do i need one!!!!

little shack

little shack

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Hi folks

I am wanting to put in shore power on my boat.I have read a couple of past posts on the subject some have been informative some beyond my basic electrical understanding.


there are a couple of points i would like help with.

1.at the moment i have shore power through a RCD (plug in type)and a surge protection unit with 4 normal three pin outlets.I have a heater that i use while on boat 2KW and leave this on frost setting while away from boat.It's cold in the north east.Do I need a galvanic isolator.
2.I am wanting to change the current system in the near future to a system that incorporates a RCD and a couple of circuit breakers and have a 2 sockets used for the appliances and a couple of lights for use while at my birth.Do i need a galvanic isolator.The shore power is supplied buy the marina and has all the usual protection.
thanks for any help.
 
little shack said:
Hi folks

I am wanting to put in shore power on my boat.I have read a couple of past posts on the subject some have been informative some beyond my basic electrical understanding.


there are a couple of points i would like help with.

1.at the moment i have shore power through a RCD (plug in type)and a surge protection unit with 4 normal three pin outlets.I have a heater that i use while on boat 2KW and leave this on frost setting while away from boat.It's cold in the north east.Do I need a galvanic isolator.
2.I am wanting to change the current system in the near future to a system that incorporates a RCD and a couple of circuit breakers and have a 2 sockets used for the appliances and a couple of lights for use while at my birth.Do i need a galvanic isolator.The shore power is supplied buy the marina and has all the usual protection.
thanks for any help.
Click to expand...
You need a Pro to carry out the work
 
You will need a galvanic isolator if the shorepower earth is bonded to the DC negative, boats internal earth or anode system.
 
As a fireman, you will appreciate how dangerous electricity is around water.

I worked with big switchgear for a number of years and have seen fried animals that got into
live sites.

There is hopefully an exprienced person around to take advice from. If not it is worth finding
one. You are putting your neighbours at risk as well as yourself if you get it wrong.

Good luck: take care!
 
little shack said:
thanks for your positive reply Vics i shall ignore the negative
Click to expand...

To add a little in the way of explanation

The diagram below shows how electrical circuits can be established via the shorepower earth connection through the water to other vessels and structures such as steel piling if the earth is connected to the boat's systems .

These circuits can lead to galvanic corrosion of underwater parts, in particular the anodes.

The purpose of a galvanic isolator is to block the current from low voltage sources such as dissimilar metals which cause this corrosion while allowing current from higher voltage sources such as the shorepower itself to pass. This maintains the effectiveness of the earth as a safety feature.

Galvanicisolator2.jpg
 
sailorman said:
You need a Pro to carry out the work
Click to expand...
This is not intellectually challenging. I did my own after reading carefully about it. Nigel Calder explains it, as do many other texts. I certainly didn't find any of it difficult. My boat has been surveyed fairly aggressively twice since I installed the system and in both cases there has been a simple observation that there is a satisfactory shore power system. I did install a galvanic isolator. I do still have some residual galvanic problems eating slowly at my propellor. Noted in the last survey, but the surveyor could not suggest any solution apart from experimenting by isolating different elements from the shared earth. (Not a criticism of him, it is hard to work out what to do next.)
 
VicS said:
..
The purpose of a galvanic isolator is to block the current from low voltage sources such as dissimilar metals which cause this corrosion while allowing current from higher voltage sources such as the shorepower itself to pass. This maintains the effectiveness of the earth as a safety feature.
Click to expand...
Slightly confusing. It is easy to read as if the shore power is supposed to go through the galvanic isolator. The earth line ensures that a dangerous fault causing connection of live to somewhere it shouldn't (eg the casing of an appliance) is safely shorted to earth rather than killing you - probably tripping a circuit breaker one the way. On a boat, a simple shared earth ends up connected to the sea, which is like the electrolyte in a battery. For sundry reasons to do with dissimilar metals and imperfect voltage matches between shore and boat, earth lines can create trickle currents which make metal bits of your boat like plates on a battery and eat them away. Galvanic isolators, by differing means, don't let a small voltage cause a trickle current on the earth, but if a fault causes a large voltage it lets the current flow using the earth as normal for safety.
 
Amulet said:
Slightly confusing. It is easy to read as if the shore power is supposed to go through the galvanic isolator. The earth line ensures that a dangerous fault causing connection of live to somewhere it shouldn't (eg the casing of an appliance) is safely shorted to earth rather than killing you - probably tripping a circuit breaker one the way. On a boat, a simple shared earth ends up connected to the sea, which is like the electrolyte in a battery. For sundry reasons to do with dissimilar metals and imperfect voltage matches between shore and boat, earth lines can create trickle currents which make metal bits of your boat like plates on a battery and eat them away. Galvanic isolators, by differing means, don't let a small voltage cause a trickle current on the earth, but if a fault causes a large voltage it lets the current flow using the earth as normal for safety.
Click to expand...

Thanks for turning a succinct description of the purpose of a galvanic isolator into something much more confusing!
 
Amulet said:
Galvanic isolators, by differing means, don't let a small voltage cause a trickle current on the earth, but if a fault causes a large voltage it lets the current flow using the earth as normal for safety.
Click to expand...

I find it easiest to think of them as exactly the opposite of a circuit breaker. Large currents get through; small ones don't.
 
sailorman said:
You need a Pro to carry out the work
Click to expand...

Amulet said:
This is not intellectually challenging. I did my own after reading carefully about it. Nigel Calder explains it, as do many other texts. I certainly didn't find any of it difficult. My boat has been surveyed fairly aggressively twice since I installed the system and in both cases there has been a simple observation that there is a satisfactory shore power system. I did install a galvanic isolator. I do still have some residual galvanic problems eating slowly at my propellor. Noted in the last survey, but the surveyor could not suggest any solution apart from experimenting by isolating different elements from the shared earth. (Not a criticism of him, it is hard to work out what to do next.)
Click to expand...

It is not difficult for those with knowledge.
From the OP
[[h=2]do i need one!!!![/h]
Hi folks

I am wanting to put in shore power on my boat.I have read a couple of past posts on the subject some have been informative some beyond my basic electrical understanding.


there are a couple of points i would like help with.

1.at the moment i have shore power through a RCD (plug in type)and a surge protection unit with 4 normal three pin outlets.I have a heater that i use while on boat 2KW and leave this on frost setting while away from boat.It's cold in the north east.Do I need a galvanic isolator.
2.I am wanting to change the current system in the near future to a system that incorporates a RCD and a couple of circuit breakers and have a 2 sockets used for the appliances and a couple of lights for use while at my birth.Do i need a galvanic isolator.The shore power is supplied buy the marina and has all the usual protection.
thanks for any help.]​

The OP acknowledges beyond his basic knowledge, hence my comment
 
bikerbill said:
Interesting reading, however, would I be safe using one of these View attachment 37012 from shore power to the boat?
Click to expand...

Yes. I have one of those aboard. Rarely used, in winter ashore, and occasionally when away staying on a marina. Used to charge phones, kids DVD player, etc. it is not attached in any way to on board 12v power systems unless induced currents can be a problem?

Perhaps induced currents can be an issue? Someone will be along in a moment to let us know I hope
 
bikerbill said:
Cheers Pablo (thumbs up thingy)
Click to expand...

Think if I used one ( or the single outlet version, which only comes with a short lead) I might try to find a permanent mounting place for it and wire it to an inlet receptacle so that a detachable lead could then be used to connect to the pontoon supply in the conventional way.

I think not having the lead through a hatch or companionway would be better and also not having a trailing 3 socket outlet a little safer.
Depends entirely on having suitable locations for it and the inlet connector of course.
 
VicS said:
Think if I used one ( or the single outlet version, which only comes with a short lead) I might try to find a permanent mounting place for it and wire it to an inlet receptacle so that a detachable lead could then be used to connect to the pontoon supply in the conventional way.

I think not having the lead through a hatch or companionway would be better and also not having a trailing 3 socket outlet a little safer.
Depends entirely on having suitable locations for it and the inlet connector of course.
Click to expand...

Thinking much the same Vic.
 
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