Stray voltage in a marina

[redhead]

Is there a test for stray voltage? Our poor rudder cannot take much more....

If this subject has been beat to death elsewhere, just point me in the right direction. Thanks all.

[Magic1st]

Informative and sad video.

https://www.youtube.com/watch?v=O7-s...e_gdata_player

Start around 55:00 to see how to test various aspects. Watch the whole thing for tons of info.

[St. Elsewhere]

Read this: ABYC Article by Stanley G. Konz

And this: http://www.cruisersforum.com/forums/...ter-50920.html

[fstbttms]

Originally Posted by Magic1st

Informative and sad video.

FYI- virtually all ESD (electric shock drowning) accidents occur in freshwater. Almost nonexistant in saltwater.

[Cheechako]

In the meantime get a big "fish" zinc a connect to the rudder stock..

[Charlie Shore]

I have sympathy for you as I had the same problem on my almost new tug. The anodes needed replacing every time I slipped the vessel and there were a lot to replace costing several hundred pounds. I bought a multi metre which measured the current travelling through a cable by placing its jaws around the cable and found that the cable from the shore (mains) was leaking current to the vessel when everything was turned off on the boat. I handed the job to a marine electrician and landed up with a sizeable bill.

[roland stockham]

The problem seems to be so common it must be classed as normal. I have on-board electrics totally isolated from shore side for that reason. Can be done with an isolation transformer but I did it by runing all mains from the inverter so have no shore powered mains on board. Shore power just charges the batteries through good quality chargers with total earth isolation. On-board earth is a separate immersed AC plate. Works for me and means I can draw any voltage/frequency/polarity without worry, just a collection of adapters. The problem goes away if you are not wired into the bank. To set it up you need good knowledge or a pro to design they system but installation is probably no problem

[mitiempo]

Originally Posted by roland stockham

....have no shore powered mains on board. Shore power just charges the batteries through good quality chargers with total earth isolation.

If your charger is case grounded as required in most charger manuals the AC ground is connected to the DC negative.

Same would be true of an inverter case grounded.

[roland stockham]

Originally Posted by mitiempo

If your charger is case grounded as required in most charger manuals the AC ground is connected to the DC negative.

Same would be true of an inverter case grounded.

External cases for all equipment are connected to the boats immersed A/C ground plate which is isolated from D/C neg (D/C system is floating earth). Isolation between shore earth line and case and DC outputs and case is certified and tested. The charger is designed to work as an isolation transformer. Much more expensive than a basic one but cheaper and easier than a separate isolation transformer. Inverter has no physical connection to the shore-side system and is only connected to DC. I practice the A/C input side of the charger 'floats' on the end of the shore power lead and is grounded to the bank via the shore power earth line. The D/C side is only magnetically coupled to shore-power via the transformers. D/C neg goes to batt ground post and case to immersed boat earth. This is exactly the same arrangement as an isolation transformer but because it is a high frequency unit it is much cheaper and lighter than any isolation transformer I have seen.
In lots of boats the D/C neg is treated as 'earth' by connecting cases and electrolysis system as well as A/C grounds to a single point but I prefer not to do this. Under US regs this is insisted on but under European regs it is recommended against. Many charger do have a common case connection to both A/C and D/C, you have to use a specific isolation type for this to work. The reason for advising that it is professionally designed/checked is that you really should use specialist test equipment to check the isolation (and other stuff) before commissioning. A multimeter only checks low voltage D/C continuity which may not show either small leaks or A/C pathways.

[mitiempo]

You are an exception. The majority of boats in North America have AC ground (green) connected to DC negative.

What charger/inverter do you have?

I agree an isolation transformer is the best solution.

[roland stockham]

Originally Posted by mitiempo

You are an exception. The majority of boats in North America have AC ground (green) connected to DC negative.

What charger/inverter do you have?

I agree an isolation transformer is the best solution.

Have a pair of ProMariner 40A chargers (not made now, don't now if the new ones are the same) and essentially 2 D/C systems, one provides domestic services and 'dirty' machinery like bilge pumps. The other supplies ships systems and com's. Because the boat started in UK most of my tools and stuff are 240v 50Hz so changing to 120v 60Hz would have meant changing lots of stuff. Also found it almost impossible to get hold of a marine isolation transformer, could have imported on but the cost was ridiculous so came up with this system instead and it has worked out very well. Will probably eventually install a fixed 120v inverter as well so I have both available. At the moment however everything is 240v or universal.

I agree about the isolation transformers and would recommend it to all cruisers as a means of coping with dodgy marina electrics.

[goboatingnow]

It's an unfortunate situation that ABYC wiring on boats causes paths that cause impressed current corrosion. AC and DC systems should be kept separate. AC safety can be improved to the point of more then acceptable by using residual current devices on a whole boat and marina installations.

The practice of connecting bonding systems , DC negative and AC protective earth is in my view the core of the issue and it's why an issue,, impressed current corrosion , isn't a big issue in 220 vac but is far greater in US 110AC systems

Dave


Sent from my iPad using Tapatalk

[roland stockham]

Originally Posted by goboatingnow

It's an unfortunate situation that ABYC wiring on boats causes paths that cause impressed current corrosion. AC and DC systems should be kept separate. AC safety can be improved to the point of more then acceptable by using residual current devices on a whole boat and marina installations.

The practice of connecting bonding systems , DC negative and AC protective earth is in my view the core of the issue and it's why an issue,, impressed current corrosion , isn't a big issue in 220 vac but is far greater in US 110AC systems

Dave


Sent from my iPad using Tapatalk

Fortunately it is only advisory for private boats so you can choose to ignore it on your own boat or as long as you are not doing commercial work to code

[mitiempo]

Originally Posted by roland stockham

Also found it almost impossible to get hold of a marine isolation transformer, could have imported on but the cost was ridiculous...

I agree about the isolation transformers and would recommend it to all cruisers as a means of coping with dodgy marina electrics.

We stock the Victron marine isolation transformers in Victoria. Sold one a few weeks ago.

[roland stockham]

No problem getting them here but I was in S Wales and nobody had heard of them, not exactly easy to post internationally! Which shop in Victoria?