Sorry for the delay answering. Lately I got "Maintenance" screens when I clicked the JOF link.
Of course you are correct about this dedicated air conditioning supply.
In my defense (weak as it may be), when I read the original post about adding the air conditioner in my mind I saw a 50 ft coil of extension cord on the ground feeding over to the trailer fed from a detached garage so I was trying to convey that voltage drop was important. That put me off on a tangent.
The 80% load factor is not really applicable to this dedicated feed, but for most convenience receptacle circuits it is best to apply that. As you say, larger wire is never a bad thing, but it can make the installation a bit more difficult.
Sorry for getting off track. vic
Originally Posted by Bob Landry
Heavier gauge wire is not required because of startup. LRA is a lot more than operating amperage, but it occurs for a very brief time, usually less than a second and is irrelevant in sizing wire for a given load. The wire length and size coming from the pedestal is also irrelevant as long as it is sized correctly and there's no need to take that into consideration either. If that's not sized right, you are going to get voltage drop regardless of what you use for the AC.
That said, use #12 wire. The rated amp draw of the AC is based on an ambient operating temperature of 95 degrees. That amperage will increase at a rate of one amp per 10 degree shift in ambient temperature. In fact that's how you check an AC for proper charge without tapping into the system, by measuring amperage and checking amp draw relative to ambient temp. As an example a unit that draws 14.5A in 95 degrees will draw15.5A in 105 temperatures, so you would exceed the capacity of the 15A breaker. When I do my marine installations, I use #12 wire and a 20A breaker for all but the smallest units Along with factoring in the possible changes in ambient temperature, you also have to realize other factors that will affect current draw, condition of bearings and components at the unit ages, dirty filters, lower than normal CG pedestal voltages, so bottom line, go with #12 wire and protect it with a 20A breaker. You can use #10, as no one ever got in trouble using larger wire, but it's more expensive, harder to work with, and just isn't needed.