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HVAC Installation ACCA Manuals S, T, and D

Unfortunately, over half of all new HVAC systems installed in the US are not properly installed according to ENERGY STAR. Improper HVAC installations can result in safety, health, and efficiency problems, including air leaks, insufficient dehumidification, and higher energy bills.

If you are thinking about installing a new HVAC system for your home or business, make sure your prospective HVAC contractors are abiding by the strict installation guidelines published by the Air Conditioning Contractors of America (ACCA).

ACCA installation manuals provide the necessary procedures, technical specifications, and guidance to facilitate a proper HVAC system installation.

ACCA Manuals S, T, and D

These three residential heating and cooling manuals are the industry standard for installing the new HVAC equipment. Any HVAC contractor worth his or her salt will know about these technical manuals. It not only makes their job easier but also helps to ensure a successful installation of complicated equipment.

Since each home is different, these manuals give instructions for how to conduct house-by-house and room-by-room analysis. To help you receive the best service possible, you should know the basics of each manual, starting with a residential load calculation.

HVAC Load Calculations

Correctly sizing loads for homes is crucial for choosing the right-sized unit. If you don’t know how much heating or cooling is needed for your indoor spaces, how will you ever choose the right system?

Load calculations are done for the entire home, taking into consideration insulation and ventilation levels, air duct tightness, number of windows and doors, roof material, local climate, and other important factors.

If you are purchasing a new heating and cooling system for your home, a load calculation will help you choose the correct size system for maximum comfort and effectiveness.

We strongly recommend making energy-efficiency enhancements to the home, such as attic insulation, replacing weatherstripping, and installing solar windows and drapes. Improving insulation levels around the home could qualify you for a smaller, less expensive HVAC system.

Ask your contractor for copies of installation procedures, including load calculations and any other measurements or testing, such as ACCA manuals S, T, and D.

Manual S – Residential HVAC Sizing and Selection

After going around the home and measuring each room’s load calculation, the next step for deciding which system to install is Manual S. Manual S provides the information for choosing the brand and size of HVAC equipment that matches the load calculations for the home.

Contractors in different areas of the country will choose different units for different climates. Manual S provides documentation for 11 types of HVAC equipment including details and nuances that take into account climate and geographic discrepancies (ACCA).

Combined with load calculation information, Manual S provides the necessary information for selecting the properly sized air conditioner, heat pump, furnace or boiler for your home’s needs.

Manual T – Residential Air Distribution

While Manual S helps determine the proper HVAC unit, Manual T determines how to distribute the airflow to meet these requirements. It shows you “how to prevent drafts and stagnant air problems caused by improper sizing or incorrect equipment selection” (ACCA).

Manual T has a lot of specifications concerning air ducts, grilles, vents, and registers. It provides technicians and manufactures the information necessary to calculate performance data, pressure losses, and how to control noises.

Even if you have the perfect unit for your home, if the air isn’t getting where it needs to go, it will just sit near the vents, making your home uncomfortable and inefficient. In order to get the proper airflow for your home, Manual T provides the guidelines for your supply and return registers and grilles. Depending on the home, you might need a different style of register, diffuser, or grill.

Manual D – Residential Ductwork Design

At last, we come to Manual D. This one is easy to remember since it has to do with Ductwork. After the technician has run load calculations, selected the right equipment, and determined how the air is to be distributed, the next step is to make sure the air ducts are installed properly.

The newly updated Manual D guidelines provide:

  • A single set of ANSI-recognized duct sizing principles and calculations that apply to all duct materials
  • System operating point (supply CFM and external static pressure), and airway sizing for single-speed and multi-speed (ECM) blowers
  • A method for determining the impact of duct friction and fitting pressure drop on blower performance and air delivery

Proper ductwork installation has to do with the location of your air handlers, the difference between your ducts and returns, and how much air must pass through the duct pipes. The type of air ducts are also important for how your air is distributed. For example, you can have cleaner ducts and a lower friction rate with sheet metal ducts as opposed to flex ducts or rigid fiberglass duct board.

In essence, Manual D is trying to balance the delivery of your air with the amount of friction and static pressure in the system. This is important since poor duct design leads to comfort and indoor air quality problems (ACCA).

In order to properly select and install a new HVAC system, your technician must use the best information available, which are ACCA’s technical manuals. Make sure you vet your prospective contractors with this information. Not only will they be impressed, but you will avoid the common HVAC pitfalls that many homeowners walk right into.

If you have any questions about how to properly size and select a new air conditioner, heat pump, furnace, or boiler, just give Penguin Air & Plumbing a call. Our goal is to inform customers of all their options so they can make the best decision for their home and family.

To schedule your FREE consultation, contact us online!

The Penguin Air & Plumbing guarantee makes sure that you are 100% satisfied with your installation. All heating and air conditioning jobs will be completed within one day but the quality of the installation will never suffer for this part of the guarantee.

For the best quality and affordable air conditioning and heating in Phoenix, sign up for the Penguin Protection Plan.


At Penguin Air and Plumbing, we’ll solve all of your air conditioning problems or your money back.

Give us a call or schedule service online. We look forward to serving you.

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