Wire size

[rl69]

My step son is tring to set up his travel tralor. 30 amp plug,80 ft from the breaker box. He ran a 10 gauge wire it wouldnt run the ac. he ran a 6 gauge still no luck.hooked up a genarator everything worked fine. He isn't tripping any breakers? Any ideas I don't have a volt meter

[Blanket]

Funny question, Load, length of run determines wire size and breakers as service

[lancem]

#6 copper should do it, aluminum you need to go to #4

[Pipefitter]

A quick lesson in electricity and RV air conditioners: I was an electrician in 2 different RV plants and an industrial electrician for a few years after that. A 13,500 BTU RV AC will draw about 18 amps when running, figure about 2-3 times that when the compressor starts.

As a rule of thumb for every 100 feet of wire between the power supply and the motor you need to up-size the wire by one gauge.
I suspect that you do not have 110 volts at the breaker box due to the wire length from the transformer to the breaker box.
You can try running a 4 gauge copper wire but that would get expensive.
I suspect that instead of tripping the breaker you are getting an interrupt from the starter on the AC compressor motor.

[Mal Paso]

#10 should do 30 amps at less than 5% voltage drop which is the usual limit.

#6 should be under 2% voltage drop which is the usual off grid limit. I would suspect the 30 amp plug and whatever is behind it.

[Plate plinker]

A quick lesson in electricity and RV air conditioners: I was an electrician in 2 different RV plants and an industrial electrician for a few years after that. A 13,500 BTU RV AC will draw about 18 amps when running, figure about 2-3 times that when the compressor starts.

As a rule of thumb for every 100 feet of wire between the power supply and the motor you need to up-size the wire by one gauge.
I suspect that you do not have 110 volts at the breaker box due to the wire length from the transformer to the breaker box.
You can try running a 4 gauge copper wire but that would get expensive.
I suspect that instead of tripping the breaker you are getting an interrupt from the starter on the AC compressor motor.


What he said. The start up is the killer. Also as suggested the power at the outlet may be inadequate. Just for giggles if every other power draw is turned off will it work?

I would check and see what size wire is behind that 30 amp outlet. Almost bet it is undersized.

[rl69]

Thank you for your responses they helped. They have confirmed what I was thinking.

He is pulling power from a breaker box inside a home. (30 amp ) the six should have been more then plenty. The ten should have done it? He has given up and says he is going to drop a new service. His wife says he isn't.

I told him to buy a 50 amp breaker,run that from the house to a breaker box outside the trailer, then Ron his plug from there. We will see where he goes from here.

is it posable for a breaker to not put out a full load but not trip?

[rl69]

We did not see if the ac would work by itself

[Plate plinker]

is it posable for a breaker to not put out a full load but not trip?


YES. That’s how some fires start.

[lightman]

My calculations, based on pulling a full 30 amps at 100ft show that #6 will have a 2% voltage drop. 2% is acceptable. I think you may have another problem. Without a voltmeter you are just guessing.

[upr45]

Dirty connections. Measure the voltage at house, then in trailer, no load should be same value. Apply a stable load like a good sized heater and see how much the voltage collapses at the trailer. The voltage will be dropped on the dirty connection(s), which will be apparent if you can measure it at each connection.

[10-x]

Ran a 100 amp service to backyard garage and half, installed 100 amp box with breakers for 240 for irrigation pump, 120 for the GFI recepticles and 30 amp for RV. RV will function with limits with 30 amps but if living in it needs 50amps. Owners manual clearly states one can not operate all elect. componernts on 30 amps. AC and maybe a 120 recpt. or 2 but no high draw components, microwave, water heater or elect. heater. Excellent advice already posted, check panel that feeds 30 amp plug, breaker size? ground ok? lastly borrow meter or get friend with one to check everything.

[jimlj]

Spend a few dollars on a volt meter. For about 7 bucks you can get one at harbor freight, or about double that if there is no HF close by. For this price range you will get one good enough for any home need.

When you say "he ran a 10 gauge wire" do you mean he only ran 1 wire? He should have 3 separate wires, 1 hot (usually black) 1 neutral (white) and 1 ground (green).

[leadman]

My RV will get the 10 gauge wires hot if I use 2 rv extension cords with the cord from the rv. This would be about the same length as what he is running. I have 2 low draw Coleman a/c units on my rv with a load controller so only one will start at a time. One unit is fine with 2 cords but I try not to do this anymore. Thinking of converting it to 50 amp service.
My 2005 travel trailer had a Chinese a/c unit on it and it would not start with 2 extension cords, barely with one extension cord. Draw was almost 40 amps when starting.
I have also noticed that most of the imported wire is not up to the size stamped on the cord.

Walmart has a decent multimeter for $20.

[Steelshooter]

With all due respect, there is no way an rv a/c unit can draw 40 amps at start up. If it does it would trip the breaker. A rv a/c unit is similar to a in the window unit for a house that plugs into your wall. The start up amps on these is less than 10 amps and run amps should be about 4 or 5 amps. In my humble opinion the op has a compressor problem. Take a look at the capacitor for rust or corrosion at the connections and maybe see if they make a hard start kit for it.

[Plate plinker]

OP states that it worked with the generator. His power source is the likely culprit.

[rl69]

Thanks guys, I found it. What is the first rule in trouble shooting? Start at the beginning,no matter how simple.

I didn't get there tell late yesterday evening,and started tweaking what he was doing. Today I started at the beginning, where his plug wire went into the trailer, and in big letters it said 120 volts.

A little embarrassing but no damage done. He needed 6 gauge wire anyway with 120 volts at that distance. Again thanks for the help.

[Pipefitter]

With all due respect, there is no way an rv a/c unit can draw 40 amps at start up. If it does it would trip the breaker. A rv a/c unit is similar to a in the window unit for a house that plugs into your wall. The start up amps on these is less than 10 amps and run amps should be about 4 or 5 amps. In my humble opinion the op has a compressor problem. Take a look at the capacitor for rust or corrosion at the connections and maybe see if they make a hard start kit for it.

Starting current is ALWAYS greater than running current. The breakers used in residential (and RV) power panels are "time delay" breakers
If it were an instantaneous trip breaker you would have to set it at 800% of full load amps. Look it up in the National Electrical Code.

[Steelshooter]

As soon as you show me a 13,500 rv a/c that uses 18 running amps.