What Actually Happens During a Proper AC Installation?
Ever Wonder What They’re Doing in Your Attic While You’re Sweating downstairs?
It’s installation day.
Your old AC is off.
The front door keeps opening.
There are tools everywhere.
Someone just carried what looks like half of your air conditioner through the house.
And you’ve heard banging coming from the attic for the last three hours.
You’re downstairs thinking:
“What the hell are they doing up there?”
Meanwhile, the installer in your attic is thinking:
“Please don’t fall through the ceiling. Please don’t fall through the ceiling.”
There is actually a lot happening.
A proper AC installation isn’t simply pulling out an old air conditioner and replacing it with a new one. On a full split-system heat pump replacement, we’re dealing with refrigerant, electrical systems, drainage, ductwork, airflow, controls and two separate pieces of equipment that have to operate together as one system.
A lot of the most important work happens where you’ll never see it.
So let’s take you behind the scenes.
Here’s what actually happens when we replace a split-system heat pump.
Step 1: Make Sure We Brought the Right Air Conditioner
This seems obvious.
It’s important enough that it’s the first thing we verify.
Before beginning the installation, we confirm that the new outdoor unit and air handler match the proposal—including the model, size and voltage.
We review the scope of work, make sure the required equipment and materials are on site, and verify that we have the installation instructions and permit information.
Because finding out you have the wrong air handler after the old one is sitting in the driveway makes for a very long day.
Step 2: Protect Your House
Before demolition starts, we protect the areas where we’ll be working.
We use drop cloths in work areas, wear shoe covers inside the home and don’t put tools or equipment directly on furniture or unprotected flooring.
Then we stage our tools and equipment.
If we’re working outside in Florida, we’re also setting up hydration and shade.
There’s a reason AC installers drink approximately 47 bottles of water during your installation.
Okay, we made that number up.
But it feels accurate.
Step 3: Shut Everything Down Safely
Before touching the existing equipment, power is turned off, breakers are locked out and we verify with a meter that voltage is actually gone.
Then we begin removing the old system.
But there’s something we have to deal with first.
The refrigerant.
Step 4: Recover the Old Refrigerant
We can’t simply cut the copper lines and let the refrigerant escape.
The refrigerant from the existing system is recovered using specialized recovery equipment and placed into an approved recovery cylinder.
We document the refrigerant and handle it in accordance with EPA requirements.
Only after that’s completed can we safely disconnect the refrigeration circuit.
This process isn’t particularly exciting to watch.
It’s also one of those things you definitely want your HVAC contractor doing correctly.
Step 5: Disconnect and Remove the Old System
Now we disconnect the electrical wiring, thermostat wiring, refrigerant piping, drain and duct connections.
Then the old equipment comes out.
The outdoor unit is usually pretty straightforward.
The air handler?
That depends entirely on where someone decided to put it when the house was built.
Garage?
Wonderful.
Closet?
Not terrible.
Attic?
Please don’t fall through the ceiling.
Once the old equipment is removed, we’re left with the infrastructure that the new air conditioner has to connect to.
And this is where a proper AC replacement starts becoming very different from simply swapping equipment.
Step 6: Inspect What the Old System Left Behind
A new air conditioner doesn’t exist in isolation.
It connects to your existing:
- Supply ductwork
- Return ductwork
- Refrigerant lines
- Condensate drain
- Electrical system
- Equipment platform
So we inspect them.
If the existing supply or return plenums are damaged or incompatible with the new equipment, they need to be repaired or replaced.
We also verify that the existing breaker, disconnect and electrical components are appropriate for the new equipment.
Putting a brand-new HVAC system on top of an existing installation problem doesn’t make the problem disappear.
Now you just have a new air conditioner with an old problem.
Step 7: Prepare the Refrigerant Lines
The copper refrigerant lines connect the outdoor heat pump to the indoor air handler.
If we’re installing a new lineset, we install it.
If the existing lineset is being reused, our procedure calls for flushing it with R-11 flush and nitrogen.
The openings are kept covered during the installation so dirt and debris don’t get inside.
If the old system had lost its refrigerant charge, we’ll pressure-test the existing lineset with nitrogen before trusting it with the new equipment.
Because finding a leak before connecting your brand-new air conditioner is considerably better than finding it afterward.
Step 8: Start Cleaning the Drain
While everything else is happening, we start working on the condensate drain.
In Florida, your air conditioner removes an enormous amount of moisture from the air.
That water has to go somewhere.
We treat the existing drain with drain cleaner and water and allow it to sit while the installation continues.
Later, we’ll finish the drain installation, prime it and test it.
This isn’t the glamorous part of an AC installation.
But neither is explaining why there’s water coming through your ceiling.
Step 9: Set the New Outdoor Heat Pump
Outside, the new heat pump is placed on its pad.
We level the pad as necessary and secure the outdoor equipment using the appropriate tie-down brackets.
The equipment also has to be positioned correctly for airflow and future service.
Then we connect the refrigerant lines to the outdoor unit.
And now we’re getting into some of the work that you probably never knew was happening.
Step 10: Braze the Copper — With Nitrogen Flowing
The copper refrigerant lines have to be brazed to the new equipment.
That means we’re using a torch and extremely high temperatures to join the copper.
Before brazing, we protect heat-sensitive components, remove components that shouldn’t be exposed to brazing temperatures, use wet rags and heat shields where necessary, and keep a fire extinguisher nearby.
But there’s another important step.
We flow nitrogen through the copper while brazing.
Without nitrogen, the extreme heat can create oxidation inside the copper tubing.
You can’t see that contamination from the outside.
But your refrigerant system can.
Nitrogen helps keep the inside of those copper lines clean while we’re making the joints.
It’s a perfect example of something you’ll probably never know whether your installer did.
But it matters.
Step 11: Pressure Test the System
Once all of our refrigerant connections are complete, we don’t immediately release refrigerant into the new system.
First, we test our work.
Our installation procedure calls for pressurizing the refrigeration circuit with nitrogen—typically around 400 PSI—and checking the joints for leaks.
If we just spent hours installing your new air conditioner, this is the point where we make sure the refrigeration system is actually sealed.
Only after it passes the pressure test do we move on.
Step 12: Change the Vacuum Pump Oil
Yes.
This gets its own step.
Our installation procedure calls for fresh vacuum-pump oil on every installation.
Why?
Because the next step is one of the most important parts of installing an air conditioner correctly.
We’re about to remove the air and moisture from inside the refrigeration system.
And we want the equipment doing that job performing as well as possible.
Step 13: Pull the System Down to 500 Microns
Now we connect a vacuum pump and evacuate the refrigeration circuit.
This isn’t simply:
“Yep, gauges are in a vacuum. We’re good.”
We measure the vacuum in microns.
Our procedure calls for evacuating the system to 500 microns and then verifying that it holds for 10 minutes.
Why does this matter?
Because air and moisture don’t belong inside a refrigeration system.
We’re trying to create a clean, dry, sealed environment before refrigerant is introduced.
This is another step that happens completely behind the scenes.
You probably won’t know whether somebody pulled a proper vacuum.
Your air conditioner might even turn on and blow cold air if they didn’t.
But “it turned on” isn’t our definition of a proper AC installation.
Step 14: Install and Seal the Indoor Air Handler
Meanwhile, somebody is still in your attic.
Sorry.
The new air handler is positioned and leveled.
We make sure the installation allows access to the filter and service panels and that doors can still open and close properly.
Then we connect the air handler to the home’s ductwork.
Those connections are mechanically secured and sealed with approved materials such as foil tape and mastic.
We also seal the connection between the duct system and the air handler itself.
Why?
Because we’re paying to condition the air inside your house.
Not your attic.
Step 15: Connect the Drain and Water Safeties
The condensate drain is connected to the new air handler and properly pitched.
We avoid improper configurations such as double traps, insulate visible drain piping where required and install float switches.
Those float switches are important.
If the drain backs up, they’re designed to shut the system down before the water causes a much larger problem.
Later, we’ll actually test them.
Not just install them and assume they work.
Step 16: Complete the Electrical Work
The new indoor and outdoor equipment now need power and controls.
We verify that the high-voltage wiring is appropriate for the equipment and heater kit and install the required disconnects.
Then we complete the low-voltage control wiring according to the equipment manufacturer’s instructions.
The air handler’s control-board and airflow settings are also configured for the actual equipment being installed.
Modern air conditioners aren’t always plug-and-play.
The equipment has to be told how it’s supposed to operate.
Step 17: Install and Configure the Thermostat
Next comes the part of the system you’ll actually interact with.
The thermostat.
If we’re installing a new thermostat, we mount and wire it, configure it for the equipment and verify its temperature reading against a reference thermometer.
Two-stage system?
Heat pump?
Auxiliary heat?
Different equipment requires different thermostat configuration.
A $10,000+ HVAC system shouldn’t be operating incorrectly because someone skipped through the thermostat setup menu.
Step 18: Release the Refrigerant and Start the System
The pressure test passed.
The vacuum reached our target.
The system held.
The electrical work is complete.
The drain is connected.
The ductwork is sealed.
Now we can finally release the factory refrigerant charge into the system and turn your new air conditioner on.
This is usually the moment the homeowner cares about most.
Cold air.
We care about it too.
We’re just not finished yet.
Step 19: Check the Refrigerant Charge
Once the system is running and has stabilized, we verify the refrigeration system’s operation according to the manufacturer’s specifications.
We measure refrigerant pressures and temperatures and evaluate things like subcooling and superheat.
If the system requires additional refrigerant because of the lineset length or operating conditions, we adjust the charge appropriately.
We aren’t charging the system based on:
“That suction line feels pretty cold.”
We’re measuring it.
Once we’re satisfied, locking refrigerant caps are installed on the outdoor unit.
Step 20: Make Sure the Water Actually Goes Down the Drain
Remember that condensate drain from several hours ago?
We’re not done with it.
We remove the temporary cap, prime the trap with water and verify that the drain flows correctly.
Then we test the float switches.
Again:
We don’t assume the safety works because we installed it.
We test it.
Step 21: Check the Air Coming Into and Out of the System
Now we measure return-air and supply-air temperatures.
We’re verifying that the system is producing an appropriate temperature difference across the indoor equipment.
It’s another piece of information that tells us whether the newly installed HVAC system is actually performing properly.
Cold air coming from a vent is nice.
Measurements are better.
Step 22: Turn the Heat On
Yes.
Even if it’s August.
Sorry.
You bought a heat pump, not just an air conditioner.
So part of properly commissioning a heat pump installation is verifying that it operates in heating mode too.
We don’t want you discovering the first cold morning of the year that something was wired incorrectly six months ago.
Step 23: Clean Up the Evidence
By this point, your old system is gone and your new system is operating.
Now we clean everything up.
Tools, copper scraps, wire, packaging and installation debris are removed.
The equipment is labeled appropriately, permit paperwork is placed where required, job information and refrigerant records are completed, and installation photos are sent to the office.
The old equipment and recovered refrigerant are taken for proper recycling or reclamation.
Ideally, when we’re finished, the only evidence that we spent the entire day tearing apart your HVAC system is:
You have a new HVAC system.
And your house is finally getting cold.
Step 24: Show You What We Did
Before leaving, we walk through the new installation with you.
We’ll show you how the system operates.
We’ll explain the thermostat.
If it’s a Wi-Fi thermostat, we’ll help get it connected and get the app set up.
We’ll answer your questions and go over the basic things you need to know about your new equipment.
Because at the end of the day, it’s your air conditioner.
You should know what we installed in your home.
So Why Does a Proper AC Installation Take So Long?
Now you know.
Recover.
Remove.
Inspect.
Flush.
Clean.
Set.
Level.
Secure.
Braze.
Nitrogen purge.
Pressure test.
Evacuate.
500 microns.
10-minute hold.
Seal the ductwork.
Build the drain.
Wire the equipment.
Configure the controls.
Start it.
Charge it.
Test it.
Test the safeties.
Test the heat.
Clean everything.
Then show the homeowner how it all works.
A proper air conditioner installation isn’t about how quickly we can make cold air come out of your vents.
It’s about everything that happens before and after that moment.
Because you may never see the nitrogen flowing through the copper.
You may never see the micron gauge.
You probably won’t crawl into the attic to inspect the inside of the duct connection.
And unless something goes wrong, you’ll probably never think about the float switches protecting your ceiling.
That’s kind of the point.
The Installation Matters as Much as the Equipment
Homeowners spend a lot of time comparing air-conditioning brands.
Goodman.
Carrier.
Trane.
Daikin.
Lennox.
Rheem.
And equipment absolutely matters.
But even excellent equipment can perform poorly when it’s installed poorly.
The quality of the installation determines whether that equipment gets the environment it was designed to operate in.
So when you’re comparing quotes for a new AC system, don’t only ask:
“What brand are you installing?”
Ask:
“How are you installing it?”
Because when your house is 87 degrees and you hear someone crawling around above your bedroom, you now know what’s supposed to be happening up there.
And he’s still thinking:
“Please don’t fall through the ceiling.”