🔧 Introduction: The Coil Is the Silent Airflow Killer (If You Don’t Align It Right)
Every installer knows the evaporator coil is important — but few understand how dramatically coil alignment affects:
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airflow
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static pressure
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temperature rise
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compressor longevity
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furnace noise
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efficiency
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dehumidification
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and capacity
You can install the most powerful furnace in the world, but if the coil sits crooked, off-center, under-sized, or misaligned, the blower can only pull air through about 60–75% of the coil surface.
That means:
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higher static
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noisier operation
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hotter heat exchangers
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colder coils
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coil freeze-ups
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poor cooling performance
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shorter ECM motor life
I’ve seen brand-new 96% Goodman furnaces sound like vacuums because the coil alignment was off by 1".
That’s why I created the Coil Alignment Trick — the method I teach every apprentice to guarantee:
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centered airflow,
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smooth static pressure,
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correct temperature rise,
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proper coil face coverage, and
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full system capacity.
This is how you pair any evaporator coil — A-coil, multi-position, case coil, or uncased — with a furnace without choking airflow.
80,000 BTU 96% AFUE Upflow/Horizontal Single Stage Goodman Gas Furnace - GR9S960803BN
📐 1. Why Coil Alignment Matters More Than Most Techs Realize
Let’s start with physics.
The blower does not pull air evenly across the coil surface by magic.
Air ALWAYS follows the path of least resistance.
If the coil is:
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offset left or right,
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crooked,
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too tall for the cabinet,
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positioned too far back,
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tilted too far forward,
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resting too low in the drain pan,
…then the blower will send most of the air through the easiest path, not the full coil surface.
This creates:
❌ Higher static pressure
❌ Reduced airflow (CFM)
❌ Reduced cooling capacity
❌ Higher temperature rise
❌ More blower wattage
❌ Uneven coil frosting
❌ Premature furnace limit trips
❌ Compressor overheating
External verified link:
• ACCA Manual S — Equipment Selection & Airflow Requirements
https://www.acca.org/standards
A misaligned coil can choke airflow as much as a dirty filter.
🧲 2. The Three Surfaces That Must Align for Perfect Airflow
Jake’s Coil Alignment Trick focuses on aligning three critical faces:
1️⃣ The Furnace Outlet (Supply Air Opening)
The rectangular supply collar on the furnace dictates where airflow begins.
2️⃣ The Coil Case or Uncased Coil Rails
The coil housing must sit perfectly centered to the furnace outlet.
3️⃣ The Coil Face (The Actual Finned Evaporator Surface)
This is where airflow enters the refrigeration circuit.
If the coil case is centered but the coil face inside the case is off-center, airflow is still choked.
Jake checks both.
🔩 3. Common Coil Alignment Mistakes That Kill Airflow
These are the mistakes I see every week on new installs:
❌ Coil set too far forward
→ Air bypasses the rear of the coil
→ Coil freezes due to uneven loading
❌ Coil “falling” into the drain pan
→ Blocks the lower third of the coil
→ Static skyrockets
❌ A-coil legs not seated in their guides
→ Coil sits crooked
→ Airflow hits only one slope
❌ Coil offset left or right
→ Airflow hits the metal instead of the fins
→ ECM motors scream
❌ Coil case smaller than the furnace
→ Air bypass along the sides
→ Loss of capacity
❌ No transition between furnace and coil
→ Turbulence → static pressure → noise
❌ Coil installed backward (yes, it happens)
→ Correct airflow direction is essential
❌ Coil blocking internal access panels
→ Makes future service impossible
Every one of these issues is prevented by the alignment method below.
🛠️ 4. Jake’s Coil Alignment Trick (The Exact Method)
Here is the field-tested process that eliminates coil-related airflow restrictions.
🟦 STEP 1 — Dry Fit the Coil on the Furnace Before Sealing Anything
Set the coil down gently and check:
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left-right alignment
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front-back placement
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overall stability
This is your chance to make adjustments before the screws and mastic go on.
🟩 STEP 2 — Align the Coil Case Width to the Furnace Width
If your furnace is 17.5" wide (like the Goodman GR9S960803BN), your coil must either:
✔ Match 17.5" width
or
✔ Use a proper transition
Do NOT “make it fit” by crushing coil walls or bending sheet metal.
External verified link:
• Goodman Coil Compatibility Guide
https://www.goodmanmfg.com
🟧 STEP 3 — Center the Coil Face to the Furnace Opening (Not the Case!)
Most techs center the coil case, but the coil face inside the case may be offset.
Jake’s trick:
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Remove the coil access panel.
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Look inside the case.
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Identify the true coil center (finned surface).
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Align THAT with the furnace supply opening.
This alone can drop static pressure by 0.1–0.2" WC.
🟥 STEP 4 — Set the Coil Back Slightly (⅜" to ½" From Furnace Front)
This gives:
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smoother airflow
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lower turbulence
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better coil face coverage
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quieter operation
Never push the coil flush to the furnace front.
🟪 STEP 5 — Make Sure the Coil Legs Are Seated in the Drain Pan Rails
A-coil legs MUST sit in:
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the molded guides
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the factory rails
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the pan slots
If they’re not seated, the coil drops into the pan and blocks airflow.
🟫 STEP 6 — Check the Slope (¼” Tilt Toward the Drain)
Coils must drain properly.
Drain toward:
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right side,
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left side,
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or front — depending on coil model.
Do NOT tilt the coil too far.
Over-tilting creates airflow imbalance.
External verified link:
• International Mechanical Code – Evaporator Coil Drainage Requirements
https://codes.iccsafe.org
🟨 STEP 7 — Seal the Coil Base to Prevent Bypass Air
Use:
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mastic
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foil tape (UL-181)
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sheet metal closure plates
Make sure air cannot sneak around the coil case.
Air must pass through the coil fins only.
Air bypass = lost tonnage.
🌬️ 5. Coil Transitions — When Jake Builds Them and Why
When the furnace is 17.5" and the coil is:
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14"
-
21"
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24"
…you MUST use a transition.
Jake’s rules:
✔ Always build a straight-shot vertical transition
✔ Keep transitions tall and smooth
✔ Use 45° angles instead of 90°
✔ Never collapse sheet metal to make it “sort of fit”
✔ Maintain proper opening size
A good transition:
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lowers static
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smooths airflow
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increases coil efficiency
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quiets the furnace
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reduces blower wattage
Transitions take time —
but they save you from high-static callbacks.
🔊 6. Noise Reduction: How Alignment Affects Sound Levels
A poorly aligned coil causes:
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blower howl
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air whistle
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vibration
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coil “pinging”
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duct rumble
Proper alignment creates laminar airflow.
Laminar airflow is:
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quiet
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smooth
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efficient
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easier on the blower
Customers notice when their system is quiet.
Proper coil alignment makes you look like a hero.
📉 7. Coil Alignment and Static Pressure (Why It’s Everything)
Static pressure is the #1 diagnostic metric in HVAC performance.
External verified link:
• Fieldpiece Static Testing Tools
https://www.fieldpiece.com
A misaligned coil commonly increases static by:
+0.15 to +0.30" WC
That may not sound like much, but on a system targeting:
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≤ 0.50" WC total external static,
this is catastrophic.
Proper coil alignment typically drops static by 10–30%.
That means:
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quieter blower
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more airflow
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better cooling
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better heating
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longer motor life
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better efficiency
All from a trick that takes 2–4 minutes during installation.
🌡️ 8. Temperature Rise and Coil Alignment (Huge Connection)
On a Goodman GR9S960803BN, proper rise is:
35°F–65°F
If rise is HIGH (65°F+), it usually means:
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airflow restriction
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coil blockage
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static too high
Most installers assume “the blower speed is wrong.”
It’s usually the coil alignment.
Align the coil → lower static → lower rise → perfect furnace performance.
🧪 9. Jake’s Post-Install Verification Tests (Do These Every Time)
✔ Test 1: Flashlight Alignment Check
Shine a flashlight upward through the furnace opening.
You should see the entire coil face illuminated perfectly.
✔ Test 2: Static Pressure Test
Target:
0.5" WC or less
✔ Test 3: CFM Test
Use airflow tables or TrueFlow grid (if available).
✔ Test 4: Temperature Rise Test
Must be within spec.
✔ Test 5: Coil Drain Test
Pour water into coil pan → verify proper drainage.
✔ Test 6: Noise Check
Listen for turbulence.
If you hear whistling, realign.
🚫 10. Jake’s “Never Do This” List for Coil Installs
These mistakes will destroy airflow and kill system performance.
❌ Never crush the coil cabinet to make it fit
❌ Never misalign the coil by more than ¼"
❌ Never install an uncased coil without sealing the perimeter
❌ Never leave a gap between the case and furnace
❌ Never block the coil with insulation or wiring
❌ Never install the coil backward
❌ Never allow the coil to rest in the drain pan
❌ Never skip a transition when coil and furnace don’t match
These are instant airflow killers.
📘 Conclusion: Coil Alignment Is the Difference Between a Good Install and a Jake Install
Every furnace needs a coil.
But not every furnace gets a coil that’s aligned correctly.
A misaligned coil:
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steals capacity
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increases static
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ruins airflow
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makes the furnace noisy
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shortens blower life
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lowers SEER/AFUE
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causes coil freeze-ups
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increases energy bills
But a Jake-aligned coil:
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sits perfectly centered
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drains correctly
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aligns to the furnace
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lowers static pressure
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boosts airflow
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improves comfort
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reduces noise
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increases system life
The Coil Alignment Trick takes 2–4 minutes.
The payoff lasts for 20 years.
This is installation craftsmanship.
This is how you eliminate callbacks.
This is how you install like a pro —
and like Jake.
Buy this on Amazon at: https://amzn.to/48HGh2g
In the next topic we will know more about: Quiet by Design: The Anti-Rumble, Anti-Whistle Installation Tricks Jake Uses on Every Furnace
