Is 3 Tons Enough?
Mike’s Real-World Sizing Guide for the Goodman 15.2 SEER2 R-32 System
Let me give you the truth right upfront:
If you don’t know how much heat your home gains during the day, you’re throwing darts at a board.
And that’s exactly how people end up with 3-ton systems that can’t cool a bedroom, or 4-ton systems that short-cycle themselves into an early death.
According to [ASHRAE Residential Load Calculation Methods], tonnage depends on heat gain — not flooring, not “rule of thumb,” not the old unit, and definitely not what your neighbor has.
This Goodman 3-Ton 15.2 SEER2 R-32 condenser paired with a 3.5-ton horizontal TXV coil is a fantastic system — but only if the building deserves a 3-ton load.
Let’s get into the real-world rules.
1. What “3 Tons” Actually Means (Reality vs Expectation)
A 3-ton AC equals:
36,000 BTUs/hour under lab conditions.
But those conditions reflect the [DOE SEER2 Efficiency Testing Requirements], not your home:
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ductwork sized perfectly
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attic temperature moderate
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humidity controlled
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static pressure low
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coil saturated evenly
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airflow between 400–450 CFM/ton
In the real world?
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weak ducts → you lose 20–40% capacity
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hot attics → capacity drops 15–20%
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high humidity → coil struggles and BTUs fall
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bad return placement → comfort tanks
A “3-ton” system might only deliver the equivalent of 2.3–2.7 tons if airflow is wrong.
If duct static pressure exceeds 0.7 (common in older homes), your real BTU output barely resembles the lab rating.
2. Why “Rule of Thumb” Sizing Is Garbage
Let me make something painfully clear:
1 ton per 500 sq ft does not work anymore.
It never did — but today’s loads are far more complex.
Solar gain.
Ceiling height.
Windows.
Occupancy.
Insulation quality.
Layout openness.
Ventilation requirement.
These matter more than square footage.
The only correct method is [Manual J Heat Load Sizing Procedure], which calculates:
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internal heat
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external heat
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infiltration
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equipment load
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latent load
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envelope losses
Manual J is the sizing bible.
Everything else is guesswork.
3. When a 3-Ton Goodman R-32 System Is Actually Perfect
This Goodman GLXS4BA3610 condenser paired with the CHPTA4230C3 horizontal coil is ideal when ALL conditions align:
Strong match for:
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1,400–2,000 sq ft homes with decent insulation
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proper ductwork supporting 1,200–1,500 CFM
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ceiling heights 8–9 feet
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moderate to low window exposure
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closed-off bedrooms with balanced supply/return
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humidity under control
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attic temps within normal range
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low to normal internal heat load
If the building is tight, insulated correctly, and follows [U.S. Department of Energy Home Cooling Best Practices], a 3-ton R-32 delivers powerful, stable cooling.
R-32’s efficiency, higher latent removal, and better heat-transfer coefficient (per [EPA R-32 Refrigerant Capacity & GWP Guidance]) give it an advantage over older R-410A units — but only if the building load matches 3 tons.
4. When 3 Tons Will Struggle — Even If the Square Footage Looks Right
Here’s where things go wrong.
A 1,700 sq ft home should, on paper, match 3 tons — but in REAL operation, these factors overpower the system:
Situations that crush a 3-ton:
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west-facing walls full of windows
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poor insulation or air sealing
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uneven duct distribution
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single return in a hallway
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long flex duct runs
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attic hitting 130–150°F
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open-concept living rooms
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high occupancy homes
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large kitchen heat loads
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bonus rooms over garages
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old ductwork with high static
Static pressure is everything.
0.36–0.50 inches WC (total external static)
Most older ducts run at:
0.70–1.20 inches WC
That’s ductwork murder.
Your 3-ton Goodman suddenly behaves like a 2-ton.
5. Why Goodman Uses a 3.5-Ton Coil With a 3-Ton Condenser
This throws people off.
Why would Goodman give a 3.5-ton coil for a 3-ton system?
Because:
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larger coil = lower static pressure
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larger coil = better coil saturation
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larger coil = better humidity removal
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larger coil = quieter airflow
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larger coil = better efficiency under real heat load
This combo is designed for REAL homes, not lab tests.
Higher SEER2 retention.
Steadier temperatures.
Less coil freeze-up risk.
Better airflow stability.
This is exactly what DOE SEER2 Efficiency Testing Requirements try to represent — but the 3.5-ton coil gives you those results in your house, not just in a lab.
6. Quick Sizing Test — Will a 3-Ton R-32 System Work in YOUR Home?
These are the questions I ask before approving a 3-ton install.
Does your return duct measure 14–16 inches?
If not, airflow will choke.
Does your home stay under 78–80°F with blinds closed on a hot day?
If not, your load is too high.
Does humidity sit between 40–55% normally?
If not, your latent load is too high.
Do you have more than 250 sq ft per supply vent?
If yes, expect hot zones.
Is your attic insulated or spray-foamed?
If not, expect tonnage loss.
Do you have more than 200 sq ft of west-facing windows?
If yes, you probably need 3.5–4 tons.
Is static pressure under 0.6?
If not, 3 tons won’t deliver full output.
7. Real Places Where a 3-Ton Goodman R-32 Works Beautifully
I’ve installed 3-ton systems in:
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ranch homes (1,500–1,900 sq ft)
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two-story homes with balanced returns
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well-insulated townhomes
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office suites, low internal heat
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modern homes built after 2010
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homes with minimal solar gain
These installs run cold, quiet, efficient, and stable.
8. Real Places Where a 3-Ton WILL Fail (Even With a Great System)
These will destroy a 3-ton’s hopes and dreams:
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2,000+ sq ft with poor insulation
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cathedral ceilings
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open concept with high solar gain
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bonus rooms above garages
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homes with only ONE return
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long, uninsulated ducts in attics
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older homes with duct leakage >20%
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heavy appliance use (kitchens, gaming setups)
Even the powerful Goodman R-32 condenser can’t compensate for major building load deficiencies.
**9. Mike’s Final Verdict:
Is a 3-Ton Goodman R-32 the Right Size?**
Here’s the final word:
✔ A 3-ton R-32 system is perfect if your heat load matches 3 tons.
✔ It is NOT decided by square footage alone.
✔ Ductwork and static pressure decide half the battle.
✔ Insulation, windows, and humidity decide the other half.
✔ The Goodman 3.5-ton coil pairing helps — but can’t override bad ductwork.
✔ If the building deserves 3 tons, this system will cool like a champ.
✔ If the building demands more, no 3-ton in the world can keep up.
Right tonnage + right ducts + right airflow =
15–20 years of great performance.
That’s the Mike way.
In the next blog, we will get to know why Goodman pairs the condenser with a 3.5-ton coil.
