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Tuesday, September 27, 2011

Understanding Wattage and Voltages of Electric Infrared Radiant Heaters

The question has been asked of me if a higher voltage unit uses less power.  Specifically, if the CeramiCercuit Flat panel electric radiant heater model 945C would use less power if configured at 240 volts than at 120 volts.

First, wattage…. The 945C uses 1000 watts and the 1445C uses 1500 watts.  The level of power is the same in wattage regardless of the voltage.  If 1000 watts comes through a 120 volt circuit (the wiring in your home or office) it is the same as if the 1000 watts were coming through a 240 circuit.  Watts is watts.

Now voltage…. The load coming in through the circuit is measured in amps.  The circuit is configured or wired by voltage.
If the circuit is wired for 120 volts the amp load is 8.3 for the 1000 watt unit and 12.5 for the 1500 watt unit.
If the circuit is 240 volts the amp load is 4.16 for the 1000 watt unit and 6.25 for the 1500 watt unit. 

As you can see, when the voltage in the wiring of the circuit goes up the amps drawn by the unit comes down. 
Let’s say the voltage of the circuit was 480 volts….the 1000 watt unit would draw 2 amps and the 1500 watt unit would draw 3.1 amps. 

A higher voltage circuit can accommodate more amp load.  That load is limited by the total amp load of the circuit.  That is what a circuit breaker does (or a fuse).  If the load goes over the max, the circuit breaks flips off or the fuse blows and needs replaced.  If the circuits maximum load is 30 amps, then the most you could put on the circuit is about 27 amps… always want a little less than the circuit can handle. 

To calculate total load of all of your units on any one circuit you figure out the wattage of the unit and the voltage of the circuit to get amps and then multiply the number of units by those amps.  Example, on a 120 voltage circuit a 945C unit pulling 1000 watts draws 8.3 amps.   Three of those units on that same circuit will draw 24.9 amps (3 units x 8.3 amps).  If the circuits max load is 30 amps, you’d stop with three units because one more unit will go over the 30 amp max load for the circuit.

Another example….  a 945C unit on a 240 volts circuit draws 4.16 amps.  If the 240 circuit has a 30 amp max load then 6, maybe 7, units can go on that circuit.  If the same circuit is 120 volts then only 3 of the 945C units could go on it.  In this example the max load of the circuit is the same, 30 amps.  The reason more units can go on a 240 volt circuit is because 240 volts lowers the amps drawn by the unit allowing more units to be on that circuit.  The units wattages remains the same, but the amps drawn by that wattage decrease as the voltage of the circuit increases.  So if the voltage of the circuit was 480 volts the amps drawn would really drop allowing for even more units to go on that circuit before maxing out the max load of 30 amps.

The higher the voltage of the circuit the lower the amp draw.  As the amp draw lowers more load can be put on a circuit.  There isn’t so much an efficiency of power with higher voltage as much as there is efficiency in the circuit.  With higher voltage more load can be on the circuit.

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