5.3001.4 Equipment Selection—Low Rise

Topic: 
Forced Air
Subtopic: 
Design
Desired Outcome: 
Equipment sized properly and operating efficiently
For supporting material, see Referenced Standards.
TitleSpecification(s)Objective(s)
5.3001.4a
Load calculation: heat loss or gain

Heat loss or gain of the building will be calculated considering the following:

  • R-values of building components
  • U-value and solar heat gain coefficient of glazing
  • Orientation and exterior shading of glazing
  • Duct heat loss or gain
  • Infiltration Infiltration The uncontrolled passage of outside air into a building through unintended leaks in the building envelope target or final infiltration Infiltration The uncontrolled passage of outside air into a building through unintended leaks in the building envelope after air sealing is completed
  • Ventilation
  • Internal gains

ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual J Residential Load Calculation, 8th ed., and ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org 5 QI HVAC HVAC Heating, ventilation, and air conditioning Quality Installation Specification requirements or ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org equivalents will be used for all residential load calculations

ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual N Commercial Load Calculation or ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org equivalents will be used for all commercial load calculations

Room-by-room calculations will be performed when installing new duct systems or in retro-commission projects

Accurately calculate sensible and latent load for the total building and each room

Properly size equipment for the load

5.3001.4b
Load calculation: design conditions of single stage or single speed equipment

Interior design temperatures will be selected based on 75° for cooling and 70° for heating, unless otherwise stated by local code

Ensure the design loads reflect peak sensible and peak latent load conditions per ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org Handbook—Fundamentals

Design sensible loads, which will dominate in dry climates, should be based upon outdoor design cooling conditions for the location (e.g., peak cooling dry bulb temperature in the ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org Handbook—Fundamentals)

Design latent loads, which are most important in moist or humid climates, should be based upon design dehumidification conditions for the location (e.g., design dew point temperature and mean coincident dry bulb temperature in the ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org Handbook—Fundamentals)

Accurately calculate sensible and latent load for the building

Properly size equipment for the load

5.3001.4c
Load calculation: design conditions for multistage, variable speed equipment

Interior design temperatures will be selected based on 75° for cooling and 70° for heating, unless otherwise stated by local code

Ensure the design loads reflect peak sensible and peak latent load conditions per ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org Handbook—Fundamentals

Design sensible loads, which will dominate in dry climates, should be based upon outdoor design cooling conditions for the location (e.g., peak cooling dry bulb temperature in the ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org Handbook—Fundamentals)

Design latent loads, which are most important in moist or humid climates, should be based upon design dehumidification conditions for the location (e.g., design dew point temperature and mean coincident dry bulb temperature in the ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org Handbook—Fundamentals)

Accurately calculate sensible and latent load for the building

Properly size equipment for the load

5.3001.4d
Equipment selection: air conditioning and heat pumps

Equipment capable of meeting the sensible and latent load of the building will be selected using the detailed capacity tables provided by the manufacturer

Equipment will not be sized by more than 115% of total load or next available size

ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual S Residential Equipment Selection, and ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org 5 QI HVAC HVAC Heating, ventilation, and air conditioning Quality Installation Specification requirements or ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org equivalents will be used for all residential equipment selection

ANSI ANSI American National Standards Institute, www.ansi.org / ACCA ACCA Air Conditioning Contractors of America, www.acca.org Manual CS Commercial Applications Systems and Equipment or ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org equivalents will be used for all commercial equipment selection

Ensure the equipment is able to heat, cool, and dehumidify the building

5.3001.4e
Equipment selection: auxiliary heat for heat pumps

Use the lowest capacity heating equipment required to heat the building, utilizing the detailed capacity tables provided by the equipment manufacturer

Equipment will be selected to provide a changeover point, calculated using information from the detailed capacity tables provided by the equipment manufacturer, weather data, and utility cost

Maximize the heating potential of the compressor

Minimize the use of auxiliary heat

5.3001.4f
Equipment selection: furnaces

The smallest capacity heating equipment will be selected that is capable of meeting the design heating load and providing the air movement required by the air conditioning

When an air-conditioning system is not designed with the furnace, the smallest capacity heating equipment will be selected that is capable of meeting the heating load

The lowest capacity cooling equipment required to cool the building will be used

Equipment will not be sized by more than 115% of total load or next available size

Ensure equipment meets the heating load of the building

Ensure equipment moves required air for air conditioning, if applicable