 440 volts between the neutral and ground. 

 

On Kimberlite I have a separate AC panel with a volt, amp, and frequency meter in addition to a  3 pole circuit breaker. The breaker  and meters are before the boats AC panel. I turn the new breaker off and then plug in. This November after the hurricane in st maarten , I plugged into my pedestal and had 110 volts between the  blue and brown and also the earth /. If I did not have my circuit  breaker off I don.t know what would have happened.  essentially everything was broken in the pedestal  the entire bonding of the boat if connected to the AC earth  would have been hot.

i can not figure what would have blown out first. If someone was touching something bonded when the plug was inserted in the pedestal i believe they might have been electrocuted.

The connecting of the Ac earth  and the boats  bonding is an argument that can be made for and against with plausible answers to both. I prefer to keep them disconnected.

Eric

 

 

 

----- Original Message -----
From: amelliahona 
Date: Sunday, February 1, 2015 1:55 pm
Subject: RE: [Amel Yacht Owners] Re: FW: inverters/chargers
To: amelyachtowners@...

> Hi Andrew:
>
> Thanks for your thoughtful reply. Let me start by saying that
> there are varying opinions on boat bonding/grounding issues,
> even between knowledgable entities (of which I am at the lowest
> levels). The Amel scenario does not comply to ABYC standards
> and the ISO standards that another author mentioned. That
> doesn't mean that Amel's scenario is wrong, their theory, that I
> suspect was very well thought out, is just different (sound
> familiar).
>
>
> You said; "surely in a correctly wired grounding system, with
> all metal components connected to the grounding system with low
> resistance connections, the path of least resistance will be via
> the grounding system and will cause a circuit breaker to trip
> not via any other route.
> Therefore in the case of a ragged extension lead, faulty water
> heater or electrical tool creating a connection to part of the
> “bonded” metal work of the boat e.g. in the engine room then if
> there is a connection to the grounding system then a low
> resistance path is formed and a circuit breaker will trip –
> which surely is a safer position than these bonded metallic
> components potentially being “hot” and undetected?"
>
>
> The key here, in my opinion, is "in a correctly wired grounding
> system", yes the fault will open the CB. The problem is that
> the grounding system may not be "correctly wired" or there may
> be a fault(s) in the grounding or bonding systems. Consider
> various fault scenarios in the 220 system that puts 220 volts
> onto the bonding system and there is a fault in the 220 volt
> grounding. Now you have 220 volts being conducted into the
> surrounding sea water via the bonding system and hence onto
> every metal part bonded. This would not open the breaker. This
> would pose an electrocution hazard to a swimmer or somebody that
> gets between the bonded part and another conducting part.
> Additionally leakage current from the AC grounding system (not
> uncommon) that is tied to the bonding system hastens anode
> erosion.
>
>
> You said; "– which surely is a safer position than these bonded
> metallic components potentially being “hot” and undetected?" An
> undetected high voltage electrification of the bonding system is
> a potential threat, but a grounding fault with an associated 220
> volt fault (e.g. faulty hot water heater element), could easily
> do just that. Hence the need for a GFCI that measures outgoing
> and return current, compares those two and if more than 30 mA
> (the Amel SM GFCI), will disconnect the supply 220 VAC.
>
>
> Bottom line is that Amel has a low EMF/low current bonding
> system that is separate from the higher EMF/higher potential
> current grounding system, not two dissimilar parallel circuits
> tied to each other.
>
>
> All that said, perhaps Olivier Beaute might chime in on
> Chantiers Amel's philosophy as to their reasoning for
> separating these two systems and whether this is a European vs
> American difference etc.
>
>
> All the best,
>
>
> Gary Silver
> s/v Liahona
> Amel SM 335
>
>

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