Running unit AC on a home extension cord

[TxCowboy]

Hi, gang. A quick question about operating the AC.

I have the 15K AC unit which is installed in a Greystone 32RL which is presently parked outside my home. I have the RV plugged into a regular home 120 VAC outlet (15W or 20W) via a 75 feet 12 guage extension cord then into a "30 amp to 50 amp adapter". I've only been using power in the unit to power a small fan for two hours per day to keep air circulating in the unit.

I'd like to run the AC in the unit tomorrow for an hour or so with nothing else operating in the RV.

Do you believe there would be any trouble starting and operating the AC unit using power from my home?

 

[Silverado23]

Check to see what the amp draw is on your AC. it should be around 15 amps. A 20 amp outlet would probably work with out tripping. However, your 12 gauge extension cord may be too long for drawing more than 15 amps over that distance without issues. A 10 Gauge extension cord would be safer.

 

[danemayer]

75' sounds pretty long. Maybe one of the electrical experts will chime in on how much voltage drop to expect and whether the circuit breaker will trip before low voltage damages anything.

 

[recumbent615]

75 ft is too long for 12 gauge and approaching too long for 10 gauge - the issue you will have is one of power loss and over heating. the first can damage your AC unit and the second can burn down your house. I have done it in the past on a 20 amp circuit, 25 ft 10gauge without any issue - I have since added 50 amp circuits in my Garage and out at the RV pad in the back yard...

I would not go 75 ft on a 12 gauge to draw 15 amps on a 20 amp circuit out of an abundance of caution.

Updated Post with Power Loss calculations

12 Gauge @ 75 Ft

4.3v loss
3.6% Loss ( acceptable max = 3% )

10 Gauge @ 75 Ft

2.75v loss
2.3% loss ( with in limits )

Even at 20 Amps - you are just at the Limit of 3% Loss on a 10 Gauge but I would not do it.

 

[pegmikef]

FWIW, I use a fifty foot 12 gauge extension on a dedicated 20 amp circuit to run the 15K A/C unit in my trailer and it works fine. I put a watt meter on the line to check the draw and after it is up and running it only draws a little over 1400 amps so I don't have a problem. Unfortunately, my meter only goes to 1800 watts and it displays an error when the A/C starts so I can't tell you what it draws to start, but it must be less than twently amps because the circuit breaker doesn't blow.

 

[TxCowboy]

All, thanks for the replies and great information. I'll not run the AC! :angel:

 

[TravelTiger]

When we had our NorthTrail, we had a 30amp receptacle put in our garage. Now with the 50amp rig, we use 30 to 50 converter and only run 1 AC when we have the rig at home.

Well worth the investment to be able to load or work in the trailer without dying of heatstroke.


Sent from my iPhone using Tapatalk

 

[hoefler]

One thing to consider, buy a 30 amp extension cord or two. This will reduce the distance you need for a smaller cord.

 

[sjs731]

You have to remember that if you don't upgrade the size of the wire in your garage that 30 amp extension cords only help the electrical load after the outlet. You will now increase the load on the 12 ga wire in your garage and up the possibility for a fire inside the wall.


Steve
Sent from my iPhone using Tapatalk

 

[pegmikef]

You have to remember that if you don't upgrade the size of the wire in your garage that 30 amp extension cords only help the electrical load after the outlet. You will now increase the load on the 12 ga wire in your garage and up the possibility for a fire inside the wall.


Steve
Sent from my iPhone using Tapatalk

Exactly the reason I didn't just replace the 20 Amp breaker with a 30 Amp breaker on the dedicated circuit I use for the trailer.

 

[cookie]

I disagree.
If the #12 wire is protected by the proper breaker, 20 amp, it will be fine.
The problem with using extension cords is the voltage loss at longer runs because of wire size.
Using a #10 wired extension cord will have less voltage loss on a longer run than a #12 wired cord.

Peace
Dave
Sent from my DROID RAZR using Tapatalk 2

 

[pegmikef]

I disagree.
If the #12 wire is protected by the proper breaker, 20 amp, it will be fine.
The problem with using extension cords is the voltage loss at longer runs because of wire size.
Using a #10 wired extension cord will have less voltage loss on a longer run than a #12 wired cord.

Peace
Dave
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I agree with the part about the extension, but if I had changed the breaker to 30 Amp, then the #12 wire in the wall between the breaker and the outlet could overheat and start a fire before it even reached a high enough amperage to blow the breaker. By not changing the breaker, the wire between the breaker and outlet is always protected from exceeding 20 amps.

 

[cookie]

That is exactly why I stated that the proper breaker for #12 wire is 20 amp.

Peace
Dave

 

[recumbent615]

I disagree.
If the #12 wire is protected by the proper breaker, 20 amp, it will be fine.
The problem with using extension cords is the voltage loss at longer runs because of wire size.
Using a #10 wired extension cord will have less voltage loss on a longer run than a #12 wired cord.

Peace
Dave
Sent from my DROID RAZR using Tapatalk 2

I have to agree with Dave here - If the wire and Breaker are correct in the house - and the extension cord is over sized then the added resistance of the extension cord is not going to affect the interior wiring. IF it was exactly the same size then the resistance would be seen over the entire extended length of the circuit. This could be an issue since the wire size was selected based on the length of the RUN inside the house not on the extra 100 ft of an extension cord. Why you may ask was it not anticipated that an extension cored would be used? Because, code does not require it to be considered.

Kevin

I'm not an electrician but I saw one on TV once...