Case Study #204: How To Determine Amperage for Heaters A customer called in and wanted to know what amperage he would be using on a machine with six heaters. The power supply was 460V, 3 phase power, and the heaters were wired in a delta configuration with 2 heaters on each branch. (See image below) To Determine the Amperage: 6 heaters ( R1 - R6 ) each at 230V, 1,000W The resistance of each heater is calculated using the following formula: R = V 2 / P So, the resistance of each heater equals 230 2 / 1,000 = 52.9O R1 = R2 = R3 = R4 = R5 = R6 = 52.9O Now, we wire two of these heaters in series between two legs of 460V, 3 phase power. Each leg looks like: In series, we can add resistances and simplify the circuit to look like this: Now, finding the current is easy. I = V / R

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