Sizing an evaporator coil is one of the most overlooked steps in HVAC planning. Most homeowners focus on the outdoor unit’s tonnage or the furnace’s BTUs, but the coil in between is just as critical. If you’re considering a 3 Ton Horizontal Cased Painted A-Coil with TXV, here’s what you need to know to decide if it’s the right fit for your house.
🔧 1. Why Coil Sizing Matters
Think of your coil as the bridge between your furnace and condenser. It’s where refrigerant absorbs heat (cooling mode) or releases heat (heating mode with a heat pump).
If the coil is sized wrong:
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Too small → the system strains, can’t keep up, and efficiency drops.
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Too big → the system short cycles, leaving you with high humidity and uneven comfort.
A properly sized coil ensures:
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Steady temperatures.
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Lower energy bills.
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Longer system lifespan.
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Fewer repairs over time.
📖 For background, the U.S. Department of Energy explains how sizing impacts performance and efficiency
📏 2. What Does “3 Ton” Really Mean?
In HVAC terms, “ton” refers to cooling capacity, not weight.
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1 Ton = 12,000 BTU/hr
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3 Ton = 36,000 BTU/hr
That means a 3 Ton A-Coil is built to handle about 36,000 BTUs of cooling per hour when matched with the right outdoor unit.
Why BTUs Matter
BTUs (British Thermal Units) measure heat energy. Your home generates heat loads through:
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People and pets
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Cooking and appliances
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Sunlight through windows
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Poor insulation
The coil must be sized to absorb that load efficiently.
👉 For deeper reading on BTU basics, see Energy Star’s HVAC guide.
🏡 3. How Big of a Home Does a 3 Ton Coil Serve?
Here’s the general “rule of thumb”:
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400–600 sq. ft. per ton of cooling (varies with insulation, windows, and climate).
By that math:
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3 Ton = 1,200–1,800 sq. ft.
Mike’s Example
“My house is about 1,700 sq. ft. in a moderate climate. The 3 Ton coil hits the sweet spot. Before I replaced my old system, it would short cycle constantly because the coil and condenser were mismatched.”
Rule of Thumb vs. Reality
While these square footage ranges give a ballpark, they aren’t enough on their own. A proper Manual J Load Calculation is the gold standard. It factors in:
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Insulation levels.
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Number and type of windows.
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Shading and orientation.
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Local climate data.
🔄 4. Matching the Coil with Your System
An evaporator coil never works alone. It must be matched to both the condenser and the furnace/air handler.
4.1 Condenser + Coil Match
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The outdoor condenser provides the refrigerant capacity.
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The coil must be designed to handle that capacity.
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Mismatched pairings reduce efficiency and void warranties.
📖 AHRI (Air-Conditioning, Heating & Refrigeration Institute) maintains a database where you can check if your indoor and outdoor units are matched (ahridirectory.org).
4.2 Furnace/Air Handler Compatibility
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The coil cabinet must physically fit your furnace or air handler.
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Blower size must handle the airflow (CFM).
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Example: a 3 Ton coil needs roughly 1,200 CFM airflow.
4.3 TXV Advantage
Your Goodman 3 Ton coil includes a TXV (Thermostatic Expansion Valve).
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Improves refrigerant metering.
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Adjusts performance under varying load conditions.
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Supports higher efficiency outdoor units (SEER2 rated).
🌡️ 5. Climate & Insulation Considerations
Sizing depends heavily on where you live and how well your house holds heat.
5.1 Hot & Humid Climates
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Require more cooling per square foot.
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Example: In Florida, a 3 Ton coil might cover only ~1,300 sq. ft. comfortably.
5.2 Cold Climates
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Cooling demand is lower, so the same coil might serve ~1,800 sq. ft.
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But heating needs (if using a heat pump) may demand additional considerations.
5.3 Insulation & Windows
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A well-insulated attic and double-pane windows can reduce load by up to 20%.
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Mike added attic insulation and noticed his 3 Ton system cycled less often.
📖 See insulation’s role in HVAC efficiency explained by Energy.gov.
💸 6. Cost & Efficiency Considerations
Coil size isn’t just about comfort—it’s tied directly to your utility bills.
6.1 Oversized Coil Problems
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Short cycles = higher wear and tear.
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Poor humidity control (sticky air).
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Higher upfront cost for larger equipment.
6.2 Undersized Coil Problems
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Runs constantly, driving up electric bills.
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May not cool on the hottest days.
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Shorter system life due to strain.
6.3 Efficiency Ratings (SEER2)
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Your system’s efficiency is rated by SEER2 (Seasonal Energy Efficiency Ratio 2).
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A mismatched coil can drag down SEER2 by several points.
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Goodman’s R-32 coils are engineered for SEER2 compliance.
🛠️ 7. Mike’s Tips for Homeowners
Here’s what Mike recommends after going through his own installation:
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Don’t size by square footage alone. Always factor in insulation and climate.
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Confirm AHRI matches. Protect your warranty and efficiency rating.
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Check ductwork. Undersized ducts can choke a 3 Ton coil, no matter how perfect the load calc.
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Get a Manual J calc. Even if you DIY, hire a pro for this one step. It’s worth it.
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Consider future add-ons. If you plan to finish a basement or add a sunroom, factor that into sizing now.
✅ 8. Is a 3 Ton Coil Right for You?
A 3 Ton A-Coil is a solid choice for:
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Homes between 1,400–1,800 sq. ft. (average insulation, moderate climate).
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Systems paired with a 3 Ton condenser and compatible furnace/air handler.
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Homeowners who want a balance of comfort and efficiency.
Not the best choice if:
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Your house is under 1,200 sq. ft. (may be oversized).
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Your house is 2,000+ sq. ft. without excellent insulation (may be undersized).
Mike’s Final Word
“Sizing isn’t guesswork. My Goodman 3 Ton coil has been running smooth for years because I matched it properly. If you’re serious about comfort and efficiency, get the sizing right—your wallet and your AC will thank you.”
In the next topic we will know more about: Single-Stage vs. Two-Stage Systems: Which Works Best with a 3 Ton TXV Coil?
