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OBSOLETE 

1986 

KEH ll~,~~ 

TCPC/RM;,m3. ~IW\ 

110 

STANDARD for 

WATERSOURCE 

HEAT 

PUMPS 

I Standard 320 I 

PROPERTY OF U.S. GOVERNI\~E"H 

AIR-CONDITIONING AND REFRIGERATION INSTITUTE 

1501 WILSON BOULEVARD • ARLINGTON, VIRGINIA 22209 
c.. .1 

OBSOLETE 

TABLE OF CONTENTS 

SEcrION PAGE 

Section 1. Purpose ............................................................................................... .. .......................... .. ...................... 

Section 2. Scope ............. . ....... . .......... . .. . ............................. . .......... . 

Section 3. Definitions ... . .................. . .................... . .. . ............. . ......... . . 

Section 4. Classification .................................................. . ....... . ........... 2 

Section 5. Testing and Rating Requirements .................................................... 2 

Section 6. Performance Requirements ..... . .. . ................................ .. ........ .. ..... 3 

Section 7 Safety Recommendations .. . ............... . .......... ; : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Section 8. Conformance . . ..................................... . ................. . ............ 6 

D 

PROPERTY OF U.S. GOVERNI\~E"JT 
_______________________________________________ ARI STANDARD 

320-86 

WATER-SOURCE HEAT PUMPS 

Section 1. Purpose 

1.1 Purpose. The purpose of this standard is to establish, 

for water-source heat pumps: definitions and classification; requirements for testing and rating; specifications, 

literature and advertising requirements; performance 

requirements; safety requirements; and conformance 

conditions. 

1.1.1 This standard is intended for the guidance of 

the industry, including manufacturers, distributors, consultants, contractors, and consumers. . 1.2 Review and Amendment. This standard.is subject to 

review and amendment as the art of the industry advances. 

Section 2. Scope 

2.1 Scope. This standard applies to factory-made residential, commercial, and industrial water-source heat 

pumps, as defined in 3.1. 

2.1.1 Energy Source. This standard applies only to 

electrically-driven, mechanical compression type 

systems. 

2.2 Exclusions. This standard does not apply to the 

rating and testing of individual assemblies for separate 

use. 

Section 3. Definitions 

3.1 Water-Source Heat Pump. A water-source heat 

pump consists of one or lmore factory-made assemblies 

which normally include an indoor conditioning coil with 

air moving means, compressor(s) and refrigerant-towater heat exchanger(s), including means to provide 

both cooling and heating or cooling only functions. 

When such equipment is provided in more than one assembly, the separated assemblies shall be designed to be 

used together, and the requirements of rating outlined 

in the standard are based upon the use of matched assemblies. 

3.1.1 Functions. Water-source heat pumps shall 

provide the function of air-circulating and cooling 

and heating with controlled temperature, and may 

include the functions of air-cleaning, dehumidifying or humidifying. 

Models designated as "cooling only" units need 

not include the heating function provided the following are met: 

1. The components of the air-conditioning refrigerant system (cooling system) are substantially the same on the heat pump system. 

2. Switches, thermostats and/or other controls of 

electrical components required for the reverse 

cycle heating mode can be altered or deleted as 

required to provide cooling only. 

3. All other chassis components, fans, motors, 

pumps, housings etc. must be substantially the 

same between both versions. 

3.2 Published Rating. A statement of the assigned values 

of those performance characteristics, under stated rating 

conditions, by which a unit may be chosen to fit its 

application. These values apply to all units of like nominal size and type (identification) produced by the same 

manufacturer. As used herein, the term "published rating" includes the rating of all performance characteristics shown on the heat pump or published in specifications, advertising, or other literature controlled by the 

manufacturer, at stated rating conditions. 

3.2.1 Standard Rating. A rating based on tests 

performed at Standard Rating Conditions. 

3.2.2 Application Rating. A rating based on tests 

performed at application rating conditions (other. 

than Standard Rating Conditions). 

3.3 Rating Conditions. Any set of operating conditions 

under which a single level of performance results, and 

which causes only that level of performance to occur. 

3.3.1 Standard Rating Conditions. Rating conditions used as the basis of comparison of performance characteristics. 

3.4 Energy Efficiency Ratio (EER). A ratio calculated 

by dividing the cooling capacity in Btuh by the power 

input in watts at any given set of rating conditions, expressed in Btuh per watt (Btuh/watt). 

3.4.1 Standard Energy Efficiency Ratio. A ratio 

calculated from the capacity and power input 

values obtained at Standard Rating Conditions. 

3.5 Coefficient of Performance (COP). A ratio calCulated by dividing the total heating capacity provided by 

the refrigeration system including circulating fan heat 

but excluding supplementary resistance heat, (Btuh) by 

the total electrical input (watts) x 3.412. [A ratio .calculated for both cooling and heating capacities by dividing 

capacity in watts by power input in watts.]. 

3.5.1 Standa;d Coefficient of Performance. A ratio 

calculated from the capacity and power input obtained in accordance with 3.5 at Standard Rating 

Heating Conditions. 

3.6 "Shall", "Should", "Recommended", or "It Is Recommended". "Shall", "should" , "recommended", or "it 

is recommended" shall be interpreted as follows: 

3.6.1 Shall. Where "shall" or "shall not" is used 

for a provision specified, that provision is mandatory if compliance with the standard is claimed. 

3.6.2 Should, Recommended, or It is Recommended . .. Should", "recommended" , or" it is recommended" is used to indicate provisions which 

are not mandatory but which are desirable as good 

practice. 1 
2 

ARI STANDARD 

320-86, ________________________________________________ ___ 

Section 4. Classification 

4.1 Classification. Nor~ally, water-source heat.~umps 

within the scope of this standard may be classified as 

shown in Table 1. 

Section 5. Testing and Rating Requirements 

5.1 Standard Rating. Standard ratings shall be established at the Standard Rating' Conditions specified in 

5.1.3. All standard ratings shall be verified by tests ~onducted in accordance with the ASHRAE Standard 

Methods of Testing for Rating Unitary Air-Conditioning 

and Heat Pump Equipment (American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 

Standard 37-78), and with the test methods and procedures as described in this standard. 

Standard Ratings relating to cooling or heating 

capacities shall be net values, including the effects .. of 

circulating-fan heat, but not including supplementary 

heat. Standard Input Ratings shall be the total power 

input to the compressor(s) and fan(s), plus controls and 

other items included as part of the model number(s). 

5.1.1 Values of Standard Capacity Ratings. These 

ratings shall be expressed only in terms of Btu per 

hour (Btuh) [watts] in mUltiples of: 

Capacities 

(Btuh) [W] 

Less than 20,000 [5.900] 

20,000-37,800 [5,900-11.000] 

38,000-64,500 [11,100-18,900] 

65.000 and above [19.000 

and above] 

Multiples 

(Btuh) [W] 

100 [30] 

200 [60] 

500 [160] 

1,000 [300] 

Table 1. Classification of Water-Source 

Heat Pumps 

Types of Water-Source Heat Pumps 

ARI 

Designation Type • Arrangement 

Single Package HSP-W I FAN I COMPI 

(Dueted) IEVAP I COND/ 

Split System HRCU-W I FAN I/COMP/ 

(Dueted) EVAP ~ 

Single Package HSP-W-O I FAN I COMPI 

(Free Delivery) IEVAP I CONDI 

Split System HRCU-W-O I FAN //COMP/ 

(Free Delivery) EVAP \CONDJ 

"Denotes cooling mode function. 

5.1.2 Values of Standard Energy Efficiency Ratios 

or Coefficients of Performance. Standard ratios of 

energy efficiency for cooling, whenever published, 

shall be expressed in multiples of the nearest 0.1 

Btuhlwatt [cooling C.O.P. in multiples of 0.1]; 

standard coefficients of performance for heating, 

whenever published, shall be expressed in multiples of the nearest 0.1. 

5.1.3 Standard Rating Conditions. The conditions 

of test for Standard Ratings shall include the following: -

5.1.3.1. Standard Rating Temperatures. 

a. Cooling 

Air temperature entering indoor. 

portion of unit.. ... 80 F [26.7D

C] dry bulb, 

67 F [19.4DC] wet bulb 

Air temperature surrounding 

unit ................. 80 F [26.7D

C] wet bulb 

Water temperature entering 

refrigerant-to-water 

heat exchanger ............... 85 F [29.4D

C] 

Water temperature leaving 

refrigerant-to-water 

heat exchanger ............... 95 F [35.0D

C] 

b. Healing (not required for cooling only models) 

Air temperature entering indoor 

portion of unit. ..... 70 F [21.1DC] dry bulb, 

60 F [15.6DC] bulb, max. 

Air temperature surrounding 

unit .................. 70 F [21.1 DC] dry bulb 

Water temperature entering 

refrigerant-to-water 

heat exchanger .. _ .......... _ .. 70 F [21.1 DC] 

Water flow rate . _ .. _ ........ as determined in 

Standard Rating 

Cooling Test 

5.1.3.2 Electrical Conditions. Recommended 

nameplate voltages for 60 Hertz systems are 

one or more of the utilization voltages shown 

in Table 1 of ARI Standard 110 for AirConditioning and Refrigerating Equipment 

Nameplate Voltages. 

Standard Rating tests shall be performed at the 

nameplate rated voltage(s) and frequency. 

For heat pumps with dual nameplate 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. 

5.1.3.3 Indoor-Side Air Quantity. All Standard 

Ratings shall be determined at an indoor-side 

air quantity, delivered against at least the • 

minimum external resistance required by 
________________________________________________ ARI STANDARD 320-86 

5.1.3.5, as outlined below. All air quantities 

shall be expressed as cfm [Us] of Standard Air 

(density 0.075 Ib per cu ft [1.2 kg/mll). 

a. Heat pumps shall be rated at the indoor-side 

air quantity delivered when operating 

against the minimum external resistance 

specified in 5.1.3.5 or at a lower indoor-side 

air quantity, if so specified by manufacturer. 

Indoor-side air quantities as referred to herein 

apply to the air quantity experienced when the 

unit is cooling and dehumidifying under the 

Standard Rating Cooling Conditions specified 

in this section. This air quantity, except as noted 

in 6.3, shall be employed in all oOther tests prescribed herein without regard to resulting external static pressure. 

5.1.3.4 Requirements for Separated Assemblies. All Standard Ratings for heat pumps 

in which the outdoor section is separated from 

the indoor section, as in Type HRCU (shown in 

Section 4), shall be determined with at least 25 

feet [7.62 m] of interconnection tubing on each 

line, of the size recommended by the manufacturer. Such heat pumps in which the interconnection tubing is furnished as an integral part of 

the machine not recommended for cutting to 

length shall be tested with the complete length 

of tubing furnished, or with 25 feet [7.62 m] of 

tubing, whichever is greater. The line sizes, insulation, and details of installation shall be in accordance with the manufacturer's published 

recommendations. 

5.1.3.5 Minimum External Resistances. Indoor 

air-moving equipment intended for use with 

field installed duct systems shall be designed to 

operate against, and tested at not less than, the 

minimum external resistance shown in Table 2 

when delivering the rated capacity and air quantity specified in 5.1.3.3. Indoor air-moving 

equipment not intended for use with field installed duct systems shall be tested at 0 in. water 

[0 Pal external pressure. 

In interpreting this requirement, it is understood that the most restrictive filters, supplementary heating coils, and other equipment 

recommended as optional parts of the heat 

pump be in place and that the net external resistances specified above are available for the external duct system. 

5.2 Part-Load Rating. Heat pumps which are capable of 

capacity control shall be rated at each step of capacity 

Table 2. Minimum External Resistance 

Minimum 

External 

Standard Cooling Capacity Ratings Resistance 

(Inches of 

(Thousands of Btuh) [kwj Water) [Paj 

Up thru 28 Up thru 8.2 0.10 24.9 

29thru 42 8.5 thru 12.3 0.15 37.4 

43 thru 70 12.6thru 20.5 0.20 49.8 

71 thru 105 20.8thru 30.8 0.25 62.3 

106thru 134 31.1thru 39.3 0.30 74.7 

135 thru 210 39.6thru 61.6 0.35 87.2 

211 thru 280 61.7thru 82.1 0.40 99.6 

281 thru 350 82.2 thru 102.6 0.45 112.1 

351 thru 400 I02.7thru 117.2 0.55 137.0 

401 thru 500 117.3thru 146.6 0.65 161.9 

501 and over 146.7 and over 0.75 186.8 

reduction provided by the heat pump and allowed by the 

controls. 0 

S.2.1 Part-Load Rating Conditions. The conditions of test for part-load ratings are the same as 

for the Standard Ratings (see 5.1) except for the 

following: 

5.2.1.1 Part-Load Rating Temperatures (Cooling). 

Air temperature entering indoor 

portion of unit ..... 80 F[26,7°C] dry bulb, 

67 F[19.4°C] wet bulb 

Water temperature entering refrigerantto-water heat exchanger ..... 75 F[23.9°C] 

Water flow rate ...... Same as determined in 

Standard Rating Cooling Test 

5.2.1.2 Part-Load Rating Temperatures (Heating-not r~quired for cooling only models). 

'Air temperature entering indoor 

portion of unit ..... 70 f[21.1°C] dry bulb, 

o 60 F[15.6°C] wet bulb max. 

Air temperature surrounding 

unit ............... 70 F[21.1°C] dry bulb 

Water temperature entering refrigerantto-water heat exchanger ..... 75 F[23.9°C] 

Water flow rate ........... as determined in 

o Standard Rating Cooling Test 

5.2.1.3 The capacity reduction means may be 

adjusted to obtain the specified step of unloading. 

5.3 Application Ratings. Ratings at conditions of temperature or air quantity other than those specified in 

5.1.3 and 5.2.1, may be published as application ratings, 

and shall be based on data determined by the methods 

prescribed in 5.1. 

3 
ARI STANDARD 

320-86 ________________________________________________ _____ 

5.4 Publication of Ratings. Wherever application ratings are published or printed. they shall include. or be 

accompanied by. the Standard Capacity Ratings plus the 

Part-Load Rating (where applicable), and their corresponding power inputs, clearly designated as such, including a statement of the conditions at which the ratings 

apply. 

5.4.1 Capacity Designation. The capacity designation used in published specifications, literature or 

advertising, controlled by, the manufacturer, for 

heat pumps rated under this standard, are to be 

expressed only in Btuh [watts] at the Standard 

Rating Conditions specified in 5.1.2 plus PartLoad Rating Conditions specified in 5.2.1, and in 

the terms described in 5.1.1 through 5.1.2: Horsepower, tons, or other units shall not be used as 

capacity designations. 

5.5 Tolerances. To comply with this standard published 

cooling capacity ratings. heating capacity ratings. ratios 

of energy efficiency for cooling. and coefficients of performance for heating. shall be based on data obtained in 

accordance with the provisions of this section. and shall 

be such that any production unit, when tested, will meet 

or exceed these ratings except for an allowance to cover 

testing and manufacturing variations; the amount of allowance to be minus 5 percent. 

Section 6. Performance Requirements 

6.1 Performance Requirements. To comply with this 

standard. water-source heat pumps shall be designed 

and produced in accordance with the provisions of thi~ 

section in such a manner that any production unit will 

meet the requirements detailed herein. 

6.2 Maximum Operating Condifions Tesf. Watersource heat pumps shall be designed and produced to 

pass the following maximum operating conditions test 

with an indoor·side coil air quantity as determined under 

5.1.3.3: 

4 

6.2.1 Temperature Conditions. 

6.2.1.1 Cooling. 

Air temperature surrounding 

unit .................... 95 F [35.0°C] dry bulb 

Air temperature entering indoor portion 

of unit ................ 95 F [35.0°C] dry bulb, 

71 F [21.2°C] wet bulb 

Water temperature entering refrigerantto water heat exchanger ......... 90 F [32.3°C] 

Water flow rate ................. Maintained same 

as in 5.1.3.1 

6.2.1.2 Heatillg (nol reqllired for cooling only 

models). 

Air temperature entering indoor 

portion of unit.. ....... 80 F [26.7°C] dry bulb 

Air temperature surrounding 

unit .................... 80 F [26.7°C] dry bulb 

Water temperature entering refrigerantto-water heat exchanger ........ 90 F [32.3°C] 

Water flow rate ................ Maintained same 

as in 5.1.3.1 

6.2.2 Voltages. 

6.2.2.1 Tests shall be run at 90 per cen t and 110 

per cent of the unit's nameplate rated voltage at 

the unit's service connection and at rated frequency, or at a lower than 90 per cent minimum 

or a higher than 110 per cent maximum voltage. 

if listed on the nameplate. 

6.2.2.2 The power supplied to the heat pump 

shall be adjusted just prior to the shut down 

period (See 6.2.3.2) so that the resulting voltage 

at the unit's service connection is 86 per cent of 

nameplate rated voltage when the compressor is 

on locked rotor. (For those dual voltage units so 

specified on eir specification sheets for a 

minimum voltage 5 per cent below the lower 

rated voltage. this locked-rotor voltage setting 

shall be 91 per cent of the lower rated voltage.) 

For the purpose of this standard. the compressor nameplate locked-rotor amperes may be 

used to determine 'this voltage. The proper 

value of no-load voltage which will give the 

specified voltage at locked-rotor conditions 

should be determined prior to the test. 

The locked-rotor current value of any motor 

shall be measured as follows: 

a. All hermetic compressor motors shall be 

tested as a compressor assembly. 

b. The motor winding temperature shall not 

exceed 77 F [25°C] when the voltage is 

applied. 

c. The current reading shall be taken within 

four seconds after the voltage is applied. 

If the test is repeated, the motor winding 

shall be allowed to cool to 77 F [25°C] or 

lower before the current is reapplied. 

d. The voltage at the unit service connection, 

at the time the current reading is taken, 

shall be the manufacturer's nameplate 

rated voltage. 

e. The locked-rotor current shall be measured with an ammeter, with the rotor actually locked. 

6.2.2.3 Within one minute after the heat pump 

has resumed continuous operation (See 

6.2.4.3), the voltage shall be restored to the 

values specified in 6.2.2.1. 

6.2.2.4 Single phase dual voltage units whose 

lower voltage is 208v., which specify on their • 
________________________ ARI STAN OAR 0 320-86 

specification sheets a minimum voltage to be 

applied at the unit service connection for the 

maximum operating conditions test, shall be 

tested at this minimum voltage in accordance 

with 6.2.2.1, 6.2.2.2 and 6.2.2.3. This provision 

applies only when the minimum voltage does 

not exceed 19Sv. 

6.2.3 Procedure. 

6.2.3.1 The heat pump shall be operated for 

two hours at the temperature conditions and 

voltage(s) specified. 

6.2.3.2 All power to the heat pump shall be cut 

off for a period sufficient to cause the compressor to stop (not to exceed five seconds) and then 

restored. 

6.2.4 Requirements. 

6.2.4.1 During both entire tests, the heat pump 

shall operate without failure of any of its parts. 

6.2.4.2 The heat pump shall operate continuously without interruption for any reason for the 

two-hour period preceding the power interruption. 

6.2.4.3 The unit shall resume continuous operation within two hours of restoration of power 

and shall then operate continuously for one 

hour. Operation and resetting of safety devices 

prior to establishment of continuous operation 

is permitted. 

6.3 Low- Temperature Operation Test (Cooling). 

Water-source heat pumps shall be designed and produced to pass the following low-temperature operation 

test when operating with initial air quantities as determined in 5.1.3.3 and with controls and dampers set to 

produce the maximum tendency to frost or ice the 

evaporator, provided su~h settings are not contrary to 

the manufacturer's instructions to the user: ' 

,6.3.1 Temperature Conditions. 

Air temperature entering indoor 

portion of unit. ........ 67 F [19.4°C] dry bulb, 

57 F [13.9°C] wet bulb 

Water temperature entering refrigerantto-water heat exchanger ......... 65 F [lS.3°C] 

Water flow rate ............... ' .. Maintained same 

as in 5.1.3.1 

6.3.2 Procedure. The test shall be continuous with 

the unit on the cooling mode, for not less than four 

hours after establishment of the specified temperature conditions. The unit will be permitted to operate under the control of a limit device, if provided. 

6.3.3 Requirements. 

6.3.3.1 During the entire test, the heat pump 

shall operate without damage to the equipment. 

6.3.3.2 During the entire test, the air quantity 

shall not drop more than 25 per cent from that 

determined under the Standard Rating Cooling 

Test. 

6.3.3.3 During the test, and during the defrosting period after the completion of the test, all ice 

or meltage must be caught and removed by the' 

drain provisions. 

6.4 Insulation Efficiency Test (Cooling). Water-source 

heat pumps shall be designed and produced to pass the 

following insulation efficiency test when operating with 

air quantities as determined in 5.1.3.3 with controls, 

fans, dampers and grilles set to produce the maximum 

tendency to sweat, provided such settings are not contrary to the ~anufacturer's instructions to "he" user. 

6.4.1 Temperature Conditions. 

Air temperature entering and 

surrounding indoor portion 

of unit ......... : .... SO F r26.7°C] dry bulb, 

75 F [23.9°C] wet bulb 

Water temperature entering refrigerantto-water heat exchanger ....... SO F [26. rq 

Water flow rate .............. Maintained same 

as in 5.1.3.1 

6.4.2 Procedure. After establishment of the 

specified temperature conditions, the unit shall be 

operated. continuously for a period of four hours. 

6.4.3 Requirements. During the test, no condensed water shall drop, run or blow off from the 

unit casing. 

6.S Tolerances .. The conditions for the tests outlined in 

6.2, 6.3 and 6.4 are average values subject to tolerances 

of ± 1.0 F [± 0.56°C] for. air wet bulb and dry bulb 

temperatures, ±0.5 F [±0.2S°C] for water temperatures and ± 1.0 per cent of the reading for voltages. 

5 
ARI STAN DA RD 320-86 _______________________ _ 

Section 7. Safety Recommendations 

7.1 Safety. It is strongly recommended that the product 

be designed, constructed, assembled and installed in accordance with nationally recognized safety standards 

and codes, appropriate for the product covered by this 

standard. 

6 

Section 8. Voluntary Conformance 

8.1 Conformance. While conformance with this standard is voluntary, conformance shall not be claimed or 

implied for products or equipment within its Purpose 

(Section 1) or Scope (Section 2) unless such claims meet 

all of the requirements of the standard. 

fNb 

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