Inverter Wiring

[Pete Masterson]

If the freezer is that small, then you shouldn't need to upgrade
anything. Just find a 120 vac outlet (socket) that's already on the
inverter (in your basement) and relocate or extend it to reach the
spot where your freezer will be placed. 95/120 is > 1 amp so it's not
a significant load. However, the concern over sine wave vs. modified
sine wave vs. square wave output from the inverter is an issue. If
the freezer has a compressor motor, it will run best on true sine
wave current. It will (likely) run, but less efficiently, on modified
sine wave (the motor will run hotter and draw more current, perhaps
1.5 amps) -- this will cause it to eventually fail sooner than it
would if run on true sine wave current. It probably won't run on
square wave inverted power. I assume you have a microwave (that works
on inverter power) so, you most probably have modified sine wave.
You're not at a great risk of overwhelming your inverter with this
additional load.

BTW, check to see if the freezer actually has a compressor -- there
are some small refrigeration devices that use a solid-state device
for cooling. They're usually pretty small (and don't draw much
power), however they're also much less demanding about the type of
wave received on the AC power. (They typically have an internal power
supply that turns the electricity back into DC for the solid state
device.)

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



On Oct 21, 2008, at 7:02 PM, Donald Spithaler wrote:

> Pete
> The freezer that I'm looking at is small. It is 115V / 95W so it
> would be drawing under 1 amp. Is that right? I would be only using
> the inverter while going down the road. We don't dry camp any. On
> the road the only thing on the inverter would be the TV & my
> laptop. I'm not ready to upgrade the inverter at this time & I
> don't want to get into that unless I have to.
> Don Spithaler
> 89 SP 36'
> Butler, PA
>
>
> On Tue, Oct 21, 2008 at 10:52 AM, Pete Masterson
> wrote
> 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
> >
>
>