running an air conditioner on 250 feet of cord

[pianotuna]

Hi,

Obviously voltage drop is going to be an issue.

If I have a 20 amp 120 volt outlet, could I use #10 wire and place an autoformer at the RV end to deal with voltage drop?

What about using just a 15 amp outlet?

[LittleBill]

greenrvgreen wrote:
Kettner's right as usual. I'm no electrical expert, but I've regularly used 200 ft of #10, and occasional 250 ft of mixed #10 and #12. No issues whatsoever all the way up to 25 amps.

Don't forget that resistance causes heat, and increases with heat, and where P Tuna camps, they don't got no heat.

whats your starting voltage? and end voltage at 25 amps?

[greenrvgreen]

Kettner's right as usual. I'm no electrical expert, but I've regularly used 200 ft of #10, and occasional 250 ft of mixed #10 and #12. No issues whatsoever all the way up to 25 amps.

Don't forget that resistance causes heat, and increases with heat, and where P Tuna camps, they don't got no heat.

[pianotuna]

Hi,

A new panel is due this spring--so I'll pay for a fifty amp outlet at the house. This is probably going to be moot as the owner is having second thoughts about allowing a gravel or rhinosnot pad to be created.

[time2roll]

pianotuna wrote:
If I had my way I would definitely trench in the proper size cable, but the owner of the cottage refuses to consider allowing that to be done even at my expense.

How about adding a basic 30/50 amp connector next to the panel?
Tell him it is way safer than maxing out the existing 15a shared circuit.

[Harvard]

Steady state current is one thing, start up surge requirement is another.

[myredracer]

If you are treating the wiring run as if it were a plug-in extension cord, you wouldn't have to comply with things like burial depth and overall jacket type. What about using some NMDU loomex pulled into a roll of poly water pipe? You could put some treated wood planks over it for protection where needed. Not sure what an inspector would say if he saw it.

[pianotuna]

Hi,

If I had my way I would definitely trench in the proper size cable, but the owner of the cottage refuses to consider allowing that to be done even at my expense.

[wa8yxm]

enblethen wrote:
Calculations are based on only 10 amps.
Have you looked into small gauge URD(underground Rural Distribution) direct burial. Yes, it is aluminum but is must cheaper. Comes in various sizes. Here is an example. #6 URD

Yes I used 10 amps. cause it is a nice round number

1.6
+.16
+.16
+.16
2.24
For a 13 amp air conditioner.

[myredracer]

You need to think about starting current too. The AC unit will draw momentary inrush current as high as 60 amps at startup (locked rotor amps) and you will get more initial voltage drop and the unit may not start. I would consider a hard-start capacitor and I think you may also need to go up another wire size or two to allow for startup.

Info. on Coleman (for example) showing startup current here: Coleman

I can't see why using a step-up and step-down transformer won't work as long as it's all done correctly. But the cost of doing all of it could be more than the extra copper cost. May be worth pricing out tho. As said, aluminum could be an option but it needs to be one wire size larger to carry the equiv. current.

What is the voltage at your panel like and how stable is it? That could be something to take into account as well.

I couldn't find info. on what a hard start. cap. would do to the required wire size, but here is info. on Supco: Supco hard start caps.

It looks to me that you need min. #6 copper for 250'. It looks like #8 Cu would give you 96 volts at startup, if you started at 120 volts, and that's too low.

This info. indicates that starting voltage should not be less than 10% based on 115 volts which is 103.5V. Advent AC unit info.

[enblethen]

Calculations are based on only 10 amps.
Have you looked into small gauge URD(underground Rural Distribution) direct burial. Yes, it is aluminum but is must cheaper. Comes in various sizes. Here is an example. #6 URD

[pianotuna]

Hi Mex,

A roll of #4 would be verrrrrrrrrrrry pricey now. I know it would be best.

[pianotuna]

Hi w8,

Thanks for the calculations. 1.6 volts I could live with and no autoformer.

[MEXICOWANDERER]

There are other HOTEL loads involved. I was not pleased to have to purchase a 250' roll of 4 gauge wire. Lucky for me it was a different era and surplus wire was available. My connection site was in a boat yard 300' from the ocean. I was working on a 60' Chris Craft and did not have time to experiment. Anything smaller would have screwed me.

[mena661]

I use #10 for 100 ft runs and I have 122V at the end of the cord. In your case, I would use #8 to "make up" for a not so good source.