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Shore Power


This was one of the projects that took me a long time to understand and plan.  There are a lot of variables, and a lot of opinions on how it ought to be done.  There's also ABYC codes providing input, and enough marketing information to make you insane.  Let's begin by examining what I was starting with.

The original CS27 shore power system consists of a Hubbell 30A inlet fitting on the starboard cabin side.  This inlet is then wired with 12G household solid core to a standard outlet in the galley.  That outlet fed an automotive 6A trickle charger in the top of the starboard cockpit locker, and then went on to supply current to a few other outlets on the boat.  There are a number of problems with this configuration, each of which I plan to address in this project.
  1. Solid core wiring should not be used on a boat.  All wiring should be stranded.  So, all of the AC wires have to go.
  2. The inlet should be connected to a main breaker before going anywhere else.  In this case I need a 30A main.
  3. The system needs a reverse-polarity warning light.
  4. Branch circuits should be protected by fuses.  In this case I will have one circuit for a charger, and a second circuit for A/C outlets.  My design goal is to have the entire boat run on DC, but when at the docks with shore power connected it can be nice to use it for power tools or chargers that may not be tied into the DC system.
  5. The boat outlets should be protected by a GFCI outlet.  This means that the first outlet on that circuit needs to be a GFCI unit.  The rest can be standard outlets.
  6. The AC system needs a galvanic isolator to be compliant with current standards.

At some point in the future I would really like to replace my inlet with a SmartPlug that incorporates a thermal breaker, and uses a more secure and watertight connection.  Unfortunately, what I have works and the budget doesn't put a high priority on that upgrade quite yet.  Maybe in a few years.

Uncovering the Inlet

The AC inlet is not the least bit convenient to get to in a stock CS27.  You need to remove trim, and the teak plywood panel on the aft cabin wall.  Removing the trim isn't difficult if you are careful and patient.  You will need a firm but small putty knife to start loosening the pieces near each nail hole, and then I switch to a small pry-bar to remove the pieces.  When you get the wood off the back it will look like the photo to the right.

You can see the black AC wire coming in from the cabin side, then down toward the outlet.  Unfortunately, just to check the connections you need to do this much dismantling.  I'm hoping this won't need to happen often, but having gone through this much effort I plan to make sure I do it right.

Battery Charger

At this point my boat has two Interstate Group 27 deep cycle batteries.  That means just about any charger is compatible.  However, I don't want to rule out the possibility of selecting AGM or other types of batteries in the future.  That means my charger needs to support multiple types of batteries.

The next criteria is the amperage capacity of the charger.  I have a 30 amp inlet and shore power cord.  That means the sum of the branch circuits cannot exceed 30A.  My plan was to have a string of 15A outlets.  Technically, that leaves 15A for a charger.  In practical use, I don't plan to have AC in use on the boat.  Since it's already there I'm keeping it, but I want 100% DC components.  For that reason I dabbled with the idea of a more powerful charger.  In the end I decided that sticking to a conservative plan would not only save me money, but make for a more reliable design.  I decided my goal would be  15A charger.

Finally, I wanted a "mainstream" unit.  I don't want an obscure charger.  I want one that a lot of other people have on their boats.  I want a charger that someone in a small port chandlery has heard of.  Yes I realize there are brands out there that make great products for less money.  I even researched one in particular that had much praise on Sailnet.  But, integrating a lesser known charger into my boat isn't the plan I'm after as a novice to boat electrical systems.  I need to be able to call in a pro if I get in over my head.

I spent much time in Sailing web sites looking at what other people had done, and which brands people had problems or high opinions of.  The more I looked, the more I realized that for every person who likes one product, there is another who doesn't like it.  I also think that people tend to post when they have a bad experience much more frequently than when they have a good one.  So, I took my research with a grain of salt.  I ended up selecting ProMariner's 1215i charger.

It can charge two battery banks independently, and it supports multiple battery types.  It was also a model that I was finding on eBay every few weeks at a good price.  When I finally received the package I set up a test in the basement with my batteries and some household wire.  It was silent, and charged both batteries quickly.  The previous owner had (significantly) over-filled the battery electrolite, so the first test run involved a lot of clean up.  I used the hygrometer to suck out the extra fluid, and tried again.  This time, it worked perfectly.

Installation is fairly simple.  14 AWG 120VAC input enters through the top and attaches with #10 ring terminals.  The two bank outputs are then jumpered on the bottom as I only need to feed the ACR (which then feeds each bank as needed).  Finally, a single positive and negative 14 AWG wire are run from the charger to the ship's main DC positive and negative busses.  No rocket science involved at all.

AC Main Panel

Panel Selection

After reading Don Casey's This Old Boat, I was planning to try to find an outdoor 30A main breaker box to save money.  I thought I could find one with two branch circuits and save a lot of money compared to purchasing a marine panel.  That plan didn't go so well.  All I could find were huge boxes.  The CS27 isn't a small boat, but there really aren't a lot of wide open surfaces to mount things in.  I quickly realized this was a dead end, and the marine units would be the only thing compact enough to fit what little space I had left.

The first thing I discovered after digging into the marine panel suppliers is that most of them start with three branch circuits.  Not too many panels have only two positions.  What's the difference between a two position and a three position?  Almost 2 inches.  Doesn't sound like much until you are trying to find a space to squeeze this thing into.  I found two products that I liked.  First was the Blue Sea Sytems 360 Panel.  The second was from BEP Marine.  While I really like Blue Sea products, I ended up selecting BEP marine primarily because it cost a bit less due to me finding one on eBay.  My decision came down to saving money, but the product I ended up with is very nice.  It's quite solidly built, so I'm not in any way disappointed.

Panel Location

There are a number of choices available in the boat.  There's probably more than this, but here's my (not ordered by preference) short list:
  1. Centered atop the companionway stairs between the main DC panel and the main DC battery switch.  This would require relocating the DC volt meter and enlarging the hole as needed.  It also means the AC panel is in a drip-prone location.  Not ideal.
  2. Recessed in the aft cabin trim plywood over the galley.
  3. Mounted high in the starboard cockpit locker, over the battery charger.  This would require making a surface-mount box to mount the panel on.  I can't cut out a hole in the bulkhead for this purpose as it would expose the back of the panel to the galley shelf.
  4. Mounted inside the engine compartment in a custom panel high, directly over the batteries.

As much as I don't want to look at this panel, I think the best place for it will be over the galley and recessed into the coaming.  It will not really look good, but it will be accessible and I will be able to see the reverse polarity light as well as access any breakers that need my attention quickly.

Galvanic Isolator

Yandina Galvanic IsolatorFor safety and protection from corrosion, this device is pretty important.  I won't get into the details because they are covered thoroughly throughout the Internet and the suggested reading list on this site.  After some research, and recommendations from other CS owners, I went with the Yandina Galvanic Isolator .  It's very reasonably priced and trivial to install. It's the large black box in the photograph above.  One wire goes to the shore power inlet while the other feeds the AC ground bus, which in turn connects back to the ship's main ground bus.

120V AC Outlets

One of the circuits on my AC Main panel feeds the battery charger, while the other feeds the AC outlets scattered about the boat.  My original wiring was two-wire (no ground), which is bad.  It also was not a stranded wire, which again fails to meet ABYC codes.  So one thing was certain; the wiring had to go.  I almost left the AC outlets out, but I thought that it might be less work to re-wire them than to fill all the voids where the boxes had been mounted.  I'm sure they will come in handy at some point.

I'm not crazy about the galvanized boxes mounted around the boat.  They are tough, but they can rust, conduct electricity, and have not even the slightest resistance to water ingress.  Traditional building materials tend to be less than ideal on a boat, and I tend to think these are better suited to homes.  Having said that, the boxes I have right now are not rusted and the boat is 34 years old.  In the interest of minimizing messes and extra work, I believe I will be retaining their service until I start to see rust appearing.

The AC Main panel will feed a GFCI in the galley.  That outlet will chain to the outlet in the wet locker (over the ice box), and that outlet will chain to one located in the V-berth.  I'd like to come up with a creative idea to mount one in the head as well, but that's a (very) low priority.

The wire is ABYC compliant 14/3 stranded triplex which I obtained from my favorite Internet shop,  The stuff was is very flexible, and the sheathing is tough.  It's a bit of a pain to strip, but it will last the remainder of this boat's life time.