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

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pianotuna

Regina, SK, Canada

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Posted: 10/01/20 01:27pm Link  |  Quote  |  Print  |  Notify Moderator

It would be a good plan to monitor the voltage.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

valhalla360

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Posted: 10/01/20 01:27pm Link  |  Quote  |  Print  |  Notify Moderator

Old-Biscuit wrote:

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


Read thru my entire post...I clarified how the legs work. I was just clarifying that your post omitted the first part where 50amp is 240v but you get 2 legs at 120v.

But that wasn't the point.

The point is 120v is a nominal rating and it's not uncommon for the power at the outlet to be below the nominal rating. Power entering the house can be 5% below the nominal rating (about 114v) then from the breaker box to the outlet, you often have voltage loss due to wiring runs and connections. So it's not uncommon to find 110v (sometimes lower) at the outlets. Add on a 100ft extension cord and you can see very marginal voltage under load.


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valhalla360

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Posted: 10/01/20 01:31pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

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


Power company only has to worry about the connection up to the meter and they automatically get a 5% deduction and are still in spec. Plus if it's hot out and the whole community is running air/con full blast, they will shrug at your complaint that it's down to 110v entering the house. They aren't going to rebuild the power grid for an issue that happens 2-3 times per year.

Depending on load and internal voltage drop from the power meter to the outlet, you can easily lose a few more volts before considering voltage drop on the 100ft extension cord.

To the OP: You may have perfectly fine voltage and it might not be an issue. My point is to check and keep an eye on the voltage. Don't wait for the smell of a burnt out air/con unit to clue you in that you have a voltage issue.

rgatijnet1

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Posted: 10/01/20 01:34pm Link  |  Quote  |  Print  |  Notify Moderator

Voltage at an outlet can only be accurate if you are reading it while it is under the full load that you plan to use.

Acampingwewillgo

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Posted: 10/01/20 04:34pm Link  |  Quote  |  Print  |  Notify Moderator

Take the two cords you have in hand and measure the voltage. If it looks decent enough than purchase the remainder of needed cord. Measure voltage again. Unless you are using all available power( 100 amps) your going to be ok using #6 flexible cord for your needs. I'd just add to keep your eye on your in RV voltage while using the airs!


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Rick Jay

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Posted: 10/01/20 05:07pm Link  |  Quote  |  Print  |  Notify Moderator

supercub,

If I'm reading your post correctly, you only NEED to add 30' to what is already there to make the 100'. So the posts above about the weight of a 100' cable are not relevant. Your current cable is 30', so you already know what a 30' cable weighs. :-)

As far as being doable, in general, I would say yes. It DOES depend on the voltage at the house. If it's in the normal acceptable range, there shouldn't be any problem. However, if it's low (either due to power utility supply, poor or old wiring in the house or localized "brown-outs"), then you'll have to be watchful of the voltage.

You can purchase plug-in voltmeters you can plug into your RV to monitor the voltage when both ACs are needed. Get two and plug each one into an outlet on each leg of the supply.

Someone brought up the point that both ACs might be on the same leg. If that's the case, I would STRONGLY recommend that one of them be moved to the opposite leg. That way, when BOTH ACs are running, the current through the neutral wire will basically be ZERO for the ACs. So you won't have any cable heating with a heavy current down the neutral. If both ACs are on the same leg, the neutral current will be the COMBINED current of the two ACs. If they're on opposite legs, the neutral current will be the DIFFERENCE between the two ACs. Assuming the ACs are similar, then that would be about zero.

Perhaps that was too much info? Sorry if it was.

By the way, I've routinely used 70' of cable at my brother's house without any issue. My RV has a 30' cord and I added a 15' and 25' extension cord. Again, if the voltage is proper at the homestead, I don't think you'll have any problem.

Good Luck, and let us know how you make out!

~Rick


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Ivylog

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Posted: 10/02/20 05:43am Link  |  Quote  |  Print  |  Notify Moderator

I’m currently running one AC on a 100’ long #10 cord plugged into a 15A outlet. I routinely run 2 15K ACs on a 30A outlet...what the OP is wanting to do using a 50A cord. Each AC (15A) SHOULD be on its own leg of the 240V/50A ...even if both AC are on the same leg (easy enough to correct) it’s not going to be a problem. Another thing that only in the RV world do we worry about ...16A on a 50A wire.


This post is my opinion (free advice). It is not intended to influence anyone's judgment nor do I advocate anyone do what I propose.

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Bill.Satellite

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Posted: 10/02/20 08:35am Link  |  Quote  |  Print  |  Notify Moderator

I carry a 40 foot 50 amp cord as my main connection. I also carry 3 - 15 foot extension cords as I am sometimes a good distance from the power source. That's 85 feet with multiple junctions and I have run for more than a month with that setup. A direct 100 foot cable should perform even better. The cable uses 3 #6 and a #8 ground wire which I believe is pretty standard.


What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?

time2roll

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Posted: 10/02/20 09:47am Link  |  Quote  |  Print  |  Notify Moderator

valhalla360 wrote:

time2roll wrote:

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


Power company only has to worry about the connection up to the meter and they automatically get a 5% deduction and are still in spec. Plus if it's hot out and the whole community is running air/con full blast, they will shrug at your complaint that it's down to 110v entering the house. They aren't going to rebuild the power grid for an issue that happens 2-3 times per year.
I would still call and insist my connection to be checked in person if the main feed was consistently 220 volts or less.


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Flyfisherman128

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Posted: 10/03/20 01:22am Link  |  Quote  |  Print  |  Notify Moderator

By store bought you mean pre-made wire sections..My experience says if your running near 50amp the plugs will burn up first

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