[boead]

Voltage drop over distance, I believe.

I just put an RV on a piece of property I own. I also had a new electric poll and service installed. New large breaker box with a 30amp outlet.
The RV has a 50amp, 25 foot cord out the back. 50 amps because it has the option for a Wash/Dryer but none ever installed. Internal breaker box has just a few 15 amp breakers to regular outlets. Since RVs generally only need 30amp service, a 50 to 30 amp adapter is included.

The electric poll is a good 75 feet from the RV. In the spring time when the ground thaws out I’m installing a full 50amp service underground close to the RV but in the mean time I bought an Extreme temp 10 gauge cord from Home Depot (100 feet), cut off the male end and put on a 30 amp plug for the outlet on the poll. The other side has an adapter I bought that converts the 50amp plug to a standard 15amp one which is plugged into the 10 gauge cord so there is a total of 125 feet of wire from the poll to the RV’s breaker box.
Voltage is only about 104 with a relatively light load on it; that’s (2) 1500w heaters, a few light bulbs and a couple of small TV’s, a DVD player and VCR. That’s it.
I bought a female 50amp connector and was planning on installing it on the 10 gauge cord and reduce the length some, maybe to 60 feet plus the RV’s 25 foot cord.

Will that help increase the voltage? Or will I have to increase the wire gauge?

[Wayner]

The 2 heaters at 1500w each, puts you at 25 amps already. A few light bulbs (60 watt?) and the other devices may suck up another 2 amps. Now, with your long length and a measuerd voltage of 104, the new equation just for the heaters is 3,000/104 = 28.8 amps. So your voltage drop is increasing your cable amperage.

Now here is another problem. Dryers run on 240 volts, so how is that working out. Unless you re-wired your RV's cord for just 120 volt, I just don't understand what you have done, unless you are running 240 out there from the pole, or maybe I misunderstood you, did you rewire the plug of the RV unit?

Anyway, yeah, you are right on the boarder with the cord gauge, lenght and the colder temperature. I would go up to 8 awg. Your voltage and amperage will have a teeter-toter effect at any rate. Voltage goes down, amperage goes up. Also, some 10 awg cables are only rated for 25 amps, so you could be over.

Wayner

[boead]

Thanks Wayner. I know i need to bring a bigger service into the RV. It wants 240 but until I can run a proper line in the spring I have to survive on 120 service like you do at most trailer stops. There is NO dryer or washer thank goodness.
I didn’t expect the voltage drop but usually you aren’t using an extension cord that large, the RVs built in (hard wired) 25' cord is normally plugged right into an outlet. Sometimes you use a short 25' extension but im using a 100' extension. I wonder if trimming it down to 75’ would make a difference?
When im going to do in the mean time is bring over an outdoor extension cord from a second but smaller 20amp 110 outlet I also have on the poll (its got ground fault protection too) into the RV and just run a single heater on it, take it off the main line and free up some power. I can also choose to run a third electric heater, its been down to around 5f these past few weeks.

[jules]

Hi boead,

if you're getting a 6V drop with a 100' cord @ 30 amps it indicates the resistance of the cord is 0.2ohm. The formula is voltage drop = resistance X current.

From this you can figure out that if you're using 20 amps the drop will be 4V. [resistance remains the same and drop = 0.2 X 20, = 4

If you reduce the length of the cord to 75' you'll reduce the voltage loss to a bit over 5V with a 30 amp draw.

Of course the above assumes that the voltage delivered to the power pole is 110V and that might not be the case. The other key unknown is what rated current the power company delivers to your pole. If they guarantee say, no more than a 2V drop for 50 amps at the pole you're in rather a different position than if they only guarantee or deliver a 4V drop for 50 amps. I have no idea what the standards are for your electrical supply though so maybe Wayner can give you the full picture here, including the temperature factor which is both beyond my experience and startlingly cold at the same time.

jules

[JakeJ]

Great advise so far, guys.

I would also like to add you might want to check each mechanical contact point (plugs) between the RV and the utility pole.  You want to make sure they have good contact and a hot plug will indicate a problem.  Also having the wire as short as possible is always best and like Wayner I'd be more comfortable with a larger size wire

Be safe,
Jake