Field Sizing Tool

Load · Static · Duct · Retrofit

Existing
—T
Static
—
Target
—T
Step 01

Job & Site

Identify the call and where the equipment lives. Drives nothing in the math — just the report header and the sales handoff record.

Region: Central Illinois (default — enter ZIP)
1
2
3
4+
No Cool
No Heat
Comfort
Maint.
Quote
Other
Basement
Attic
Crawl
Closet
Garage
Mech Rm
Roof
Step 02

Existing Equipment

Nameplate data off the installed system. The existing tonnage and blower type are the load-bearing inputs here.

Outdoor Unit condenser / heat pump
AC + Furnace
Heat Pump
Package
Heat Only
−
3.0tons
0.53.06.0
+
= 36,000 BTU/hr cooling
−
13SEER
826
+
−
10yrs
030
+
R-22
R-410A
R-454B
R-32
Other
Single
Two-stage
Inverter
Indoor Unit furnace / air handler
Gas
Oil
Electric
Air Handler
Package
−
80kBTU
0150k
+
−
80%
6098
+
−
0kW
030
+
−
1200CFM
02400
+
Nameplate. Cross-check vs tonnage × 400 = 1200 CFM
PSC
ECM (const-torque)
Variable-speed
Sets default max static: PSC 0.50″ · ECM/VS up to 0.80–1.0″
−
0.50in. wc
0.301.20
+
Coil & Controls
Matched
Mismatched
Unknown
Basic
Program.
Smart
Zoning
Zoning system present
Step 03

Static Pressure Test

Dual-port manometer. Return probe after filter / before blower. Supply probe after coil/blower / before branches. TESP = |supply| + |return|. Drag the sliders — readings snap to 0.01″.

Test Conditions
Cooling
Heating
Fan Only
Filter clean & installed
Coil dry
Pressure Readings in. w.c.
−
0.15in. wc
00.40 flag1.0
+
−
0.20in. wc
01.0
+
−
0.08in. wc
00.10 max0.5
+
−
0.25in. wc
00.20–0.30 typ0.6
+
Measured Airflow optional
Airflow was measured (flow grid / temp-rise)
−
1100CFM
02400
+
= 367 CFM/ton (target 350–450)
Step 04

Duct System

Geometry of the existing distribution. The supply trunk size and total return free area drive the velocity and balance checks.

Supply Trunk
Round
Rectangular
−
14in
424
+
−
20in
636
+
−
8in
424
+
Sheet Metal
Duct Board
Flex
Flex adds ~30% friction vs smooth metal
Conditioned
Attic
Crawl
Return System
1
2
3
4
5+
Single central return is the most common defect
−
600sq in
02400
+
Target ≥ 2 sq in per CFM. Needs ≥ 2400 sq in at target.
Dedicated bedroom returns
Transfer grilles / jumper ducts
Adequate door undercut
Branches, Registers & Condition
−
8
030
+
−
9
030
+
None
Minor
Significant
Mastic
Tape
None
Crushed / kinked flex present
Step 05

Home & Load Screen

Field screen for the demand side — central IL is IECC Zone 5A. This estimates the proper size; it does not replace a room-by-room Manual J. The report flags when a full calc is warranted.

Structure
−
1800sq ft
4006000
+
−
8ft
714
+
1
1.5
2
3
−
1980
19002026
+
Envelope
Poor
Average
Good
Excellent
Poor
Average
Good
Single-pane
Double-pane
Low-E
Low
Moderate
High (W/S glass)
Leaky
Average
Tight
Mild
Moderate
Severe
Ducts in unconditioned space
Step 06

Comfort Symptoms

Tap everything the customer reports. The report correlates these against the measured data.

Reported Issues multi-select
Can't keep up (hot)
Can't keep up (cold)
Short cycling
Runs constantly
Hot / cold rooms
High humidity
Whistling / noise
High bills
Blower strained
Step 07

Assessment Report

Existing-system findings, the right-sized recommendation, and three solution paths. Confirm the target tonnage — that and the existing tonnage are what cross to the sales tool.

Sales Handoff
Existing
3.0T
→
Target (Confirm)
3.5T
−
3.5tons
0.5screened: 3.56.0
+
Screened recommendation shown above. You make the final call — adjusting this re-runs the duct check.
● Auto-sized from load
Furnace — sized to the heating load (independent of the AC)
Existing Furnace Out
77kBTU
→
Target (Confirm)
60kBTU
−
60,000BTU out
30kscreened: 60k140k
+
Heating load drives this — sized separately from the AC tonnage. Sales picks the matching furnace.
● Auto-sized from load
Existing System Findings
Key Metrics
Solution Paths
Output & Handoff
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