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From: LYN Williams (no email)
Date: Sat Mar 03 2001 - 16:51:13 EST
George Geist wrote:
>
> Mr. Ohms is spinning in his grave <smile>
> A resistive load rated at 1500 Watts 240 Volts, but used at only120
> Volts will draw about one quarter or some 375 Watts.
George, you are correct and my fast mental math was in error about the
final wattage. However, the question of whether it would be too slow
or not must be answered by the user who has the need.
To look at the problem again, we can determine that the resistance
required to draw 900 watts at 120 volts is R=120*120/900 = 16 ohms.
Now to find a water heater which would have a 16 ohm resistance and
would normally operate on 240 volts, the power rating at 240 volts
would be P = 240 * 240/16 = 3600 watts. Calling LOWES and asking
whether they have a water heater which draws 3600 watts, I was told
that their item number 14041 is a mobile home water heater which
requires 3500 watts at 240 volts. Given this wattage, it would have a
resistance R = 240 * 240/3500 = 16.457 ohms. Using this heater on the
120 volt generator would cause it to draw P = 120 * 120/16.457 = 875
watts, which would be within the rating of the generator. By looking
around some, perhaps a more suitable heater could be found. (This one,
at 30 gallons, might be too large.)
Thanks for correcting my mistake, George. This discussion illustrates
the technique and math for others to use if desired.
Rob also has a good point - there are other ways to get hot water.
I was basically answering a specific question without thought as to
whether the inquirer might be satisfied some other way.
Lyn
THE AWAY TEAM
L
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