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Manual S – Selecting the Right HVAC Equipment for Your Home

When designing an HVAC system, it’s not enough to just calculate the heating and cooling loads (Manual J) or design the ductwork (Manual D). Choosing the right heating and cooling equipment — in both size and type — is just as critical. That’s where Manual S comes in.

Manual S, developed by the Air Conditioning Contractors of America (ACCA), outlines the process for selecting HVAC equipment that meets the unique needs of a home. It ensures your system is properly matched to your home’s design, climate, and comfort requirements — maximizing performance and efficiency.

What Is Manual S?

Manual S is the ACCA standard for selecting HVAC equipment based on the results of a Manual J load calculation. It helps determine the correct capacity (in BTUs), model, and specifications for your furnace, heat pump, air conditioner, or other HVAC units.

How We Complete a Manual S at DesignRight Mechanical

1. Review Manual J Load Results

We begin with your home’s heating and cooling loads, which detail the BTUs required to maintain indoor comfort. These values are determined by a Manual J calculation and form the foundation of equipment selection.

2. Consider Climate and Local Weather Data

We take into account your local design temperatures (outdoor highs/lows) to ensure the equipment can handle the conditions without oversizing or undersizing.

3. Match Equipment to Load

Using manufacturer performance data, we compare the equipment’s rated output to the home’s calculated load. We factor in sensible and latent capacity, ensuring the system can adequately handle both temperature and humidity.

4. Account for Airflow and Static Pressure

The selected system must be compatible with your ductwork and provide the proper airflow (CFM) for every zone in the house. We make sure the equipment operates within manufacturer guidelines.

5. Provide a Manual S Summary Report

We deliver a clear, formatted report showing the matched equipment with model numbers, performance specs, and compliance with Manual S criteria. This document is often required for permits and inspections.

Benefits of Proper Manual S Equipment Selection

• Ensures your HVAC equipment isn’t oversized or undersized

• Improves comfort and energy efficiency

• Extends equipment life by preventing short cycling or excessive wear

• Reduces humidity and improves indoor air quality

• Helps pass code and permitting requirements

• Enhances system compatibility with duct design and home layout

Why Builders and Contractors Choose DesignRight Mechanical

We specialize in helping builders, designers, and HVAC contractors streamline the equipment selection process. Our Manual S reports are accurate, compliant, and ready to submit for permitting or installation. Combine with our Manual J and Manual D services for a full HVAC design package.

Get It Right — The First Time

Choosing the right HVAC equipment is about more than picking a brand — it's about matching your system to the specific needs of the home. Let us help you make the smart, code-compliant choice.

Understanding Manual D – The Key to Efficient and Comfortable Air Distribution

When it comes to designing an efficient HVAC system, load calculations (Manual J) are only one part of the equation. Equally important is how the conditioned air actually moves through your home — and that’s where Manual D comes in.

Manual D is the industry-standard method for designing residential duct systems. Developed by the Air Conditioning Contractors of America (ACCA), it ensures that your HVAC ducts are sized and laid out properly to deliver the right amount of air to every room — quietly, efficiently, and comfortably.

What Is Manual D?

Manual D focuses on the design of ductwork for heating and cooling systems. It’s used in conjunction with Manual J (load calculations) and Manual S (equipment selection) to complete the full residential HVAC design process. A properly completed Manual D ensures that airflow is balanced, static pressure is within range, and every room gets the air it needs.

How the Manual D Process Works at DesignRight Mechanical

1. Review Manual J Load Results

We start by reviewing the room-by-room heating and cooling loads determined by a Manual J calculation. These loads tell us how much air each room needs to maintain comfort.

2. Determine Equipment & Air Handler Specs

Based on Manual S equipment selection, we reference the total system airflow (in CFM) and available external static pressure. This ensures that ductwork is compatible with the selected system.

3. Layout Duct Runs

We design the physical layout of supply and return ducts. This includes trunk and branch lines, grille and register placement, and duct type (flex, metal, or rigid). We consider space constraints like trusses and framing.

4. Size the Ducts

Using software or ACCA-approved methods, we size each duct section to deliver the required airflow at acceptable velocities and pressures. We take into account duct length, fittings, and airflow resistance (friction loss).

5. Create a CAD or PDF Duct Layout

We generate a clean, professional layout showing duct sizes, equipment locations, airflow values, and key specs — all ready for construction or permit submission.

6. Provide a Static Pressure Budget

We calculate the total system pressure drop, including supply, return, filter, coil, and fittings, to ensure it falls within your HVAC system's limits.

Benefits of a Proper Manual D Duct Design

• Ensures each room gets the right amount of air (balanced comfort)

• Reduces noise from air turbulence or high velocities

• Prevents energy waste from poorly sized ducts

• Avoids hot/cold spots in the home

• Helps systems pass inspection and meet code requirements

• Improves system longevity and efficiency

• Creates a professional deliverable for builders and permit officials

Why Choose DesignRight Mechanical for Manual D

We specialize in fast, accurate Manual D designs tailored to your build. Whether you’re a builder, contractor, or architect, we provide CAD-quality layouts with precise airflow values and code-compliant documentation. We also offer bundled Manual J and Manual S services for complete HVAC design solutions.

Need Duct Design Help?

Let’s get your next project off the ground — efficiently, affordably, and with confidence. Contact us today for a quote or sample report.

What Is a Manual J Load Calculation – And Why It Matters for Your Home’s Comfort

If you’re building a new home or renovating an existing one, you may have heard the term Manual J thrown around by your HVAC contractor, designer, or even your local building department. But what exactly is it, and why is it so important?

Let’s break it down.

Manual J is an industry-standard calculation developed by the Air Conditioning Contractors of America (ACCA). It determines the precise heating and cooling load of a home, in other words, how much energy is needed to keep the home comfortable year-round.

The goal? To right-size your HVAC system. That means choosing heating and cooling equipment that’s not too big and not too small, but just right.

Without a Manual J calculation, contractors may size your HVAC system based on guesswork or outdated rules of thumb, like “1 ton per 500 square feet.” The problem? Every home is unique. Factors like insulation, window size, ceiling height, and sun exposure vary widely.

This often leads to oversized systems, which cost more, short cycle, wear out faster, and leave you with hot/cold spots.

At DesignRight Mechanical, we complete your Manual J using professional software approved by ACCA. Here’s what goes into it:

We Gather Your Home’s Details

We collect plans or measurements of your home, including:

• Square footage

• Number and size of rooms

• Window types and orientations

• Ceiling heights

• Insulation levels

• Duct locations (attic, basement, etc.)

• Climate zone and local weather data

We Input the Data

Using tools like WrightSoft or Cool Calc, we enter all of this information into load calculation software. This software simulates how your home gains or loses heat in both summer and winter.

We Break It Down Room-by-Room

The Manual J report shows the BTU requirements for each room — so your HVAC system and ducts can be designed to deliver exactly the right amount of air, where it’s needed.

We Share a Clear, Code-Compliant Report

You receive a professionally formatted report (PDF), ready for your contractor, architect, or permit submittal. It includes:

• Heating & cooling loads (sensible and latent)

• Design temperatures

• Infiltration and ventilation assumptions

• Total building and room-by-room results

Why Builders and Contractors Use DesignRight Mechanical

We support homebuilders, HVAC contractors, and designers who want accurate, fast, and affordable HVAC calculations. Our reports help:

• Avoid over- or under-sizing

• Prevent costly HVAC changes during inspections

• Speed up code compliance and permit approval

• Improve system performance and homeowner satisfaction

Get It Done Right – The First Time

Whether you're building a custom home, flipping a house, or planning a remodel, don't leave HVAC sizing to guesswork. Manual J calculations are the foundation of comfort and efficiency in any residential HVAC system.

Need a Manual J for your next project? We offer fast turnaround and bundled services with Manual D (duct design) and Manual S (equipment selection). Contact us today.