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extension cord info
Yahoo Message Number: 109534
Trying to choose the extension cords to carry? Maybe this will help.

I found an old Belden catalog and it has ratings in it for the “common” extension cords that they made. I checked the packaging on several at the local Wally World the other day, and the ratings match the old catalog. I think most of us throw away the package and use the cord. Some of us forget what was on the package… [] So I thought I’d post the information. Since the CFB code uses proportional fonts (and spacing), I can’t do a good table, but will try to make it readable.

The table is wire gauge, the length, the maximum current and the maximum wattage (they use 125 volts, the maximum voltage rating, to compute the wattage).

16 gauge, 25 or 50 feet, 13 amps, 1625 watts 16 gauge, 100 feet, 10 amps, 1250 watts

14 gauge, 25 or 50 feet, 15 amps, 1875 watts 14 gauge, 100 feet, 13 amps, 1625 watts

12 gauge, 25, 50 or 100 feet, 15 amps, 1875 watts

There is also a 10 gauge, 25 foot cable with the common household plugs that is rated at 15 amps being sold by RV supply places. The common plugs are ANSI/NEMA 5-15, and are rated for 15 amps maximum and thus the rating. The same cord with the TT-30 connectors (the common 30 amp RV connectors) is rated for 30 amps.
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Voltage drop in extension cords.

I decided to attempt to provide an estimate of the voltage drops in the various extension cords.
The reference data I’ve chosen may not exactly fit the cords, but the results should be pretty close. To do this, I got the resistance per 1,000 feet for each of the gauges from Table 8.
Conductor Properties, in Chapter 9 of my old 1993 NEC book. The resistance is for coated wires, 7 strands, at 75 degrees C, or 167 degrees F. I have calculated the voltage drop for 15 amps – in all cases – through 200 feet (100 feet for the hot lead, 100 feet for the neutral lead) of the gauge wire.

The “table” is wire size, resistance per 1,000 feet, voltage drop for 15 amps in 100 feet of extension cord.

16 gauge, 5.29 ohms, 15.9 volts

14 gauge, 3.14 ohms, 9.4 volts

12 gauge, 2.05 ohms, 6.0 volts

10 gauge, 1.29 ohms, 3.9 volts

8 gauge, 0.809 ohms, 2.4 volts

6 gauge, 0.510 ohms, 1.5 volts

Notes:

1. For a 50 foot cord, divide the voltage drop  will be half, for a 25 foot cord, one fourth.

2. 10 gauge wire is used in the cables in RV’s with 30 amp service.

3. 6 gauge wire is used in the cables in RV’s with 50 amp service.

4. This does not include any losses in the connectors on the cables.

5. The 15 amps exceeds the maximum current rating
 for the 100 foot 16 and 14 gauge cables.

I chose 15 amps as that is the approximate current of the 13,500 btu air conditioners – the one thing we are always trying to run when the electrical power is a problem and we’ve had to dig out extension cords.

This is only the voltage loss in the extension cord, and does not include the loss in the connectors and RV wiring.

I hope this helps in your choices.
Gini Free and Junah, canine xtrodinaire "Kooch" our little red home on wheels "Growing old is mandatory. Growing wise is optional."

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Gini Free and Junah, canine xtrodinaire
"CHERRYOTTE" our little red home on wheels
"Growing old is mandatory. Growing wise is optional."