5.3001.6 Load Calculation and Equipment Selection—Mid and High Rise

Topic: 
Forced Air
Subtopic: 
Design
Desired Outcome: 
Equipment sized properly and operating efficiently
For supporting material, see Referenced Standards.
TitleSpecification(s)Objective(s)
5.3001.6a
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

5.3001.6b
Equipment selection

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

5.3001.6c
Variable refrigerant flow selection

When applicable, multiple indoor units will be supplied by a single outdoor unit

When applicable, manufacturer specifications will be used to determine allowable overage of indoor unit capacity in relation to the outdoor unit

When applicable, units will be selected that offer ducting options (e.g., ceiling cassette units have a knock out for a 5" or 6" duct)

When applicable, units with an outdoor air intake will be selected

When design temperature is less than temperatures in the capacity tables, units will be derated in accordance with manufacturer specifications

Ensure equipment operates at optimal efficiency

5.3001.6d
Ductless mini split selection

When applicable, multiple indoor units will be supplied by a single outdoor unit

When applicable, manufacturer specifications will be used to determine allowable overage of indoor unit capacity in relation to the outdoor unit

When applicable, units will be selected that offer ducting options (e.g., ceiling cassette units have a knock out for a 5" or 6" duct)

When applicable, units with an outdoor air intake will be selected

Reduce total system cost

Ensure equipment operates at optimal efficiency

5.3001.6e
Package terminal air conditioner (PTAC) or package terminal heat pump selection

Package unit will be selected with outdoor air intake unless other ventilation strategy is present

Primary heating of newly installed PTAC units will not be electric resistance heat

Ensure equipment operates at optimal efficiency

5.3001.6f
Cooling towers (rain water option) selection

Elevation of tower will be selected in relation to the net positive suction head required at the pump and in accordance with manufacturer specifications

Ensure equipment operates at optimal efficiency

5.3001.6g
Economizer selection

The need for an economizer outdoor air damper will be determined in accordance with ASHRAE ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers, www.ashrae.org 90.1 minimum requirements or local code

Ensure occupant health