Electrical, AC Distribution Panel, Part I: Analysis and Installation

The AC distribution panel within its mahogany trim piece
Every cruising sailboat, except those whose owners are minimalists to the extreme, has a battery bank. It's possible to charge this bank by means of a wind generator or solar panels. These means of generating power, however, are not only expensive to implement, but also often inefficient, unpredictable, and in the case of the wind generator, obnoxious. For the most part, if you wish to charge the battery bank in a consistent, reliable, and timely fashion you must have an alternator or a generator, or both. Alternators, typically found on diesel engines, will generate sufficient power to charge a battery bank, if properly regulated, and if the engine is run for a sufficient amount of time each day. For those who do not have diesel engines, but instead have outboards, these motors also have alternators that can supply power to a battery bank. Typically, though, they do not supply enough power, unless they are used throughout the day. This means that for those who usually sail a lot and motor just a little, a generator is a necessary piece of equipment for charging a battery bank. The generator is powered either by diesel or by gasoline, usually the latter. The generator, powered by one of these fuels, produces AC (Alternating Current). This, in turn, powers the battery charger, which then charges the bank. Normally, the generator is not connected directly to the charger. Instead, the AC power, which the generator produces, is routed to the AC main breaker. From there it is routed to an AC distribution panel, which contains breakers for the individual circuits. One of these individual circuits is dedicated to the battery charger.
Obviously, an AC distribution panel is an important component of the electrical system on any cruising sailboat, whether that boat be big or small. Oystercatcher, my Ericson 25 would definitely fall into the latter category. On account of its status as a trailerable pocket cruiser, space issues (and by this I mean living-space and storage-space issues) are paramount on a boat such as the Ericson 25. In the first part of this two-part article I describe my rationale for the place in which I chose to install the AC distribution panel and the methods I used to install it. As always, my guiding principle for this project was that this installation be both functional and aesthetically pleasing.
The panels for the original electrical system on the boat that I purchased were located on the port side of the vessel. One panel was adjacent to the lazarette access door. The other was adjacent to the stove. Both of the panels were for the distribution of DC power. There was no AC panel. So how did the previous owner charge the battery that powered the DC electrical system? He used a standard trickle charger - you know, the kind that you commonly find in an automotive store. He had his own private dock, and at the end of his dock there was an AC receptacle. From this receptacle he ran an extension cord into the boat where his trickle charger sat. He only used the boat for day sailing, so he never had to worry about maintaining the battery for more than a short period of time.
The DC panel adjacent to the lazarette access door was not original to the boat. Either the previous owner or the first owner (there were only two owners before me) had installed it. This was not really a good location for an electrical panel. Sure, it was close to the battery (which was just behind that small access door), but it was a little too close. Flooded lead batteries produce gas when they are being charged. This gas in high enough concentrations can explode if ignited. Therefore, any electrical equipment in the lazarette must be ignition protected. Was this DC panel ignition protected? No. Are DC panels typically ignition protected? No.
The DC panel adjacent to the stove was original. Having seen the Ericson 25 manual and many pictures of many other Ericson 25s, I can say that this was the standard, factory-installed location for the DC panel on this boat. Why did Ericson choose this location and not another? I would say, because it was close to the battery, without being too close. Why on this side of the galley and not on the other? My guess would be that Ericson judged this side to be the safer side. Sure this one would be near the stove.
The other one, however, would be near the icebox and sink. Electrical equipment and water, of course, don't go well together, so the choice was pretty obvious.
According to the original Ericson 25 manual, an AC shore power inlet was an option at the time of purchase. My Ericson 25, at the time of purchase, did not have one.
Installation on Oystercatcher of a shore power inlet, the subject of a separate article
Also, according to the options list (not here pictured), a battery charger was an option. Below is a page from the original manual where shore power is discussed. If you're having trouble reading the words below, simply click on them.
Nowhere in this section from the manual is anything said about an AC distribution panel, and in the Ericson 25 shop manual there are no instructions for the installation of such a panel. I should mention also that there are no instructions for the installation of a shore power inlet or a charger. In terms of the AC distribution panel, one can only assume, therefore, that when someone opted for a shore power inlet and charger at the time of purchase, these electrical components were installed without an AC distribution panel as an intermediary. The manual does indeed mention an AC breaker. Obviously, then, the AC power from the shore power inlet passed through a breaker and from there to the charger. From the charger, the power passed directly to the battery without first passing through a distribution panel.
Why, then, would anyone bother to install an AC distribution panel, if the primary purpose of the shore power inlet is to power a charger that will, in turn, charge the battery bank? Well, there are several reasons.
First, it might be nice to have an AC receptacle for power tools or household appliances (such as a hot plate) when AC power is available.
An AC receptacle with boxes and stainless steel face plates
Secondly, it might be nice to have an air conditioner on board, especially if you live in a climate that is extremely hot and humid, such as you find in the southeastern part of the United States and the whole of the Caribbean. To power a small window-unit style air conditioner (such as fits in the box below), you must have an AC receptacle. This AC receptacle could also be used to power an electric heater in the cold months.
Finally, if you happen to have a battery charger that is not hard-wired to the battery bank, but instead requires a standard AC receptacle, then you'll want to have an AC distribution panel.
The Iota 45 charger on Oystercatcher
If you choose to install an AC distribution panel, as I did on my boat, then you next must decide where to install it. Is there enough room for it beside the original DC panel on the Ericson 25? Not really. Is there enough room for it somewhere else in the galley? Not really. The back of the Blue Sea Systems AC panel, which I purchased, projects some four inches from the panel itself. Moreover, to be in compliance with ABYC (American Boating and Yachting Council) regulations, the back of this panel must be covered by a protective box. The cockpit locker, which sits behind the bulkhead (on which the DC panel is located), is the only space that will accommodate this the Blue Sea Systems AC panel and the protective box. This means that if you wish to install an AC panel such as this one on the dry side of the galley (as opposed to the wet side by the icebox and sink), then there really is no other place to put it than in the space that is occupied by the original DC panel. This means that the DC panel or panels must go somewhere else. But where?
My solution was to put the DC panels in the alcove box behind the stove. In the picture below, you see the alcove box just above the mahogany spice rack. Here, you see just an open hole. Soon afterwards, a panel of Spanish cedar would cover this hole. In this Spanish cedar would be mounted the new DC panels. For more on this part of project, see my article, "Electrical, DC Distribution Panels."
Having settled on putting the AC panel in the space formerly occupied by the original DC panel, I next had to decide exactly where to put it, since there were other parts of this electrical system that I had to take into consideration. There were two bilge pump switches, a DC breaker, a battery monitor, a battery switch, and an AC receptacle. To make sure that I could make all of this fit into this tight space, I made cardboard mockups. This article, of course, is focused on the AC distribution panel. In terms of the other parts of the electrical system that I mentioned above, see my separate articles on each of those separate parts.
Wanting the appearance of this AC distribution panel tie in with the appearance of everything else on this boat, I decided to mount the AC panel in a piece of mahogany trim. The rest of the boat was originally trimmed with mahogany, so this would make the AC panel look as if it had been there from the start. I was fortunate to have a 1/8 inch piece of solid mahogany that was six inches wide and about six feet long. This piece (and several other pieces of the same size) I had purchased at Southern Lumber here in Charleston, South Carolina. This was where I had purchased other pieces of sapele mahogany for this refitting. Normally, the thinnest mahogany that is available is rough-sawn 4/4 inch, i.e., 1 inch. This means that if you want anything thinner, you must plane it down to the appropriate thickness. Occasionally, at this lumber yard there are scraps of mahogany that are available as left-overs from the millwork division of the yard. One day when I stopped by the yard, these thin pieces just happened to be available. Figuring that I could one day use them as trim of some sort, I bought them. Now that day had come.
Once I had cut a piece of the 1/8 inch mahogany to the appropriate size, I used the template provided by Blue Sea Systems to mark the mahogany with lines for the cut-out.
I really had to take it slow when cutting the material. One careless move and I would have snapped the mahogany from the vibrations of the saw or the weight of it pressing down on an unsupported end.
The finished trim-piece.
Next I dry-fitted the panel into the trim-piece. By the way, this is the Blue Sea Systems PN 8043. I bought this particular panel because it had everything I needed in one panel: an AC voltmeter, an AC breaker, and three separate circuits.
Fortunately, I took my time with the planning for the rewiring of the boat and did not make any hasty decisions in terms of the mounting of any of the switches or panels. If I had, I probably would have centered the new AC panel on the existing DC panel hole. This would have prevented me from constructing the spice rack which you see pictured below. Since I had to work around the spice rack, I had to offset the AC panel with regard to the existing hole.
Before I did any cutting, I made sure to dry-fit all the mahogany trim pieces to make sure that my calculations based on the cardboard mock-ups had been correct.
Satisfied with the dry-fit, I moved forward with my plans to expand the existing hole to make room for the AC panel. Before I could do this, I needed to drill the mounting holes in the trim piece.

Back in the boat, I screwed the trim piece into place so that I could mark the area that needed to be cut.
I also got together the tools that I would need for this job - the Makita jig saw and the Dremel with the fiberglass cutting bit.
With everything cleared out of the way, it was time to get to work. As always, despite the fact that I had measured and re-measured, I approached this job with some trepidation. There's no turning back once the cutting begins.
After drilling a pilot hole, I began to cut the fiberglass with the jig saw. Note the shape sketched in pencil to the right of the hole. That was where I had originally intended to put one of the bilge switches. That's what I meant above when I talked about taking my time and thinking all of this through. If I had mounted the bilge pump switch in that spot, I would not have been able to situate the spice rack in the space where it is now located.
The cut-out got bigger . . .
and bigger, until I could no longer cut what I needed to cut with the jig saw.
At this point, I had no choice but to break out the drill.
The Dremel, with the fiberglass cutting bit, brought me close to finishing the job.
The keyhole saw closed the deal.

One last hit with the Dremel.
Presto. This job, or at least this part of the job, was done. Looks sort of lonely and not very attractive sitting there by itself, right? After this AC panel got a few neighbors, who were also trimmed in mahogany, it would not look so bad.
This ends this posting on my installation of the AC distribution panel in Oystercatcher, my Ericson 25.

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