Extension cord length

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Beardog

Beardog

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Nov 1, 2008
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We have a 50 Amp outlet on the side of our house, but can only get our motorhome within about 75 feet of the outlet. I have a 20 ft., 50 amp cord on a power reel, and a 30 ft. extension cord. Will we have too much voltage drop if we add another 30 ft. extension cord? I have a fifty foot 30 amp cord, too, but there may be times that we will need all fifty amps, like over the holidays, when we stay out in the motorhome for several nights,, and relatives are filling our house.

Thanks for any advice!!
 
Measure the voltage at the motorhome's main load center with your current 30A extension in use to reach the outlet. If it is above about 112v, you should be OK using multiple 50A cords.  If it is around 110, it might be barely ok but any less is likely to be real trouble.

You aren't likely to find a 30 foot 50A extension - they are pricey so there isn't much market for them. Have one made or do it yourself. Or use three 20 footers (but each connection is another source of voltage drop).
 
This discussion could get complicated..... but to put it simply: You want to have the least voltage drop possible at the Motorhome end of the connection. The problem will be finding a 30' extension cord that will be rated for 50 Amps at 75'. The three things to be considered are the wire AWG (guage), the total length, and the number/quailty of any connections . A #4 AWG 75 foot run @ 50 Amps would give you about 2 volts of drop (6 AWG gets you 3 and 8 AWG gets you 5), this does not include any intermidiate connections. A less than perfect connection (plug) will cause a certian amount of voltage drop at the connection and will heat up. How much heat? That could be the bad part. The two recomendations I would make are: Don't plug two smaller extensions together to get your length, have a special extension cable made for the entire length from the Motorhome to the outlet OR Have a Master Electrician (some one who knows what he is doing) come and wire a 50 AMP outlet closer to the locaton of your Motorhome so you can plug into it directly.
 
Thanks for the quick answers! It sounds like my options are to try three cords and measure the voltage drop at my motorhome, or have 4 AWG cord made. Running a 50 amp outlet closer to my motorhome would be difficult, because of needing to cross multiple sprinkler system pipes/wires, and our septic system.
 
As Roamer said, Hook up a volt meter in the rig, only way to be sure

However here is a guidline.. If you are running one A/C you will be good.  One A/C and the water heater, you should be good  Two A/C's no water heater you should be good. Everything in the house (Water heaters, converters with dead batteries, television and sat receiver, every light in the place on, Both A/C's or two space heaters,  You I suspect you are hitting 50/50 on odds of being good... Those are really good odds if you have a volt meter in place

Here is another question: How big is the generator on your coach.. IF, like me, you have an Onan 5500  (or equivlent) you will be good  iF you have 10,000 watts or more.. You will be marginal with EVERYTHING running.
 
The voltage drop is not real important as long as you end up with enough volts at the motorhome and that voltage holds up under typical loads. Your appliances are designed to run at 110-125vac and the pumps and compressors will suffer if voltage drops below 108 under full load.  For example, power line monitoring systems usually shut down the power if it drops below 106 vac.

A standard 50A power cord or extension is 8 gauge wire. Coupling two 30 foot extensions to your 20 foot shore cord is stretching it a bit on 8 ga, but if the voltage at the source is high enough you should be OK at the other end. Keep an eye (and a finger) on the connections (plugs) to make sure none of them are getting hot. A little warm is OK, but not hot.
 
If you have an IR thermometer, anything less than 120 F is OK.  Probably up to about 150 but that depends on the quality and type of cord and should only be done if you have direct knowledge of this.
 
120 degrees feels quite hot to the touch - many people would consider it "burning hot". The hot water coming from your tap rarely is that hot, even after running a while.
 
When designing for controls, 120 F is the "ouch" temperature for most people but is not hot for electronics and wiring where most are good to about 160 to 180 F at the actual item like the cable connector.  I know most people get worried when electronics is hot to the touch but not to worry if you can still touch it with out sizzle!!.  VBG
 
Another consideration would be to use an Autoformer in addition to the extn cords.  It would provide a boost making up for the IR drops in the cords.  A bit expensive, but then you would have it on the road too.  Camping world has one http://www.campingworld.com/shopping/product/autoformers/3251
 
I split off the ensuing autoformer discussion into its own topic here.
 
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