The problem is that a 20 amp circuit is rated such due to the wiring size.
The larger the wire, the more current (amps) it can carry. As you begin to
exceed the rated current the wire begins to heat and the voltage presented
to the AC unit starts to drop due to the resistance in the wiring. As you
exceed the rated current of the wiring, it can melt the insulation and short
out and in the process cause a fire. Dometic AC units have a minimum rated
voltage of 103.5 volts. If you try to run them below that voltage the
compressor overheats and you damage the unit. It typically will not fail
immediately, but damage is done the result is premature failure later down
the road. The AC units only require a 30amp circuit during initial
compressor startup and then the current requirement drops back to below
20amps, but on a hot day, the running current requirement is VERY close to
20amps, so a 20amp circuit is NOT a good idea.
It is NOT EVER a good idea to use an adapter to plug a trailer into a
standard 115volt household type plug for ANYTHING OTHER THAN JUST charging
the batteries. NEVER try running the AC in that configuration as you are
tempting fate with the result potentially being a fire at the receptacle.
Household type receptacles are rated at 15 amps so they will overheat and as
I stated, they can cause a fire. The reason that the breaker is rated at
20amps is that multiple power outlets are connected to a single breaker.
Only use an extension cord rated for 30amp service as the voltage drops
encountered with typical household cords at the current levels a trailer AC
will require will pull the voltage down dangerously close the 103.5 levels
(or below).
David
> Since my understanding of electricity is "if it lights up and doesn't smoke,
> it's hooked up right," I have a question about amps.
> "They" say that operating the airconditioner on our '69 Sovereign (fairly
> new airconditioner) on an extension cord from the house may damage it. The
> reason given appears to be: that since the house has 20 amp circuits and an
> RV park has 30 amp circuits, it would somehow provide insufficient
> electricity for the unit. Howzatgonnawork? Seems like the unit would draw
> the same power from either source up to the point of blowing the circuit
> breaker. Wouldn't it? I am betting it is one of those:
> amps x volts + ohms = volts - mu x barometric pressure divided by your moon
> sign, sorta things. The things I missed while passing notes to my girlfriend
> in school. Maybe it's that water in the hose under pressure analogy. Is
> there an electricial engineer in the house?