Virtually all industrial power is generated as 3 Phase power. At the generating plant, it is generated as three phase power, because it is MUCH more economical to generate power as three phase. The power is then transmitted as three phase power. Just look at power transmission lines. You always see the lines in sets of three. Sometimes the heaters use all 3 phase voltages and sometimes they use one phase of the power. A single phase heater can run off of one of the phases of the 3 Phase power, connected either between two of the phases or between one of the phases and a neutral return path (0 Volts).
You want to build a band heater as a 3 Phase heater to reduce the current in the wires going to the heater. When you carry the power through three wires rather than the same power through two wires, the current is less. Why do you want the current to be less? Higher current requires larger wire which costs more. Also, failures frequently occur where connections are made and the higher the current in a connection, the greater the likelihood of a failure. Some of these connections are inside the heater.
Generally, you can start considering making the band heater a three phase heater when the total wattage gets in the range of 2000 watts. You probably should make the band heater a three phase heater when the wattage reaches 5000 watts and almost definitely be a three phase when the heater reaches 10,000 watts.
What happens sometimes is that someone is told that the heater will be running off of three phase power. That does not necessarily mean the heater has to be a three phase heater. All single phase power comes from three phase power. The question is how much is the current or wattage? In the heater we are talking about, the current is 700 W/480 v = 0.69 amps. Thus, even connecting the heater as a single phase heater, the current is 0.69 Amperes. This is just a little more than a 60 watt light bulb. Making this band heater a three phase heater would make the current even less. A three phase heater is more complex to build than a single phase heater. Thus, there are more things that can go wrong and it cost more. Why choose a heater that is more expensive and less reliable?
All power starts out as three phase power. Just because the power source is three phase does not mean the heater has to be a three phase heater. To answer the question, does the heater need to be three phase, look at the current or wattage. Don’t order a heater as a three phase unless it really needs to be one.
Written by Jim Dixon
Edited by Shelby Reece
Date Published: 10.30.2017
Last Updated: 09.06.2019