Power the AC with household circuit

spud1957 wrote:
You can use 14g wire for a 20A breaker under certain conditions, NEC 210.19(4).

Could you please post the rule or a link to it?

spud1957 wrote:
You can use 14g wire for a 20A breaker under certain conditions, NEC 210.19(4).

Wasn't going to get into the NEC specifics.
In the case of a long run inside & then outside to an RV, I would not recommend 14AWG.

You can use 14g wire for a 20A breaker under certain conditions, NEC 210.19 (A)(4).

As was mentioned several times, make sure nothing in the house is active on the circuit supplying your RV. Use the shortest heaviest gauge cable you have.
15 amps supplying ONLY the RV AC should allow it to work.
Additionally, if you have an electrical savvy friend, get them to check the circuit breaker panel. As long as the wire on that household circuit is 12AWG or 10AWG, you can upgrade that circuit to a 20 amp circuit breaker. A LOT of older homes have 14AWG on a 15amp breaker and should remain as 15 amp. All new construction, AFAIK, require 10AWG for many AC runs and 12AWG for general use outlets.
All my exterior AC outlets are separated 20 amp circuits. I'm running my 13.5K BTU AC and fridge right now while packing up for a trip.

I have a 13.5K BTU A/C and have also run it many times on a 15A house circuit. It's a dedicated circuit that only feeds the one outlet so if your 15A circuit is feeding something in the house and the outlet you're plugging the RV into you might trip the circuit breaker.

dup.

It's all about the voltage. (Cue Meghan Trainor...)

If you read the tech specs on your AC unit, you'll find it is supposed to have a 20 amp breaker and wire over 50' needs to be min. #10. For longer runs, even larger wire may be needed. The overall wire length includes all wire from the terminals at the AC unit to the breaker in the panel. The breaker only has to be large enough to allow an AC unit to start (within normal operating voltage specs) so a 15 amp breaker is okay if it doesn't trip. Also depends on other loads in an RV running at the same time.

Sometimes even the wire from your house panel out to the street can be a factor in voltage drop. That's why lights can in some cases flicker when a fridge compressor or washing machine motor starts up.

Besides the running current of an AC unit, it draws about 5-6 times the full load amps on the momentary startup which is around 60 +/- amps depending on unit BTU rating. That is why the wire over a certain length needs to have a current higher than the breaker or full load current draw of the AC unit. If wire size is too small, the voltage at the AC unit can drop very low.

Low voltage will damage AC units and should never be allowed to drop below 105 volts. The damage is cumulative and while it may *seem* like it's running fine, it can fail prematurely for no apparent reason. Too small wire size can cause large voltage drop on startup or running that damages the motor windings. AC units draw more current as voltage goes down, further exacerbating voltage drop.

Installing a permanent voltmeter inside an RV is always a good idea so you can monitor voltage wherever you happen to be. Voltage can also fluctuate widely over 24 hours depending on other nearby users.

Ensure cord plug blades are kept clean 'n shiny. The inside of receptacles and cord connectors can't be seen so if they look well used and abused, you may want to replace them.

My AC runs from a 15 amp circuit. If voltages is too low (below 107) I use an autoformer. The autoformer allows me to use voltage as low as 97 without damage to my RV. It does push the outlet HARD to do this, so make sure all the wires are bright and tight.

My 15k A/C has a 20 amp breaker in the RV. It will run when plugged into a 20 amp breakered house outlet but will trip a 15 house breaker.

Around thirty years ago I summered in the tropics in Mexico. Hot and humid. The house a was parked next to was not being used. I looked at the electrical and it turned out to be typical Mexican -- 8 gauge wire service drop to a pair of 30-amp breakers.

I ran new 10-AWG romex wire forty feet to a newly placed receptacle alongside the rig. I installed a Hubbell spec grade receptacle outlet and used an adapter from RV 30-amp to household 20-amp. By staying away from hot water heating I powered 24/7 air conditioning, the converter and refrigerator all summer long. Including numerous early morning A/C high head re-starts. The receptacle and plug never got warm.