Bridge Active

Data imported from Manual S Selection:

Imported baseline: CFM • in. w.c. ESP •

Manual D baseline unlocked

CFM, ESP, and device losses were prefilled from the selected blower path.

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Step 1: Environmental Baseline

BTU

Calculated per Manual J procedures.

°F

Baseline: 20°F Cooling / 30-70°F Heating.

Cooling mode applies a wet-coil pressure multiplier. Heating mode keeps the entered coil value dry.

ANSI/ACCA Manual D Requirement: Air density decreases at higher elevations. This tool applies an Altitude Correction Factor (ACF).
FT

No Equipment Selection?

Select Equipment & Airflow First
CFM
Imported from Manual S at CFM
Caution: Airflow mismatch. Manual S was verified at CFM. Changing this may invalidate your equipment selection.

If entered, this value takes precedence over BTU/ΔT.

CFM

Auto-derived only when manual CFM is blank.

Technical Source: This value must be derived from the Manufacturer Blower Performance Table at your specific Design CFM.
IWC
ESP imported from selected blower point

Step 2: Device Pressure Losses

Component Budget

Deduct the static pressure consumed by filters, coils, and grilles from the Blower ESP to find your Available Static Pressure (ASP).

Pressure Drop
IWC

Cooling mode applies a wet-coil factor to the entered coil pressure drop. Heating mode keeps the entered coil pressure drop in dry-coil condition.

Preset values are reference benchmarks at 1200 CFM and remain manually overrideable.

IWC

*Using Manual D Smart Default: IWC.

Available Static (ASP)

Step 3: Circulation Path (TEL)

Supply Side (Longest Run)

Equivalent Length Audit
FT
Flex Duct Modifier
4% Perfect 1.0x
15% Compressed 2.0x
30% Poor 4.0x

Return Side (Intake Run)

FT
Return Flex Modifier
4% Perfect 1.0x
15% Compressed 2.0x
30% Poor 4.0x

Total Path Audit (TEL)

Terminal checks now use entered terminal CFM first, then inherit from a linked run when assigned, with system-CFM screening fallback preserved for backward compatibility.

Governing Total Effective Length (TEL)

Step 4: Critical Path, Validation & Sizing

Current Base Path

The fittings you selected in Step 3 automatically populate the first critical-path candidate.

Supply TEL / Return TEL / Total

Branch CFM Sanity Check

Assigned Runs

Assigned Total

System Airflow

Sanity Band

Critical Path Auto-Selection

Governing TEL

Duct Sizing Output

Diagnostic Results Dashboard

System Friction & Performance Summary

FAIL ⚠

Diagnostic Friction Rate

0.100 FR

Preferred operating band: 0.06 to 0.18 in. w.c. / 100 ft.

Design CFM

Altitude Corrected

Available Static Pressure

Total Effective Length

Section N4 Fitting Matrix Map

Critical Path

System Warnings

Diagnostics Requiring Review

These results are theoretical design baselines generated from user-provided inputs using Manual D–style calculations. They do not guarantee system performance, code compliance, or installation suitability. Field verification by a qualified professional is required.

Recommended Duct Sizes

Primary action output

Pressure Budget Breakdown

ESP → DPL → ASP

Blower ESP

Component DPL

Available ASP

Governing Path Explanation

Why this path controls the design

Governing Path
Reason
Governing TEL

System Snapshot

Airflow Source
Blower Point
ACF
DPL
ASP
FR

Project Block

Project
Address
Company
Phone
License

Warnings & Errors

Technical Review

Manual D Duct Design Reference Context

This workflow follows ACCA Manual D® residential duct design methodology using upstream Manual J® load calculations and Manual S® equipment selection inputs. Results support structured evaluation of available static pressure (ASP), total equivalent length (TEL), and friction rate (FR) before final duct sizing and layout decisions.

Code Audit Date: April 2026

Verify blower tables, manufacturer performance data, local code requirements, and project-specific field measurements before final installation or system balancing decisions.

HVAC Design Workflow

Load → Equipment → Duct Design

Duct sizing depends on both calculated system load (Manual J) and selected equipment airflow characteristics (Manual S). Use this tool to validate distribution performance based on those upstream design decisions.

Manual D Validation Badge

Primary issue:

View Manual J → Load Calculation Return with Manual D validation status, primary issue, and governing path context. View Manual S → Equipment Selection Return with Manual D airflow validation so equipment selection can be reviewed against duct restrictions.

Manual D Engineering Logic & Logic Matrix

The Governing Equations

Available Static Pressure (ASP)

ASP = ESP - (DPL_Coil + DPL_Filter + DPL_Grilles)

Manual D Friction Rate (FR)

FR = (ASP × 100) / TEL

Normative Section N4 Reference Table

Common Fitting TypeStandard EL (FT)
90° Round Elbow (Adjustable)20-35
Wye Branch (45° Degree)25-40
Plenum to Round Collar (Entry)35
Standard Supply Boot (Rect to Round)30

Verified Manual D Reference Engine

This tool applies ACCA Manual D duct design relationships used in real-world system sizing and diagnostics. Friction rate (FR), available static pressure (ASP), and total effective length (TEL) calculations are aligned with reference tables and field-standard engineering practices.

View Code Citations & Source Mapping →

Manual D Technical Documentation

ApplicationRecommended FPM
Supply Trunk700–900
Supply Branch500–700
Return Trunk600–800
Return Branch400–600
Flex Duct< 600
ConditionFR (in. w.c./100 ft)
Preferred Band0.06 – 0.18
High Restriction> 0.20 ⚠
Very Low / Oversized Indicator< 0.05
ComponentTypical Drop (IWC)
MERV 8 Filter~0.20
MERV 13 Filter~0.35
Cooling Coil0.20 – 0.30
Supply + Return Duct System0.10 – 0.20
Compression LevelApprox. Delivered Airflow
4% (Ideal)~100%
15%~85–90%
30%~60–70% ⚠
Approx. CFMCommon Round Size
1006 in.
2007 in.
3008 in.
4009 in.
60010 in.