Method of Testing For Rating Computer and Data Processing Room Unitary Air Conditioners [PDF]

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ANSI/ASHRAE Standard 127-2012 (Supersedes ANSI/ASHRAE Standard 127-2007)

Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners Approved by the ASHRAE Standards Committee on January 21, 2012; by the ASHRAE Board of Directors on January 25, 2012; and by the American National Standards Institute on February 24, 2012. ASHRAE Standards are scheduled to be updated on a five-year cycle; the date following the standard number is the year of ASHRAE Board of Directors approval. The latest edition of an ASHRAE Standard may be purchased on the ASHRAE Web site (www.ashrae.org) or from ASHRAE Customer Service, 1791 Tullie Circle, NE, Atlanta, GA 30329-2305. E-mail: [email protected]. Fax: 404-321-5478. Telephone: 404-636-8400 (worldwide) or toll free 1-800-527-4723 (for orders in US and Canada). For reprint permission, go to www.ashrae.org/permissions. © 2012 ASHRAE

ISSN 1041-2336

© ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.

ASHRAE Standard Project Committee 127 Cognizant TC: TC 9.9, Mission Critical Facilities, Technology Spaces and Electronic Equipment SPLS Liaison: Craig P. Wray J. Fred Stack, Chair* John H. Bean* Donald L. Beaty* Thomas A. Davidson

Gregory R. Jeffers* Mukesh K. Khattar* Geoffrey M. Lawler* David C. Meadows, II

David V. Quirk* Terry L. Rodgers* Davis D. Wilson*

*Denotes members of voting status when the document was approved for publication ASHRAE STANDARDS COMMITTEE 2011–2012 Carol E. Marriott, Chair Kenneth W. Cooper, Vice-Chair Douglass S. Abramson Karim Amrane Charles S. Barnaby Hoy R. Bohanon, Jr. Steven F. Bruning David R. Conover Steven J. Emmerich Allan B. Fraser

Krishnan Gowri Maureen Grasso Cecily M. Grzywacz Richard L. Hall Rita M. Harrold Adam W. Hinge Debra H. Kennoy Jay A. Kohler Frank Myers

Janice C. Peterson Douglas T. Reindl Boggarm S. Setty James R. Tauby James K. Vallort William F. Walter Michael W. Woodford Craig P. Wray Eckhard A. Groll, BOD ExO Ross D. Montgomery, CO

Stephanie C. Reiniche, Manager of Standards SPECIAL NOTE This American National Standard (ANS) is a national voluntary consensus standard developed under the auspices of ASHRAE. Consensus is defined by the American National Standards Institute (ANSI), of which ASHRAE is a member and which has approved this standard as an ANS, as “substantial agreement reached by directly and materially affected interest categories. This signifies the concurrence of more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that an effort be made toward their resolution.” Compliance with this standard is voluntary until and unless a legal jurisdiction makes compliance mandatory through legislation. ASHRAE obtains consensus through participation of its national and international members, associated societies, and public review. ASHRAE Standards are prepared by a Project Committee appointed specifically for the purpose of writing the Standard. The Project Committee Chair and Vice-Chair must be members of ASHRAE; while other committee members may or may not be ASHRAE members, all must be technically qualified in the subject area of the Standard. Every effort is made to balance the concerned interests on all Project Committees. The Manager of Standards of ASHRAE should be contacted for: a. interpretation of the contents of this Standard, b. participation in the next review of the Standard, c. offering constructive criticism for improving the Standard, or d. permission to reprint portions of the Standard.

DISCLAIMER ASHRAE uses its best efforts to promulgate Standards and Guidelines for the benefit of the public in light of available information and accepted industry practices. However, ASHRAE does not guarantee, certify, or assure the safety or performance of any products, components, or systems tested, installed, or operated in accordance with ASHRAE’s Standards or Guidelines or that any tests conducted under its Standards or Guidelines will be nonhazardous or free from risk.

ASHRAE INDUSTRIAL ADVERTISING POLICY ON STANDARDS ASHRAE Standards and Guidelines are established to assist industry and the public by offering a uniform method of testing for rating purposes, by suggesting safe practices in designing and installing equipment, by providing proper definitions of this equipment, and by providing other information that may serve to guide the industry. The creation of ASHRAE Standards and Guidelines is determined by the need for them, and conformance to them is completely voluntary. In referring to this Standard or Guideline and in marking of equipment and in advertising, no claim shall be made, either stated or implied, that the product has been approved by ASHRAE.

© ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.

CONTENTS

ANSI/ASHRAE Standard 127-2012 Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners SECTION

PAGE

Foreword ................................................................................................................................................................... 2 1 Purpose .......................................................................................................................................................... 2 2 Scope ............................................................................................................................................................. 2 3 Definitions....................................................................................................................................................... 2 4 Classification .................................................................................................................................................. 3 5 Rating Requirements...................................................................................................................................... 3 6 Conformance .................................................................................................................................................. 7 7 References ..................................................................................................................................................... 7 Normative Annex A: Tests Required .................................................................................................................... 8 Normative Annex B: Test Procedure for Measuring Airflow and Static Pressures on Downflow Units ................ 9 Informative Annex C: Climate Zone Bin Data with Population Weighting........................................................... 10 Informative Annex D: Comparison of Test Results (Simulated) ......................................................................... 11

NOTE Approved addenda, errata, or interpretations for this standard can be downloaded free of charge from the ASHRAE Web site at www.ashrae.org/technology.

© 2012 ASHRAE 1791 Tullie Circle NE · Atlanta, GA 30329 · www.ashrae.org · All rights reserved. ASHRAE is a registered trademark of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. ANSI is a registered trademark of the American National Standards Institute.

© ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.

(This foreword is not part of this standard. It is merely informative and does not contain requirements necessary for conformance to the standard. It has not been processed according to the ANSI requirements for a standard and may contain material that has not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.) FOREWORD ANSI/ASHRAE Standard 127 was first published in 1988 and revised in 2001 and 2007. This revision of the standard makes some significant changes to the 2007 edition. The major revisions and the rationale for them are summarized in the following paragraphs. Definitions The previous terms sensible coefficient of performance (SCOP) and adjusted sensible coefficient of performance (ASCOP) have been replaced with the new terms net sensible coefficient of performance (NSenCOP) and integrated sensible coefficient of performance (iNSenCOP) to remove the confusion caused by the use of the prior terms being used in other ASHRAE documents with different definitions. Some common industry terms used within the standard have been added as well. Rating Requirements 1.

2.

3.

4.

5.

6.

7.

2

The standard has been modified to cover four different product application classifications. This reflects the industry need to modify equipment to accept higher and higher return temperatures, thus increasing efficiency. The chilled-water conditions have been adjusted on the chilled-water air handlers to emphasize the higher system efficiency when higher temperatures are used, even though the specific units involved will appear to be lower in capacity and efficiency. The paragraphs have been reorganized to minimize the confusion between capacity ratings and efficiency ratings. A “normalized” or “weighted” efficiency rating has been created to provide a single efficiency number, thus simplifying the comparison of similar units. The raw numbers were retained, however, so engineers can continue to calculate the unit’s efficiency at any geographic location. The test points on water-cooled (evaporative) direct expansion (DX) units have been adjusted to correspond to AHRI 340/360 as well as a typical cooling tower approach. The Test D values have been adjusted to correspond to the values required in ANSI/ASHRAE/IES Standard 90.1 for 100% free cooling. Normalizing values were provided for fluid coolers, fluid cooler pumps, and chilled-water-loop pumps so all technologies could be more easily compared.

1. PURPOSE The purpose of the standard is to establish a uniform set of requirements for rating computer and data processing room unitary air conditioners (CDPR). 2. SCOPE This standard applies to classes of unitary equipment that are used to air condition a computer room and data processing equipment. This standard does not apply to the rating of individual assemblies, such as condensing units or direct expansion fan-coil units, for separate use. 3. DEFINITIONS computer and data processing room unitary air conditioner (CDPR): a computer and data processing room unitary air conditioner consisting of one or more factory-made assemblies, which include a DX evaporator or chilled-water cooling coil, an air-moving device, and air-filtering devices. The air conditioner may include a compressor, condenser, humidifier, or reheating function. Where DX equipment is provided in more than one assembly and the separate assemblies are to be used together, the requirements of rating outlined in this standard are based upon the use of matched assemblies. The functions of a CDPR, either alone or in combination with a cooling and heating plant, are to provide air filtration, circulation, cooling, reheating, and humidity control. computer room air conditioner (CRAC): generally refers to computer-room cooling units that utilize dedicated compressors and refrigerant cooling coils rather than chilled-water coils. computer room air handler (CRAH): generally refers to computer-room cooling units that utilize chilled-water coils for cooling rather than dedicated compressors. cooling system energy coefficient of performance (COP): a ratio calculated by dividing the net total cooling capacity in watts by the total power input in watts (excluding reheaters and humidifiers) at any given set of rating conditions. The net total cooling capacity is the total gross capacity minus the energy dissipated into the cooled space by the blower system. net sensible coefficient of performance (NSenCOP): a ratio calculated by dividing the net sensible cooling capacity in watts by the total power input in watts (excluding reheaters and humidifiers) at any given set of rating conditions. The net sensible cooling capacity is the gross sensible capacity minus the energy dissipated into the cooled space by the fan system (further explained in Section 5.1). integrated sensible coefficient of performance (iNSenCOP): an NSenCOP value that provides a consistent evaluation of the energy efficiency of a unit operated in different ambient temperatures. It is calculated by the method defined in Section 5.2. fluid economizer: a system configuration potentially available when an external fluid cooler is utilized for heat rejection. It utilizes a separate cooling coil within the unit for cooling

ANSI/ASHRAE Standard 127-2012

© ASHRAE (www.ashrae.org). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE’s prior written permission.

and the cooled fluid returning from the external fluid cooler to provide cooling much like a chilled-water unit (i.e., without the use of compressors). This process is sometimes referred to as free cooling. standard rating: a rating based on tests performed at standard rating conditions (see Section 5.1). application rating: a rating based on tests performed at application rating conditions (i.e., conditions other than standard rating conditions). Application ratings do not require retesting but can be extrapolated from standard rating tests. Application ratings are not required but may be published at the manufacturer’s option (see Section 5.8). rating conditions: any set of operating conditions under which a single level of performance results occurs, and which causes only that level of performance to occur. standard rating conditions: rating conditions used as the basis of comparison of performance characteristics. 4. CLASSIFICATION 4.1 Normally, CDPR units within the scope of this standard can be classified as shown below. There are five basic types of unitary air conditioners: a. b.

c.

d.

e.

Single-Package Unit. A complete stand-alone unit. Condensing Unit with Separate Coil and Fan. The remote part of this unit contains the compressor and condenser while the indoor part of the unit is an evaporator and blower. Unit with Remote Condenser. The remote part of the unit is an air-cooled condenser only while the indoor part of the unit contains the compressor(s), evaporator coils, and fan. Unit with Remote Air-Cooled Fluid Cooler or Cooling Tower. The indoor part of the unit contains the compressor(s), evaporator coil, fan, and condenser. The heat rejection is by means of a remote device (a cooling tower or air-cooled fluid cooler) that uses water or glycol to transfer the heat. Chilled-Water Unit. The indoor part of the unit is an air handler with a water-cooled coil that is connected to the building chilled-water system.

Note: Any of the above types may utilize a second, or dual, cooling coil that provides cooling by means of a freecooling liquid economizer or a separate building chilled-water system.Any of the above types may contain an internal humidifier and/or reheat capabilities. 5. RATING REQUIREMENTS Section 5 describes all of the testing and rating requirements for this standard. A summary listing of the tests required is provided in Normative Annex A. 5.1 Cooling System Standard Capacity Ratings. Rated cooling is defined as 100% of the unit’s max capacity and is sometimes referred to as standard rating. Standard rating capacity shall be established at the standard rating conditions

ANSI/ASHRAE Standard 127-2012

specified in rated cooling Test A of Table 1 for each application class that applies for this equipment. Standard cooling capacity shall be stated as sensible cooling capacity and shall be net values, reflecting the effects of circulating fan heat. 5.1.1 Value of Standard Capacity Ratings. These ratings shall be expressed in terms of kilowatts with three significant digits (e.g., 10.2 kW and 105 kW). 5.1.2 Standard Rating Conditions. The conditions of test for standard ratings shall include the following. 5.1.2.1 Standard Cooling System Rating Temperatures. All indoor and outdoor conditions for testing are defined in Table 1. Also defined in Table 1 are the various fluid temperatures that shall be used for heat rejection purposes on non-air-cooled systems. A unit shall be rated at all of the application classes that apply. 5.1.2.2 Voltage and Frequency. Nameplate voltages for 60 Hz shall be one or more of the following utilization voltages: 115, 200, 208, 230, 265, 460, and/or 575. Standard rating tests shall be performed at the unit nameplate rated voltages and frequency. For air conditioners with dual voltage ratings, standard rating tests shall be performed at both voltages or at the lower of the two voltages if only a single standard rating is to be published. If desired, 50 Hz ratings at 230 and/or 400 volts may be published using this standard but are not required. 5.1.2.3 Cooling Coil Air Quantity. Standard cooling system ratings shall be determined at a total air quantity (cooling coil plus bypass) delivered against at least the minimum external static pressures required by Section 5.1.2.5, as outlined below. The air volume for Class 1 and 2 applications shall not exceed 289 CMH/kW [170 cfm/kW] and Class 3 and 4 applications shall not exceed 221 CMH/kW [130 cfm/kW]. Air quantities shall be expressed as cubic meters per hour (CMH) of standard air (density = 1.2 kg/m3). If desired, cubic feet per minute (cfm) of standard air may also be expressed as defined in the 2005 ASHRAE Handbook—Fundamentals1, Chapter 2 (e.g., 164.2 CMH [96.6 cfm]). All values are at sea level conditions. Air conditioners shall be rated at those air quantities specified by the manufacturer while in the rated cooling mode at conditions in Test A of Table 1. Once these conditions are established for this standard rating test, no further adjustment to the air volume shall be made. 5.1.2.4 Condenser/Air-Cooled Fluid Cooler Air Quantity. Standard ratings for units that are air cooled or glycol cooled with an air-cooled fluid cooler shall be determined at the condenser/air-cooled fluid cooler air quantity that is inherent to the air conditioner when operated with all the resistance elements associated with the inlet or discharge attachments that the manufacturer considers normal installation practice. If fan speed control, or partial fan operation in a multifan condenser, is utilized for condensing temperature control, it may be utilized in this test as defined by the manufacturer. Air quantities must be expressed as cubic meters per hour (CMH) of standard air (density = 1.2 kg/m3). If desired, cubic feet per minute (cfm) of standard air may also be expressed as defined in the 2005 ASHRAE Handbook— Fundamentals1, Chapter 2 (e.g., 164.2 CMH [96.6 cfm]).

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TABLE 1

Standard Rating Conditions (Cooling/Efficiency) Rated Cooling Application Classes

A

Class 1

23.9°C (75.0°F)

23.9°C (75.0°F) 23.9°C (75.0°F) 23.9°C (75.0°F)

Class 2

29.4°C (85.0°F)

29.4°C (85.0°F) 29.4°C (85.0°F) 29.4°C (85.0°F)

Class 3

35.0°C (95.0°F)

35.0°C (95.0°F) 35.0°C (95.0°F) 35.0°C (95.0°F)

Class 4

40.5°C (105°F)

40.5°C (105°F)

11.1°C (52.0°F)

11.1°C (52.0°F) 11.1°C (52.0°F) 11.1°C (52.0°F)

35.0°C (95.0°F)

26.7°C (80.0°F) 18.3°C (65.0°F)

4.4°C (40.0°F)

Entering water temperature

28.3°C (83.0°F)

21.1°C (70.0°F) 12.8°C (55.0°F)

1.7°C (35.0°F)

Leaving water temperature

35.0°C (95.0°F) Max = Test A2

Max = Test A2

Max = Test A2

Glycol-cooled units Entering glycol temperature (connected to a Leaving glycol temperature common glycol loop with a solution of 40% propylene gly- Fluid flow rate col by volume)5

40.0°C (104.0°F) 29.4°C (85.0°F) 18.3°C (65.0°F)

1.7°C (35.0°F)

Entering water temperature

10.0°C (50.0°F)

Leaving water temperature

16.7°C (62.2°F)

Air temperature surrounding indoor part of unit (control is on return temperature)

Air-cooled units: temperature Dry-bulb temperature surrounding remote air-cooled condenser

Chilled-water air-handling units3

Fluid flow rate

Reheating

40.5°C (105°F)

Max = Test A2

Max = Test A2

Max = Test A2

Base Rating Return dry-bulb temperature

23.9°C (75.0°F)

Steam reheat units

Entering steam supply conditions

100 kPag (14.5 psig) and 121°C (250°F)

Hot-water reheat units

Water temperature entering unit

80.0°C (176.0°F)

Water temperature leaving unit

70.0°C (158.0°F)

Humidification/Dehumidification

Humidification

Dehumidification

Return dry-bulb temperature

29.4°C (85.0°F)

29.4°C (85.0°F)

Return dew-point temperature

5.5°C (42.0°F)

15.0°C (59.0°F)

Return relative humidity Steam humidifier units

40.5°C (105°F)

46.0°C (115.0°F)

All units

All units

D1

C

Return dry-bulb temperature

Return dew-point temperature

Evaporative-cooled units (connected to cooling tower)4

B

Entering steam supply conditions

60% 19 kPag (2.76 psig) and 105°C (221°F)

1) Test D is optional. If Test D is not performed, the results for Test D are the same as those for Test C. 2) Test setup is as in Test A, but the head pressure control may lower the flow rate. 3) Add pump power to unit total consumption Wpump = GPM · H · SG / 3.448 or Wpump = LPS · h · SG / 0.65 where W = watts; GPM = gallons per minute; LPS = liters per second; H and h = feet or kilopascals of water pressure drop from the entrance to the exit of the unit; SG = specific gravity of fluid; and a combined pump/motor efficiency of 65% is assumed. 4) Add cooling tower power and condenser loop pump to the energy consumption = 5% of the unit sensible capacity. Temperatures are the temperatures of the fluid leaving the evaporative unit to the unit under test and return. 5) Add drycooler fan and condenser pump to the energy consumption = 7.5% of the unit sensible capacity.

Note: Users should be aware that the mass flow rate and cooling capacity of CDPRs typically decreases at elevations higher than sea level. Manufactures should be consulted for capacity and airflow ratings at these higher elevations to make sure that the CDPR mass and volume flow rates and cooling capacity meet the requirements of the IT equipment (ITE) being cooled. It should be noted that the flow rate of the ITE will likely increase at the higher elevations.

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5.1.2.5 External Static Pressures, Duct Connected, Free Air Discharge, and Floor Plenum. For the appropriate system configuration described below, the external static pressure shall be as stated. For up-flow units, follow the procedure in ASHRAE Standard 372 exactly as written, without any modifications. For down-flow units, follow the procedure in ASHRAE Standard 372 as modified by the changes to the procedure that are shown in Normative Annex B. For the purposes of this test, the down-flow unit is effectively inclusive of

ANSI/ASHRAE Standard 127-2012

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the floor-stand with the discharge out the front of the floorstand and the other three sides enclosed. 5.1.2.5.1 Ducted Systems. Air conditioners intended to be connected to supply and/or return ductwork shall be tested as follows: those with standard sensible cooling ratings of less than 20.0 kW shall be tested at an external static resistance of 200 Pa (0.8 in. w.c.). Those with standard sensible cooling ratings of 20.0 kW or more shall be tested at an external static resistance of 250 Pa (1.0 in. w.c.). Standard air quantity capacity is specified in Section 5.1.2.3. 5.1.2.5.2 Free Discharge Systems. Air conditioners intended for free air discharge shall be tested at an external resistance of 0.0 Pa (0.0 in. w.c.). Filters, heating devices, and other equipment recommended as part of the air conditioner shall be in place, and the net external resistance specified above shall be available for the system. Standard air quantity capacity is specified in Section 5.1.2.3 5.1.2.5.3 Raised Floor Plenum Systems. Air conditioners intended for use with field-installed raised floor plenums shall be tested at an external resistance of 50 Pa (0.2 in. w.c.). Filters, heating devices, and other equipment recommended as part of the air conditioner shall be in place, and the net external resistance specified above shall be available for the plenum system. Standard air quantity capacity is specified in Section 5.1.2.3. 5.2

Unit Efficiency Calculations

5.2.1 Net Sensible Coefficient of Performance Rating (NSenCOP). The efficiency rating (NSenCOP) is a measurement of net sensible cooling capacity kW/input power kW. It shall be published at five conditions: the “normalized zone condition” (iNSenCOP defined in Section 5.2.2) and at each of the four test points (A, B, C, and D) defined in Table 1. For tests B through D the unit’s net sensible cooling load shall be fixed at the sensible capacity established in Test A. During the test, the room temperature must be maintained to a tolerance of ±1°C (± 2°F). If the test tolerance cannot be maintained, use the values from Test A for that test. An NSenCOP ratio shall be established at the defined test points by dividing this net sensible capacity by the average kilowatt per hour input power over a two-hour period. Air volume (cubic feet per minute) is allowed to deviate from Test A provided that the net sensible capacity is held constant. Standard input power rating shall be the total power input to the compressor(s), fan(s), control(s), air-cooled condenser fan(s) if used (excluding reheaters and humidifiers), and any other items included as part of the model number(s). The values of NSenCOP and iNSenCOP should not be used to compare between system classifications (air-cooled versus water-cooled versus CW, etc.) since the accuracy for estimating the power of some of external system components (pumps, cooling towers, etc.) are just estimates and could vary from job to job. 5.2.2 Integrated Net Sensible Rating (iNSenCOP) Calculation. The iNSenCOP rating is to be provided as a single “normalized” value to simplify unit to unit comparisons. The method shown below for calculating the normalized iNSenCOP may be used to calculate the unit’s value at a specific geographic location. When iNSenCOP ratings are

ANSI/ASHRAE Standard 127-2012

published, they are the normalized value. The normalized value is calculated as described below based on the “weighted” geographic location defined in Normative Annex C. The published iNSenCOP is a calculated value based on the NSenCOP test results from Tests A, B, C, and D. A weighted average of each of these test results is used based on the normalized values of A = 13.4%, B = 27.1%, C = 38.1%, and D = 21.5% as shown in Normative Annex C. iNSenCOP = (.134 × Test A NSenCOP) + (.271 × Test B NSenCOP) + (.381 × Test C NSenCOP) + (.215 × Test D NSenCOP) If a value for a specific geographic location is desired, first obtain from the weather bureau or other reputable source the percentage of time the climate in the target location is in each of the test temperature ranges shown below (examples of this data for cities in each of the DOE climate zones as defined in ANSI/ASHRAE/IES Standard 90.13 are found in Informative Annex C). a. b. c. d.

 26.7C (80F),  18.3C and < 26.7C (65F and 80F), > 4.4C and < 18.3C (40F and 65F); and  4.4C (40 F).

Use these percentages as relative weightings the of the NSenCOP values obtained in Tests A–D. Example: Assume the percentage values for the above climate temperature ranges are called Ta, Tb, Tc, and Td, respectively: iNSenCOP = (Ta × Test A NSenCOP) + (Tb × Test B NSenCOP) + (Tc × Test C NSenCOP) + (Td × Test D NSenCOP) (1) Suppose that a unit has the following NSenCOP test results: Test Result

A

B

C

D

2.72

2.94

3.31

3.86

This results in an iNSenCOP normalized value of 3.25. However, if you want to know the product’s efficiency in a specific city, this can be found by analyzing the temperature hour bins for that particular city. If the temperature range percentages shown in Informative Annex C for San Francisco are used, the resulting iNSenCOP is 3.26. If the temperature range percentages for Chicago are used, the resulting iNSenCOP is 3.38. See Informative Annex C for other selected cities in North America. (See Note 1 in Table 1 if optional Test D is not performed.) 5.2.3 Values of Standard Cooling System Power Input Ratings. These cooling ratings shall be expressed in terms of kilowatts with three significant digits (e.g., 10.2 kW and 105 kW).

5