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Residential hvac design Knowledge FAQ:  What is ACCA Manual J?  What is ACCA Manual S?  What is ACCA Manual D? Manual j service questions

Manual J FAQ  - ACCA Manual J load calculations, the 1st step in the HVAC design process

What is Manual J?

Manual J is a calculation of your home’s heating and cooling requirements as required by building codes to obtain an HVAC.  A variety of home building factors that greatly affect the choice of equipment and its capabilities are used in a Manual J calculation such as window size/type, insulation R-value in wall, floors and ceiling, duct location, and annual weather conditions for your homes location.  A Manual J designer must use the correct set of building materials, geographical location, orientation, infiltration, ventilation and internal gains to be accurate.    Manual J VIDEO: Please watch This Old House define "What is an ACCA Manual J load calculation?" on our "What is Manual J" page    READ More...

Why does your home need a Manual J load calculation?

The most important reason to have a Manual J calculation for your home is MONEY.  Oversized HVAC’s require more money for installation.  The oversized equipment also costs more than properly sized equipment.  More money is needed for oversized refrigerant lines, vents, and larger duct and more money is also needed in labor to install the extra stuff.  Next, oversized equipment starts and stops more than necessary.  An ACCA Manual J can save money, promote prolonged equipment life, improve comfort and conserve energy.

Manual S FAQ  - ACCA Manual S HVAC selection, the 2nd step in the HVAC design process

What is Manual S?

Manual S, Residential HVAC Equipment Selection, is the ANSI-recognized national standard providing clear instruction for interpreting and applying original equipment manufacturers' (OEM) expanded performance data.  The goal of Manual S HVAC sizing is to select an HVAC system that will maintain the design comfort conditions determined in the Manual J calculation.   The manufacturer’s OEM data is required to verify Manual S sizing has the correct CFM, EDB, EWB and outdoor temperatures.  AHRI data is inaccurate as it tests the unit at 80 F indoor and does not consider grains of moisture (humidity) for you city/area.  A properly sized HVAC prevents many problems such as excess expense, unnecessary wear, decreased comfort and marginalized performance.  READ More...

Manual D FAQ  - ACCA Manual D duct design, the 3rd step in the HVAC design process

What is Manual D?

Manual D duct designis the ACCA calculation used to determine the supply and return duct lay-out including the individual duct branch sizes. Before designing the residential duct system, the HVAC designer should perform a Room by Room Manual J load calculation and complete Manual S HVAC selection using the manufacturer’s OEM data.  Manual D designs the duct system to distribute the right amount of heating and cooling air to each room and provide a low resistance path from each room back to the HVAC system.  Proper air distribution is critical to home comfort.   READ More...