Galvanic Isolator installation

[Exodus]

So this past weekend one of my projects was going to be the installation of a galvanic isolator.

I have decided to mount it behind the panel in the green wire before the bus bar.  Reason being that my air conditioner compressor is in the cockpit locker and I have no access the the rear of the AC inlet without tearing out and replacing a lot of insulation.

Question:  In looking at the schematics I do not see a ground to the engine from the AC system.  I assume that the bus bar is grounded to the engine, but was unable to trace the wire.  Is this correct?  Would I be safe to mount the isolator behind the panel or is there a ground between the shore power inlet and the panel?

My zincs seem to only last about three to four months.  On my old boat located in the same marina they seemed to last at least 6-8 months.  I hope that the isolator will extend my zinc life.

 

[Stu Jackson]

Jason,

As I recall there have been some discussions about whether or not Catalina connected the AC and DC grounds on our boats.  I haven't been able to find one on my boat.  I don't keep her plugged in when I'm away from our boat, and many have noted their zincs last longer when they're not plugged in all the time, since sometimes galvanic corrosion can occur from other boats on your dock and their poor wiring.

Whether or not you (already) have a connection between the AC and DC grounds, you should simply be able to connect the new isolator ground to the engine block, since you already know the DC is there already, rather than relying on guessing if Catalina did, or the alternate of even trying to find that connection.  I recall you have an 88 model (?).

[Exodus]

Thanks Stu,

Having looked at some of the older posts it appears the general consensus is that the AC system on the MKI is not grounded to the engine.

I also looked at the schematics for the MKII which came from the factory with a Galvanic Isolator, but it still appears that the AC is not grounded to the engine.

Question to MKII owners:  Where did Catalina locate the Galvanic Isolator and is the AC grounded to the engine?

I am not an electrician by any means, but it seems to me if there is no ground to the engine the Galvanic Isolator would not be necessary as the AC and DC systems are isolated from one another.

[Joe Kern]

My isolator from the factory came located in the port aft lazerette not that far from the show power connection.   Don't know where it is grounded.

[Stu Jackson]

I am not an electrician by any means, but it seems to me if there is no ground to the engine the Galvanic Isolator would not be necessary as the AC and DC systems are isolated from one another.

I'm no electrician either, but I did stay at a Holiday Inn Express a few years ago!

I just employ the best of what I read, ask about, and try to learn about it.  You can in more detail if you'd like, unless, as I suppose, you already have.

The DC is already grounded, add the AC from the isolator, if you choose to do it, and you'd be done.  If you don't, the only thing you can't control is your neighbor's boat and the quality of the electrical work on their boats if you're both plugged in.

[BillG]

http://www.kp44.org/ftp/GreenWireControversy.pdf

This is an excellent article on the importance of grounding the AC and  DC circuits.  It also explains
the ramifications of doing so and why a galvanic isolator is important to protect your boat.

[sailaway]

Jason I have to agree with Catalina with not putting a green ac ground wire on your engine. The grn ac ground rod is driven in the earth at the meter or service. That is where you want the the lighting or trouble to go. If you put a grn ac wire on your engine it could act as a ground rod.  The other reason is if you have grn ac wire on your engine and your neighbor has a grn ac on his engine and you have different types of of metal props you can get galvanic action. The other reason is AC & DC are different system their is no need to mix them.  Charlie the Electrician

[karista]

http://www.kp44.org/ftp/GreenWireControversy.pdf

This is an excellent article on the importance of grounding the AC and  DC circuits.  It also explains
the ramifications of doing so and why a galvanic isolator is important to protect your boat.

I don't quite agree, I installed a Galvanic Isolator about 2 years ago, it was a waste of money and time, my zinc's still need to be replaced every 5-6 months, just like before I installed the Isolator.

[Stu Jackson]

Bernd's right.  It has been reported, also in Calder's, that usefulness is sometimes, if not often, questionable, if not complete.  My comments were based on your own decision to buy one.  I suggest you read Calder's full discussion, which IIRC, concludes that if you really have an issue, an isolation transformer is necessary, with obvious weight and space issues.  We just don't know how deeply you've weighed in on the whole bunch of issues other than your original question about the ground, rather than discussing the pros and cons.

[mainesail]

Catalina is building boats to ABYC standards and I believe they comply, at least mine have. In order to comply with E-11, the ABYC electrical standard, the green AC ground wire MUST be tied into the DC ground buss or DC ground system. You may not find a "green" wire on the engine as usually only one wire runs from the DC ground system to the engine ground and it is a large black DC battery cable.

My C-310 and C-36 were properly wired to meet ABYC E-11. Many PO's who are not marine electricians have removed the bridge between AC ground and DC ground unknowingly thinking they do know.... This has been an industry accepted wiring practice for well over 30 years or more. Even my 1979 Canadian built vessel was wired this way.


Info below from ABYC E-11:

"11.5.3. FOR AC SYSTEMS

11.5.3.1. The system shall be polarized as
defined in E- 11.4

11.5.3.2. A grounded neutral system is required.
The neutral for AC power sources shall be grounded
only at the following points:

11.5.3.2.1. The shore power neutral is
grounded through the shore power cable and shall not
be grounded on board the boat.

11.5.3.3. The main AC system grounding bus
shall be connected to

11.5.3.3.1. the engine negative terminal or the
DC main negative bus on grounded DC systems, or
11.5.3.3.2. the boat's DC grounding bus in
installations using ungrounded DC electrical systems.

11.5.3.5. There shall be no switch or overcurrent
protection device in the AC grounding (green)
conductor.

[Exodus]

Thanks to all who have replied. 

Bernd, if I could get 5-6 months out of my zincs I would be happy.  Mine are lasting 3-4 months. 

Stu, I don't think an isolation transformer is a viable option on a C34 due to space and weight constraints.  Has anyone installed one before?

Anyone else have any pros or cons on Galvanic Isolators?  I figure that if Catalina feels that they are important enough to be installed as standard equipment on new boats then it is a worthwhile upgrade.  My .02, but I very well could be wrong.  If this doesn't work then I will try something else, like leaving the boat unplugged.    I really don't want to do that though because I like to run the dehumidifier and enjoy having cold beer waiting on me in the summer

[Ken Juul]

I think the vast majority if not all the shore power outlets on the c34 are in the stern or cockpit.  A galvanic isolator is smaller than a shoe box.  There is plenty of room to mount it in the unused space aft of the fuel tank.  When I installed mine, I removed the engine instrument panel and used it as my access point.  It is located just forward of the engine instruments thru bolted to the cockpit side wall.  Mine is about 12-14" from my shore power plug, wiring it was easy.