Shore power and anode wear

[richardsn9]

I understand that time spent using shore power can accelerate anode wear - this certainly seems to be borne out in practice from my experience.

Like many people, I leave my shore power lead plugged in whenever I am in my home berth. If the electrics are switched off on board when the boat is left, does this stop this happening, or will the higher wear continue even though there is not current draw?

Any suggestions or help would be appreciated!

 

[Vara]

A galvanic isolater or the more expensive isolating transformer should sort out any problems with electrolysis and anode erosion while connected to shore power...well it worked for me... But this electrolysis is a bit of a dark art.

 

[maby]

The issue is the connection of the boat's underwater metalwork to the mains earth so, unless your switches disconnect the earth, you will still be suffering. If you have an electrical fault on your boat that is actually adding to the earth leakage, then switching off may reduce the rate of anode erosion, but it will not eliminate it.

 

[VicS]

I understand that time spent using shore power can accelerate anode wear - this certainly seems to be borne out in practice from my experience.

Like many people, I leave my shore power lead plugged in whenever I am in my home berth. If the electrics are switched off on board when the boat is left, does this stop this happening, or will the higher wear continue even though there is not current draw?

Any suggestions or help would be appreciated!

If you leave your shore power connected, even if not in use, for prolonged periods you should fit a galvanic isolator ( or an isolation transformer)

Older systems, and simple systems using a campsite/caravan unit, may not have the shorepower earth bonded to the boat's DC negative, anodes etc. In this case there should be no problem and a GI is not necessary.

A GI blocks any current from the very low voltage sources that cause galvanic corrosion but allow current from higher voltage sources to pass. The safety aspects of the earth are therefore maintained.

 

[Murv]

Sorry to hijack slightly, but is there an easy way of testing whether the boats DC system is bonded to the earth? without tracing wiring back through, anyway.

 

[VicS]

Sorry to hijack slightly, but is there an easy way of testing whether the boats DC system is bonded to the earth? without tracing wiring back through, anyway.

The lowest ohms range on multimeter would be a start. The continity test buzzer marginally better. Alternative

 

[Murv]

The lowest ohms range on multimeter would be a start. The continity test buzzer marginally better. Alternative

Thank you. So I'd take a resistance reading between both negatives on the batteries and the Earth out on the shorepower connection?
Would it work if I took a voltage reading from the batteries and used the Earth on the shorepower instead of the battery, so, no connection, no voltage?

 

[maby]

Disconnect the shore power and use a resistance meter to check for continuity between the earth pin of the shore power socket of the boat anx your propeller shaft or sail drive casing

 

[Murv]

Disconnect the shore power and use a resistance meter to check for continuity between the earth pin of the shore power socket of the boat anx your propeller shaft or sail drive casing

Gotcha, thank you, I posted above as you were posting.

 

[VicS]

The lowest ohms range on multimeter would be a start. The continity test buzzer marginally better. Alternative

To continue using a proper computer with a keyboard:

Alternatively a bulb and battery.

Do it with the shorepower completely disconnected.

If you are trying to establish that the two are bonded then find the point at which they are connected to verify.

 

[KellysEye]

>I understand that time spent using shore power can accelerate anode wear

it shouldn't do that unless there is stray current corrosion caused by a bad earth on the marina 240v supply or you are in water that has a mix of fresh and salt. As said fit a galvanic isolator and see if there is less wear on the anode. If there is less wear tell the marina they have a bad earth, assuming you are not in fresh/salt water.

 

[maby]

>I understand that time spent using shore power can accelerate anode wear

it shouldn't do that unless there is stray current corrosion caused by a bad earth on the marina 240v supply or you are in water that has a mix of fresh and salt. As said fit a galvanic isolator and see if there is less wear on the anode. If there is less wear tell the marina they have a bad earth, assuming you are not in fresh/salt water.

It can be due to a variety of reasons including things that are outside the marina's direct control. A bad earth alone will not cause anode wear - it needs something to be dragging the poor quality earth wire above genuine ground potential in order to trigger anode erosion.

 

[oldsaltoz]

You also need to consider the fact that many marinas used an Impressed Cathodic protection system to protect steel pylons, this puts current into the water that 'should' go the wired anodes.

Good luck and fair winds.

 

[VicS]

>I understand that time spent using shore power can accelerate anode wear

it shouldn't do that unless there is stray current corrosion caused by a bad earth on the marina 240v supply or you are in water that has a mix of fresh and salt. As said fit a galvanic isolator and see if there is less wear on the anode. If there is less wear tell the marina they have a bad earth, assuming you are not in fresh/salt water.

The loss of anode material when shorepower is connected is very likely to be just galvanic corrosion due to dissimilar metals. The zinc anode and the steel piling of the marina for example or perhaps a nearby steel hulled boat. This is what a galvanic isolator will protect against. The effectiveness of a galvanic isolator is not an indication of any faults in the marina electrical system. Its when a galvanic isolator is not effective that you have to start looking for other causes of the anode loss.

Intrigued though by your suggestion that a mix of fresh and salt water can be the cause of anode loss. You you care to explain further?

 

[targa31]

Hope this is not drifting too far from topic.

I have terrible trouble with duo props rotting (in about 12 months they start to go powdery). I don't leave shore power plugged in except when away for a few days on the boat in the summer. I am in the upper hamble (mix salt and fresh water) near some steel house boats and a rather large steel rail bridge. Any ideas on how to reduce the damage? Would hanging an anode off the back connected to the engines help?
Thanks in advance

 

[William_H]

The whole question of unusual anode depletion and power connections is quite complex. There are many possible cuases of current and so depletion. As suggested the marine protection system will be connected to mains earth. So to all the other power users any one of whom could have a power leakage type fault may cause a problem.
I would suggest that disconnection of the power connector to disconnect the earth is best to do when leaving the boat as it will avert many of these possible problems.

If you must leave the power on then use a proper installation using a galvanic isolator. or just a power lead to individual devices. Like a heater or dehumidifier that is double insulated no earth connection or battery chager that has insulation earth to negative and pos output. Things like calorifier will have connection earth wire to ships plumbing hence to ships ground. Hence diconnect every thing you can from the installed wiring when leaving the boat. good luck olewill