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4F3: AC Inverter System
The Inverter Makes AC from DC...
As we said, the Inverter system is used to provide
AC to the boat when there is no shore power. It is
wonderful, for example, to use the inverter to make a pot of
coffee when the engine is running and you are underway,
or to watch TV in a quiet anchorage, or use a hair dryer for
a few minutes in the morning. But for long-period use of
AC by large appliances, the engine or generator must be
running or you must have shore power available.
Now the microwave, for example, will draw about 50
amps of DC when using the inverter to run it, so in six
minutes you use one-tenth of an hour at 50 amps, or five
ampere-hours. That's okay. But what if you want to cook a roast for 30 minutes? You would
use up a lot of energy on that one job alone! That’s too much use for the inverter, and the
generator should be started.
For a short task, the inverter is great: no starting the generator, no noise, no fuss, the
power is there. If the engine are running, use it all you wish, as long as you don't try to do two
huge jobs at once: The inverter produces a maximum of 3,500 watts of energy at a time. So
the inverter is only wired to the outlets and the microwave. It will not run the water heater,
battery charger or refrigeration.
Note: Only the breakers in the panel illustration on page 4.12 with an
asterisk (*) are powered by the inverter!
...and also is a Battery Charger, Making DC from AC!
The Inverter can also do the reverse: If there is AC power available from a shore-side
source or the generator, it can recharge the house batteries. The battery charger function
receives that power through the “Inverter Battery Charger” breaker on the AC panel. Since this
breaker must be “On” for the batteries to charge using AC power, and you will want to charge
the batteries at every opportunity, we suggest that you leave it “On” for the duration of your
cruise.
As noted above under the “Connecting Shore Power” section, be mindful that the
Inverter can draw a lot of current when charging the batteries, especially when first activated
upon connection to shore power. Thus, you need to be careful not to overload a shore power
circuit by running other high-draw AC appliances at the same time. Monitor the AC Ammeter to
make sure the load remains below the available current as determined by the shore power
service from the marina, normally 30 amps.
(More next page)
The boat has a Xantrex 2500-watt inverter in the aft
stateroom hanging locker.
Section 4F: Electrical Systems, AC 4.10