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ACCA Technical Bulletins keep our members apprised of new developments in the field and to offer suggestions on performance improvement that can be used in your business.

» Filtration--A Primer
This bulletin explores the basics of filters, including how HVAC equipment modifications are often required when a filter change results in increased system pressure drop through increased filter resistance.

» Temperature Differences in Residential Applications
According to ACCA's Manual RS (Comfort, Air Quality, and Efficiency by Design), residential HVAC systems should control the temperature at the thermostat to within a few degrees of the set point during all but the most unusual weather conditions. This Technical Bulletin explains comfort guidelines and why, for some hours, on some days, some rooms in most well designed HVAC systems, will not be able to remain at the recommended temperature difference from the central thermostat’s set point.

» Ensuring Compliance with ASHRAE 62.2
ASHRAE 62.2 has been a standard for ventilation and acceptable indoor air quality in low-rise buildings since 2007. In this technical bulletin, ACCA covers airflow calculation methods for constant volume and intermittent/variable speed applications that comply with the 62.2 standard. It also covers design considerations and weather related restrictions.

» Replacing R-22 Systems with R-410A Systems
R-410A can not be used as a drop in replacement for R-22. The higher operating pressures will damage R-22 compressors and components. Additionally, many R-410A units have a larger footprint than their R-22 counterparts. Therefore, when complete HVAC system change-outs are planned, space allocation must be reevaluated. These and other issues are addressed in this ACCA Technical Bulletin.

» Altitude Adjustments for Heating & Cooling Equipment
This bulletin provides a procedure for estimating HVAC equipment capacity at any topological altitude as well as discusses the impact that altitude (in wet and in dry climates) has on equipment performance and duct sizing. Adjustment factors are provided for altitude and temperature corrections.

» Cooling Load Produced by Lighting in Commercial Buildings
This technical bulletin evaluates four industry procedures for estimating cooling load needed to offset internal heat gains produced by lighting fixtures installed in commercial buildings. It is observed that the various procedures provide adequate guidance for selected lighting scenarios, but that each procedure has a unique set of sensitivities, capabilities, omissions, and deficiencies and that the use and extrapolation of their guidance requires exceptional skill, judgment, and experience.

» Manual N Procedure for Cooling Load by Lighting
Building on the last Technical Bulletin on lighting (N5-3), this Technical Bulletin explains why one method was selected as the preferred approach and how that procedure was modified for use in the updated Fifth Edition of ACCA Manual N (N5, Commercial Load Calculations).

» Outdoor Design Conditions for Manual N
This technical bulletin evaluates several methods for producing monthly weather values for outdoor dry bulb temperatures and discusses how outdoor design conditions were determined for ACCA Manual N, 5th Edition. The bulletin compares and contrasts derivations between the ‘traditionally-based four months of the warmest weather’ (typically the 2-1/2 percent summer dry bulb values in older weather tables) and the ‘24-hour, twelve-month’ (typically the newer weather tables) approaches.

» Infiltration Loads for Small Commercial Buildings
For ACCA Manual N, 5th Edition (being released in February 2008), infiltration rate estimates are used to compute the heating infiltration load, the sensible-cooling infiltration load, and the latent-cooling infiltration load for small commercial buildings that are three stories or less. This bulletin provides the rational for the infiltration rate values that appear in N5. Specifically addressed are issues related to ‘converting infiltration rate to infiltration load,’ ‘ventilation load,’ ‘space pressure and effect,’ ‘duct leakage effect,’ ‘door infiltration’ and ‘door traffic rate.’ (24 pages long)

» Basic Principles: Residential Duct Sizing Calculations
This bulletin introduces the basic principles that are associated with sizing duct runs, so that proper air side design can be achieved.

» Comfortable & Healthy Homes by Design
This bulletin brings factors such as temperature, humidity, and indoor air quality in balance with the metabolic activity and respiratory requirements of the occupants of a home.

» Blower Performance - Residential Equipment
This bulletin provides information about the types of centrifugal fans, or blowers, that are associated with residential HVAC equipment.

» Carbon Monoxide
This bulletin covers detailed information on the colorless, odorless gas and how to prevent its harmful exposure.

» Balancing Residential Air Distribution Systems (Part 1)
This bulletin describes the characteristics of air and the physics of duct flow.

» Balancing Residential Air Distribution Systems (Part 2)
Second in a multi-part series based on the concept that the air-side of residential comfort systems must be tested, adjusted, and balanced in order to avoid equipment failure.

» Balancing Residential Air Distribution Systems (Part 3)
Third in a four-part series. This bulletin focuses on instrumentation and tools.

» Balancing Residential Air Distribution Systems (Part 4)
Last in a four-part series. This bulletin discusses return- and supply-side balancing procedures, air-flow measurements, seasonal balancing, and the final balancing report.

» Adjusting the Manual D Procedure to Increase Airflow
This bulletin demonstrates a variation of the Manual D procedure that allows the designer to trade airflow velocity for fitting efficiency.

» Direct-Fired MUA Equipment (Part 1)
First in a four-part series of bulletins covers specifications for, and operation of, direct-fired MUA equipment.

» Direct-Fired MUA Equipment (Part 2)
Second in a four-part series covering specifications for, and operation of, direct-fired MUA equipment.

» Direct-Fired MUA Equipment (Part 3)
Third in a four-part series of bulletins covering specifications for, and operation of, direct-fired MUA equipment.

» Direct-Fired MUA Equipment (Part 4)
Last in a four-part series covering specifications for, and operation of, direct-fired MUA equipment.

» Evaluating Residential Zoning Requirements
This bulletin discusses how all or some rooms in a residential structure may be grouped into a single zone.

» Heat Pump Supply Temperature vs. Comfort
This bulletin covers the distinction between these two complaints about cold supply air temperatures and cold drafts.

» Heat Pump Balance Points & Resistance Heater Sizing
This bulletin discusses how oversized heat pump equipment affects efficiency, operating cost and comfort.