Mastervolt Digital DC Distribution, Beginnings…

If you don’t know what is ‘Digital DC Distribution’ or ‘Distributed Power’ and are a fairly new reader of this blog, digital DC distribution is a newer means of controlling DC power over the traditional circuit breaker panel. Instead of mechanical breakers, circuits are controlled via solid state relays, which in turn are controlled by a computer network. These relays have electronics that monitor current and can be programmed to “trip” at specific current loads, acting like a circuit breaker. Blocks of these relays are placed strategically throughout the boat, (near the items they control requiring much less wire). Instead of a main breaker panel, there are many kinds of user interface devices (touch screens, soft switches, or your own computer), that connect to the network to control the circuits.

Installation of the Mastervolt DC distribution system has begun. Despite having positioned components in CAD, in pursuit of the ideal layout, having the actual devices in hand has caused a rethink (of course!). I ultimately ended up staring at the bulkhead for about an hour to find the best layout and wire runs given the space. Oh well.

This is what I have so far…

The main DC distribution ‘manifold’

This first picture is the main “DC manifold” which distributes DC current between the main batteries, the boat’s electrical loads, and power sources (like battery chargers). It is composed of three devices connected end-to-end. From left to right: MasterShunt, DCD-500, and another DCD-500.

‘Mastershunt’ (shown without cover) provides main circuit protection and current monitoring

The MasterShunt stands between the batteries and the rest of the system. It provides 300amp DC protection (big round fuse in the picture) and a shunt for measuring total current in or out of the batteries. Both the fuse and shunt are replaceable.

DCD-500 (shown without cover or fuses) provides high current distribution and protection of up to five circuits.

This last picture is of the DCD-500 (one of two). It is the interface point for the high current supply leads. Two of these chained together provides a total of nine connection points, eight of which are fuse protected. These connection points are wired as:

  • port-forward DC leg
  • port-aft (aft cabin) DC leg
  • starboard-forward DC leg
  • 24VDC battery charger
  • 24VDC-12VDC converter
  • engine room 24VDC loads

This leaves three unused connections for future devices that may include, but not limited to

  • AC inverter charger
  • DC generator
  • solar panel charger
  • wind generator

Unlike the MasterShunt, the DCD-500 does not provide current monitoring for each connection (would be nice if it did), but it does monitor the state of each fuse and will provide an alert if any internal fuse happens to blow.

4 comments for “Mastervolt Digital DC Distribution, Beginnings…

  1. June 11, 2012 at 4:22 pm

    Sounds like you went back to the old fashioned way of doing it. LOL

    "I ultimately ended up staring at the bulkhead for about an hour"

    Bill Kelleher

  2. June 12, 2012 at 1:06 pm

    I am about to wire my 32 ft sailboat (new build) and have been looking for sources of basic info about distributed systems. Any suggestions?
    Cecil Borel

  3. June 12, 2012 at 1:41 pm

    Cecil, I know of no "one stop" source for such info. But Nigel Calder has written a series of articles over the years on the subject, for Professional Boatbuilder magazine ( You can access back issues on their site electronically (for a fee).

  4. June 13, 2012 at 2:02 am

    Rob, great work as usual.

    Cecil, I can also recommend Don Casey.

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