Front Page  Johanson DMS, Inc.  Product Descriptions  Stock Heaters
Useful Formulas  Ordering Information
 Therm. Cond. of Materials
Johnson DMS, Inc. 
Design Hints  If the Volts and Watts are known, find the resistance in ohms, and browse the stock heater table that was sorted by ohms values. Then select some possible sizes to fit the application. Cutting Watts by Half  The use of a properly rated diode in line would halve the power (watts) when used with AC voltage. Doubling Voltage  The power is increased four times the original value then the voltage is doubled. 
SOME USEFUL FORMULAS  

VALUE ASSIGNMENTS 

POWER FORMULAS P=I^{2} R P=E * I P=E^{2} / R 
CURRENT FORMULAS I = E / R I = P / R 
DELTA CONNECTION I _{LINE} = I _{LEG} * 3 E _{LINE} = E _{LEG} P _{LEG} = P _{TOTAL} / 3 P _{LEG} / (E _{LINE} OR E _{LEG}) = I _{LEG} E _{LEG} / I _{LEG} = R _{LEG} 
RESISTANCE FORMULAS R = E / I R = P / I^{2} R = E^{2} / P 
RESISTORS IN SERIES R_{S} = R_{1} + R_{2} + R_{3} 

VOLTAGE FORMULAS E = I * R E = P * R 
RESISTORS IN PARALLEL R_{P} = (R1 * R2) / (R1 + R2) 
WYE OR "Y" CONNECTION I _{LINE} = I _{LEG} E _{LEG} = E _{TOTAL} / 3 I _{LEG} = P _{LEG} / E _{LEG} R _{LEG} = E _{LEG} / I _{LEG} 
More useful electrical formulas  

Watts = Current X Voltage  Degree C = (F32 X 5/9 
Watts = (Voltage X Voltage) divided by Resistance (Ohms)  Degrees F = (C X 9/5) + 32 
Watts = (Current X Current) X Resistance  
Warmup Watts (Watt Hours) req'd = C x M x (T2T1) x .293  
Voltage = Current X Resistance (Ohms)  where C = specific heat of mat'l, M = mass in lbs. 
Current = Voltage divided by Resistance (Ohms)  T2 = ending temperature, T1 = starting temperature 
Resistance (Ohms) = Voltage divided by Current 
Front Page  Johanson DMS, Inc.  Product Descriptions
 Stock Heaters
Useful Formulas  Ordering Information
 Therm. Cond. of Materials