Installation Guide: Mike’s Step-by-Step Walkthrough for His 3 Ton Horizontal Goodman AC

🛠️ 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.

  • Rule of thumb: 1 ton ≈ 450–600 sq. ft. (LearnMetrics)

  • My home: 1,650 sq. ft. × 9 ft ceilings = ~36,000 BTUs.

  • 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:

  • Mechanical permit before starting.

  • Electrical permit for the 240V line.

  • 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?

  • My attic ceiling is too low for a vertical air handler.

  • Horizontal units make duct branching easier in tight spaces.

  • 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

  • Removed the old air handler and vacuumed up years of dust.

  • Built a new ¾” plywood platform, reinforced with joist bracing.

  • 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

  • Shut off breaker to old unit.

  • Checked for live voltage with a multimeter.

  • 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:

  • Installed a solar-powered gable fan.

  • 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

  • Outdoor condenser (factory-charged with R-32).

  • Horizontal air handler with coil.

  • Thermostat (optional upgrade).

  • Installation manual, safety labels, warranty packet.

📑 3.2 Double-Checking Specs

Always check model numbers. Mine: Goodman GPCH33631.

  • Capacity: 36,000 BTU (3 ton).

  • Refrigerant: R-32.

  • Voltage: 208/230V, single phase.

  • Orientation: Horizontal.

Link: The Furnace Outlet product page.


🔧 4. Installation Steps

Here’s where the rubber meets the road.

🏗️ Step 1: Platform & Leveling

  • Placed air handler on reinforced platform.

  • Checked level with torpedo level — critical for condensate drainage.

👉 Even ¼” tilt can cause water pooling and overflow.

🌡️ Step 2: Ductwork

  • Connected supply plenum to main trunk.

  • Sealed seams with foil tape + mastic (never duct tape).

  • Insulated exposed ducts with R-8 wrap.

Resource: Energy.gov – Duct Sealing.

💧 Step 3: Condensate Drain

  • Installed primary drain line with ¼” per foot slope.

  • Added secondary (emergency) pan with float switch.

  • Tested by pouring a gallon of water through — no leaks.

👉 In humid climates, clogged drains = #1 cause of service calls.

⚡ Step 4: Electrical Work

  • Ran new 240V line to a disconnect box near condenser.

  • Bonded air handler ground to panel.

  • 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

  • Installed pre-insulated copper: ¾” suction, ⅜” liquid.

  • Routed through attic with wide bends to avoid pressure drop.

  • 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:

  • Pressurized with nitrogen to 300 psi for 30 minutes.

  • Evacuated with vacuum pump to 500 microns.

  • Verified vacuum hold.

Resource: HVAC School – Proper Vacuum Technique.

🔓 Step 7: Charging R-32

  • Opened service valves to release factory charge.

  • Adjusted for line set length (longer runs = extra refrigerant needed).

  • Checked pressures vs Goodman’s charts.

👉 Only a licensed HVAC pro can legally handle refrigerant (EPA 608 certification).

📲 Step 8: Thermostat Setup

  • Installed a smart Wi-Fi thermostat.

  • Configured for 2-stage cooling.

  • Synced to my phone for remote monitoring.

🔊 Step 9: Startup & Commissioning

  • Checked airflow: ~1,200 CFM total (400 per ton).

  • Verified superheat & subcooling matched manufacturer spec.

  • Confirmed no abnormal vibrations or noise.


🔍 5. Mike’s Tool List

Here’s what I actually used:

  • Cordless drill + bits

  • Torpedo & 4-ft level

  • Sheet metal snips

  • Foil tape + mastic brush

  • PVC cutter (for drains)

  • Nitrogen regulator (loaned from tech)

  • Vacuum pump (tech supplied)

  • Multimeter (for verifying power off)

  • Torque wrench (for line set flares)


⏱️ 6. Timeline & Workflow

  • Day 1: Demo old unit, reinforce platform, prep ducts.

  • Day 2 morning: Install air handler + duct connections.

  • Day 2 afternoon: Electrical + drain setup.

  • Day 3: Tech arrives for line set, vacuum, charge, commissioning.

👉 From tear-out to first cold air: ~3 days.


💰 7. Cost Breakdown

Item Cost
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:

  • Platform secure & level

  • Duct seams sealed

  • Drain lines tested

  • Breaker correctly sized

  • Pressure & charge verified

  • Airflow balanced

  • Thermostat calibrated


🧹 9. Maintenance Routine

Keeping the system healthy:

  • Replace filters every 60–90 days.

  • Flush condensate line with vinegar every spring.

  • Rinse outdoor condenser coils twice per year.

  • Annual pro inspection (check charge, coils, amps).

Resource: Energy Star – AC Maintenance Tips.


🧭 10. Lessons Learned

  1. Permits add time — apply early.

  2. Prep is 50% of the job — strong platform, sealed ducts make all the difference.

  3. Don’t skimp on drain safety — my float switch already saved me once.

  4. Respect R-32 — mildly flammable, requires certified handling.

  5. 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:

  • Saved ~15% on labor

  • Gained confidence in the system’s quality

  • Future-proofed against the R-410A phase-out

  • 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.

Cooling it with mike

Leave a comment

All comments are moderated before being published