Acca Manual D Pdf Free Download

[Michele Firmasyah]

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This manual gives you the loads for single-family detached homes, small multi-unit structures, condominiums, town houses, and manufactured homes according to the national ANSI-recognized standard. Proper load calculation, as it is defined by this manual, is required by national building codes and by most states and municipalities.

Manual S helps you choose the appropriate heating and cooling equipment for a home based on the local climate and construction specifications. It covers 11 types of heating and cooling equipment and explains how to use the manufacturer's performance data in your planning.

These HVAC technical manuals are the basis for proper HVAC installations and most technicians worth their salt will follow them to a T. Unfortunately, over half of all HVAC systems are improperly installed, which can increase inefficiencies by as much as 30%!

If you are an HVAC contractor or home energy rater, you know what Manual J is and how important it is for properly sizing an HVAC system. These HVAC guidelines apply to any residential unit that has a HVAC and exhaust system:

Manual D works in conjunction with the other manuals to provide proper design, sizing, and installation of residential duct systems. After you have determined the heating and cooling loads (Manual J), selected the right HVAC equipment (Manual S), and figured out how to distribute the air (Manual T), you can now design the duct system (Manual D).

Shopping for a new A/C requires a bit of work, but finding the right one will ensure consistent, dependable comfort for years to come. If you are in the market for a new unit, start your search with Hiller. We offer quality HVAC service, stock all the popular brands and have an affordable maintenance plan to keep your system running efficiently.

Great suggestion. ACCA J and D are primarily residential standards and there are severeal options for users to export the geometry information into third party tools for these calculations. Currently Insight 360 provides design load calculations for the early design decision making. Since Autodesk tools are used worldwide, the development team is looking at options for supporting generic standards. Thank you for the suggestion.

I'd be interested in some of these options you think are available. Unfortunately for ACCA and Manual D calculations one of the flagship tools is Wrightsoft, and it does not support 3D geometry. I appreciate you seeing the suggestion valuable. Design load calculations become nearly meaningless when it comes down to accurate duct sizing and heat loads on buildings. It would be nice not to have to waste time generating design oriented calculations, and to have more practical ACCA approved, and ASHRAE 90.1 approved calculations. I mean if we're spending time prepping the model once for these calculations wouldn't it make sense not to have to run it separately in some other tool a second or third time?

This option seems like a logical progression. It is inefficient and redundant to use another piece of software to achieve code compliance using ACCA manual J & D. Looks like manual D compliance would require little more than ACCA certifying Revit as approved software.

For many years some professional HVAC businesses have believed that residential HVAC equipment selection was performed following guidance in ACCA Manual J. For example, a home with a 30,000 Btu/h cooling load would use a 2.5 ton air conditioner, right?

WRONG!!

Manual J is only used to calculate the heating and cooling loads. The current, nationally-recognized Manual J8 guides HVAC system designers to use ACCA Manual S Residential Equipment Selection to select equipment that is the right size (see section 10-4).

Why use Manual S

There are three good reasons to use Manual S: It is the nationally-recognized standard, it prevents problems associated with equipment over and under sizing, and it's a requirement in the 2009 International Residential Code (IRC).

Manual S, Residential Equipment Selection, is the ANSI-recognized, national standard providing clear instruction for interpreting and applying original equipment manufacturers' (OEM) expanded performance data. Manual S instructs designers how to select equipment which meets the application requirements (heating, sensible cooling, and latent cooling) at the design conditions that were used for calculating the loads.

Manual S also sets equipment sizing limits, as summarized in Table 1. These sizing limits ensure equipment capacities will keep customers comfortable while preventing the problems associated with equipment over and under sizing which include: health issues associated with excessive humidity, callbacks from comfort complaints, higher building costs (larger equipment is more expensive, more materials are needed, and more labor is used to install it), larger energy consumption, and greater wear and tear on the equipment1.

"Heating and cooling equipment shall be sized in accordance with ACCA Manual S based on building loads calculated in accordance with ACCAManual J or other approved heating and cooling calculation methodologies."

How to Apply Manual S: Heating Example (Part I)

Manual J heating load calculations produce values, in Btu/h, for selecting the heating equipment. This heating example will select a furnace for a home that has a heating requirement of 56,000 Btu/h. The furnace needed must have the capacity to deliver 56,000 Btu/h in order to maintain 70F in the home when the outdoor temperature dips to the outdoor design temperature (refer to Section 3-6 and Table 1A of Manual J8).

How to Apply Manual S: Cooling Example

Load calculations produce cooling capacity requirements for selecting the HVAC equipment. For this cooling example, we will select an air conditioner for a home with the following Manual J cooling loads:

Latent load is the heat associated with airborne moisture (produces relative humidity as measured by a hygrometer or humidistat). During the cooling process, moisture is extracted from indoor air. High latent heat or high relative humidity feels humid, clammy, or steamy. An example is a home that shows a cool temperature on the thermostat but, because of high humidity, still feels uncomfortable. When you walk into this home your initial impression is that it is cool, but then as your body adjusts to the room temperature, you begin to feel sticky, clammy, and uncomfortable. You may even feel warm again. This is why two homes that have the same reading on a thermometer or thermostat can feel very different.

1. Set the design parameters

2. Estimate the target airflow

3. Search for equipment candidates

4. Evaluate and select the acceptable candidates (more than one candidate may be offered to the customer)

Step 1. Design Parameters

There are many design parameters to consider. Some of these parameters were decided during the system design procedure: Equipment type, location, fuel, etc. However, the design parameters considered now come from the load calculations, Manual S, and the OEM performance data.

Two of the design parameters listed in Figure 3: Cooling Design Parameters relate to the design conditions used to calculate the cooling load. Unlike heating equipment, the cooling equipment capacity varies with the outdoor conditions. The outdoor (and indoor) design conditions that were used to calculate the cooling load must be used when selecting the equipment. In this case the indoor conditions were a 63F wet bulb temperature (this is equivalent to 75F dry bulb, 50%Rh), and an outdoor design temperature of 95F.

Step 2. Estimate the Target Airflow

Target airflow for the cooling system must be estimated. Manual S provides instructions2 to use the home's sensible heat ratio (SHR) to calculate the target airflow. This target airflow narrows the search for equipment candidates. The home's SHR also indicates whether the air conditioner will need exceptional moisture removal (humid climates) or extra temperature control (hot and dry climates). This airflow rate is only a target; the actual airflow will be based on the OEM expanded performance data.

ƒT = Temperature difference in the air between the inlet and outlet of the furnace or cooling coil

SBtu/h = Home's sensible capacity requirement for the cooling system

CFM = Cubic feet per minute; volume of air moved through the furnace by the blower assembly

1.1 = A physical air constant (derived from the laws of physics)

ACF = Altitude Correction Factor; 1.0 applies to sea level.

Step 3. Search for Equipment Candidates

The third step in the cooling equipment selection process is to search for candidate equipment combinations. However, the HVAC designer should always select a MATCHED system, a system that is rated by AHRI or certified by the OEM to deliver the specified capacity under the design conditions. Diligent HVAC system designers should examine different product lines and equipment styles when searching for equipment candidates. In addition to package and split systems, there are other low capacity heating and cooling systems which will serve small loads (e.g., ductless mini-split systems, radiant panels, and packaged terminal air conditioners).

Different OEMs will present their performance data in various formats. However, each format will generally include the same basic information: required airflow through the coil, entering air wet-bulb temperature4, outdoor temperature, and the equipment's cooling capacities (usually total and sensible capacities). Based on a cooling requirement of 30,000 Btu/h is a 2.5 ton system the proper unit to select?

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