Re: [A/S] '64 Globetrotter 19' electricals

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Chris,

Thanks for the clarification on the inverter. Unless it's quite large,
the best way of using it is to have a seperate 120VAC outlet fed by the
inverter and a switch to energize it "as needed". Make sure to install a
pilot light near the switch so you don't leave it on accidentially.

I like a light bulb for testing purposes in addition to a DVM. A tiny
strand of wire or other leakage will show "power" with the DVM, yet
won't supply enough current to actually DO anything. A good heavy
lightbulb needs more than leakage to light it. My original suggestion
was to use the light bulb in SERIES with your system to avoid blowing
fuses; a direct short would only cause the bulb to glow at full
brilliance.

No doubt your fridge should be connected to that receptacle near it if
it's to work on 120VAC.

I personally prefer a relay for isolation because it has almost no
voltage drop. A diode always has a few tenths of a volt drop across it,
making a bad situation worse. It's very hard to charge your trailer
battery to any degree from the tow vehicle unless you wire the
connection with #4 welding cable and a forklift-type connector. My
eMeter shows only a few amps of charge current when the vehicle is
running, due to the 35' or so of #10 wire between the batteries. Maybe
it'd do more if the battery was nearly dead, but I doubt it. The relay
that I use looks like a Ford starter relay ("solenoid") that's rated for
continous use. The coil is connected to the ACC feed on the truck, so is
closed only when the engine is running.

That transformer thing is crude, at best. You're right that you
shouldn't need a switch for "battery/Shore" power, it should be
automatic. Both my A/S and my Avion simply have the entire 12VDC system
connected to the battery. The converter/charger is also connected
directly to the battery. I do have a 50-amp fuse and Master Disconnect
Switch in the main battery lead for disaster isolation. This is quite
important, and not always incorporated in the older trailers. Remember
that a regular ol' 12-volt battery is capable of several hundred amps of
current for plenty long enough to melt every wire in your trailer, and
you do need to protect that main wiring that's ahead of your branch
circuit fuses/breakers.

BTW: I got a "file not found" on your "modified wiring diagram".

                              <<Jim>>