Saturday, October 27, 2012


LUX has been equipped with a couple of small DC to AC inverters to allow for charging of small devices. We could run the blender off one of the inverters, allowing us to make frozen drinks. However, we couldn't use anything as powerful as a microwave.
Design Sketch
In preparation for our trip to Marsh Harbor, I wanted to install a more powerful inverter that could handle all the AC outlets and that could run a microwave oven. LUX also had the original Dometic Sentry battery charger which was not a multi-stage charger. I had adjusted the set points on the Sentry to keep from overcharging the batteries, but the result was that the batteries were never fully charged. After doing research on various systems, I decided on the Vectron Multi 3K, which would fit in the space where the Sentry had been located, provide us with 3000 watts of inverter power, a four-stage battery charger, and could also augment the AC output for starting surge loads, such as one of our 16,000 BTU A/C units. It has two AC outputs, one of which is only active if the AC input is active. So I designed the installation to run the outlets all the time from AC Out 1 and run the A/C system from AC Out 2 (the switched output). The design is shown in the first picture. The top drawing is the conceptual design, showing the addition of a 5KW generator in the future and how the system will be connected. The lower drawing shows the details of connections for the current installation. I worked with Peter Kennedy at PKYS to purchase the unit, the supplies I needed, and to review the design.

The installation took about 24 hours over 3 days. The AC cables need to handle 50 A, so that means working with 6 gauge cables (ugh)! The battery connections are specified to be two 1/0 cables for both positive and negative.
Victron to Stbd Under Galley Sink
I had also previously purchased the Victron BMV600 battery monitor and wanted to install the shunt at the same time. Getting the AC cables led to the terminal blocks was a chore. I removed the screws that held the bottom plate in place to provide more working room to bend the wires. Upon the advice of others who have installed the Victron, I installed the wires before mounting the unit. I couldn't have installed them otherwise. Victron should take a look at making it easier to run the wires into the system.
The DC wires are easy to install. Peter helped make up a few 2/0 cables that are needed for the case ground and for the connections to the battery monitor shunt. I have a Greenlee crimper that handles up to 1/0 cable (I should have bought the larger crimper that could do 2/0). The resulting Victron installation is shown here, with all the cables connected. It is located to port under the galley sink.

DC Cabling to Port Under Galley Sink
The DC wiring is to starboard under the galley sink, so the battery cables are short. I used a short 2/0 cable to jumper from the battery negative fuse to the BMV-600 shunt, then bolt the negative cable bus bar to the other side of the shunt, shown below. The inverter battery connections were made to a terminal post that I added, which is connected to the battery switch load terminal. The positive cables were upgraded to 2/0. The BMV-600 shunt is polarized, so it has to be installed such that the load side is down. The connection to the display head faces aft, making it easy to access. I did have to modify the fiberglass cover to fit over the modified cables, but the modification didn't affect the safety. I also added wire ties after the photo to secure the cables.

The AC panel is behind the port, aft cabin access panel. There wasn't enough room on the existing panel to install the required terminal blocks, so I mounted the plywood that I cut out for the A/C return air duct to the back of the panel. The 6 Ga wires come in on the left and the connections to the panel are on the right. A piece of lexan was cut and now covers the terminal strip to prevent accidentally touching a live wire connection.
AC Wiring Section of Wiring Panel

There is a nice conduit that runs from behind the electrical panel to under the battery connections. It was easy to run the wires using a snake. I also removed the old house bank charging wire and will be removing the starting battery charging cables. A pair of Blue Sea Systems Automatic Charging Relays connect the house bank to the starting batteries when the house bank is being charged and the voltage reaches the relay trigger voltage.

The system is running well, giving us a good battery charge. The BMV-600 shows the state of battery charge and the amount of current going into the battery bank. The microwave and outlets are usable. They are still protected by the existing GFCI outlets in the main salon, which was one of the key requirements.

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