When choosing your transfer switch, a less understood factor is how many poles you need. A pole is a discrete switching position on the contactor where the utility, generator and load can be connected for one lead.
2-Pole
A 2-pole switch has two hot wires coming into it for 120/240 single phase. This also is a solid neutral design – the utility, generator and building neutral are permanently connected.
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3-Pole
A 3-pole switch has three hot wires coming into it for 120/208, 120/240, 277/480, and 346/600 three phase. This is also has a solid neutral design – the utility, generator and building neutral are permanently connected.
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3-Pole Switched Neutral
A 3-pole switch has two hot wires coming into it for 120/240 single phase plus an additional pole for the neutral. A switched neutral will only allow the utility or the generator neutral to be connected to the building at a time.
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4-Pole Switched Neutral
A 4-pole switch has two hot wires coming into it for 120/208, 120/240, 277/480, and 347/600 three phase, plus an additional pole for the neutral. A switched neutral will only allow the utility or the generator neutral to be connected to the building at a time.
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