Split-Phase vs. 3-Phase - Short #253

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 19 August 2025

⏱️ 12 minutes

🔗️ Recording | iTunes | RSS

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Summary

In this short podcast episode, Bryan breaks down the differences between split-phase and 3-phase power in HVAC systems. Split-phase is a form of single-phase power, and it's common in residential HVAC. Three-phase power is more common in commercial and industrial applications.

Single-phase power uses only one of the three phases of power produced by the power company. When there is a neutral and two sides of 120V power, that is split-phase power. Transformers on power poles for residential service only have one line going into them (and only one sine wave). That power gets stepped down to ~240V. Most household appliances and electronics we use are rated for 120V or 240V power.

However, we use split-phase power by tapping the center of the transformer secondary; there are two 120V halves. We can see the "differences" between split-phase and single-phase power with an oscilloscope. These halves may look like two different sine waves if we use neutral as a reference, but an oscilloscope will only show one 240V sine wave from leg to leg (without neutral). Therefore, split-phase power really is just single-phase power with a center reference point, and split-phase power doesn't matter to the HVAC unit.

We get three-phase power when all three phases of power come in from the utility, not just one. Each individual phase is 120V, and all three can make up 208V power because the phases are 120 degrees out of phase.

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Transcript

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0:00.0	Zippity Zap. This is the HVAC school podcast. I'm Brian. And this is the podcast where we do short episodes sometimes and talk about things that you forgot along the way. Maybe some things you forgot to know in the first place. And today we're talking about single phase and three phase. I've talked about this a lot. So this is not new content, really,
0:23.7	maybe just a little bit of a new take, but it's one of the really commonly confused areas.
0:29.0	And it's one of the areas for resetexts, if they want to better understand, not only what they see,
0:34.9	but also what they're going to see if they start working on three phase.
0:38.3	This is a helpful, I don't want to say first step, but one of the first steps in understanding
0:42.1	it.
0:42.7	But before that, we want to thank our great sponsors.
0:46.3	Carrier and Carrier.com.
0:48.4	Fieldpiece.
0:49.7	Fieldpeace.com.
0:51.5	Our friends over at UEI at UEI test.com.
0:56.3	Refrigeration technologies at refrigetec.com and specifically the new Viper Wetrag
1:01.9	Heat Shield, the revolutionary flame-resistant welding pad designed to be used either wet or dry.
1:10.0	Find a Viper wet-rag heat shield at a distributor near you or go to TrueTechT wet or dry. Find a viper wet rag heat shield at a distributor near you
1:12.4	or go to TrueTechTools.com
1:15.0	and use offer code, get schooled for a great discount at checkout.
1:20.4	All right, so what is split phase?
1:22.6	What is split phase?
1:23.8	It is actually single phase.
1:25.1	So when we say split phase or we say single phase,
1:27.2	we really are saying the same thing because both split phase and single phase are single phase. Now, not all single phase is split phase. And that's especially true in other countries where they have single phase power, but they do not necessarily split it the way that we do here. So single phase is typically seen in residential.
1:45.8	That's essentially the only place you see it. And then three phase you're going to see in
	...

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