🛠️ Installation Guide: Mike’s Step-by-Step Walkthrough for His 3 Ton Horizontal Goodman AC
🧰 Introduction — Why I Wrote This Guide
I’m Mike, and I’ve been through more HVAC installs than I care to admit. When my old R-410A system started struggling in 2024, I knew I needed to upgrade before another sweltering summer hit.
The big decision? I went with a 3 Ton Goodman Horizontal AC using R-32 refrigerant. It wasn’t just about swapping equipment — it was about future-proofing, cutting bills, and setting up a system I could trust for the next 15–20 years.
While refrigerant handling and electrical hookups must be done by licensed pros, there’s still a ton of work a homeowner can do to prepare and support the install. That’s what this guide is about: my step-by-step process from planning to post-install maintenance.
📏 1. Pre-Installation Planning
Good installs don’t start with a wrench. They start with a notepad.
📐 1.1 Confirming the Load Size
I didn’t guess that 3 tons was right — I ran the numbers.
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Rule of thumb: 1 ton ≈ 450–600 sq. ft. (LearnMetrics)
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My home: 1,650 sq. ft. × 9 ft ceilings = ~36,000 BTUs.
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Verified with an online Manual J tool (RemodelingCalculator).
👉 Pro tip: Don’t rely on square footage alone. Factor in insulation, windows, duct losses, and climate zone.
📋 1.2 Permits and Inspections
HVAC isn’t plug-and-play. My county required:
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Mechanical permit before starting.
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Electrical permit for the 240V line.
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Final inspection to confirm A2L refrigerant compliance.
I pulled permits early so there were no delays once the system was ready.
📍 1.3 Choosing Horizontal
Why horizontal?
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My attic ceiling is too low for a vertical air handler.
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Horizontal units make duct branching easier in tight spaces.
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Goodman offers dedicated horizontal R-32 models designed for attic installs.
Comparison of horizontal vs vertical installs: Larson Air.
🧱 2. Preparing the Site
Prep work is where I saved money and headaches.
🔨 2.1 Clearing & Reinforcing
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Removed the old air handler and vacuumed up years of dust.
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Built a new ¾” plywood platform, reinforced with joist bracing.
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Added rubber vibration pads to reduce noise transfer.
👉 Lesson learned: My old platform sagged, which caused drainage issues. This time, I made it bulletproof.
🛑 2.2 Safety First
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Shut off breaker to old unit.
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Checked for live voltage with a multimeter.
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Wore gloves, safety glasses, and a mask (fiberglass dust in attic = misery).
🌬️ 2.3 Ventilation
My attic hits 120–140°F in summer. To help both me and the AC, I:
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Installed a solar-powered gable fan.
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Added extra soffit vents for intake.
Cooler attic = better working conditions and higher system efficiency.
📦 3. Unboxing the Goodman Horizontal Unit
📦 3.1 What Came in the Box
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Outdoor condenser (factory-charged with R-32).
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Horizontal air handler with coil.
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Thermostat (optional upgrade).
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Installation manual, safety labels, warranty packet.
📑 3.2 Double-Checking Specs
Always check model numbers. Mine: Goodman GPCH33631.
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Capacity: 36,000 BTU (3 ton).
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Refrigerant: R-32.
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Voltage: 208/230V, single phase.
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Orientation: Horizontal.
Link: The Furnace Outlet product page.
🔧 4. Installation Steps
Here’s where the rubber meets the road.
🏗️ Step 1: Platform & Leveling
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Placed air handler on reinforced platform.
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Checked level with torpedo level — critical for condensate drainage.
👉 Even ¼” tilt can cause water pooling and overflow.
🌡️ Step 2: Ductwork
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Connected supply plenum to main trunk.
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Sealed seams with foil tape + mastic (never duct tape).
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Insulated exposed ducts with R-8 wrap.
Resource: Energy.gov – Duct Sealing.
💧 Step 3: Condensate Drain
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Installed primary drain line with ¼” per foot slope.
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Added secondary (emergency) pan with float switch.
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Tested by pouring a gallon of water through — no leaks.
👉 In humid climates, clogged drains = #1 cause of service calls.
⚡ Step 4: Electrical Work
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Ran new 240V line to a disconnect box near condenser.
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Bonded air handler ground to panel.
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Verified breaker: 40A double pole.
👉 ⚠️ Licensed electrician only. I handled conduit runs but left terminations to a pro.
Code basics: NEC HVAC Electrical Guide.
🌀 Step 5: Refrigerant Line Set
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Installed pre-insulated copper: ¾” suction, ⅜” liquid.
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Routed through attic with wide bends to avoid pressure drop.
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Secured every 4 ft with hangers.
👉 Pro tip: Avoid touching copper directly with bare hands — oil contamination can cause leaks.
🧪 Step 6: Leak Test & Evacuation
Tech steps:
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Pressurized with nitrogen to 300 psi for 30 minutes.
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Evacuated with vacuum pump to 500 microns.
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Verified vacuum hold.
Resource: HVAC School – Proper Vacuum Technique.
🔓 Step 7: Charging R-32
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Opened service valves to release factory charge.
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Adjusted for line set length (longer runs = extra refrigerant needed).
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Checked pressures vs Goodman’s charts.
👉 Only a licensed HVAC pro can legally handle refrigerant (EPA 608 certification).
📲 Step 8: Thermostat Setup
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Installed a smart Wi-Fi thermostat.
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Configured for 2-stage cooling.
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Synced to my phone for remote monitoring.
🔊 Step 9: Startup & Commissioning
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Checked airflow: ~1,200 CFM total (400 per ton).
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Verified superheat & subcooling matched manufacturer spec.
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Confirmed no abnormal vibrations or noise.
🔍 5. Mike’s Tool List
Here’s what I actually used:
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Cordless drill + bits
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Torpedo & 4-ft level
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Sheet metal snips
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Foil tape + mastic brush
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PVC cutter (for drains)
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Nitrogen regulator (loaned from tech)
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Vacuum pump (tech supplied)
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Multimeter (for verifying power off)
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Torque wrench (for line set flares)
⏱️ 6. Timeline & Workflow
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Day 1: Demo old unit, reinforce platform, prep ducts.
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Day 2 morning: Install air handler + duct connections.
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Day 2 afternoon: Electrical + drain setup.
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Day 3: Tech arrives for line set, vacuum, charge, commissioning.
👉 From tear-out to first cold air: ~3 days.
💰 7. Cost Breakdown
Item | Cost |
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Goodman GPCH33631 | $2,750 |
Line set & misc. | $450 |
Electrical labor | $600 |
Refrigerant hookup & commissioning | $750 |
Permits & inspection | $120 |
Platform/duct supplies | $300 |
Total | ≈ $4,970 |
✅ 8. Post-Install Checklist
Before calling it “done,” I checked:
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Platform secure & level
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Duct seams sealed
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Drain lines tested
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Breaker correctly sized
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Pressure & charge verified
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Airflow balanced
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Thermostat calibrated
🧹 9. Maintenance Routine
Keeping the system healthy:
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Replace filters every 60–90 days.
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Flush condensate line with vinegar every spring.
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Rinse outdoor condenser coils twice per year.
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Annual pro inspection (check charge, coils, amps).
Resource: Energy Star – AC Maintenance Tips.
🧭 10. Lessons Learned
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Permits add time — apply early.
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Prep is 50% of the job — strong platform, sealed ducts make all the difference.
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Don’t skimp on drain safety — my float switch already saved me once.
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Respect R-32 — mildly flammable, requires certified handling.
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Budget wiggle room — my total ran ~$300 higher than expected due to extra PVC and mastic.
🏁 Conclusion — Was It Worth It?
Absolutely. My Goodman R-32 horizontal AC has been running smoothly, efficiently, and quietly. The install wasn’t “easy,” but by tackling the prep and knowing when to call in pros, I:
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Saved ~15% on labor
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Gained confidence in the system’s quality
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Future-proofed against the R-410A phase-out
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Learned a ton I can apply to future projects
If you’re planning your own install, I hope my walkthrough helps you avoid pitfalls and set up a system you can rely on for decades.