electrician question: voltage drop at outlet to TT

myredracer wrote:
Another thing to be aware of is an AC unit typically draws about 60 amps during the momentary startup.

It is likely much higher than that during startup, but also for only a small fraction of a second.

Another thing to be aware of is an AC unit typically draws about 60 amps during the momentary starup. When using small gauge wire like #12 and runs like 30', you can have significant voltage drop that is hard on the motor windings and eventually lead to premature AC unit failure. The 60 amps is also in addition to anything else operating like say the converter/charger at perhaps 4-5 amps.

I would use a #10 shore power cord with 30 to 15 amp adapter, or a #10 extension cord in addition to the shore power cord. As mentioned, you also need to consider the length of the branch circuit from the house's panel to the 20 amp receptacle which can greatly increase voltage drop.

Always have a permanent voltmeter mounted inside an RV and keep an eye on it. If it gets down to 104-105 volts, shut the AC unit off as it will cause damage. Best thing is an EMS which automatically shuts you down on low voltage. Also, always ensure the blades on your cords are kept clean and shiny and never plug in the RV with power on.

2oldman wrote:
I'll bet some connectors are getting hot.

X2

I'll bet some connectors are getting hot.

You could check the voltage all along the line, from the main panel, to the outlet, at the end of the extension cord and finally as close to the A/C as possible to see the various drops. It ain't just the cord involved.

I ran a voltage drop calculator and the drop from my fuse panel to the side of the house where I plug in, is only 1.3 V drop at 12 amps load. So according to that, the voltage at my outlet shouldn't drop below 118. Hmmmmmmm

You could check the voltage at the A/C AC input to be sure there is no significant RV drop - but don't know where you measured.

It means you have a normal voltage drop for 20A. If the plug or elsewhere is warm then OK, if hot you have a maintenance issue. Below 108V (120 - 10%) start being more aware and 104V is rather iffy.