Rank: Senior Member Groups: Registered, Moderator Joined: 7/25/2009(UTC) Posts: 2,209
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WE START WITH A HEAT ELEMENT THAT IS 240 VOLTS AND 6000 WATTS. WE WILL USE FORMULAS INSTEAD OF AN OHMMETER TO CALCULATE THE RESISTANCE OF THE ELEMENT. There are more direct formulas available but let us work with the most common and easiest to manipulate.
FORMULA #1 the basic ohms law formula (((E=IXR))) E = Electromotivr force in (((VOLTS I = Current in (((AMPS)) R = Resistance in (((ohms)))
FORMULA # 2 the basic power/watts formula. (((P=IXE))) P = POWER IN (((WATTS)))-- I and E are defined in formula 1
OK NOW LETS FIGURE THE APROXIMATE current drawn by THE HEAT ELEMENT.-- ONCE WE HAVE THAT WE ARE IN THE HOME STRETCH
USING FORMULA #2-- P=IXE WE HAVE 6000=IX240 or I=6000/240 which equals 25 Then I=25 amps drawn at 240 volts applied to the heat element.
using formula 1 we can find the approximate resistance of the heat element E=IXR or 240=25xR so R=240/25=9.6 ohms of resistance
(((((PLEASE NOTE)))) that the resistance of the heat element does not change when diferent voltages are applied-- ((( AND )))__ You can apply 120 to a 240 element (((but ))) CAN NOT apply 220 volts to a 120 element.
(((((OK NOW LETS FIND OUT WHAT HAPPENS TO OUR 6000WATT 240 VOLT ELEMENT WHEN ONLY 120 VOLTS IS APPLIED
USING THE BASIC OHMS LAW FORMULA, WE CALCULATE E=IX9.6 OR 120VOLTS= I X 9.6 OHMS RESISTANCE OR 120/9.6=12.5 amps
(((( FINALLY WE HAVE ENOUGH INFORMATION TO CALCULATE THE WATTAGE OUTPUT DELIVERED AT 120 VOLTS
P IN WATTS = 12.5 AMPS X 120 VOLTS OR 12.5X 120 = 1500 WATTS OUTPUT
SO WHEN YOU APPLY 120 VOLTS TO A 240 VOLT ELEMENT, THE OUTPUT WATTAGE IS REDUCED TO 25% OF ITS RATED WATTAGE..
DO NOT APPLY 240 VOLTS TO AN ELEMENT RATED FOR 120 VOLTS
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