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Saturday, March 24, 2012

Electrical System: Phased Approach

So I have been making some headway on the electrical schematics. Suffice to say, you don't want to "wing it" without some design, lest someday find yourself wired into a corner (and ripping/changing things out). We are using a "phased" approach by taking each and every feature we could ever want and placing them into three successive phases: "phase I: must have", "phase II: nice to have", "phase III: may never have". While ensuring that each phase builds on the previous. The key is to design the system such that power can be added (with more batteries, charge sources and converters) with the increase in power demands of each phase. All the while building on the previous phase at the same time (minimizing re-wiring and "ripping out").

The system can be divided into three "sub-systems": 24VDC, 12VDC, 120VAC.

24VDC
It is this 24 volt sub-system that most of the "house" loads will be attached. This includes pumps, lights, switches, etc. We will be using Mastervolt's ship-wide digital switching system. One feature of this technology is the ease of future expansion as you do not need a master switch panel that every device (and the associated wire) homes to. Instead, you wire the new device to the nearest digital switch block (or install a new switch block), configure the system, (via computer) to see the new device, and you are done. Having said that, basic load calculations should be done to determine a minimum primary wire size (that is being handled in another worksheet).

12VDC
There are in fact two 12 volt sub-systems: one contained inside ("internal"),  and one entirely outside ("external") the 24 volt system.

The internal 12 volt system provides the ability to use the same switching network of the 24 volt system, for certain 12 volts devices. We are planning on some devices that, at this time, are only available in a 12 volt version. Using these devices in the switching network is enabled by installing a 24 volt to 12 volt converter behind the switch blocks.

The external 12 volt system includes that of the diesel engine and communication loads (radios, etc.). The engine's starter battery, starter motor and alternator are 12 volts. The communications battery (for things like SSB equipment), is also 12 volt. Devices powered by this battery will have a small traditional switch panel and will not be switched by the Mastervolt system (to avoid any RF noise potential). There will be switches to completely isolate the communications battery, and it's loads, from the rest of the system.

120VAC
It is this sub-system for which most of this planning is important. As 120VAC loads are added, more large things like batteries, inverters and generators need to be added. These are items for which one needs to allocate future "physical" space. There are a number of AC items planned, that we may never install.

Phase I
Phase I
The basic system:

  • 24VDC: main house distribution (with some internal 12VDC devices)
  • 12VDC: engine/communications
  • 120VAC: battery chargers, outlets, microwave, hydronic assist (cabin heater)

Phase II
Phase II

Phase I system plus:

  • 24VDC: second/expanded house battery, forward battery, thruster, windlass, second inverter
  • 12VDC: nothing added
  • 120VAC: second house charger, compressor, A/C units


Phase III
Phase III
Phase II system plus:

  • 24VDC: solar cells, wind generator
  • 12VDC: nothing added
  • 120VAC: appliances, generator


Of course, in the end, things may never go *exactly* like this. They never do. We reserve the right to move devices forward or backward through phases, or add more phases altogether. The point of this is to try and plan for the future, requiring minimal effort to adapt.

These diagrams will no doubt be updated a number of times. Those interested can find the latest version by clicking the 'Electrics' tab at www.westsail42.com.

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