Wattage Calculator for Hot Water Heater Elements

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sanders5x

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Does anyone know of a calculator for water heater elements? More specificly I have a 240V 4500Watt model and am wondering what it would take at 110V. I am also wondering if it would take different wattage at say 220v thanks.
 
V = IR, and P = IV. That's all you need to know.

4500W = I x 240V
I = 4500W / 240V = 18.75A

240V = 18.75A x R
R = 240V / 18.75A = 12.8 Ohms

220V = I x 12.8 Ohms
I = 220V / 12.8 Ohms = 17.1875A

P = 17.1875A x 220V = 3781.25W

Same math applies for 110V.
 
To skip a few steps and condense all Yuri's math down to a single equation for this particular case:
P=(V^2)/R
P2=P1*(V2^2)/(V1^2) where P1,V1 are the rated power & voltage (4500 &240), and V2 is the voltage you want to run it at.
P2=4500*(120^2)/(240^2)=1125W
 
I was working on my control box today:

box1.jpg


Anyone got a couple of feet of t-type thermocouple wire ?
 
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