Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 07-03-2015, 09:37   #1
Registered User
 
redhead's Avatar

Join Date: Mar 2011
Location: PNW 48.59'45N 122.45'50W
Boat: Ian Ross design ketch 63'
Posts: 764
Images: 5
Stray voltage in a marina

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.
__________________

__________________
redhead is offline   Reply With Quote
Old 07-03-2015, 09:56   #2
Registered User

Join Date: Dec 2014
Location: Dryland
Boat: Wannabe Sailing
Posts: 25
Re: Stray voltage in a marina

Informative and sad video.



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

__________________
Magic1st is offline   Reply With Quote
Old 07-03-2015, 09:56   #3
Registered User

Join Date: May 2010
Location: Elsewhere on the Water
Posts: 571
Re: Stray voltage in a marina

Read this: ABYC Article by Stanley G. Konz

And this: How to Measure Stray Current in the Water
__________________
St. Elsewhere is offline   Reply With Quote
Old 07-03-2015, 10:01   #4
Marine Service Provider
 
fstbttms's Avatar

Cruisers Forum Supporter

Join Date: Oct 2006
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 3,594
Re: Stray voltage in a marina

Quote:
Originally Posted by Magic1st View Post
Informative and sad video.
FYI- virtually all ESD (electric shock drowning) accidents occur in freshwater. Almost nonexistant in saltwater.
__________________
fstbttms is offline   Reply With Quote
Old 07-03-2015, 10:09   #5
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,365
Re: Stray voltage in a marina

In the meantime get a big "fish" zinc a connect to the rudder stock..
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 08-03-2015, 12:25   #6
Registered User

Join Date: Aug 2013
Posts: 12
Re: Stray voltage in a marina

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.
__________________
Charlie Shore is offline   Reply With Quote
Old 08-03-2015, 14:37   #7
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 935
Images: 4
Send a message via Skype™ to roland stockham
Re: Stray voltage in a marina

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
__________________
roland stockham is offline   Reply With Quote
Old 08-03-2015, 14:54   #8
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,743
Re: Stray voltage in a marina

Quote:
Originally Posted by roland stockham View Post
....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.
__________________
mitiempo is offline   Reply With Quote
Old 08-03-2015, 15:52   #9
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 935
Images: 4
Send a message via Skype™ to roland stockham
Re: Stray voltage in a marina

Quote:
Originally Posted by mitiempo View Post
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.
__________________
roland stockham is offline   Reply With Quote
Old 08-03-2015, 16:27   #10
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,743
Re: Stray voltage in a marina

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.
__________________
mitiempo is offline   Reply With Quote
Old 08-03-2015, 17:17   #11
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 935
Images: 4
Send a message via Skype™ to roland stockham
Re: Stray voltage in a marina

Quote:
Originally Posted by mitiempo View Post
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.
__________________
roland stockham is offline   Reply With Quote
Old 08-03-2015, 17:31   #12
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: Stray voltage in a marina

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
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 08-03-2015, 17:49   #13
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 935
Images: 4
Send a message via Skype™ to roland stockham
Re: Stray voltage in a marina

Quote:
Originally Posted by goboatingnow View Post
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
__________________
roland stockham is offline   Reply With Quote
Old 08-03-2015, 21:54   #14
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,743
Re: Stray voltage in a marina

Quote:
Originally Posted by roland stockham View Post
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.
__________________
mitiempo is offline   Reply With Quote
Old 08-03-2015, 23:01   #15
Registered User

Join Date: Sep 2013
Location: Alert Bay, Vancouver Island
Boat: 35ft classic ketch/yawl.
Posts: 935
Images: 4
Send a message via Skype™ to roland stockham
Re: Stray voltage in a marina

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?
__________________

__________________
roland stockham is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Stray Current Detector Ian R Electrical: Batteries, Generators & Solar 7 10-02-2012 14:58
We Are Stray Dogs robbob123 Meets & Greets 9 12-11-2011 16:16
Stray Current MartinMayer Electrical: Batteries, Generators & Solar 32 10-01-2011 05:48
How to Measure Stray Current in the Water erict Electrical: Batteries, Generators & Solar 11 03-12-2010 12:07
Stray Current Corrosion . . . Boracay Electrical: Batteries, Generators & Solar 29 29-09-2010 07:13



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:23.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.