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Quick Hot Water Heater question #177490 05/04/08 05:36 PM
Joined: Mar 2004
Posts: 193
G
GA76JW Offline OP
Member
One of my buddies from school was doing some work at his uncle's house and called me with a question.

Apparently someone had wired the Hot water Heater through a nearby receptacle. The water heater is 208/240 and the receptacle is 120.

My understanding of it is the element will still work, just at half capacity. Is this incorrect?

He is currently correcting it. I just wanted to hear some opinions on the matter.


"If common sense was common, everyone would have it"-not sure, someone here

Work Gear for Electricians and the Trades
Re: Quick Hot Water Heater question [Re: GA76JW] #177491 05/04/08 05:49 PM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
One-quarter the heat.

Re: Quick Hot Water Heater question [Re: twh] #177493 05/04/08 07:04 PM
Joined: Mar 2004
Posts: 193
G
GA76JW Offline OP
Member
Originally Posted by twh
One-quarter the heat.



Could you throw some theory at me to show how that happens?


"If common sense was common, everyone would have it"-not sure, someone here

Re: Quick Hot Water Heater question [Re: GA76JW] #177497 05/04/08 07:18 PM
Joined: Jul 2004
Posts: 9,540
G
gfretwell Offline
Member
Resistance is fixed. Amps is volts divided by resistance. Watts is amps times volts.
Notice volts figures in both equations and one feeds the next so volts gets used twice. Twice the volts is twice the amps and that is again multiplied by volts.
The power formula sums it up with watts equals the square of the volts times the resistance (P=I2R)


Greg Fretwell
Re: Quick Hot Water Heater question [Re: GA76JW] #177498 05/04/08 07:20 PM
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
At 240 volts and a 24 ohm element:
E = I x R
240 = I x 24
10 = I

W = E X I
W = 240 X 10
W = 2400

At 120 Volts and a 24 ohm element:
E = I x R
120 = I x 24
5 = I

W = E x I
W = 120 x 5
W = 600

Or .5 of the voltage x .5 of the current = .25 of the watts.

Re: Quick Hot Water Heater question [Re: twh] #177521 05/05/08 03:28 PM
Joined: Mar 2004
Posts: 193
G
GA76JW Offline OP
Member
Thanks for clearing that up guys.

It makes more sense now that you threw the numbers up.


"If common sense was common, everyone would have it"-not sure, someone here


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