Inverter Wiring

[Pete Masterson]

The inverters in a BB are set up with their own distribution wiring
(separate from the main 120 vac panel). So, follow the output wires
from the inverter and you should find a distribution system (possibly
with circuit breakers) somewhere nearby. You can 'join' a new wire
there (or set up an additional circuit breaker) to run to the
location of the freezer.

Load: you first need to determine what the general load on the
inverter is at present. What devices are attached and how many are
used at the same time? It may be that all the available load is
(potentially) used up by the existing appliances.

Appliances almost always have watt or amp ratings on them (usually on
a tag by the manufacturer's name on the back). To ease calculations,
convert all ratings to either watts or amps. (Amps x volts (120) =
watts or Watts divided by volts (120) = amps) So, a 1500 watt
inverter can handle about 12.5 amps in total. You should leave a
couple hundred watts (2 amps or so) "free" to allow for calculation
errors and electrical efficiency. Motors (which don't "like" certain
types of inverters) prefer "true sine wave" power -- something an
older inverter may not provide. Motors (the freezer compressor) also
draw as much at 50 more power at start up than their rating, so
allowance must be made for that, as well.

In all probability, the inverter on your coach is already wired up to
use most of its maximum rated power for the appliances already
attached. I expect, depending on the size of the freezer, that you
will find that it draws anywhere from 6 to 8 amps up to around 10
amps. (Remember to add for the brief overload for motor start up.)

So, the solution(s) are (1) upgrade the existing inverter from a 1500
watt unit to a 2500 watt, true sine wave unit or (2) add a second
inverter of about 1000-1500 watts (depending on the size of your
freezer) to handle only the freezer circuit.

Keep in mind that the additional 'juice' required for the inverter
will come at the expense of the batteries. If you only use the
freezer/inverter while on the road, the engine alternator should be
replenishing the house batteries to offset the load, but while
parked, the house batteries will need to provide the inverter power,
and I know from personal experience (I have a home-style 22 cu ft
side-by-side refrigerator-freezer) that refrigeration can draw down
batteries rather quickly. You may need to consider adding additional
house batteries (or otherwise increasing the available amp-hours) to
compensate for the additional demand.

Pete Masterson
'95 Blue Bird Wanderlodge WBDA 42
aeonix1@...
On the road at Edinburg, VA



On Oct 20, 2008, at 8:42 PM, Don Spithaler wrote:

> Guys---I want to set a small freezer in one my outside bays. There is
> a plug there but how do I wire it to run off the inverter while going
> down the road? How would I know if it will run off a 1500 W inverter?
> Thanks
> Don Spithaler
> 89 SP 36'
> Butler, PA
>