For those on shore power

[SimbaDog]

I am interested to know how many people who are in marinas & on shore power are using a galvanic isolator?

If you have one I would be interested to know what make.

Thanks.

 

[AIDY]

i'm in a marina... use shore power.... but always disconnect when i leave the boat... No galvonic isolator but have been thinking about it.... just to save some wear on the anodes that seem to disapear too quickly at least there doing there job

 

[ianj99]

I have a steel ketch and use a 1600va 1:1 isolating transformer.

http://www.airlinktransformers.com/transformer/wp1631-weatherproof-transformer.asp

This totally eliminates any galvanic currents from the shore power since the earths are also separate.

 

[Leighb]

I am in a marina, using shore power which I generally leave connected. The hull anode only wears at a normal rate, am replacing it this year after 2 years and it still has about 1/3 zinc left. I just thought it might not do for another season.

 

[Boathook]

My electrics are disconnected when not on board and the electrical circuit is not attached to any part of the boat. It also goes through a double pole RCD so should be ok for France !!

 

[Ripster]

Just fitted one. Dead easy to do and fairly cheap. We spend overnighters in Marinas with SP connected, so that is why I thought it a good idea.

 

[prv]

The boat is fitted for shore power, but there's none on the pontoon!

It might therefore get the odd use over nights away, but I don't plan to stay in marinas if I can help it. So the lack of a galvanic isolator is neither here nor there.

Pete

 

[gasdave]

Fitted a Safeshore Marine GI - straightforward.

 

[Refueler]

Having wired up all the boats I've had over the years .... I've studied book after book about this ... and came to conclusion, right or wrong .... that they were only needed when bonding and connections took on levels that 'created' stray currents etc.
My present main boat has had main to hull anode bonding cable disconnected by yard after they replaced my shaft, engine bearers etc. 6 years later ? No effect whatsoever. Made absolutely no difference at all. Anode still there, nothing wasted away .... So why fit a GI ?

One electrician will give one opinion, another will say different ... same as all the books I've read ... none seem to agree completely.

All I can assume is that if you follow the school that connects all negatives and then bonds that .... then I is probably needed or advised. But if like me, in the school of isolate different circuits and don't bond - then what's point ?

Before others jumo on me - I have no intention of changing my set-up. It agrees with various textbooks i have and also my pal - an electrician.

 

[VicS]

Before others jumo on me

JUMP

Seriously, the current wisdom is that, short of an isolating transformer,

"The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal"​

Quoted from ISO13297: Small craft — Electrical systems — Alternating current installations.

once you do that then of course a GI becomes next to essential if you leave the shorepower connected for prolonged periods.

However ISO13297 does allow for that connection not to be made provided there is a "whole craft" RCD.

"NOTE If an RCD (whole-craft residual current device) or an isolation transformer is installed in the main supply circuit of the
a.c. system (see 8.2), the negative ground terminal of the d.c. system need not be connected to the a.c. shore ground
(protective conductor)."​

I am advised though that this exception will probably be dropped from the next revision of the standard.

Other provisions exist for boats with fully isolated DC system, and with metal hulls of course the shorepower earth is connected to the hull ... no debate!

 

[Playtime]

Having wired up all the boats I've had over the years .... I've studied book after book about this ... and came to conclusion, right or wrong .... that they were only needed when bonding and connections took on levels that 'created' stray currents etc.
My present main boat has had main to hull anode bonding cable disconnected by yard after they replaced my shaft, engine bearers etc. 6 years later ? No effect whatsoever. Made absolutely no difference at all. Anode still there, nothing wasted away .... So why fit a GI ?

One electrician will give one opinion, another will say different ... same as all the books I've read ... none seem to agree completely.

All I can assume is that if you follow the school that connects all negatives and then bonds that .... then I is probably needed or advised. But if like me, in the school of isolate different circuits and don't bond - then what's point ?

Before others jumo on me - I have no intention of changing my set-up. It agrees with various textbooks i have and also my pal - an electrician.

I'm with Refueler on this one.

JUMP

Seriously, the current wisdom is that, short of an isolating transformer,

"The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal"​

Quoted from ISO13297: Small craft — Electrical systems — Alternating current installations.

once you do that then of course a GI becomes next to essential if you leave the shorepower connected for prolonged periods.

However ISO13297 does allow for that connection not to be made provided there is a "whole craft" RCD.

"NOTE If an RCD (whole-craft residual current device) or an isolation transformer is installed in the main supply circuit of the
a.c. system (see 8.2), the negative ground terminal of the d.c. system need not be connected to the a.c. shore ground
(protective conductor)."​

I am advised though that this exception will probably be dropped from the next revision of the standard.

Other provisions exist for boats with fully isolated DC system, and with metal hulls of course the shorepower earth is connected to the hull ... no debate!

I believe this is more 'nanny state' recommendations, made for spurious safety reasons (to protect people who can't wire plugs correctly etc.) without regard to the other implications, like galvanic isolation.

I shall also continue to keep my AC and DC circuits completely separate.

 

[VicS]

I believe this is more 'nanny state' recommendations, made for spurious safety reasons

I think you will find it is the considered opinion of expert electrical engineers with experience in this field.

I am rather surprised that as a chartered electrical engineer you should be suggesting that other people should not conform to the international standards. It seems a very unprofessional attitude to me!

 

[Playtime]

I think you will find it is the considered opinion of expert electrical engineers with experience in this field.

I am rather surprised that as a chartered electrical engineer you should be suggesting that other people should not conform to the international standards. It seems a very unprofessional attitude to me!

Retired actually. However, I do feel entitled to a personal opinion, based on past experience and training.

BTW, do you have written permission to reproduce extracts from the Standard?

"All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch[/I]"

 

[Evenspread]

electricity charges/isolation

Yes I have fitted one.(Safeshore Marine --provided excellent service) but it certainly has not helped the electricity charges which have topped £220 this quarter.
Yes I know, it has nothing to do with the isolator, just further annoyed with the various costs of being in this particular marina (which has also suffered from a plague of thefts from boats on a regular basis for several months now)
This sum is far in excess of the cost of running a large family house for the same period so difficult to justify, especially as it was about £30 per quarter last year. Know doubt they will have some imaginative suggestions to offer.
Sorry about the high-jack .. Moan over ...I should take up bowls if I can't take the flak...

 

[ianabc]

Question

quote ..."with metal hulls of course the shorepower earth is connected to the hull ... no debate!"


I believe there is.....

Connecting shore power ground/earth to a metal hull is exactly what we are trying to AVOID.

I believe if you are swimming, diving, cleaning the bottom of a boat you would perhaps appreciate there being no stray current in the water or on a metal boat hull.

 

[VicS]

Connecting shore power ground/earth to a metal hull is exactly what we are trying to AVOID.

At the risk of infringing the copyright laws again, ISO 13297 says:

4.3 For craft with fully insulated d.c. systems (see ISO 10133), the a.c. protective conductor shall be connected
to the hull of a metallic hull craft, the craft external ground (earth) or the craft lightning-protection ground plate, if
fitted.
4.4 Metallic craft hulls shall not be used as conductors.
4.5 The protective conductor shall be connected to metallic hulls at a location above any anticipated water
accumulation.​

The earth connection to the hull will prevent fault currents passing through the water by providing a direct path for them.
If the hull is not earthed and a fault ( from live to the hull) occurs on board then the path to earth for the fault current will be through the water, putting swimmers at risk.

 

[ianabc]

GFI's

5 and 30 milliamps interrupt

http://www.edsboattips.com/maintenance-a-diy/21-introducing-the-elci

 

[ccscott49]

My DC circuit is insulated return, no stray currents there, I have shorepower, genny and I do not have my earth connected to my DC negative, earths go to central earth for genny and shorepwoer. I have an all boat RCD. Thats all I intend to fit. Oh! The hull on my boat is wood and the anodes are bonded to engines, sterntubes, rudder and seacocks.