Galvanic isolator

KREW2

KREW2

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My Seaward 25 is presently on a berth in Weymouth council Marina, with no power. I am about to move to a berth with electricity. I wont be leaving the boat hooked up permanently, but a 240v supply is handy for doing jobs on board, so main use will be via an extension lead. However there will be occasions in the winter when I may want to use the onboard Sterling charger for a battery top up.
My question is, does just being in a marina where there are other boats that seem to be permanently hooked up mean I should install a galvanic isolator?
 
 
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No. Connection of your boat to pontoons and other boats is via the earth wire of a three-core cable. This could result in your anodes protecting other boats or the pontoon. If you are only using a temporary wander lead the risk is negligible.
 
vyv_cox said:
No. Connection of your boat to pontoons and other boats is via the earth wire of a three-core cable. This could result in your anodes protecting other boats or the pontoon. If you are only using a temporary wander lead the risk is negligible.
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I have been on websites but still don't fully understand about galvanic corrosion. Are you saying that isolators can do more harm than good.
 
 
On your boat does your AC earth wire have an electrical path to the sea (earth)? If yes, a galvanic isolator is sensible. If no then there is no point fitting one, it won't do anything.
 
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Poey50 said:
On your boat does your AC earth wire have an electrical path to the sea (earth)? If yes, a galvanic isolator is sensible. If no then there is no point fitting one, it won't do anything.
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That's a simple and concise answer. How do I find out if I have an earth to the sea? Maybe the sterling battery charger through the batteries, engines and the prop shaft, or am I showing my ignorance here
 
KREW2 said:
I have been on websites but still don't fully understand about galvanic corrosion. Are you saying that isolators can do more harm than good.
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No, that's not what I am saying, I am saying that a galvanic isolator is not needed. If the boat's earth is connected to the pontoon supply on an occasional basis there is no need for an isolator.

E.g. I do not have one. We use marinas or town quays occasionally, often not taking power as we are largely self sufficient. My shaft anode lasts 4 years, my prop anode for 2 years. I have no unexplained corrosion on board.
 
vyv_cox said:
No, that's not what I am saying, I am saying that a galvanic isolator is not needed. If the boat's earth is connected to the pontoon supply on an occasional basis there is no need for an isolator.

E.g. I do not have one. We use marinas or town quays occasionally, often not taking power as we are largely self sufficient. My shaft anode lasts 4 years, my prop anode for 2 years. I have no unexplained corrosion on board.
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Thank you.
 
KREW2 said:
My Seaward 25 is presently on a berth in Weymouth council Marina, with no power. I am about to move to a berth with electricity. I wont be leaving the boat hooked up permanently, but a 240v supply is handy for doing jobs on board, so main use will be via an extension lead. However there will be occasions in the winter when I may want to use the onboard Sterling charger for a battery top up.
My question is, does just being in a marina where there are other boats that seem to be permanently hooked up mean I should install a galvanic isolator?
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If your charger is simply plugged into an extension lead. No.
 
this has been on my mind too in regards to adding shore power...is it safe to just run a cable and rely on 'domestic' systems of fuses? It's certainly a cheaper option but for say an occasional weekend in a marina with kettle use as well as a bit of battery charging, is this cheap and non invasive option a risk? apologies for thread drift - i think the galvanic Q is answered and if i was happy about the safety aspect i would probably just run the cable and save myself hundreds! thx.
 
KREW2 said:
That's a simple and concise answer. How do I find out if I have an earth to the sea? Maybe the sterling battery charger through the batteries, engines and the prop shaft, or am I showing my ignorance here
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If you are considering using a long roving lead ashore you almost certainly don't need a GI as others have said. However my slight doubt is that you mention a permanently installed Sterling charger. Does this have a fixed A/C cable secured in place and running through the boat, or does it just have a 3-pin plug ready to plug into your roving lead? I suspect the latter but, If the former, look out for any cable leading off from the earth wire of the fixed A/C cable - often green but not always. That may connect to any point that has a path to earth (the sea).
 
Can I just ask, I had a look online for a Seaward 25 and a yacht and a motor boat both go under that name, which one does the O.P. have?
 
It i all a question of time that the boat is connected to the mains electricity. If it is limited to a few hours or even 2 or 3 days no concern. It is the 24/7365 connection that causes worries. Even then as aid if there is no connection of mains earth wire to boat wiring or metal parts then still ok. ol'will
 
Nauti Fox said:
Can I just ask, I had a look online for a Seaward 25 and a yacht and a motor boat both go under that name, which one does the O.P. have?
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It's a seaward 25 motor boat.
Poey50 said:
If you are considering using a long roving lead ashore you almost certainly don't need a GI as others have said. However my slight doubt is that you mention a permanently installed Sterling charger. Does this have a fixed A/C cable secured in place and running through the boat, or does it just have a 3-pin plug ready to plug into your roving lead? I suspect the latter but, If the former, look out for any cable leading off from the earth wire of the fixed A/C cable - often green but not always. That may connect to any point that has a path to earth (the sea).
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The Sterling charger is built in, and is powered via a direct connection to a consumer unit, as is the hot water immersion on the calorifier, and 3 x 240 volt sockets. All having individual trip switches.
The cable connecting to the shore is one of these.
Marinco Shore Power Cable 32A 15M With European Plug
 
KREW2 said:
The Sterling charger is built in, and is powered via a direct connection to a consumer unit, as is the hot water immersion on the calorifier, and 3 x 240 volt sockets. All having individual trip switches.
The cable connecting to the shore is one of these.
Marinco Shore Power Cable 32A 15M With European Plug
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OK. Clearly you aren't simply bringing a roving cable aboard as I and others had assumed. If there is a connection from your earth wire to the sea then a possible place would be from the earthing point in your consumer unit. With the cable disconnected from shore power, open up the consumer unit to check. If no connection there or elsewhere (the earthing point in 240 volt sockets are another slim possibility) then I think it safe to assume there is no connection and that a GI is not needed.

By the way those Marinco plugs have been the cause of fires. Personally, I'd change that.
 
Thanks for that. Glad I post a link to the shore power cable. Googling has shown Marinco have certainly proved a problem for some.
 
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