Klein Trade Program — Week 10
Heating Systems & Apparently We’re Building an HVAC Lab Now
Saturday, June 20, 2026
HVAC Theory Certificate Program — Heating Systems
Welcome to Week 10 of the Klein Trade Program.
Last week we covered Heating Fundamentals.
Yes.
In Florida.
We survived.
😂
This week we continued HVAC Theory with:
Heating Systems
But something else happened this week too.
We installed another HVAC system in the shop.
Not a shiny new training simulator.
Not some purpose-built educational equipment that has never seen the inside of a customer’s house.
This was an actual system we had removed from a customer’s home.
And instead of getting rid of it?
We brought it back to the shop.
Because apparently we’re building an HVAC lab now.
Which is pretty cool.
From Somebody’s House to Our Classroom
One of the advantages of running an HVAC company and a trade program at the same time is that we come across equipment.
Lots of equipment.
Old equipment.
Broken equipment.
Working equipment that’s being replaced for another reason.
Components.
Motors.
Boards.
Compressors.
Coils.
And every once in a while, something comes out of a customer’s house and we look at it and think:
“We can teach with that.”
So we do.
That’s exactly what happened this week.
We took a system we’d removed from a customer’s home and installed it in the shop.
Now it gets a second life.
Not cooling somebody’s house.
Teaching somebody how to work on one.
That’s a pretty good retirement plan for an air conditioner.
😂
Why Real Equipment Matters
There are beautiful HVAC training boards available.
Everything is labeled.
Everything is clean.
Every wire is perfectly visible.
Every component is mounted at eye level.
That’s useful.
But that’s not what the equipment looks like when you walk into somebody’s garage.
Real equipment has:
Dust.
Old wire connectors.
Factory wiring.
Field wiring.
Previous repairs.
Tight spaces.
Components mounted somewhere that makes you wonder whether the engineer was angry that day.
😂
That’s what students eventually need to become comfortable around.
We want both.
Learn the concept clearly.
Then find it on real equipment.
What Are We Learning This Week?
Week 10 continued our HVAC Theory Certificate Program with:
Heating Systems
Last week we introduced the fundamentals.
Heat pumps.
Electric resistance heat.
Auxiliary heat.
Emergency heat.
Defrost.
Combustion heating.
This week we’re taking the next step and looking more closely at the systems that actually provide heat.
How are they arranged?
What components are involved?
How are they controlled?
How does airflow interact with heating?
And how does everything we’ve already learned about electrical and refrigeration apply?
Heat Pumps: The Big One for Florida
If you’re going to work residential HVAC in Florida, heat pumps matter.
A lot.
We’ve already learned the refrigeration cycle.
We’ve already learned about reversing valves.
Now we put those pieces together.
In cooling mode:
Indoor coil = evaporator
Outdoor coil = condenser
In heating mode:
Indoor coil = condenser
Outdoor coil = evaporator
The refrigeration cycle didn’t disappear.
We changed where we’re moving the heat.
That’s the fundamental concept.
The Outdoor Unit Didn’t Suddenly Become a Heater
This is worth reinforcing.
A heat pump isn’t simply an air conditioner with some mysterious “heat mode” added to it.
The same refrigeration circuit is being used to transfer heat.
The compressor still matters.
The coils still matter.
The metering devices still matter.
Refrigerant pressure and temperature still matter.
Airflow still matters.
The reversing valve changes refrigerant flow so the equipment can move heat in the direction we need.
Which means all those Saturdays we spent learning refrigeration?
Still relevant.
Imagine that.
😂
The Air Handler
Now let’s look indoors.
In many Florida homes, the indoor equipment is an air handler.
Inside, we may have components such as:
Blower assembly.
Evaporator/indoor coil.
Electric heat kit.
Control board or relays.
Transformer.
Float switches.
Thermostat wiring.
We’ve already met most of these things individually.
Now we’re seeing them as one piece of equipment.
This is why the program builds progressively.
Week 5:
Here’s a transformer.
Here’s a thermostat.
Here’s a float switch.
Here’s a motor.
Build a circuit.
Now:
Oh. That’s basically what we’ve been looking at inside the equipment.
Exactly.
Electric Heat Strips
Inside many Florida air handlers, we’ll find electric resistance heat.
Heat strips are relatively simple in concept.
Electric current passes through a resistive element.
The element gets hot.
The blower moves air across it.
Warm air enters the duct system.
But simple doesn’t mean insignificant.
These heaters can draw substantial current.
Which means our electrical fundamentals become very important.
Voltage.
Amperage.
Wire sizing.
Breakers.
Connections.
Relays.
Sequencers.
Airflow.
Safety limits.
Everything starts stacking.
Staging Electric Heat
Larger electric heat kits may not necessarily energize every heating element at once.
Heating can be staged.
Why?
Among other reasons, staging can help manage electrical demand and heating output.
Depending on the equipment, controls may use:
Relays.
Sequencers.
Control boards.
And different thermostat/control strategies.
Eventually, when a customer says:
“The heat works, but it doesn’t seem very warm,”
we need to determine whether the system is actually operating as designed.
Maybe all stages aren’t being energized.
Maybe there’s an electrical failure.
Maybe there’s an airflow issue.
Maybe there’s nothing wrong.
Measure first.
Sound familiar?
Sequencers
Ah, sequencers.
Another component that looks considerably more mysterious before somebody explains what it does.
😂
Electric heat can require multiple heating elements to operate in stages.
A sequencer can help bring those loads on and off in sequence rather than energizing everything simultaneously.
At the beginner level:
Understand the job.
Later:
We’ll troubleshoot them.
And when we do, we’ll go back to the same electrical process we’ve already started learning.
What should be happening?
What is actually happening?
Where did those two things stop matching?
Limits and Safety Controls
Heating equipment creates heat.
Amazing observation.
😂
That also means we need safeguards.
Heating systems can incorporate temperature limits and other safety controls designed to interrupt operation when conditions aren’t appropriate.
This is where technicians need to understand something important:
A safety opening is information.
Don’t just bypass it.
Don’t just replace it.
Ask:
Why did it open?
Is there an airflow problem?
Is something overheating?
Is the control itself faulty?
What’s the underlying condition?
A safety device may be telling you about another problem.
Listen to it.
Guess Who’s Back?
AIRFLOW.
😂
We told you this guy wasn’t going away.
Cooling?
Airflow.
Refrigeration?
Airflow.
Heating?
Airflow.
An electric heater with inadequate airflow can overheat.
A heat pump with incorrect airflow can perform poorly.
Temperature measurements can become misleading.
Comfort suffers.
Equipment suffers.
And eventually we’re going to get much deeper into:
CFM.
Static pressure.
Temperature rise.
Blower setup.
Duct systems.
For now, just remember:
Airflow keeps showing up because airflow matters.
The Thermostat Is Running the Show
Now we’re also beginning to understand what happens when somebody changes the thermostat from:
COOL
to:
HEAT.
That simple button press can initiate an entirely different equipment sequence.
Depending on the system and conditions:
The reversing valve may be positioned for heating.
The compressor may operate.
The outdoor fan may operate.
The indoor blower operates.
Auxiliary heat may stage in.
Defrost may eventually occur.
The thermostat isn’t creating the heat.
It’s telling the system what we want it to do.
Then the controls make that happen.
Assuming everything works.
Which is why we have jobs.
😂
Defrost: Heating Gets Weird for a Minute
We introduced defrost last week.
Now that we’re talking about actual heating systems, let’s reinforce it.
During heat-pump heating operation, the outdoor coil is functioning as an evaporator.
Under certain conditions, frost can accumulate.
The system needs to remove it.
So it enters defrost.
And for a short period, the equipment does something that can look very strange to somebody who doesn’t understand what’s happening.
Steam outside.
Operating sounds change.
Auxiliary heat may be used indoors.
Customer looks outside.
“KEVIN. THE UNIT IS SMOKING.”
😂
Understanding normal operation matters because otherwise perfectly normal equipment can look broken.
What About Furnaces?
Yes.
We covered heating systems beyond heat pumps and electric heat.
Gas furnaces exist.
Even in Florida.
Not nearly as dominant in our particular market, but HVAC theory needs to include the fundamentals.
A furnace may include components such as:
Inducer motor.
Pressure switch.
Ignition system.
Gas valve.
Burners.
Flame sensor.
Heat exchanger.
Blower.
Limit switches.
And importantly:
A sequence of operation.
That’s the concept we really want students beginning to understand.
Sequence of Operation
This idea is huge.
Equipment doesn’t just:
“Turn on.”
Things happen in an order.
One condition is satisfied.
Then another component operates.
Then another control verifies something.
Then the next thing happens.
If the sequence stops?
Now we have somewhere to troubleshoot.
This applies to furnaces.
Heat pumps.
Air conditioners.
Pretty much every piece of HVAC equipment with controls.
Instead of staring at the entire machine thinking:
“Why doesn’t it work?”
Ask:
“What was the last thing that happened correctly?”
Then:
What should have happened next?
Now you’re troubleshooting.
Meanwhile… We’re Installing an Air Conditioner in the Classroom
While we’re learning heating systems, our shop is also becoming a better training facility.
This week we installed that system we’d removed from a customer’s home.
And I love this because it represents exactly what we’re trying to do with the Klein Trade Program.
Use what we have.
We don’t need a million-dollar trade-school laboratory.
We need real equipment.
A place to work.
Tools.
People willing to learn.
And somebody willing to teach them.
Customer replaces equipment?
Maybe the old system has training value.
Component gets replaced?
Maybe we save the old one and cut it apart.
Motor fails?
Perfect.
Let’s see why.
Compressor comes out?
We’re keeping that thing.
😂
Every piece of equipment can become a lesson.
The Shop Is Becoming Its Own HVAC System
At this point, this isn’t just a room where we sit around and talk about HVAC.
We’re installing equipment.
Building electrical circuits.
Running motors.
Connecting gauges.
Brazing copper.
Taking components apart.
Following wiring diagrams.
And adding systems we can deliberately mess with.
That last part is important.
😂
Because once equipment belongs to the lab?
We can create problems.
Pull a wire.
Open a control.
Install a failed component.
Change a setting.
Create a restriction.
Then tell the students:
“It’s broken. Find it.”
That’s where this program is eventually headed.
Stuff That Isn’t in the Manual
Save the Old Parts
This is something I strongly recommend when you’re learning HVAC.
If you replace something interesting and it’s safe and practical to keep:
Keep it.
Bad contactor?
Take it apart.
Failed capacitor?
Look at it.
Motor?
Open it up.
TXV?
Cut it open.
Compressor?
Let’s see what’s inside.
Control board?
Look at the relays and circuitry.
It’s one thing to see a picture.
It’s another thing to hold the component in your hand.
And when it’s already broken?
You can’t make it much more broken.
😂
Perfect learning opportunity.
Stuff That Isn’t in the Manual
“Why Did They Replace This?”
This is another benefit of using actual removed equipment.
Not every system gets replaced because it completely died.
Maybe it was old.
Maybe it had repeated repairs.
Maybe the homeowner wanted higher efficiency.
Maybe there was a major component failure.
Maybe comfort was poor.
Maybe the equipment was still running.
That gives us another opportunity to teach something important:
Replacement isn’t automatically a diagnosis.
We want technicians who can evaluate equipment honestly.
Sometimes repair makes sense.
Sometimes replacement makes sense.
Sometimes either one is reasonable and the homeowner gets to decide.
Our job is to understand the equipment well enough to explain the options.
Sometimes We Get It Wrong Too
This belongs in these classes because it’s part of becoming a technician.
We’re going to diagnose things incorrectly sometimes.
We’re going to wire something wrong.
We’re going to forget something.
We’re going to make a callback.
We’re going to look at something later and think:
“Yep. I screwed that up.”
That’s part of learning a trade.
What matters is what happens next.
Do you hide it?
Blame the previous technician?
Make something up?
Or do you say:
“I got that wrong. Let’s figure out why.”
That’s why we work so hard to keep learning.
Equipment changes.
Technology changes.
The technician who thinks he already knows everything is eventually going to get humbled by an air conditioner.
Usually on a Friday afternoon.
In July.
😂
What Should a Student Know After Week 10?
We’re not expecting anybody to become a heating-system expert after one Saturday.
We’re building skills.
By the end of Week 10, students should be more comfortable with:
- Understanding the basic operation of a heat-pump heating system
- Identifying common components inside an air handler
- Understanding electric resistance heat
- Understanding that electric heat can operate in stages
- Recognizing relays, sequencers and heating controls
- Understanding the purpose of safety limits
- Recognizing the importance of airflow during heating
- Understanding heat-pump defrost at a basic level
- Recognizing major furnace components
- Understanding the concept of sequence of operation
- Connecting heating systems to previously learned electrical and refrigeration theory
- Seeing how real removed equipment can be used for training
And this week we added something else:
Another working system to our shop.
Our lab is growing right alongside the students.
That’s pretty cool.
Ten Weeks In
This is Week 10.
Think about where we started.
Week 1:
I pointed at an HVAC system and started talking like these guys had ever thought about one before.
Blank stares.
😂
So we backed way up.
Now?
We’ve covered:
Tools.
Brazing and soldering.
Multimeters.
Wiring.
Electrical troubleshooting.
Refrigeration fundamentals.
The refrigeration cycle.
Gauges.
Refrigeration equipment.
Heating fundamentals.
Heating systems.
We’ve built circuits.
We’ve made braze joints.
We’ve put gauges on operating equipment.
And now we’re installing additional equipment specifically so we can learn on it.
Ten weeks ago:
“What’s that?”
Now we’re starting to ask:
“How does that work?”
That’s a big difference.
And we’re just getting started.
See You in Week 11
We’re documenting the Klein Trade Program week by week inside A/C University.
The weekly articles aren’t meant to pretend somebody can become an HVAC technician by reading a blog.
You need to put your hands on equipment.
But the articles give us the roadmap.
The classroom gives us the theory.
The shop gives us somewhere to practice.
And the real world eventually gives us the problems nobody thought to put in the textbook.
That’s how you learn a trade.