Tips on
Electrical System Use and Maintenance
Part IV: Adding New Equipment
by David H. Pascoe, Marine surveyor
Adding New Equipment
Most boats, particularly smaller ones, are unfortunately
not designed with the idea of adding equipment, even though nearly
everyone does. But the primary reason why systems gets so messed
up results from the attempt to force something in where there is no
provision for it.
The best way to deal with this is to simply add a new
panel, whether AC or DC. Doing this is neither very difficult nor
expensive, especially considering the cost to repair all the problems
you're likely to create when you try to cram something onto a system not
designed to handle it. A six breaker DC panel will cost less than $200
and is a whole lot better than scattering inline fuses all over the
place, and with installation will run less than $500. Plus, the new
panel can be added at any location where it will be convenient.
Adding a second shore power circuit is especially useful
for those boats with single 30 amp shorelines where the addition of new
equipment will tax the system. It's not very convenient to have to turn
the water heater off to turn the air conditioning on, or constantly be
managing equipment as breakers keep popping off. You have two options
here, the first of which is to increase your shoreline to 50 amps. To do
that you have to change the main breaker, power receptacle and the shore
cord, which is a lot bigger and heavier. The other option is to
add a second 30 amp circuit, which means adding a new panel, receptacle
and shore cord, which costs a bit more.
Adding a second circuit has the advantage of separating
the air conditioning onto a separate line, which is the way all good
systems are designed. That's because of the high power demand, combined
with frequent dock power faults, makes it desirable to separate it from
the main service.
Multiplex Systems
A multiplex system is a multiple power source system which permits
switching from one line to another, from one power source to another.
For travelers, this is extremely useful to deal with unreliable dock
power, or sudden faults in your own system. It allows you to choose
which line you want to run equipment on, and particularly if you have a
generator, it provides a great deal of flexibility. Let's say a
circuit breaker on the dock goes out while you're cooking dinner and
it's very hot this day. Instead of only being able to turn the AC off
and go on cooking in the heat, you can fire up the generator to run the
failed circuit simply by switching it over. The better larger boats
invariably have this kind of system.
The reason why low cost boats don't have this kind of
system is because it requires the use of very expensive rotary switches
that costs $300 - $600, plus some more complex wiring. But it is an
extremely good system to have. See photo below.
 |
| As
versatile as it can get. This boat has (2) 125 and
(1) 250 shorelines plus generator for a total of 4
power sources. These are controlled by the six rotary
switches, each with four positions, so that
any combination of power sources on any branch circuit
can be selected. |
Posted November 15, 1998
(First posted July 14, 1998 at
www.yachtsurvey.com. Revised and added two pictures November 02,
1998. Page design changed for this site.)
