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Welcome to the future, technologies and innovations that sculpt our industry.

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This session was recorded live at the 2023 National HVACR Education Conference.

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To learn more about MyDIA, visit mydia.com.

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All right, Kyle Hunter from MyDIA.

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Thank you so much for joining us today.

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So let's talk a little bit about inverter technology.

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Inverter is one of my passions.

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We spend a lot of time talking about incentives that will be coming way for contractors and

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homeowners hopefully through things like IRA, and really investing in the electrification

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of America.

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So in that, as technicians, we have a lot to learn.

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We have a lot to understand.

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In our educational programs, many of us end up in training that really haven't dove into

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inverter technology a lot.

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And man, we've had a great conversation about inverters.

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So let's talk a little bit about operational conditions inside of an inverter.

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What's happening outside?

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We have a lot of thoughts, but let's talk about what's actually happening in our outdoor

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unit.

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So the inverter is not a magic box.

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It's not something that you just have to accept what's going on and just go, oh, it's doing

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its job because the compressor's running.

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What job is it doing?

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And really, the inverter is just an old term that a lot of people understand as a frequency

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drive.

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Variable frequency.

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And that's exactly what we're doing with an inverter is changing the frequency.

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Because if you understand motor drives and how many poles or winding sets a motor has,

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that sets your speed of your motor.

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So if you have a two pole bathroom fan hooked to 60 hertz, it's going to run at a potentially

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set speed of 3,600.

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You have drag, you have load that will never reach 3,600.

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But that's the potential.

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That's the max potential.

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And so what the inverter does is it takes that 60 hertz and it will just take it and

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modulate the speed.

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And on all the inverters, you have a three phase motor hooked to a single phase source,

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for the most part, residential single phase.

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And so you have that single phase source.

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You have only 60 hertz.

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You can take that, sorry, 230 volts and you rectify it with diodes.

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And that's the first phase of an inverter is a rectifier.

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It takes the 230, rectifies it optimally to 310 volts DC.

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Exactly.

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310 volts DC through some capacitors and what's called a reactor to kind of clip and make

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the voltage as clean and flat as possible.

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And then you have these gates, switches, switches basically, IGBTs, insulated gate, bipolar

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transformers, transistors, sorry.

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And all they're doing is turning off and on at a set speed.

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And that set speed when you have your DC positive and your DC negative, you turn on the positive

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gate, you turn on a negative gate, you have a circuit.

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And then you flip them and the same gates, you flip them and now you have your positive

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below and your negative on top and you create a sine wave.

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So you just alternate up and down on those insulated gate transformers and you can create

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a sine wave.

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Exactly.

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So it's a simulated sine wave.

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It's a simulated sine wave.

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You don't just turn on and off.

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These transformers, they're time-based transistors.

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That's right.

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They're time-based.

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So the longer they stay on, the more voltage is allowed to pass.

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And you can also turn them on a little bit.

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You apply smaller voltage, you get some leak through.

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You apply full voltage, you get the full 310 volts.

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So you can stagger them on.

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So you go slight voltage, a little bit higher, a little bit higher.

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You get that nice slow opening and then you have your nice slow closing and you alternate

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that.

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And then you have your nice smooth sine wave instead of a square sine wave.

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Because that's when we first had them, that's what we had.

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We had slower processors.

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And so we can only do on and off.

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And the speed of our transistors, our processors dictated that.

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Now we have faster and better electronic components.

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And we can go a lot quicker stages.

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So we have that nice smooth sine wave.

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You get six of these sets, you get your three phase.

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And so on a motor, on a compressor, you have U, V, and W.

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Our three phases.

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You have a U positive and you have a U negative, IGBT on the board.

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You have a V positive, V negative, W positive, W negative.

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And so it just alternates those, gets your speed, gets your voltage, also is modulated.

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So that way when you're running at a slower speed, you have the right amount of voltage

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to still have the proper torque.

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And so it just doing that, it's not sci-fi.

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It's just something new.

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It's something new.

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Absolutely.

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And testing a compressor is no different than testing a three phase system blower.

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If you have a big three phase motor, three phase pump, three phase anything that you've

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...

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Same resistance between windings.

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... 20, 30 years ago, you just ohm out your windings on most compressors.

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They're very low resistance.

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Hardly ever over two ohms.

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And the key is, I don't care what the resistance is.

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I don't have it specked out on any of my products, as long as they're the same.

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As long as they're the same.

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We're running identically.

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Yeah.

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So you disconnect off the terminals, you ohm them out.

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U, V, W, three readings under two ohms and matching, compressor's good.

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Absolutely.

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Let's say, let's just talk about, let's say a ductless mini split for a minute.

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Right?

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I love those.

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Oh, I bet you do.

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I know that's why we're having this conversation.

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You're a very intriguing person and I love talking to you about this because you have

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a very good way of simplifying the operation of a ductless mini split.

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So let's think about the primary components of our outdoor unit and let's visualize, let's

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mentally visualize how each of these components are operating, how they're responding.

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So you have your compressor, you have your outdoor fan motor, and your other load that

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a lot of people don't think about is your expansion valve.

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Yeah.

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So you have your mini split, those expansion valves, your metering devices on the outdoor

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unit.

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So everything's outside and those three units, those three components are really isolated

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components doing their own thing.

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Absolutely.

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You have your compressor, your compressor's responsibility is of course pump refrigerant

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throughout the system.

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And its happy point is a cool shell.

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Right.

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It wants to stay cool.

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So the hotter the load inside, the hotter refrigerant coming back to the compressor.

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So it's going to run faster to get cool refrigerant back to itself to stay cool.

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And that's all that compressor speed is doing.

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I know, it's kind of crazy.

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I'm simplifying it.

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Yeah, no, no, no.

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This is what we want.

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True.

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It is a very, it might be over simplification, but that is in the logic.

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The compressor speed is really dictated by how hot the compressor is.

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It doesn't care about the indoor temperature.

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It knows the indoor temperature because of how hot the refrigerant coming back is.

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Yeah.

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It's not the thermostat telling it how fast to run.

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Exactly.

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Big misconception in the industry.

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It's your discharge sensor on your compressor.

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It wants to stay cool.

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It stays cool by speeding up.

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Right.

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And then pumping more refrigerant through the pump.

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And then your outdoor fan motor is variable speed as well.

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And it's going to try to keep a certain temperature.

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So that way your saturation levels are proper coming out.

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Exactly.

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And so that's going to speed up and slow down depending on...

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Based on the temperature of the coil.

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Exactly.

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So low charge is going to cause the fan to go slow.

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It's not going to go faster.

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It wants to build up the heat.

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And if there's not enough refrigerant in the system, the fan's going to slow down to build

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up the heat.

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Okay.

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So the fan can be running at a disproportional speed of the compressor.

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And it's because they're running fairly isolated from each other.

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So and then you have your expansion valve.

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Your expansion valve is really looking at the temperature of the return and the temperature

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of the supply of your refrigerant.

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And so it's going to modulate.

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It's going to open and close.

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Do what a metering device likes to do.

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It's going to try to keep that calculated superheat.

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It does exactly what every metering device has ever done.

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And the odd thing is it's in the outdoors.

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So technically from your service port back to the service port, that is your evaporator.

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And that's why it's critical.

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The entire system.

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That's why you insulate both lines.

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Yeah.

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You want to minimize your heat loss from your outdoor unit back.

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And so the expansion valve is going to open and close to keep that temperature.

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Right.

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And so those three components working in concert with each other, trying to maintain a harmonic

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cooperative system.

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And so if you run into a charge issue, your compressor is going to go faster because it's

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going to get hot.

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And your amp draw might drop because the load goes away.

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Your expansion valve is going to open up too far because the temperature difference is

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not going to be there.

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So your expansion valve is going to start going to open almost full.

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Your fan, outdoor fan, is going to slow down because there's no refrigerant to build heat

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on the coils.

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And so one thing that's really nice with some diagnostic tools, you can see those three

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components.

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Right.

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When you understand the system, you can see what is my amp draw?

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What's my compressor speed?

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What's my discharge temperature?

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Is it too hot?

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What's my expansion valve?

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That is a good sign.

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All indicators of performance.

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Of an issue.

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If I have a 700-step EEV and I'm running over 600 steps, there's something wrong with this

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system.

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It should never get that high.

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Yeah, exactly.

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Very cool.

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Yeah.

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When you learn what those three components are trying to do individually to work together

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to create a cool indoor, you can understand how to see the operating system.

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I love it.

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Love it.

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Simplified to a point where we take out some of the demystification, talk about the future

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of our industry because we are definitely moving towards inverter technology and many

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people are afraid because they don't understand the operation.

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When we talk about inverters, many people have told me that there's no sequence of operation

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on an inverter or mini-split.

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I'm like, are you kidding me?

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Everything has a sequence of operation.

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We don't have outputs without inputs.

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What they are doing, they are working very independent to form a complete operating system.

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When we're looking at our particularly in this scenario, our ductless inverter, we're

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looking at three different scenarios all operating simultaneously so we have sequences to look

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at for each one.

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Take the time, learn a little bit about the changes in our industry and welcome to the

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future of inverters.

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It's great.

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It's wonderful and it's here to stay.

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It's something that we have to embrace and understand and work with and when you know

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the systems, you're going to be able to increase that profit because you're going to minimize

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your returns.

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You're going to minimize your guessing.

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That's the biggest problem is the guessing.

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How many boards have been replaced?

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It's disproportionate.

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Oh absolutely.

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There's so many boards being replaced for no reason other than the technician doesn't

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understand what the system is doing and so it has to be the board.

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We run into this topic quite often in the commercial applications.

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In the commercial HVAC industry, the replacement parts ratio is somewhere around 6 to 7 percent.

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When we get into the residential side, now we're getting up over 60 percent.

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What's the difference between the residential and the commercial?

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The skill level of the technician.

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That's it.

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That's what we're here for is to help simplify these things that are changing in our industry

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and just bring you closer to the future of technology.

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Thanks Kyle.

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Hey, it was fun.

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It was a blast.

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Thank you.