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ASHRAE-90.1-2022- - Page 106

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  1. Alterations to existing buildings .
  2. Loading docks.

6.5.11 Refrigeration Systems. Refrigeration systems that comprise refrigerated display cases, walk-in coolers, or walk-in freezers connected to remote compressors, remote condensers, or remote condensing units shall meet the requirements of Sections 6.5.11.1 and 6.5.11.2.

Exception to 6.5.11: Systems using transcritical refrigeration cycle or ammonia refrigerant. 6.5.11.1 Condensers Serving Refrigeration Systems. Fan-powered condensers shall conform to the following requirements:

a. Design saturated condensing temperatures for air-cooled condensers shall be less than or equal to the

design dry-bulb temperature plus 10°F for low-temperature refrigeration systems and less than or equal to the design dry-bulb temperature plus 15°F for medium-temperature refrigeration systems .

  1. Saturated condensing temperature for blend refrigerants shall be determined using the average of liquid and vapor temperatures as converted from the condenser drain pressure. b. Condenser fan motors that are less than 1 hp shall use electronically commutated motors, permanent

split-capacitor-type motors, or three-phase motors. c. All condenser fans for air-cooled condensers, evaporatively cooled condensers, and air- or water-cooled

fluid coolers or cooling towers shall incorporate one of the following continuous variable-speed fan control approaches and shall reduce fan motor demand to no more than 30% of design wattage at 50% of design air volume:

  1. Refrigeration system condenser control for air-cooled condensers shall use variable set-point control logic to reset the condensing temperature set point in response to ambient dry-bulb temperature.
  2. Refrigeration system condenser control for evaporatively cooled condensers shall use variable set- point control logic to reset the condensing temperature set point in response to ambient wet-bulb temperature. d. Multiple fan condensers shall be controlled in unison. e. The minimum condensing temperature set point shall be no greater than 70°F.

6.5.11.2 Compressor Systems. Refrigeration compressor systems shall conform to the following requirements:

a. Compressors and multiple-compressor systems suction groups shall include control systems that use

floating suction pressure control logic to reset the target suction pressure temperature based on the temperature requirements of the attached refrigeration display cases or walk-ins. Exceptions to 6.5.11.2(a):

  1. Single-compressor systems that do not have variable-capacity capability.
  2. Suction groups that have a design saturated suction temperature equal to or greater than 30°F, suction groups that comprise the high stage of a two-stage or cascade system, or suction groups that primarily serve chillers for secondary cooling fluids.

b. Liquid subcooling shall be provided for all low-temperature compressor systems with a design cooling

capacity equal to or greater than 100,000 Btu/h with a design saturated suction temperature equal to or less than –10°F. The subcooled liquid temperature shall be controlled at a maximum temperature set point of 50°F at the exit of the subcooler using either compressor economizer (interstage) ports or a separate compressor suction group operating at a saturated suction temperature equal to or greater than 18°F.

  1. Subcooled liquid lines are subject to the insulation requirements of Table 6.8.3-2. c. All compressors that incorporate internal or external crankcase heaters shall provide a means to cycle the

heaters off during compressor operation.

6.6 Alternative Compliance Path 6.6.1 Computer Rooms Systems Path. The Computer Room System Path is an optional path for compliance where the following conditions are met:

a. HVAC systems that only serve the heating, cooling, or ventilating needs of a computer room with IT

equipment load greater than 10 kW shall comply with ASHRAE Standard 90.4, Energy Standard for Data Centers . b. All other HVAC systems shall comply with the applicable requirements in Section 6.5.

6.6.2 Mechanical System Performance Path 6.6.2.1 Scope. The Mechanical System Performance Path is an optional path for compliance where the following conditions are met:

104 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)

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