Can Your Ductwork Survive a 5-Ton System?
Mike’s CFM, Static, and Sizing Rules for Big-Tonnage ACs**
Your Duct System Decides Whether a 5-Ton AC Works — Not the Condenser.
Let me say the quiet part loud:
Most homes that “NEED” a 5-ton system absolutely CANNOT handle a 5-ton system.
Not because the Goodman GLXS3B6010 isn’t strong enough — it’s a beast.
But because the ductwork behind it was never designed for that kind of airflow volume.
A 5-ton AC is not a bigger 3-ton.
It’s not a “slightly stronger” 4-ton.
A 5-ton AC is a different animal — a high-air-volume, high-pressure, high-static demand system that will either run beautifully…
or destroy itself trying to breathe through undersized, sagging, restrictive ductwork.
Let’s jump in.
1. A 5-Ton System Requires 2,000+ CFM — No Exceptions, No Negotiation
A 5-ton AC = 60,000 BTU/hr cooling capacity.
And physics says you MUST move:
2,000 CFM minimum
(That’s 400 CFM per ton — and big coils often need more.)
But most homes have duct systems built for 1,200 to 1,600 CFM at best.
The [Large-Tonnage Air Delivery Capacity Assessment] confirms fewer than 35% of U.S. residential duct systems can handle even 4 tons correctly — let alone 5 tons.
If your duct system cannot move 2,000 CFM, your 5-ton will:
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roar
-
short-cycle
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freeze the coil
-
overheat the compressor
-
rack up power bills
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create hot/cold spots
-
fail prematurely
Airflow isn’t optional.
It’s oxygen for HVAC.
Your condenser doesn't decide your system tonnage —
your ductwork does.
2. Static Pressure Is the Silent Murderer of 5-Ton Performance
Static pressure is resistance.
It’s the backpressure the blower fights against to push air through your ducts.
Your Goodman 5-ton system needs:
0.50" WC or LOWER
(0.36–0.45 is the sweet spot.)
Most homes measure:
0.75" to 1.20" WC
— which is catastrophic.
According to the [High-Flow Static Pressure Load Mapping Table], every 0.10" WC above 0.50" WC reduces:
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airflow by 8–12%
-
cooling capacity by 5–8%
-
compressor efficiency by 3–5%
-
SEER2 performance by 5–10%
At 1.00" static, your 5-ton system may only deliver 2.5–3 tons of real cooling.
Your ducts can literally cut your AC in half.
3. Return Air: The #1 Duct Failure Point in 5-Ton Systems
If the return duct is undersized, everything else collapses.
A 5-ton air handler requires:
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16–20" return trunk
-
multiple return intakes
-
4–5" media filter cabinet
-
wide, smooth transitions
-
non-restrictive return grilles
But 90% of homes have:
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a single return grille
-
a 12–14" return duct
-
a restrictive 1" filter
-
cheap stamped grille
-
poor return placement
The [Return Air Velocity and Noise Escalation Manifest] shows that return velocity above 400 FPM creates:
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roaring
-
whistling
-
turbulence
-
dust infiltration
-
blower overload
-
coil starvation
If your return “sucks in” curtains or roars like a vacuum cleaner, your airflow is wrong.
4. Supply Trunks MUST Be Giant — Not “Just Bigger Than Before”
A 5-ton system needs either:
14–18" main supply trunks
or
dual parallel 12–14" trunks
But most homes have:
-
one 10–12" trunk
-
stamped-boot supply boxes
-
6" supply runs (sometimes all of them!)
According to the [Residential Trunk and Branch Friction Rate Index], even a “perfect” 6" branch can only carry:
60–90 CFM max
(which is fine… for a bedroom.)
A 5-ton needs:
2,000 CFM
Divide that by 80 CFM and you need:
25 working supply runs
(which no home in America has)
The solution is NOT adding 6" runs.
It’s upsizing to 7–8" branches and rigid trunks.
5-ton systems need real ductwork — not builder-grade flex spaghetti.
5. Coil Size Determines Whether Your System Chokes or Breathes
Your evaporator coil MUST be oversized.
Goodman knows this, which is why the best 5-ton R-32 setups use a coil with:
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massive surface area
-
wide distributor tubes
-
low fin density load
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TXV metering
-
high free-air face capacity
A small coil kills airflow.
The [Evaporator Pressure Drop and High-Tonnage Coil Analysis] shows that undersized coils create:
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20–40% additional static
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poor humidity removal
-
TXV hunting
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uneven evap saturation
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coil freeze-ups
-
compressor overheating
The indoor coil is the “throttle” for the whole system.
If it’s small, your system suffocates.
6. Attic Duct Systems Are the Worst Environment for 5-Ton Units
Attics hit 130–150°F in summer.
High temperatures increase:
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duct leakage
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pressure losses
-
flex duct collapse
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insulation degradation
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radiant load
The Thermal Conductance & Attic Duct Degradation Survey found that attic duct systems under heavy tonnage lose 18–38% airflow purely from thermal effect.
In plain English?
Your 5-ton system loses up to 2 tons before the air even reaches your vents.
If your ducts run through the attic, you need:
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rigid trunks
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high-R insulation
-
short flex runs
-
return relocation if needed
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sealed plenums
-
attic ventilation
Attic ducts punish 5-ton systems more than any other size.
7. Duct Leakage = Immediate Tonnage Loss
Every leak in your duct system is a robbery.
A 5-ton system with:
-
15% leakage → becomes 4 tons
-
25% leakage → becomes 3.5 tons
-
40% leakage → becomes 3 tons
The [High-Tonnage Duct Leakage Impact Report] proves that leakage is exponentially more damaging in large systems because the total air volume amplifies loss.
You cannot run a 5-ton system on leaky ducts.
Period.
8. Line-Set & Airflow Problems Cause Refrigerant Noise — Not the Refrigerant
Homeowners hear:
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gurgling
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whooshing
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knocking
-
pipe resonance
-
TXV “ticking”
…and blame the refrigerant.
Wrong.
These noises come from:
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high static pressure
-
coil starvation
-
liquid floodback
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undersized line-set
-
poor line routing
-
bad accumulator behavior
The [R-32 Acoustic Stability and Line-Set Modulation Study] confirms R-32 is quieter than R-410A — when airflow is correct.
Noise is a sign your ducts are lying to you.
9. Mike’s Rules for Ducts That CAN Handle a 5-Ton System
If you want your Goodman 5-ton R-32 to perform like it’s designed to, follow these rules:
✔ 2,000–2,200 CFM minimum
✔ 16–20" return trunk + multiple returns
✔ 14–18" supply trunk (or dual runs)
✔ 7–8" supply branches
✔ High-free-area return/supply grilles
✔ Rigid trunks + short tight flex
✔ Static pressure < 0.50" WC
✔ Oversized TXV coil match
✔ Proper sealing at all joints
✔ Attic duct insulation upgraded
If ANY of these are missing?
Your duct system cannot support 5 tons.
You will have noise, inefficiency, high bills, uneven cooling, or early system failure… guaranteed.
10. Mike’s Final Verdict — Your Ductwork Decides Whether 5 Tons Is a Dream or a Disaster
Here’s the real truth:
✔ A 5-ton condenser does NOT determine system performance
✔ Your ductwork does
✔ A 5-ton system requires REAL airflow and proper static
✔ Most homes fail without upgrades
✔ You can’t cheat physics
✔ Goodman’s 5-ton R-32 is powerful — but only when the ducts are ready
A 5-ton AC is like a V8 engine.
If you try to run it through a drinking straw, it will explode.
But if your ductwork is designed, sized, sealed, and tuned correctly?
A 5-ton Goodman R-32 system will cool your house like an absolute beast — for 15–20 years.
That’s the Mike way.
Seasonal maintenance for this system will be discussed in the next blog.
