How long can you go on a 50 amp extension cord?

[supercub]

How long can you go on a store bought 50 extension cord? I need to run both AC's and lights TV etc, the normal things. Is 100 feet safe? or 75? or 50? or ? It's for a 38 ft Class A diesel.

Was able to measure this morning, total length will be 100. My cord in the motorhome is about 30 ft. My brother in law, already has 40 length to his trailer, which I'll unplug from his trailer that is in storage and plug into that. So I need to get a 30 foot extension, for a total of 100 feet. Yes, I have a surge protector at the motor home too.

[time2roll]

If you only see 220 at the outlet with no load in a single family home it is time to call the power company.

Real continuous load is probably closer to 20 or 25 amps max for those voltage drop calculations.

[Old-Biscuit]

valhalla360 wrote:

Old-Biscuit wrote:
100' with 50A #6 power cord 40A load will have roughly a 3-4 Volt drop from source to RV
120VAC....116/117VAC

You are assuming the house has good strong voltage and it won't sag under heavy load (and you are thinking 120v when a 50amp is 240v)

If the outlet is 50am, it should be 240V but don't be surprised to see 220v at the outlet.

At 220v, 20amp per leg jumps to around 22amps per leg (assuming the air/con units are on separate legs). So each leg sees 22amp @ 110v at the outlet and with voltage drop around 108v at the RV.

That's marginal for me where I start considering if should deploy the voltage booster or break out the generator.

If for some reason both air/con units are on the same leg, the amps doubles on that leg and voltage drop results in around 106v.

This ignores bad connections or issues with the wiring in the house, so you could easily lose another 2-3 volts in real life.

It's only 240VAC if you measure voltage across BOTH Hot Legs
Each Leg is 120VAC rated for 50 amps
Each leg feeds 1/2 of RV Main AC Panel Buss
40A on one leg will drop 120VAC down to roughly 116/117 VAC
Each leg can handle that amp load w/o issue

240VAC only comes into play IF the RV has a 240VAC appliance which very few have such appliances

[DrewE]

BB_TX wrote:

supercub wrote:
.......
I'm trying to plug into a house with 50 amp plug. Thanks

I hope this is a 50 amp plug wired for an RV and not a 50 amp dryer plug.

A 50A four wire range socket is exactly the same as a 50A RV socket. They're both standard NEMA 14-50 connectors. If it's an older three wire socket, they're physically incompatible since the socket has fewer connections than the plug.

Electric dryer circuits are usually 30A circuits. The main problem for RV sockets being mistaken/miswired are with 30A RV connections, which are superficially similar to the older 3 wire 30A dryer connections but wired quite differently, with 120V rather than 240V service.

[joelc]

I have gone with the cord that came with my unit and an extension. ?? 50'. I do not remember the formula for voltage drop, but you should be okay. Do you have a surge/EMS protector? This might assist.

[BB_TX]

supercub wrote:
.......
I'm trying to plug into a house with 50 amp plug. Thanks

I hope this is a 50 amp plug wired for an RV and not a 50 amp dryer plug.

[wa8yxm]

With most things electrical it is like the Senior answer to the question "Boxers or Briefs"
The youngsters said "Briefs"
The middle aged said "Boxers"
The seniors "Depends".

Now the 50 amp cord is designed to carry 50 amps for, based on the wire size, about 100 feet if I'm not mistaken.

But not many motor homes pull the full 50 amps on either leg. Usually around 30 is peak load

50 amps round trip on one leg 100' takes 4ga wire
but 30 amps takes 6

This calculator may be a bit confusing espically at 50 amps because you use every amp in the less loaded leg twice. (IE if one leg is 30 amp and one is 20 the effect is to reduce voltage drop.

[valhalla360]

Old-Biscuit wrote:
100' with 50A #6 power cord 40A load will have roughly a 3-4 Volt drop from source to RV
120VAC....116/117VAC

You are assuming the house has good strong voltage and it won't sag under heavy load (and you are thinking 120v when a 50amp is 240v)

If the outlet is 50am, it should be 240V but don't be surprised to see 220v at the outlet.

At 220v, 20amp per leg jumps to around 22amps per leg (assuming the air/con units are on separate legs). So each leg sees 22amp @ 110v at the outlet and with voltage drop around 108v at the RV.

That's marginal for me where I start considering if should deploy the voltage booster or break out the generator.

If for some reason both air/con units are on the same leg, the amps doubles on that leg and voltage drop results in around 106v.

This ignores bad connections or issues with the wiring in the house, so you could easily lose another 2-3 volts in real life.

[theoldwizard1]

FYI - 100' of 6/4 SOOW would weigh close to 70 lbs and the cord alone (no ends) would cost about $275.

[Old-Biscuit]

100' with 50A #6 power cord 40A load will have roughly a 3-4 Volt drop from source to RV
120VAC....116/117VAC

[time2roll]

100' is fine. If you will be in this place often I would consider making a custom cord of the correct length.

[wopachop]

supercub wrote:

I'm trying to plug into a house with 50 amp plug. Thanks

Have someone measure the distance. Every 25 feet makes a big difference.

Even if someone was to count steps that would be just fine for an estimate.

After you post that distance number people can tell you what size wire you need.

[Ed_Gee]

I see no reason whatsoever why you can't run your RV on a 100' 50A extension ..... but do you have any idea how heavy that is going to be? I believe 50A cable is 6AWG. That is going to weigh a ton! I built a 100' 30A cable for my previous ClassA.....out of 10AWG cable from Home Depot....worked great but a bit of a pain to coil up and store.... A properly sized 50A cable is going to be a lot worse.......but again, yes, it will work fine.

[supercub]

I've rebuilt 5 Cubs over the years and Yes, one was a Super Cub. Sold it a few years back. I'm just almost finished rebuilding a J-3 that I'm converting to a PA-11.

[wopachop]

Do you fly the real supercub??
I learned to fly RC on the fake supercub.

[pianotuna]

Rich,

It depends more on the size of the wire.

SuperCub the entire run from the house panel to the RV needs to be considered. There are tables and voltage drop calculators that would give you a good idea of how thick the wire would need to be.

https://www.southwire.com/calculator-vdrop