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Galvanic Isolators

ted_reshetiloff

Contributing Partner
Anyone out there know much about these units? I see them offered for 30 amp systems from about $200 and up. Tom M. on another thread mentions a Defender model for $95, didn't see that one when I looked. There is some one on Ebay selling them in the UK for around $50 US but I have no idea what makes one version any better than another.

Heres the Ebay version:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7221761687&rd=1&sspagename=STRK:MEWA:IT&rd=1

Heres what I saw at Defender:

http://www.defender.com/product.jsp?path=-1|328|303336&id=52807
 

ted_reshetiloff

Contributing Partner
I run 30 amp service on my 38 if that makes a difference. What do you suppose is the deal with the huge swing in prices? I have seen these things as high a $270 and not the isolation transformer variety. I wonder what makes any one version better than the other?
 

rssailor

Moderator
Galvanic Isolator

Ok, a few years ago ABYC revised their spec on galvanic isolators. To meet the new requirement, you need to be able to monitor the neutral and ground and compare the two for voltage and amps. The guest 2530P would work well and they have a remote for it to show you status. Contact me off line if you have more questions Ted. Ryan
 

cawinter

Member III
Yandina

I got the Yandina 50A unit for under $100. They produced the old West Marine brand one, but they are not ABYC-compliant due to their lack of monitoring. Not being burdened with too much electrical engineering background that works for me...
 

JAS

New Member
In my opinion there is no reason not to install one of these devices on your boat, other than the cost. The thing to remember is that while they will protect your boat from stray currents leaking into the dock ground system. They will not protect from stray currents leaked into the ground on your own boat. You can measure this potential with a common multimeter to see how severe it is. Another option is an impressed current cathodic protection system. This system controls the potential between the water around the boat and the boat itself. It positively energizes the water and turns your bonded boat into a negative ground. This protects the metal parts of your boat. This system is the only way to fully insure that your boat is protected. An isolation transformer would cost as much or more and take up more space than this system and would not protect you from stray currents onboard your own boat any more than would the isolator.

To me, all of this seems unnecessary and overly cautious in the wrong way. A properly bonded boat with properly mounted anodes will be protected as long as the anodes hold out. Hauling your boat out of the water each year is part of proper maint. I have seen too many times, failures below the water line such as propellers falling off or rudder failures due to lack of haul out and inspection. Not to mention antifouling paint is eco friendly now and must be reapplied if one wants to travel though the water with ease and speed.
 

ted_reshetiloff

Contributing Partner
Yeah I'm with you on the stray currents on board. I've been through the majority of the electrical system, which is what has led me to the discussion on this thread. My question is specifically about these galvanic isolators and how to differentiate between the qualities of one brand over another. I see 30amp units that range from $100-$400 and am having a hard time telling the difference. Can anyone enlighten me on the ABYC requirements on these units and do the cheaper ones not meet them? Are the cheaper units less effective? Do they not last as long?
 

JAS

New Member
Ted,

Get the cheap one. The chance of having a 30 amp ground fault on your boat with such a simple electrical system is not very likely and if you do the breaker on shore will trip. That being said the amps traveling through the 30 amp breaker may reach a value much higher than 30 if a dead short occured but then the duration would be reduced. It sounds like you have a sound understanding of this already. It may be that the more expensive isolators can handle more amps and for a longer duration but I wouldn't spend the extra money myself.

While I'm not the fastest sailer here or even really good at it I have been working on the water and on commercial boats for the last 20 years. I hope I was able to help you!

Good sailing!
 

ted_reshetiloff

Contributing Partner
Still a little undecided here. The expensive ones are still rated for either 30 or 50 amp systems. I guess I just dont have a very good grasp on exactly how these things work. The internal components on the more expensive units must be of higher quality I would guess. At least the units made by reputable companies like Xantrex or Outback.
 

John Butler

Member II
Ted,
What did you end up doing about getting a galvanic isolator? We want to keep our E38 plugged in so that we can keep the refrigerator running as we're on the boat periodically throughout the week. I did a test yesterday from boat AC ground to grounded metal ashore and measured DC amps (as expected). So I think I should install a galvanic isolator. I think this article from BoatUS is informative:
http://www.boatus.com/seaworthy/galvanic/default.asp

I suppose part of what may differentiate GIs is whether or not they have a capacitor (which seems important). Another thing would be the built in monitoring. I'd appreciate any information you can give me on what you've found.

Thanks!
John
 

ted_reshetiloff

Contributing Partner
I decided it was cheaper for me to just unplug the boat for now...:egrin:

Then again it is hauled out getting a new bottom and prop...
 

John Butler

Member II
Yes, cheaper to unplug the boat! For peace of mind, I installed a Galvanic Isolator (GUEST 30 AMP with full time status monitoring). My partner is not very technical and kept asking why we can't keep the boat plugged in and the DC refrigerator running (she works in Annapolis and likes to stop by the boat during her lunch break -- can't blame her). I figure the $150 was worth it.

It was relatively easy to install (worked it in with some other AC wiring changes I was doing). I still need to purchase and connect the remote monitor to meet ABYC regulations.

John
 

ted_reshetiloff

Contributing Partner
Still on my wish list, but then I spent $200 on a used spin pole at Bacons yesterday. Need to redo one of the ends too... A new one was going to run me 1200 so I guess its not too bad. I have been leaving the boat unplugged and it has worked well this year. I keep my boat in Annapolis on the South River, actually its Hillsmere community. If you just want to run a fridge so your wife can have cold drinks at lunch how about a tiny dorm style fridge? AC powered with its own cord not tied into your whole system? Probably get one one used in the pennysaver for $50...
 
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