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In HVAC VFDs, Is 2-Contactor Bypass Really Better than 3-Contactor Bypass?

Feb 20, 2019

Much has been made in the ongoing debate about the merits of 2-contactor bypass and 3-contactor bypass since the 1990s. Figure 1 shows diagrams depicting 2-contactor bypass with fuses, 2-contactor bypass with service switch, and 3-contactor bypass configurations. Back and forth VFD manufacturer salesmen go, jockeying for customers — whether it be to retain their own or to steal them away from the competition. Until now, nobody has seen the debate for what it really is — a more technical (and not to mention much less entertaining) version of, “Tastes great! Less filling!” If you’re shaking your head right now, I’m not surprised.

Over the next few minutes, we’re going to address the two major claims that have been floating around out there for decades, to clear the waters, air, and whatever else needs clearing once and for all on who the winner of this great debate (no, not the fun one) really is. We will expose just the facts, and ONLY the facts. You’ll want to freshen up your coffee and make sure you’re comfortable in your chair as you read this piece through to its exciting conclusion.

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