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Fitting a galvanic isolator Earth Bonding


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Quick question, WE don't have shore power but I'm fitting a galvanic isolater & at the moment there is only a DC bond to the hull. I understand best practice is to add a bolt within a couple couple of inches from the existing bond my question is is there a BSS standard size 230v earth cable, or what size cable is recommended?

Thanks.

 

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28 minutes ago, Clodi said:

Quick question, WE don't have shore power but I'm fitting a galvanic isolater & at the moment there is only a DC bond to the hull. I understand best practice is to add a bolt within a couple couple of inches from the existing bond my question is is there a BSS standard size 230v earth cable, or what size cable is recommended?

Thanks.

 

 

My question is why spend money you don't need to. Even if you have an inverter or generator on board for 230V AC power they can not cause hull corrosion. It is the main's earth wire that causes that and why a GI is a very good idea.

 

I thought mains earth cables were usually 4 sq mm CCSA but more than happy to be corrected. Remember multi-strand flexible cable.

  • Greenie 1
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To expand on what Tony B has said - if you are not connected up to a shore-line onto a bollard and with other boats on the same earth (not necessarily the same bollard) then you do not need a GI.

 

You get you corrosion / erosion by a current flow between boats having differing metals creating a cell.

 

 

(If you are chained to steel piling / armco, and another boat is also chanied to the pilings / armco, then yes, you could possibly also generate a 'cell')

 

 

 

 

 

Galvanic Corrosion.gif

Edited by Alan de Enfield
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Regardless of the need for a GI any  240 V system in the boat should be bonded to the hull.  A 4 sq mm or 6 sq mm green and yellow cable is suitable for most normal arrangements.   It should connect to the hull adjacent to, or on  the bond for the 12V DC negative.  If you have more than about 6 KW of installed AC generating capacity (inverters as well as generators) you might want to talk to an electrical engineer (not an electrician) about earth cable sizing.

 

If you go to one of the DIY sheds they will sell you an earth cable pipe clamp for not much money.  Part of that clamp is  a metal label which says 'Safety Electrical Earth Do Not Remove". Take the label off the clamp and attach the label to your 240 V system earth bond.

 

N

 

  • Greenie 1
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Thanks everyone,

To reply to Tony about not spending money I don't need to, and god knows things are getting tighter. I cannot foresee us ever staying any period of time in a marina on pontoon moorings etc, but, as we get older it's possible we may have to escape the mud during the worst of the winter months & seek refuge in a boat-park & it makes sense to future-proof.

Alan. thanks for the diagram, I just used it to explain to my son exactly what the potential problem could arise.

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1 hour ago, Clodi said:

Thanks everyone,

To reply to Tony about not spending money I don't need to, and god knows things are getting tighter. I cannot foresee us ever staying any period of time in a marina on pontoon moorings etc, but, as we get older it's possible we may have to escape the mud during the worst of the winter months & seek refuge in a boat-park & it makes sense to future-proof.

Alan. thanks for the diagram, I just used it to explain to my son exactly what the potential problem could arise.

 

Stand by for incoming! If you are happy with your present boat electrical system then when in a marina for a period of time you could do as I did when living on the  boat. Use a modern car battery charger (10 amps should be plenty) extension lead style connected to the battery.

  • Greenie 1
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19 minutes ago, Tony Brooks said:

 

Stand by for incoming! If you are happy with your present boat electrical system then when in a marina for a period of time you could do as I did when living on the  boat. Use a modern car battery charger (10 amps should be plenty) extension lead style connected to the battery.

 

 

Same here.

Everything 12v except the battery charger supply.

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