Klein Trade Program — Week 9
Heating Fundamentals: Yes, We Have to Learn This in Florida
Saturday, June 13, 2026
HVAC Theory Certificate Program — Heating Fundamentals
Welcome to Week 9 of the Klein Trade Program.
We’ve spent the last several weeks working through refrigeration.
Refrigeration cycle.
Gauges.
Pressure and temperature.
Superheat.
Subcooling.
Refrigeration equipment.
This week, HVAC Theory took us somewhere slightly less exciting for a bunch of people learning air conditioning in Florida:
Heating Fundamentals.
😂
Yes.
We have heat in Florida.
Yes.
People use it.
No.
It’s probably not going to become the majority of our service calls.
But it’s part of HVAC.
So…
Let’s learn heat.
“Do We Really Need to Know This?”
Yes.
😂
We live and work in Florida.
Our summers are long.
Our cooling season is brutal.
And if you’re entering residential HVAC here, you’re going to spend a whole lot more time dealing with:
No cooling.
Poor cooling.
Humidity.
Drain problems.
Airflow.
Refrigeration.
than you will diagnosing furnaces.
But Florida homes still need heat.
And the equipment we work on has heating modes.
Most importantly for our market:
Heat pumps.
Those are absolutely relevant.
So even if nobody in Palm Coast is preparing for six months of frozen tundra, we still need to understand heating fundamentals.
Florida Cold Is Different
Let’s establish something before we continue.
Florida cold is not the same as actual cold.
😂
In Pennsylvania, 45°F might mean:
“Nice day.”
In Florida, 45°F means somebody has put on:
A winter coat.
Gloves.
A beanie.
Possibly two pairs of socks.
And they’re calling us because:
“THE HEAT ISN’T WORKING.”
It’s been off for seven minutes.
This is now an emergency.
Welcome to Florida heating season.
It lasts approximately three afternoons.
😂
What Are We Learning This Week?
Week 9 continued the HVAC Theory Certificate Program with:
Heating Fundamentals
We’re introducing the major ways residential HVAC systems provide heat and the principles behind them.
That means talking about things like:
Heat transfer.
Heat pumps.
Electric resistance heat.
Gas heating fundamentals.
Heating controls.
Safety.
And how the equipment we’ve already been studying changes when we switch from cooling to heating.
We’re not trying to turn anybody into a furnace expert in one Saturday.
Especially in Florida.
We’re building the foundation.
Heat Still Moves From Hot to Cold
This is one of those fundamental concepts that follows us everywhere.
Heat naturally moves from a warmer area toward a cooler area.
That’s true when we’re cooling a house.
It’s true when we’re heating one.
And it’s important because air conditioning and heating aren’t really two completely separate worlds.
We’re still dealing with:
Heat transfer.
In cooling mode, we’re trying to remove heat from inside the house and reject it outside.
In heating mode, we need to add heat to the indoor space.
How we accomplish that depends on the equipment.
The Heat Pump
This is the big one for us.
Heat pumps are extremely common in Florida.
And here’s the cool part:
We’ve basically already learned how one works.
Remember the refrigeration cycle?
Compressor.
Condenser.
Metering device.
Evaporator.
We’re still using it.
But a heat pump has the ability to reverse the refrigeration cycle.
That’s why we introduced the reversing valve last week.
In cooling:
The indoor coil acts as the evaporator.
The outdoor coil acts as the condenser.
In heating:
They switch jobs.
Now the outdoor coil absorbs heat.
The indoor coil rejects heat into the home.
Same fundamental refrigeration principles.
Different direction.
Yes, There’s Heat Outside When It’s Cold
This can seem strange at first.
If it’s 40°F outside, how can we pull heat from the outdoor air?
Because:
40°F is not absolute zero.
😂
There is still thermal energy available.
The refrigerant can evaporate at temperatures below the outdoor-air temperature, allowing it to absorb heat from that air.
The compressor raises the refrigerant’s pressure and temperature.
Then that heat can be rejected indoors.
That’s the beauty of a heat pump.
We’re not simply creating all the heat with electric resistance.
We’re moving heat.
Which is why everything we learned about refrigeration still matters in heating mode.
Keep Learning: How Air Conditioning Works 101
Our basic A/C University lesson focuses primarily on cooling, but the refrigeration-cycle foundation carries directly into understanding heat pumps.
If the compressor, condenser, evaporator and metering device are still new concepts, start here:
How Air Conditioning Works 101 →
Once you understand how refrigeration moves heat, reversing that process becomes much easier to understand.
The Reversing Valve
We introduced this component during Refrigeration Equipment last week.
Now we have a reason to really care about it.
The reversing valve changes refrigerant flow so the system can operate in either cooling or heating mode.
This is what allows the indoor and outdoor coils to switch roles.
And eventually, when we’re troubleshooting heat pumps, the reversing valve becomes another piece of the diagnostic puzzle.
Is it being energized?
Is it shifting?
Is the control signal present?
Is refrigerant actually flowing correctly?
But remember:
Don’t blame the component before you test the circuit.
Week 5 taught us better than that.
Electric Resistance Heat
Most Florida heat-pump systems also have some form of auxiliary electric resistance heat.
These are commonly called:
Heat strips.
And the concept is much simpler than the refrigeration cycle.
Pass electrical current through a resistive heating element.
The element gets hot.
Move air across it.
Now we have warm air.
Simple.
Effective.
And capable of pulling a whole lot of amperage.
😂
Which means everything we’ve learned about:
Voltage.
Current.
Electrical circuits.
Sequencers or relays.
Breakers.
Wire sizing.
starts becoming important again.
Heat Strips Are Not Free Heat
This is something homeowners sometimes discover when the electric bill arrives.
😂
A heat pump is generally moving heat.
Electric resistance heat is converting electrical energy directly into heat.
That’s an important distinction.
Auxiliary heat can be necessary and useful.
But if the system is running electric resistance heat excessively because something isn’t operating correctly?
The electric meter may start doing cardio.
Very expensive cardio.
That’s something technicians eventually need to recognize.
Auxiliary Heat
So why have heat strips if the heat pump works?
Because there are times when the heat pump may need help.
Outdoor conditions.
System capacity.
Defrost operation.
Large temperature changes.
Equipment design.
The thermostat and controls may bring on auxiliary heat when needed.
That doesn’t automatically mean something is wrong.
Again:
Understand how the equipment is designed to operate.
Don’t diagnose based on one thing you saw one time.
Emergency Heat
This is another term students need to recognize.
Emergency heat generally allows the auxiliary heating source to operate without relying on normal heat-pump heating operation.
It’s not:
“Make the house hotter faster” mode.
😂
That’s not what the word emergency means here.
It’s intended for situations where normal heat-pump operation isn’t available or appropriate.
Eventually we’ll get deeper into thermostat logic and controls.
For now:
Know the distinction.
Defrost: Why Is the Outdoor Unit Smoking?
Ah yes.
Florida winter.
Customer looks outside.
The outdoor unit is covered in steam.
They call:
“MY AIR CONDITIONER IS ON FIRE.”
😂
Probably not.
During heat-pump heating operation, the outdoor coil is acting as the evaporator.
Under the right conditions, frost can form on that coil.
The system needs a way to remove it.
That’s where the defrost cycle comes in.
The system temporarily changes operation to warm the outdoor coil and melt accumulated frost.
During that process, you may see steam.
That’s normal.
Understanding defrost becomes an important part of heat-pump service.
Heating Still Requires Airflow
Here comes our recurring character:
Airflow.
😂
Cooling?
Airflow matters.
Refrigeration?
Airflow matters.
Heating?
Guess what?
Airflow matters.
Electric heat strips need proper airflow.
Heat-pump heating performance depends on airflow.
Temperature rise depends on airflow.
Equipment safety can depend on airflow.
This is why we’re eventually going to spend plenty of time measuring it.
HVAC isn’t a collection of separate subjects.
Everything starts connecting.
What About Gas Furnaces?
We need to learn them.
Even in Florida.
Gas furnaces exist here.
And if you’re going to call yourself an HVAC technician, you should understand the fundamentals of combustion heating.
That means eventually understanding components and concepts such as:
Gas valves.
Ignition systems.
Flame sensors.
Heat exchangers.
Inducer motors.
Pressure switches.
Limit switches.
Venting.
Combustion safety.
Are we going to spend the same amount of time on furnaces that an HVAC school in Minnesota might?
Probably not.
😂
Our training should reflect the equipment our technicians are most likely to encounter.
But fundamentals matter.
Stuff That Isn’t in the Manual
Florida Heating Calls Are Weird
You can go months without thinking much about heat.
Then we get three cold mornings.
And suddenly:
EVERYBODY’S HEAT IS BROKEN.
😂
Systems that haven’t operated in heating mode since last winter suddenly have to work.
Heat strips come on.
Reversing valves shift.
Defrost controls matter.
Thermostat configurations matter.
And homeowners discover smells they haven’t smelled since January.
Which brings us to…
“Something Is Burning”
Sometimes, when electric heat is first used after sitting for a long period, dust accumulated around the heating components can produce an odor when the system starts heating.
That doesn’t mean every burning smell should be ignored.
Obviously.
But this is where customer communication matters.
Listen to what they’re describing.
Inspect the equipment.
Determine what’s actually happening.
Don’t dismiss concerns.
Don’t panic either.
Investigate.
That’s the job.
Stuff That Isn’t in the Manual
Don’t Laugh at the Customer Because They’re Cold
Okay.
You can laugh with us here.
😂
But if somebody says their house is freezing at 67°F?
They’re cold.
That’s what matters.
We’re not there to explain that somebody in Wisconsin would currently be grilling outside in shorts.
We’re there because the customer’s heating system isn’t doing what they expect.
Listen.
Ask questions.
Check the equipment.
Explain what you find.
Remember:
We fix HVAC systems. We don’t set the customer’s thermostat for them.
The Cool Part: Everything Is Connecting
This is what I like about this point in the program.
Look at what we’ve already learned.
Electrical troubleshooting taught us how controls and circuits operate.
Refrigeration taught us how heat moves through the refrigeration cycle.
Refrigeration equipment introduced the reversing valve.
Now:
Put those together.
The thermostat calls for heat.
The control circuit responds.
The reversing valve determines refrigerant flow.
The compressor runs.
Refrigerant moves heat.
Auxiliary heat may be brought in when needed.
The blower moves heated air through the house.
It’s all one system.
That’s when HVAC starts getting really interesting.
What Should a Student Know After Week 9?
We’re not expecting anybody to become a heating expert after one Saturday.
Especially not in Florida.
😂
We’re building skills.
By the end of Week 9, students should be more comfortable with:
- Understanding basic heat-transfer principles
- Understanding how a heat pump provides heating
- Understanding that a heat pump reverses the refrigeration cycle
- Understanding the basic purpose of a reversing valve
- Recognizing electric resistance heat and heat strips
- Understanding auxiliary heat
- Understanding emergency heat at a basic level
- Understanding why heat pumps require defrost
- Recognizing that airflow matters in heating operation
- Understanding the basic existence and purpose of combustion heating equipment
- Connecting heating operation to previously learned electrical and refrigeration concepts
Most importantly:
Students should understand that heating isn’t an entirely different universe from air conditioning.
The fundamentals we’ve already learned still apply.
Yes, We Have to Learn Heat in Florida
Would I spend six months teaching residential heating before teaching somebody how to handle a no-cool call in Palm Coast?
No.
😂
Our training should reflect the work we’re actually going to do.
But there’s a difference between prioritizing the most relevant skills and ignoring everything else.
We work on HVAC systems.
Not just:
“The cold part.”
A good technician understands the entire system.
And when that first 42°F Florida morning hits and the phone starts ringing?
You’ll be glad we spent a Saturday talking about heat.
See You in Week 10
We’re documenting the Klein Trade Program week by week inside A/C University.
At this point, the foundation is getting pretty substantial.
Tools.
Brazing.
Electrical.
Wiring.
Troubleshooting.
Refrigeration.
Gauges.
Refrigeration equipment.
And now heating.
Every week adds another piece.
Eventually those pieces become a technician.
For now?
Yes. Florida has heat.
Lesson complete.
😂