NISTIR 6803 

A Comparison of Rating Water-Source Heat Pumps 

Using ARI Standard 320 and IS0 Standard 13256-1 

W. Vance Payne 

Piotr A. Domanski 

U. S. DEPARTMENT OF COMMERCE 

Technology Administration 

National Institute of Standards 

Building and Fire Research Laboratory 

Gaithersburg, MD 20899-8230 

and Technology 

NlST CENTENNIAL. 

National Institute of Sfandsrds and Technology 

Technology Administration, U.S. Department of Commerce 

NISTIR 6803 

A Comparison of Rating Water-Source Heat Pumps 

Using ARI Standard 320 and IS0 Standard 13256-1 

W. Vance Payne 

Piotr A. Domanski 

U. S. DEPARTMENT OF COMMER4E 

Technology Administration 

National Institute of Standards 

Building and Fire Research Laboratory 

Gaithersburg, MD 20899-8230 

and Technology 

September 200 1 

U.S. DeDartment of Commerce 

Donald L. Evans, Secretary 

National Institute of Standards and Technology 

Karen H. Brown, Acting Director 

A Comparison of Rating Water-Source Heat Pumps 

Using ARI Standard 320 and IS0 Standard 13256-1 

W. Vance Payne, Piotr A. Domanski 

National Institute of Standards and Technology 

Gaithersburg, Maryland USA 20899 

Abstract 

This investigation compares performance ratings obtained when testing water-source heat 

pumps using the Air-conditioning and Refrigeration Institute (ARI) Standard 320 and the 

International Standards Organization (ISO) Standard 13256- 1. Multiple tests were run using 

two heat pumps of different capacities from different manufacturers. These tests included a 

ducted 1.75 kW (0.5 ton) unit and a non-ducted 3.52 kW (1.0 ton) unit. Air external static 

pressure and water flow were varied at the IS0 conditions to determine the correction in 

capacity and total power mandated by the IS0 standard. The effects of this variability were 

measured and compared to test results using the ARI Standard 320 as the baseline test. IS0 

cooling capacity for the first and second units were 0.1 % higher and 1.1 % lower than the 

ARI capacity, respectively. IS0 cooling energy efficiency ratio (EER) for the first and second 

units were 4.5 96 higher and 3.9 % lower than the ARI, respectively. IS0 heating capacity for 

the first and second units were 4.8 % lower and 2.9 % lower than the ARI capacity, 

respectively. IS0 heating coefficient of performance (COP) for the first and second units 

were 6.2 % higher and 1 .O % lower than the ARI, respectively. 

Keywords: Air conditioner, ARI Standard 320, Capacity, COP, EER, Heat Pump, IS0 

Standard 13256-1, Water-Source Heat Pump 

i 

Acknowledgement 

This study was sponsored by the United States Department of Energy, Office of Building 

Technology, State and Community Programs under contract DE-AI0 1 -99EE27572. The 

authors thank Dr. Samuel Yana Motta of Honeywell and Mr. David Yashar of NIST for their 

review and comments on the draft of this report. We also thank Mr. Anthony Downs for his 

assistance with the testing of these heat pumps and the analysis of data. 

Use of Non-SI Units in a NIST Publication: The policy of the National Institute of Standards and Technology is 

to use the International System of Units (metric units) in all of its publications. However, in North America in 

the heating, ventalation and air-conditioning industry, certain non-SI units are so widely used instead of SI units 

that it is more practical and less confusing to include some measurement values in customary units only. 

.. 

11 

Table of Contents 

Abstract .................................................................................................................... 1 

.. Acknowledgment .................................................................................................... 11 

... Table of Contents ................................................................................................... 111 

List of Tables .......................................................................................................... iv 

List of Figures ........................................................................................................ vi 

Nomenclature v11 

.. ........................................................................................................ 

1 . 

2 . 

3 . 

4 . 

5 . 

6 . 

7 . 

Introduction .................................................................................... .................. 1 

Experimental Setup ........................................................................................... 2 

2.1: Test Setup ............................................................................................ 2 

2.2: Instrumentation and Data Acquisition ................................................ 3 

Experimental Procedure and Test Conditions ................................................... 4 

Units Tested. Tests Performed and Data Reduction ......................................... 5 

Experimental Results ......................................................................................... 6 

5.1: Unit 1 - 1.75 kW (0.5 Ton) 

5.2: Unit 2 - 3.52 kW (1.0 Ton) 

Nominal Cooling Capacity, Ducted System ....................................... 6 

Nominal Cooling Capacity, Non-ducted System .............................. 10 

Summary ......................................................................................................... 14 

References ....................................................................................................... 16 

Appendix A: Uncertainty Analysis ....................................................................... 17 

Appendix B: Heat Pump Test Data ....................................................................... 28 

Appendix C: Summary of Manufacturer and NIST Test Data .............................. 32 

... 

111 

List of Tables 

2.1 Measurement uncertainties ............................................................................... 3 

3.1 ARI cooling conditions .................................................................................... 4 

3.2 IS0 cooling conditions ..................................................................................... 4 

3.3 ARI heating conditions ..................................................................................... 5 

3.4 IS0 heating conditions ..................................................................................... 5 

4.1 Test matrix summary for the cooling and heating modes ................................ 5 

5.1 ARI and IS0 cooling test results for Unit 1 ..................................................... 8 

5.2 ARI and IS0 heating test results for the Unit 1 ............................................... 9 

5.3 ARI and IS0 cooling test results for Unit 2 ................................................... 11 

5.4 ARI and IS0 normal aifflow 

heating test results for Unit 2 ......................................................................... 13 

5.5 ARI and IS0 low aifflow 

heating test results for Unit 2 ......................................................................... 14 

6.1 ARI 320 and IS0 13256- 1 capacity comparison ........................................... 15 

6.2 ARI 320 and IS0 13256-1 efficiency comparison ......................................... 16 

A . 1 : Measurement uncertainty for typical tests ................................................... 27 

B . 1: Unit 1, data #I .............................................................................................. 28 

B.2: Unit 1. data #2 .............................................................................................. 28 

B.3: Unit 1. data #3 .............................................................................................. 29 

B.4: Unit 1. data #4 .............................................................................................. 29 

B.5: Unit 1. data #5 .............................................................................................. 30 

B.6: Unit 2. data #1 .............................................................................................. 30 

B.7: Unit 2. data #2 .............................................................................................. 30 

iv 
List of Tables (continued) 

B.8: Unit 2. data #3 .............................................................................................. 31 

B.9: Unit 2. data #4 .............................................................................................. 31 

C . 1 : Manufacturer cooling test results for Unit 1 ................................................. 32 

C.2: Manufacturer and NIST cooling test results for Unit 1 ................................ 33 

C.3: Manufacturer heating test results for Unit P ................................................. 33 

C.4: Manufacturer and NIST heating test results for Unit 1 ................................ 34 

C.5: Manufacturer cooling test results for Unit 2 ................................................. 34 

C.6: Manufacturer and NIST cooling test results for Unit 2 ................................. 35 

C.7: Manufacturer heating test results for Unit 2 ................................................. 35 

C.8: Manufacturer and NIST heating test results for Unit 2 ................................. 36 

V 
List of Figures 

2.1 Water-source heat pump test apparatus ............................................................ 3 

vi 

Nomenclature 

COP 

DP 

DT 

EER 

h.p. 

9 

Wrt 

AP 

heating coefficient of performance (W/W) 

pressure difference (Pa) 

temperature difference measured by a thermopile ("C) 

cooling energy efficiency ratio (Btu/Wh) 

heat pump 

air or water flow rate (Us) 

static pressure drop (Pa) 

with respect to 

mpa 

rl 

fan or pump power adjustment (W) 

dimensional constant of 0.3 .lo3 [(L/s)(Pa)( IN)] as prescribed by the IS0 Standard 

13256-1 

vii 

1: Introduction 

Globalization of the economies creates new marketing opportunities and increases the 

importance of international standards. The use of international standards becomes 

particularly important for the manufacturing sector which products can be shipped 

internationally. The adoption of an international standard offers substantial economic 

benefits, but the transition from a national to international standard poses a question 

whether the ratings obtained by using these standards are equivalent. 

This study was concerned with rating obtained for water-source heat pumps test using 

two standards: the standards developed by the Air-conditioning and Refrigeration 

Institute (ARI), ARI Standard 320 (1998), and the standard developed by the 

International Organization for Standardization (ISO), IS0 Standard 13256- 1 ( 1998). The 

IS0 standard is increasing in use. On January 1, 2000, the ARI adopted the IS0 standard 

as the basis for its certification programs. The standard developed by the American 

Society of Heating, Refrigerating, and Air-conditioning Engineers, ASHRAE Standard 

90.1 (1999), references both the ARI standard and the IS0 until October 29, 2001, with 

the IS0 standard designated as the exclusive standard starting at this date. The goal of 

this study was to evaluate the differences in rated energy efficiency ratio (EER) for 

cooling operation and coefficient of performance (COP) for heating operation obtained 

when using these two test methods. 

The test and rating results obtained when using the ARI standard and IS0 standard are 

expected to be somewhat different because of three inherent differences between these 

standards : 

(1) The first difference is the slightly different dry-bulb and dew-point temperatures. 

These different operating conditions are related to different temperature scales 

(Fahrenheit vs. Celsius) and do not represent a significant difference in the test 

operating temperatures.. 

(2) The second difference between the ARI standard and the IS0 standard is the 

external air static pressure applied during the test. Under the ARI standard, the 

unit must be tested while operating against the external air static pressure that is 

specified by the standard for a given system's capacity. Under the IS0 standard, 

the unit must be tested against static pressure specified by the manufacturer. 

After completion of the test, a credit is given for the indoor fan power to the total 

energy input, and the system capacity is credited for the heat added by the indoor 

fan. 

(3) The third difference is the treatment of the energy input to the water pump. Under 

the ARI standard, this energy input is not included in the calculation of the total 

energy input, and the standard specifies the water flow rate that results in a 5.6 "C 

(10.0 OF) temperature change across the heat exchanger. Under the IS0 standard, 

the test must be performed at the mass flow rate specified by the manufacturer, 

and the energy input to the water pump is measured and included in the total 

energy input. 

1 
The following sections present the experimental apparatus, systems tested, and laboratory 

test results obtained by the ARI and IS0 standards. Tests of one ducted and one nonducted water-source heat pump provided comparison data for these two test procedures. 

In addition to “standard” testing carried out using the two standards, expanded testing 

was performed under IS0 testing conditions with varied air external static pressure and 

water flow rates. These tests provided information regarding the effect on the rating of 

these two parameters that are specified by the manufacturer of the heat pump. The 

appendices include the uncertainty analysis and the comparison of NIST test results those 

obtained on the same model units by their manufacturers. 

2: Experimental Setup 

2.1: Test Setup 

The main components of the experimental apparatus are shown below in Figure 2.1 ; these 

include the tested heat pump, the nozzle chamber, and the pull-thru fan. The watersource heat pump was supplied with distilled water conditioned to the appropriate 

temperature and flow rate. Inlet air was conditioned by the environmental chamber to the 

appropriate dry-bulb and dew-point temperatures required by either the IS0 or ARI 

standard. 

Mixers were included in the ductwork before the thermopile and thermocouple grids to 

ensure well mixed air. The 15-node thermocouple grid before and after the test unit was 

used to verify that the air was well mixed. Air temperature difference across the test unit 

was measured by a 10-junction thermopile. Dew-point temperature was measured before 

and after the test unit. For the unit equipped with ductwork connections, air pressure 

drop was measured across the system. These measurements were collected according to 

ASHRAE Standard 37- 1988. 

The nozzle chamber was constructed according to ANSYAMCA 210-85 (1985). The 

nozzle chamber measured the volume flow of air thru each unit. Airflow rate was 

controlled by a variable frequency drive on the pull-thru fan. All airflow rates were 

converted to standard conditions as described in the standard. 

The test heat pump was supplied with conditioned distilled water at the appropriate flow 

rate and temperature. Water temperature difference was measured by a 1 0-junction 

thermopile located in a well inserted in the inlet and exit water lines. Water temperatures 

were measured by individual thermocouples inserted into the thermopile wells. Water 

coil temperature change was measured by a 10-junction thermopile. Water coil pressure 

drop was measured by a wet-wet differential pressure transducer. The water coil pressure 

drop was used by the IS0 standard to correct for pumping power consumption. 

2 
Nozzle Chamber 

.......................... 

@ Water-Source Heat Pump Temperature difference 

@ Dry-bulb, Dew-point temperatures 

@ Temperature 

-18 "C to 93 "C 

(0 "F to 200 OF) 

0 "C to 28 "C 

(0 "F to 50 OF) 

0 "C to 50 "C 

(32 "F to 122 OF) 

0 mm Hg to 1270 mm Hg 

(0 in Hg to 50 in Hg) 

0 Pa to 1245 Pa 

Figure 2.1 : Water-source heat pump test apparatus 

k0.3 "C 

(+OS OF) 

k0.3 "C 

(+OS OF) 

M.2 "C 

(fo.4 OF) 

k0.34 mm Hg 

(k0.0135 in Hg) 

k1.0 Pa 

2.2: Instrumentation and Data Acauisition 

difference 

Water coil pressure 

Data were gathered using a personal computer and a multiplexed data acquisition unit. 

Over 50 data points were monitored throughout the testing. Table 2.1 lists measured 

quantities and their 95 % confidence limits. Appendix A gives a detailed uncertainty 

analysis for capacity and EER or COP. 

(0 in H20 to 5.0 in H20) 

0 kPa to 69 kPa 

(k0.004 in H20) 

k0.17 kPa 

Table 2.1 : Measurement uncertainties 

difference 

Air nozzle pressure 

Ouantitv 

(0 psid to 10 psid) 

0 Pa to 623 Pa 

(M.025 psid) 

fo.87 Pa 

Temperature 

difference 

Total power 

Temperature change 

(0 in H20 to 2.5 in H20) 

0 watts to 2000 watts 

(+0.0035 in H20) 

k5.0 watts 

Dew-point temperature 

Barometric pressure 

Air coil pressure 

Range I Uncertainty* 

3 
3: Experimental Procedure and Test Conditions 

Location 

Indoor Dry-bulb Temperature 

Indoor Dew-Doint 

For both heating and cooling tests, the refrigeration chamber was maintained within 

0.3 OC (0.5 OF) of a constant dry-bulb temperature and dew-point temperature. 

Setpoint Tolerance 

26.7 OC M.3 "c 

(80.0 OF) (M.5 OF) 

15.8 OC a.3 OC 

Distilled water was brought into the system at a temperature specified by the appropriate 

standard (Tables 3.1, 3.2, 3.3 and 3.4). In the cooling mode, the water flow rate was 

adjusted to give a 5.6 "C (10.0 OF) temperature increase for the ARI standard and as 

specified by the manufacturer for the IS0 standard. 

Temperature 

Inlet Water Temperature 

Outlet Water Temperature 

Inlet air dry-bulb and dew-point temperatures were maintained for one hour within the 

specified range with the systems at steady-state before tests began. The temperature 

across the exit thermocouple grid was monitored to ensure well mixed air. Air coil static 

pressure drop was measured and recorded for the ducted unit tested. 

(60.4 OF) (+OS OF) 

29.4 OC a.3 "c 

(85.0 OF) (20.5 OF) 

35.0 OC a.3 "c 

(95.0 OF) (d.5 OF) 

In the heating mode, all fan settings and water flow rates were maintained the same from 

the respective cooling tests. For the IS0 standard, the fan power correction was added to 

the heating capacity and to the total power. All other procedures followed those used 

during the cooling tests. 

Location Setpoint 

27.0 "C 

(80.6 OF) 

Indoor Dew-point 14.7 OC 

Temperature (58.5 OF) 

30.0 "C 

(86.0 "n 

Indoor Dry-bulb Temperature 

Inlet Water Temperature 

Table 3.1 : ARI cooling: conditions 

Tolerance 

M.3 "c 

(&OS OF) 

M.3 OC 

(&OS OF) 

M.3 "c 

(20.5 "F) 

Water flow specified by the manufacturer I Water Flow I 

4 
Location Setpoint 

21.1 "c 

(70.0 OF) 

21.1 "c 

(70.0 "F) 

Indoor Dry-bulb Temperature 

Inlet Water Temperature 

Same water flow as the cooling test I 

/WaaFiow I 

Tolerance 

M.3 "c 

(H.5 OF) 

ko.3 "c 

(M.5 OF) 

Table 3.4: IS0 heating conditions 

Location 

Indoor Dry-bulb Temperature 

Maximum Dew Point 

Inlet Water Temperature 

Setpoint Tolerance 

20.0 "c M.3 "c 

(68.0 OF) (M.5 OF) 

11.7 "C M.3 "c 

(53.1 "F, (M.5 OF) 

20.0 "c H.3 "c 

(68.0 "F) (M.5 OF) 

I Same as in the cooling test above I Water Flow I 

ARI 320 

IS0 13256-1 

4: Units Tested, Tests Performed and Data Reduction 

Normal Normal 

Normal Normal 

Two water-source heat pumps were selected for this study. The first unit was a ducted 

design with a nominal cooling capacity of 1.75 kW (0.5 ton). The second unit was a nonducted console type design with a nominal cooling capacity of 3.52 kW (1 .O ton). For the 

non-ducted unit, the air static pressure at the exit of the unit was maintained at zero for all 

tests. Neither unit included a pump for circulating water through the water coil. Both 

units were tested according to ARI Standard 320 and IS0 Standard 13256-1. Table 4.1 

below summarizes the tests performed on each unit for the cooling and heating modes. In 

addition to the "normal" IS0 test with airflow and water flow specified by the 

manufacturer, tests with increased and decreased air static pressure and water coil 

pressure drop were performed to examine their effects upon EER and COP. These tests 

are described in Table 4.1 as Modified IS0 tests. 

High 

LOW 

Normal 

Normal 

Modified IS0 

Table 4.1 : Test matrix summary for cooling and heating modes 

I I External Air Static Pressure* I Water coil Pressure DroD I 

Normal 

Normal 

High 

LOW 

* The non-ducted unit was maintained at zero exit static pressure for all tests. 

5 
Air-side capacity was calculated using the measured air flow rate, specific heat, and 

changes in air dry-bulb temperature and moisture content. Barometric pressure was also 

used to calculate air properties for the given conditions. The nozzle pressure drop was 

converted to a volumetric flow rate. The nozzle temperature and humidity ratio were 

used to calculate the air density and convert volumetric flow rate into a mass flow rate. 

For the IS0 standard, a correction to the air-side capacity and total power were calculated 

based on the external static air pressure drop of the air coil and the pressure drop across 

the water coil. This correction was calculated by Equation 4.1 below with the Ap being 

the static pressure drop of the fluid considered, air or water. The fan power correction, in 

watts, was added to the total power consumption and subtracted from the total capacity 

for the cooling tests. The fan power correction was added to the total power consumption 

and capacity for the heating tests. Pumping power was added to the total power for all 

heating and cooling tests. 

where apU is the pump or fan power adjustment (watts) 

q is the nominal fluid flow rate (Us) 

Ap is the measured pressure drop (Pa) 

q is 0.3. lo3 as specified by IS0 Standard 13256- 1. 

Total power was measured by a wattmeter during the test period, which was never shorter 

than 30 min. The total power measurement was combined with the water coil capacity as 

a secondary calculation of the air-side capacity. For the ARI standard, the reported 

capacity is based on the air-side measurements. For the IS0 standard, the reported 

capacity is the average of the air-side and secondary method capacities. The agreement 

between the two methods was within 5.0 % for all tests. Note that the corrected values of 

capacity, EER, and COP are the heat pump ratings obtained from the IS0 test procedure. 

5: Experimental Results 

5.1 : Unit 1 - 1.75 kW (0.5 Ton) Nominal Cooling Capacity, Ducted System 

Cooling tests 

Table 5.1 summarizes the cooling test results for Unit 1. For the IS0 test, the table 

presents detailed information; the uncorrected capacity, power, and EER are presented 

first. The following entries are system operating parameters, IS0 corrections for capacity 

and power, and the corrected capacities and EERs. These corrected values are the 

reported capacities and EERs when tests are performed using the IS0 method. 

6 
Under the ARI cooling conditions, air-side capacity and EER were 2352 W (8024 Btu/h) 

and 13.2 1, respectively. For the IS0 13256- 1 cooling conditions, air-side capacity and 

EER were 2353 W (8028 Btu/h) and 13.80. The IS0 results include the fan power, 

capacity corrections, and the pump power correction. Correcting the capacity and power 

for the fan and pump, according to Equation 4.1, changed the EER from 12.89 (the 

uncorrected value in Table 5.1) to 13.80 (an increase of 7.06 %). 

Air static pressure and water flow rate to the unit were varied to determine their effects 

upon capacity and EER within the IS0 13256-1 conditions. Air static pressure has the 

greatest effect upon capacity and EER due to the capacity correction of Equation 4.1 and 

fan power correction required by the IS0 standard. For the low and high air static 

pressure tests air-side, capacity changed by 0.3 % and -3.6 %, respectively, as air volume 

flow changed by +30 % and -30 %. EER change due to the changes in air volume flow 

rate were -0.7 % and -2.2 %. Changes in water flow rate through the water coil 

produced even smaller effects upon the IS0 cooling test results. As water flow was 

varied by -10 % and +10 %, IS0 air-side capacity changed by -1.6 % and +0.1 %, 

respectively. EER changed by -1.4 % and +0.7 %. 

ARI capacity was 1.6 % higher than the IS0 uncorrected capacity. EER was 1.6 % 

higher than the IS0 uncorrected EER. These differences were due to the differences in 

test conditions (dry-bulb and dew point). Capacity increased by 1.6 % due to correcting 

for fan capacity according to equation 4.1. The pump power correction produced a 

minimal effect upon EER as it was less than 1.5 % of the total power for all tests. EER 

increased by 7.0 % due to the corrections for fan heat, fan power, and pump power. 

7 
Table 5.1: ARI and IS0 cooling test results for Unit 1 I 

Cooling 

Using IS0 13256-1: 

Uncorrected Capacity, W 

(Btuh) 

Uncorrected Total Power, W 

Uncorrected EER, BtuNVh 

Water Flow, L/s 

Water Temp Change, "C 

(mm) 

External Air Static Pressure Water 

Low I Normal 1 High Low 

2326 2316 2227 2276 

(7935) (7902) (7598) (7766) 

620 613 610 617 

12.80 12.89 12.46 12.59 

0.128 0.127 0.127 0.1 19 

5.44 (9.8) 5.44 (9.8) 5.38 (9.7) 5.83 

(2.0) (2.0) (2.0) (1.9) 

(OF) I I (10.5) 

Corrected EER, Btu/Wh I 13.65 I 13.80 I 13.50 I 13.56 

2316 

(7902) 

613 

12.89 

0.127 

(2-0) 

5.44 (9.8) 

2318 

(7908) 

610 

12.97 

0.135 

5.17 (9.3) 

(2-1) 

:oil Pressure Drop I 

Water Pressure Drop, Pa 

(psid) 

Air Flow, Ws (cfm) 

Air Temp Change, "C 

(OF) 

Air Static, Pa 

(in H20) 

IS0 Capacity Adjustment: 

For Fan Heat, W (Btu/h) 

IS0 Power Adjustment : 

For Fan Power, W 

ForPumpPower,W 

13807 14134 I 13578 11038 

(2.00) (2.05) (1.97) (1.60) 

155 (328) 142 (301) 127 (270) 141 (299) 

10.22 10.6 1 11.0 10.67 

(1 8.4) (19.1) (19.8) (19.2) 

(0.28) (0.3 1) (0.40) (0.33) 

36 (122) 37 (126) 42 (144) 39 (132) 

36 37 42 39 

I 6 I 6 I 6 I 4 

I 69 78.2 99.4 82 

14134 

(2.05) 

142 (301) 

10.6 1 

(19.1) 

78.2 

(0.3 1) 

37 (126) 

16368 

(2.37) 

143 (302) 

10.72 

(19.3) 

79 

(0.32) 

37 (128) 

37 

6 

Heating - tests 

37 

7 

Table 5.2 Under the ARI heating 

conditions air-side capacity and COP were 3270 W (1 1 157 Btu/h) and 4.8 1, respectively. 

For the IS0 13256-1 cooling conditions air-side capacity and COP were 3 114 W (10624 

Btu/h) and 5.1 1. 

summarizes the heating test results for Unit 1. 

Corrected Capacity, W 

(BtW 

Air static pressure and water flow rate to the unit were varied to determine their effects 

upon capacity and COP within the IS0 13256-1 conditions. Air static pressure had the 

greatest effect upon capacity and efficiency due to the capacity correction and fan power 

correction. For the low and high air static pressure tests, air-side capacity changed by 

1.8 % and -1.6 %, respectively, as air volume flow changed by +30 % and -30 %. COP 

change due to the changes in air volume flow rate were 1.7 % and -2.3 %. Changes in 

2361 2353 2269 2315 

(8057) (8028) (7742) (7898) 

8 

2353 

(8028) 

13.80 

2355 

(8036) 

13.86 

; 

2352 

(8024) 

608 

13.21 

Using ARI 320 

Capacity, W (Btu/h) 

Total Power, W 

EER, Btu/Wh 

2352 

(8024) 

608 

13.21 
water flow rate through the water coil produced even smaller effects upon the IS0 

heating test results. As water flow was varied by -10 % and +10 %, IS0 air-side capacity 

changed by -0.8 % and +0.7 %, respectively. COP changed by +0.2 % and +O.O %. 

' Using IS0 13256-1: 

Uncorrected Capacity, W 3213 

(Btuh) ( 10964) 

ARI capacity was 1.2 % higher than the IS0 uncorrected capacity. COP was 1 .O % lower 

than the IS0 uncorrected COP. These differences were due to the differences in test 

conditions (dry-bulb and dew point). Capacity decreased by 0.3 % due to correcting the 

tests for fan capacity according to equation 4.1. The pump power correction produced a 

minimal effect upon COP as it was less than 1.5 % of the total power for all tests. COP 

increased by 5.0 % due to the corrections for fan heat, fan power, and pump power. 

0.124 0.125 

(1.97) (1.987) 

4.72 4.67 

13600 13983 

1 (1.973) (2.028) 

l 147 136 

' (311) (287) 

19.0 20.0 

(34.2) (36.0) 

(8.5) (8.4) 

Table 5.2: ARI and IS0 heating test results for Unit 1 

(0.393) (0.427) 

Air Static Pressure 

0.124 

(1.97) 

4.72 

(8-5) 

13600 

(1.973) 

~ 147 

' (311) 

19.0 

(34.2) 

Water 

0.136 

(2.149) 

4.39 

(7-9) 

16237 

(2.355) 

148 

(315) 

19.1 1 

(34.4) 

:oil Pressure Drop 

- ~~~ ~ 

98 

(0.393) 

48 (163) 

Externa 

LOW Heating 

90 

(0.362) 

45 (152) 

Normal I High LOW Normal I High 

(10787) (10618) 2 (10787) (10914) 

3153 

(10757) 

Uncorrected Total Power, W I 646 648 

Uncorrected COP I 4.97 4.85 I 4.74 4.87 4.85 I 4.89 

Water Flow, LIS (gpm) 0.125 I (1.982) 

0.106 

(1.684) 

5.44 

(9.8) 

9990 

( 1.449) 

Water Coil Temp Change, 

(mid) (2.046) 

Air Flow, Us (cfm) 156 

(331) 

149 

(3 15) 

18.89 

(34.0) 

Air Coil Temp Change, -~~ "C T ;iiyi 

(OF) 

Air Static, Pa (in H20) I mE9, 

91 

(0.366) 

IS0 Capacity Adiustment: 

45 (154) 

48 1 48 45 48 I 45 

5.6 I 5.8 3.5 5.6 I 7.3 

Corrected Capacity, WCorrected COP 

(Btu/h) -1 (108 :r 18) 

3107 

( 10603) 

- 5.13 "I (11157) 

Using ARI 320 

Capacity, W (Btu/h) 

Total Power, W 

(1 1157) 

EER, Btu/Wh I 4.81 I 4.81 

9 
5.2: Unit 2 - 3.52 kW (1 .O Ton) Nominal Cooling Capacity, Non-ducted Svstem 

Results for capacity, EER, and COP are reported below. Unit 2 was a console heat pump 

designed for wall mounting with no ductwork; therefore, air static pressure was 

maintained at zero for all tests to simulate free discharge to the indoor space. 

Cooling tests 

Table 5.3 summarizes the cooling test results for Unit 2. Under the ARI cooling 

conditions, air-side capacity and EER were 3085 W (10528 Btuh) and 14.18, 

respectively. For the IS0 13256- 1 cooling conditions, air-side capacity and EER were 

3051 W (10412 Btuh) and 13.63. 

Water flow was varied to determine the effects upon capacity and EER. Changes in 

water flow rate through the water coil produced a small effect upon the IS0 cooling test 

results. As water flow was varied by -20 % and +20 %, IS0 averaged capacity changed 

by -1.3 % and -0.3 %, respectively. EER changed by -2.8 % and +0.2 %. Unit 2 was 

designed for free air discharge to the conditioned space and, therefore, tests with varying 

external air static pressure were not performed. 

ARI capacity was 1.1 % higher than the IS0 uncorrected capacity. EER was 2.4 % 

higher than the IS0 uncorrected EER. These differences were due to the differences in 

test conditions (dry-bulb and dew-point temperatures). The pump power correction 

produced a small effect upon EER as it was less than 2.8 % of the total power for all 

tests. EER decreased with respect to the IS0 raw results by 1.6 %. 

10 
Table 5.3: ARI and IS0 cooling test results for Unit 2 

Cooling 

Using IS0 13256- 1 : 

Water Coil Pressure Drop 

LOW I Normal I High 

Uncorrected Capacity, W 

(Btfi) 

Uncorrected Total Power, W 

Uncorrected EER 

Water Flow, Us 

(gpm) 

(OF\ 

Water Coil Temp Change, "C 

3010 305 1 3043 

( 10272) (10412) ( 10382) 

769 752 739 

13.36 13.85 14.05 

0.136 0.170 0.204 

(2.15) (2.694) (3.23) 

6.67 5.33 4.44 

( 12.0) (9.6) (8.0) 

-Water Pressure Drop, Pa 1 14403 2 1774 30585 

(psid) (2.09) (3.16) (4.44) 

(cfm) (335) (332) (333) 

i 158 157 157 1 Air Flow, Us 

Air Coil Temp Change, "C 12.39 12.44 12.39 

(OF) (22.3) (22.4) (22.3) 

Air Static, Pa (in H20) 3.74 (0.015) 2.74 (0.01 1) 2.74 (0.01 1) 

IS0 Capacity Adiustment: 

IS0 Power Adjustment: 

For Fan Heat, W (Btuh) 0 0 0 

For Fan Power, W 0 0 0 

I For PumD Power. W I 7 I 12 I 21 

Corrected Capacity, w 

(Btuh) 

Corrected EER 

Using ARI 320 

Capacity, W (Btu/h) 

Total Power, W 

I EER I I 14.18 I 

3010 3051 3043 

( 10272) (10412) (10382) 

13.25 13.63 13.66 

3085 

(10528) 

742 

11 
Heating - tests 

Tables 5.4 summarizes the heating test results for Unit 2. Table 5.4 does not include tests 

at a low water flow rate. Two tests were performed at a lowered water flow rate, but they 

were excluded due to unacceptable variations (pulses) in water flow rate through the 

water coil. 

Under the ARI heating conditions and normal airflow (Table 5.4), air-side capacity and 

COP were 4668 W (15927 Btuh) and 4.94. For the IS0 13256-1 normal airflow heating 

conditions air-side capacity and COP were 4534 W (15469 Btuh) and 4.89. For the 

normal airflow tests, the change in pumping power from normal to high water flow rate 

produced a minimal effect upon capacity and COP. When water flow rate was increased 

by 16.9 %, capacity increased by 0.8 % and COP decreased by 1.6 %. For the high water 

flow rate case, the pump power correction was 3.5 % of the total power. ARI capacity 

was 1.2 % higher than the IS0 uncorrected capacity. COP was 2.6 % lower than the IS0 

uncorrected COP. These differences were due to the differences in test conditions (dry 

bulb and dew point) between the IS0 and ARI standards. The pump power correction 

produced a minimal effect upon COP as it was less than 2.8 % of the total power for all 

tests. 

In addition to the tests of Table 5.4, several tests were performed during the heating with 

varied water flow rate at a lowered airflow rate due to increased external static pressure. 

These low airflow tests were performed to determine whether consistent changes in 

capacity and COP were produced with changes in the water flow rate at the low and 

normal airflow rates. Under the ARI heating conditions and low airflow (Table 5.5), airside capacity and COP were 4269 W (14567 Btu/h) and 4.23. For the IS0 13256-1 

heating conditions and low airflow, air-side capacity and COP were 4210 W (14367 

Btuh) and 4.26. Lowering the water flow rate by 20.9 % had the effect of decreasing the 

capacity by 1.7 % and increasing the COP by 0.5%. Increasing the water flow rate by 

21.7 % increased the capacity by 1.2 % and decreased the COP by 0.2 %. The lower 

water flow rate decreased the pumping power correction by 47.1 % from 17 W to 9 W. 

The higher water flow rate increased the pumping power by 70.6 % from 17 W to 29 W. 

The highest water flow rate, the pumping power correction was 3.0 % of the total power 

requirement. 

12 
Table 5.4: ARI and IS0 normal airflow heating test results for Unit 2 

L - 

Using IS0 13256- 1 : 

Heating 

Air Temp Change, "C (OF) 

Air Static, Pa (in H20) 

I Water Coil Pressure Drop 

21.39 (38.5) 21.56 (38.8) 

1.5 (0.006) 1.5 (0.006) 

I Normal I High 

IS0 Power Adiustment: 

For Fan Power, W 

For Pump Power, W 

Corrected Capacity, W 

(Btuh) 

Corrected COP 

0 0 

21 32 

4534 457 1 

(15469) ( 15598) 

4.89 4.8 1 

Uncorrected Capacity, w 4534 I (Btuh) 1 (15469) 

Capacity, W (Btuh) 

Total Power, W 

457 1 

(1 5598) 

(15927) 

946 

I Uncorrected Total Power, W I 91 1 I 919 

Uncorrected COP 

Water Flow, LIS 0.198 

(3.135) 

Water Coil Temp Change, "C 4.28 (7.7) 

(OF) 

4.97 

0.23 1 

(3.666) 

3.72 (6.7) 

Water Pressure Drop, Pa 3 1523 I (mid) 

42 154 

(6.1 14) 

I Air Flow. Us (cfm) I 188.6 (400) I 188.9 (400) 

IS0 Capacity Adiustment: I For Fan Heat. W (Btuk) 0 0 

Using ARI 320 I 4668 I 

13 
Table 5.5: ARI and IS0 low airflow heating: test results for Unit 2 

Water Pressure Drop, Pa 

(psid) 

Air Flow, Us (cfm) 

Air Temp Change, "C (OF) 

Air Static, Pa (in HzO) 

Water Coil Pressure Drop 

LOW I Normal I High Heating 

18568 27676 39073 

(2.69) (4.0 1 ) (5.67) 

146 (310) 146 (310) 146 (310) 

24.56 (44.2) 25.06 (45.1) 25.28 (45.5) 

23.9 1 23.41 23.66 

(0.096) (0.094) (0.095) 

IS0 CaDacitv Adiustment: 

For Fan Heat, W (Btu/h) 0 0 0 

I For Fan Power. W lo lo Io I IS0 Power Adjustment: 

Corrected Capacity, W 4140 4210 4259 

Corrected COP 4.28 4.26 4.25 

Using; ARI 320 4269 

Capacity, W (Btuh) (14567) 

Total Power, W 1010 

COP 4.23 

(Btuh) (14128) (14367) (14534) 

I 

6: Summary 

The purpose of this experimental investigation was to examine differences in watersource heat pump performance ratings obtained from tests according to ARI Standard 320 

and IS0 Standard 13256- 1. This investigation also included tests at different volumetric 

flow rates of air and water to examine the effect of capacity and power corrections on the 

rating obtained by the IS0 test procedure. Two water-source heat pumps were tested 

according to both standards. 

Tables 6.1 summarizes results for capacity changes. IS0 cooling capacity for the ducted 

unit and non-ducted unit were 0.1 % higher and 1.1 % lower than the ARI capacity, 

14 
respectively. In the heating mode, the IS0 capacities were 4.8 % lower and 2.9 % lower 

than the ARI capacities. Variation of the external air static pressure had a greater effect 

than the variation of the water flow rate. The range of capacity change was from -3.6 % 

to 1.8 %. 

As shown by Table 6.2, the IS0 cooling EERs for the ducted unit and the non-ducted unit 

were 4.5 % higher and 3.9 % lower than the ARI EERs, respectively. The IS0 heating 

COPs for the first and second units were 6.2 % higher and 1.0 % lower than the ARI 

COPs, respectively. The range of IS0 EER and IS0 COP changes due to variation of the 

external air static pressure and water flow rate was from -2.8 % to 1.8 %. Similar 

differences between IS0 and ARI EERs and COPs were obtained by manufacturers of 

these two units. As shown in Appendix C, the differences between the IS0 and ARI 

EERs and COPs obtained by NIST were smaller than those obtained by the 

manufacturers with the exception of the heating COP for the non-ducted system. In this 

case, the manufacturer reported no difference between the two COPs while NIST 

measurements showed a 1.4 % lower IS0 COP than the ARI COP. 

The uncertainties for NIST results were calculated applying the uncertainty propagation 

law and considering the uncertainties of all involved temperature, pressure, and power 

measurements. For the 95 % confidence level, the maximum uncertainty for EER and 

COP was found to be 5.2 % and 5.9 %, respectively. Hence, the differences between the 

IS0 and ARI ratings are near or within the limits of uncertainty. 

Table 6.1: ARI 320 and IS0 13256-1 

Test 

Cooling Capacity % 

Ducted Non-duc ted 

IS0 I 0.1 I -1.1 

Cooling Capacity % 

Difference wrt IS0 .' 

IS0 Low 

Airflow 

IS0 High 

Airflow 

IS0 Low Water 

Flow 

IS0 High 

Water Flow 

-1.6 -1.4 

0.1 -0.3 I I I 

*Tests performed at a lower airflow across the in 

by the manufacturer 

:apacity comparison 

Heating Capacity % 

Difference wrt ARI 

Ducted 

-4.8 

Heating Capacity % 

Difference wrt IS0 

-1.6 NA NA 

1.8 NA NA 

-0.2 -1.7 NA 

1.3 1.2 0.8 

loor air coil than specified 

15 
Table 6.2: ARI 320 and IS0 13256-1 efficiency comparison 

Test 

IS0 

Cooling EER % Difference Heating COP % Difference 

wrt ARI wrt ARI 

Ducted Non-duc ted Ducted Non-ducted 

h.p. h.p. h.p. h.p. 

4.5 -3.9 6.2 0.7* I -1.0 

Cooling EER % Difference Heating COP % Difference 

wrt IS0 I wrt IS0 I 

-2.2 NA -2.4 NA NA 

-1.1 NA 1.8 NA NA 

-1.7 -2.8 0.4 0.5 NA 

0.4 

IS0 Low 

Airflow 

IS0 High 

Airflow 

IS0 Low Water 

Flow 

IS0 High 0.2 0.2 -0.2 -1.6 

*Tests performed at a lower airflow across the indoor air coil than specified 

by the manufacturer 

7: References 

ANSVASHRAE Standard 37-1 988. Methods of testing for rating unitary air 

conditioning and heat pump equipment. American Society of Heating, Refrigerating and 

Air-conditioning Engineers. 179 1 Tullie Circle NE, Atlanta, GA, USA. 

ANSVAMCA Standard 210 or ANSVASHRAE Standard 51-1985. Laboratory methods 

of testing fans for rating. American Society of Heating, Refrigerating and AirConditioning Engineers. 179 1 Tullie Circle NE, Atlanta, GA, USA. 

ARI Standard 320- 1998. Standard for water-source heat pumps. Air-conditioning and 

Refrigeration Institute. 430 1 North Fairfax Drive, Arlington, VA, USA. 

ASHRAE Standard 1 16- 1993. Method of testing for seasonal eficiency of unitary airconditioners and heat pumps. American Society of Heating, Refrigerating and AirConditioning Engineers. 179 1 Tullie Circle NE, Atlanta, GA, USA. 

ASHRAE Standard 90.1 - 1999. Energy Standard for Buildings Except Low-Rise 

Residential Buildings. American Society of Heating, Refrigerating and Air-conditioning 

Engineers. 1791 Tullie Circle NE, Atlanta, GA, USA. 

DOE-1999. U. S. Department of Energy rule making regarding Test Procedures and 

Efficiency Standards for Commercial Air Conditioners and Heat Pumps, Docket Number: 

EE-FW/TP-99-460, Comment 5. 

IS0 13256- 1-1998. Water-source heat pumps-Testing and rating for pe~ormance-Part I: 

Water-to-air and brine-to-air heat pumps. International Organization for Standardization. 

Case postale 56, CH- 12 1 1 Geneva 20, Switzerland. 

16 
Appendix A: Uncertainty Analysis 

A. 1 General Remarks 

The uncertainty analysis was performed to gain knowledge about the uncertainty of the 

measured and calculated data. This Appendix presents the major equations used for the 

uncertainty analysis. 

A.2 Theory 

The uncertainty of a quantity R calculated from n independent measurements xi is a 

function of the individual uncertainty of each measurement. 

When each measurement, xi, has a given uncertainty, dxi , the maximum uncertainty of R 

is given by: 

However, using the maximum error to judge the uncertainty of a calculated quantity is 

not common. Usually the standard deviation (root sum square) is regarded to be a much 

better approach to a quantity’s uncertainty. 

2 

+ [ $dx2I2 + [E dx, +. . . . .+[Ed&] 

The absolute error calculated with equation (A.3) is often converted to a relative error 

having the units of percent. 

E, e, =-loo 

R 

A.3 Temperature Measurements 

Most of the temperature measurements performed for these tests were determined by 

thermocouples. Their voltage signals were measured with the data acquisition system and 

then converted into a temperature. 

The equation used in the test rig’s control program to convert the voltage signals into 

temperatures was a sixth degree polynomial of the form: 

17 
(A3 

9 

5 

I?= f(V)=-(A+BV+CV2+DV3+E V4+F V5+GV6)+32 

where: 

79 - temperature (OF) 

V - measured voltage (pV) 

If one premises that the uncertainty of the equation itself can be neglected, only one 

derivation is needed to evaluate the uncertainty in the temperature measurements. 

e=z(B+2C V+30 V2 +4E V3 +5F V4 +6G V') dv 5 

According to the manufacturer of the datalogger voltmeter, the 95 % uncertainty of the 

voltage measurement (VM) was: EvM = dV(VM) = k 0.007 % of reading + 5 pV. 

The measurement of a temperature (I9 ) actually is the measurement of the difference to a 

reference temperature. The data acquisition system provided a temperature compensation 

to 0 "C (32 OF) with a given uncertainty of: ETC = dTC = k 0.2236 "C = k 0.4025 OF. 

Rewriting equation A.3 for the measurement of the absolute temperature gives: 

2 

ET = ./( $ dVM) + (dTC)2 

In addition to the common thermocouple measurements, the dew-point temperature in the 

air duct was measured to evaluate the humidity ratio of the moist air in the duct. 

The manufacturer of the dew-point hygrometer specified the 95 % uncertainty in this 

measurement to be: E, = dT,,, = k 0.05 % of reading. 

A. 4 Temperature Difference Measurements 

The evaluation of the uncertainty of a temperature difference (A79) measurement using a 

thermopile is slightly more complicated than that for a normal temperature measurement. 

The uncertainty evaluation is presented using the air duct temperature difference as an 

example, because this shows the most complicated case. 

18 
Again there are two independent uncertainties being part of the measurement uncertainty. 

The first is the uncertainty caused by the voltage signal measurement, discussed in 

section A.3. The cause for the second uncertainty influencing the measurement of a 

temperature difference is the nonlinear character of the temperature/voltage function (see 

equation AS). The nonlinearity requires temperature at one end of the thermopile used 

for the temperature difference measurement to be known. 

The temperature difference across the indoor coil was calculated using both the voltage 

signals of the temperature difference measurement ( AV ) and the average voltage signal 

(Vav.) of the entering temperature measurement of the air duct. The equation used to do so 

was: 

The entering temperature was measured using 15 thermocouples equally distributed over 

the air duct's cross section. The average of the 15 temperature signals was considered to 

be the entering temperature. For the uncertainty in this average entering temperature the 

average voltage measurement uncertainty of the 1 5 measurements was calculated. 

(A. 10) 

x=l 1J 

All 15 thermocouples were connected to the same temperature compensation. This means 

the overall uncertainty of the air's average entering temperature voltage signal Vav. was: 

(A. 1 1) 

To evaluate equation A. 1 1 the uncertainty in the temperature compensation must be 

rewritten to have the unit of pV. Using equation AS one finds that an uncertainty of 

ETc = dTC = M.2236" C = k 0.4025 "F in the temperature compensation to 0 "C (32 OF) 

is equivalent to a voltage signal uncertainty of dVav.(TC) = k 8.6264 pV. As already 

mentioned, the uncertainty of the voltage signal measurement was given from 

manufacturer data. 

The nonlinearity of the voltage/temperature function (AS) causes an uncertainty, dsZope, 

in the temperature difference that depends on the uncertainty in the entering temperature 

voltage signal Vav.. 

(A. 12) 

19 
where: 

Vav. 

dV.,. 

AV 

= entering temperature voltage signal (pV) 

= uncertainty of the entering temperature voltage signal (pV) 

= temperature difference voltage signal ( pV) 

Remembering that an additional uncertainty in the temperature difference is caused by 

the voltage measurement of the temperature difference voltage signal (AV), the 

uncertainty of the air duct temperature difference is given to be: 

112 

EA* = dA6 = [ [ $ dN)2 + dslope2 1 

A. 4 Uncertainty of the Air Side Capacity 

The air side capacity of the heat pump was evaluated using the equation: 

Qc = Qs +QL 

(A.13) 

(A. 14) 

where: 

Qs 

QL 

= sensible capacity, kW (Btu/h) 

= latent capacity, kW (Btu/h) 

The sensible capacity is the heat needed to cool or heat the moist air passing the heat 

pump’s indoor coil. The latent capacity is the heat rejected by water vapor condensing on 

the air coil. Condensation does not occur in the heating mode. 

The two different capacities were calculated separately and then added (A. 14). Therefore 

the uncertainty of the air-side capacity can be written as: 

I /2 

EQc -[(~dQs~+[%dQL~] - JQL =(d@ +d$2)1’2 

The equations for both the sensible and latent capacities and their uncertainties are 

presented on the following pages. 

A. 4.1 Uncertainty of the Sensible Capacity 

(A. 15) 

According to ASHRAE Standard 1 16- 1993 the sensible capacity Qs is given by: 

20 
[ 2 gc APn Pnact ] (A.16) Q, = 3600 CD A, (0.24 + 0.444 Wav,)(Sl - 8) e 144(1-p2) 

where: 

nozzle discharge coefficient (0.986) 

nozzle throat area, m2 (ft') 

(We + w) / 2 average humidity ratio, kg H20/ kg dry air 

(lb H2 OAb dry air) 

indoor coil air temperature rise, "C (OF) 

gravity constant (32.174 ft - Zb, / Zb, s') 

static pressure drop across nozzle, kPa (psia) 

density of the moist air, kg/m3 (Zb / ft3) 

unit conversion factor from in2 toft2 

area relation factor (0 for nozzle chamber) 

The partial derivatives required for the uncertainty analysis of Qs are: 

-- 2 gc APn Pnact 

'An 144(1- p') 'Qs - 3600 CD (0.24 + 0.444 WaV,)(6l - 6,) 

r 1112 

= 1800 CD A, 0.444 (61 -fie)[ 2 gc APn Pnact J 

'We 144(1- p') 

112 '" = 1800 CD A, 0.444(IY, -fie)[ 2 gc APn Pnact ] 'w, 144(1- p') 

112 

'Qs 

'('1 - 'e) 

= 3600 C, A, (0.24 + 0.444 KV,) 2 gc APn Pnact 

(A.17) 

(A. 1 8) 

(A. 19) 

(A.20) 

112 

'Qs 1800 CD A, (0.24 + 0.444 Wav.)(61 - fie) (A.21) 

'APn 

-- 'QS 2gc APn 

'Pnact '~(1- P2)Pnact 

- 1800 CD A, (0.24 + 0.444 W,,.)(I~, - fie) 

112 

(A.22) 

21 
r 7 112 

-- 'QS - 3600 CD A,(0.24 + 0.444 wv.)(6, - 6, )p 2 gc bn ~nact 

JP (A.23) 

Using the above partial derivatives for rewriting equation A.3 gives: 

112 +[ 'QS d(6, - 6,)]* + [ * dpnaCtl2 + [ $ dp)] (A.24) 

w, - 6,) 'P nact 

Equation A.24 can be evaluated to give the uncertainty of QS if each of the individual 

uncertainties is known. However, A, p , We , Wl and pnact are calculated quantities, so 

their uncertainties were not known, but had to be calculated using equation A.3. 

The flow in the air duct was measured using an ASME nozzle. The nozzle throat area 4, 

which is part of equation A.16, was calculated from the throat diameter. Thus its 

uncertainty can be evaluated very easily. 

n: dn2 

An =4 (A.25) 

(A.26) 

The uncertainty of the throat diameter was given to be: Edn = dd, = k0.254 mm = k- 0.01 

in. 

The required uncertainty in the inlet diameter was also 

Edm = dd,, = kO.254 mm = k 0.01 in. 

The humidity ratios We and Wl are a function of the water vapor pressure pw and the 

atmospheric pressure p. 

Pw W= 0.62 198 * - 

P- Pw 

(A.27) 

The factor 0.62198 comes from the ratio of the mole weights of the two components, 

water and air. 

22 
The required partial derivatives of equation A.27 are: 

= 0.62 I98 Pw 

dp (P- Pw)2 

dW 

dW P 

dpW (P- PW)’ 

- = 0.62 198 

They lead to the uncertainty in W 

The water saturation 

had to be calculated. 

112 

E, =dW=[[$dp]’ +($dpwj2] 

(A.28) 

(A.29) 

(A.30) 

pressure is a calculated quantity itself, which means its uncertainty 

The equation that was used to calculate the saturation pressure from the dew-point 

temperature, Gew, (OR), is given below. The equation was assumed to cause no additional 

uncertainties. 

The partial derivative of equation A.31 with respect to Tdew is: 

2 + c10 + 2cl, Tdew -k 3cl, Tdew 

The uncertainty in pw is now given by: 

dTdew 

- dpW 

adew 

E =dpw - PW 

(A.32) 

(A.33) 

As already mentioned in section A.3, the uncertainty of the dew-point temperature 

measurement was given to be: E, = dTdew = k 0.05 % of reading . 

Finally, the uncertainty in the moist air’s density pnaCt had to be evaluated. The density 

was calculated using the ideal gas equation and the humidity ratio. 

(A.34) 

23 
The factor 1.6078 is the ratio of the molar weights of air and water. 

The partial derivatives of equation A.34 are: 

144 (1+W) 

R Tn (1 + 1.6078 W) -- - 'P nact 

dp, 

'Pnact - -p, 144 (1+ W) - 

an R Tn2 (1 + 1.6078 W) 

'Pnact - -0.6078 pn 144 - dw R Tn (1+1.6078 W)2 

Rewriting equation A.3 with the above partial derivatives gives: 

(A.35) 

(A.36) 

(A.37) 

(A.38) 

The pressure p, in the nozzle throat was calculated as the difference of atmospheric 

pressure and nozzle pressure drop. The uncertainty of the nozzle pressure can be derived 

as follows: 

The uncertainties of the pressure measurements were given from manufacturer data: 

E 

EDpn = dDp, = f2.489 mmH,O = 

= dp,, = M.3429 mmHg = k 0.0135 in Hg and PaUn 

0.098 in H20. 

A. 4.2 Uncertainty of the Latent Capacity 

The latent cooling capacity (ASHRAE Standard 116-1983) is given by: 

r 11/2 

(A.4 1) 

where: 

CD = nozzle discharge coefficient (0.986) 

24 
nozzle throat area (ft ) 

entering humidity ratio (lb H,O/lb dry air) 

leaving humidity ratio (lb H20/lb dry air) 

gravity constant (32.174 ft - lb, / lb, - s2 ) 

static pressure drop across nozzle (psia) 

density of the moist air ( lb / ft3 ) 

unit conversion factor from in2 to ft2 

area relation factor (0 for a nozzle chamber) 

The partial derivatives of this equation are: 

L 'Q = 63600 60 CD (We - W), 

'An 

r 

1112 

J 2 gc APn Pnact 

144 (1 - p2) 

112 

- 

'QL 2 gc APn Pnact = 63600 60 CD An 

'We 

112 

- 

'QL 2 gc 4Jn Pnact = -63600 60 C, An 

Jwl 

r 11/2 1 - 

'QL 2 gc Pnact = 31800 60 C, An (We - y)[ JMn 144(1-P2)4Pn 

I- 1112 

r 7112 

(A.42) 

(A.43) 

(A.44) 

(A.45) 

(A.46) 

(A.47) 

If the above derivatives are used to rewrite equation A.3, one obtains the uncertainty of 

the latent capacity: 

25 
(A.48) 

In this equation, all the needed uncertainties are known. Either because the quantities are 

directly measured or their uncertainties have already been calculated in Appendix A.4.1. 

The final step was calculating the uncertainty of the air-side capacity by using the now 

known uncertainties of sensible and latent capacity in equation A. 15. 

A. 5 Uncertainty of the COP 

To calculate the COP’S uncertainty it is necessary to know the uncertainties of the airside capacity, & and the mechanical power, P. 

(A.49) e COP = - 

P 

The uncertainty of the COP is determined by: 

All of these components are directly measured or know from the above calculations. 

26 
A. 6 Uncertainty Analysis Results for Selected Tests 

Table A.l gives an example of the error associated with COP and air-side capacity for 

several tests. 

Standard 

Heating 

Table A. 1 : Measurement uncertainty for typical tests 

3.23 3278 2 122 W 

(1 1 184 2 417 Btuh) Capacity 

Filename 

Standard 

Cooling 

IS0 

F010411B 

3.92 

EER 13.13 fi 0.51 5.21 

2338 2 105 W 

(7977 fi 360 Btuh) Capacity 

F0104 12A 

Standard 

Cooling 

F010412B 

~~ 

5.17 2920fi 111 W 

(9964 2 379 Btuh) Capacity 

F010413A 

Standard 

Heating 

WO 10607A 

5.84 4139 f 178 W 

(14121 f 607 Btuh) Capacity 

W010611A 

WO 106 12A 

WO 10620A 

Value 

Percent 

Uncertainty at a 

95 % Confidence 

Limit on the Mean 

ARI i EER I 13.29 2 0.58 I 3.91 

Standard 

Cooling: I 2364 f 52 W 

(8068 2 178 Btuh) Capacity I 3.83 

ARI 1 COP I 4.97 fi 0.19 I 3.29 

I Standard 3317 fi 122 W 

Heating (1 1317 f 418 Btu/h) I capacity I 3.20 

IS0 I COP I 5.02 f 0.19 I 3.32 

IS0 I EER I 13.01 fi 0.60 I 4.00 

ARI I COP I 4.17 f 0.18 I 5.82 

I Standard 4208 fi 18OW 

Heating I Capacity 1 (14357 2 613 BtuW 5.80 

IS0 I COP I 4.26 0.18 I 5.86 

ARI I EER I 14.18 2 0.47 I 4.44 

I Standard 3085 2 100 W 

Cooling (10528 -C 340 Btuh) I Capacity 1 4.39 

27 
Appendix B: Heat Pump Test Data 

Filename 

FO10502A 

FO10425A 

This appendix provides detailed tests data for tests performed at NIST. The designation 

of the heat pumps tested (Unit 1 and Unit 2) is consistent with that used in Section 5. 

In-H20 Pa Psid Pa cfm LIS 

0.32 79.7 1.924 1 3265.5 299.30 141.25 

0.32 79.7 1.925 13272.4 298.79 141.01 

Table B.1: Unit 1, data #I 

F010426A 

FO10502A 

F010502B 

0.329 81.9 1.601 1 1038.5 299.33 141.26 

0.32 79.7 1.924 13265.5 299.30 141.25 

0.267 66.5 1.956 1 3486.1 328.00 154.79 

FO10426C 

F010501A 

F010509A 

F010427A 

0.402 100.1 2.053 141 54.9 269.47 127.17 

0.312 77.7 1.897 13079.3 297.55 140.42 

0.401 99.8 1.933 13327.5 306.67 144.73 

0.362 90.1 2.355 1 6237.1 31 4.60 148.47 

F0104276 

F010509A 

FO10427C 

F010430A 

F010507A 

0.366 91.2 1.449 9990.5 31 4.77 148.55 

0.401 99.9 1.933 13327.5 306.67 144.73 

0.329 82.0 2.046 141 06.6 331.24 156.32 

0.427 106.4 2.028 13982.5 287.1 9 135.53 

0.402 100.1 1.929 13300.0 308.63 145.65 

28 
Water Water Sensible Latent 

Mass Flow Flow Capacity Capacity 

lb/h kg/h G PM Us Btdh W Btdh W 

F010502A 1003.1 455.0 2.00 0.126 6383 1871 1677 492 

F010425A 1004.1 455.4 2.01 0.127 6292 1844 1648 483 

F010426A 1071.5 486.0 2.14 0.135 6458 1893 1528 448 

F010502A 1003.1 455.0 2.00 0.126 6383 1871 1677 492 

F010502B 1001.6 454.3 2.00 '0.126 6633 1944. 1389 407 

F010426C 1026.0 465.4 2.05 0.129 5940 1741 1539 451 

F010501A 1001.7 454.4 2.00 0.126 5898 1729 2082 610 

F010509A 979.8 444.4 1.96 0.123 10884 3190 0 0 

F010427A 1075.6 487.9 2.15 0.136 11149 3267 0 0 

F010427B 843.1 382.4 1.68 0.106 11008 3226 0 0 

F010509A 979.8 444.4 1.96 10.123 10884 3190 0 0 

-------- 

SHR Total Wate -side 

Capacity Cap 

Btdh W Btdh 

0.792 8060 2362, 7794 

0.792 7940 2327 7776 

0.809 7986 2340 7831 

0.792 8060 2362 7794 

0.827 8022 2351 7827 

0.794 7480 2192 7758 

0.739 7981 2339 7885 

1 10884 3190 10620 

1 11149 3267 10679 

1 11008 3226 10506 

1 10884 3190 10620 

F010427C 

F010430A 

F010507A 

992.1 450.0 1.98 3.125 11266 3302 0 0 1 11266 3302 10662 

994.7 451.2 1.99 0.125 10640 3118 0 0 1 10640 3118 10596 

980.5 444.7 1.96 0.124 10997 3223 0 0 1 10997 3223 10728 

F010502B 

F010426C 

F010501 A 

F010509A 

F010427A 

F01 O427B 

F010509A 

FOlO427C 

F01043OA 

F010507A 

7924.61 2322 ' 620.2 

761 8.85 2233 608.9 

7932.74 2325 608.2 

10751.75 3151 650.8 

IO91 3.67 3198 653.7 

10757.15 3153 647.9 

10751.75 3151 650.8 

10964.14 3213 646.1 

1061 7.73 3112 656.2 

10862.53 3183 667.2 

El 

2294 

3144 I 

Table B.4: Unit 1. data #4 

Average Capacity Total 

Filename 

Uncorrected Uncorrected Fan Power and Heat 

EER1 COP Adj us trnen t 

BtuMlh WNV W I Btu/h 

Fan Heat 

F010502AI 7926.99 I 2323 I 613 12.931 I 3.790 I 37.529 1128.064 

F010425AI 7857.95 1 2303 I 614.4 12.790 I 3.748 1 37.465 1127.846 1.627 I 

F010426AI 7766.17 I 2318 I 616.8 12.591 I 3.690 I 38.588 1131.679 1.696 I 

F010502AI 7926.99 I 2323 I 613 12.931 I 3.790 I 37.529 1128.064 1.616 I 

12.778 3.745 34.31 6 1 17.1 00 

12.51 2 3.667 42.447 144.846 

13.043 3.823 36.377 124.1 32 

16.521 4.842 48.1 87 164.432 

1.478 

1.565 

1.529 1 

16.695 4.893 1.395 I 

4.042 

1.432 I 

1.529 I 

1.329 I 

16.181 I 4.742 I 48.052 1163.971 1.544 I 

16.281 I 4.771 I 48.615 1165.896 1.527 I 

29 
Filename 

FO10502A 

FO10425A 

Fan Only Fan Pump Pump&Fan WNV BtuNVh 

Corrected Corrected Capacity Power (W) Corrected Corrected Corrected 

Tot Power (W: (Btu/h) W Adjustment Tot Power (W) COP EER4 

575.5 8055 2361 5.590 581.061 4.062 13.863 

576.9 7986 2340 5.599 582.534 4.01 7 13.709 

FO10426A 572.5 

FO10502A 575.5 

8036 2355 4.371 582.583 3.973 13.557 

8055 2361 5.590 581.061 4.062 13.863 

F010502B I 585.9 I 8042 I 2357 I 5.675 1 591 559 

F010507A I 618.6 I 10697 

3.984 I 13.594 

FO10426C 

F010501 A 

f010509A 

FO10427A 

FO10427B 

f010509A 

3107 I 3.538 I 606.296 I 5.125 I 17.488 

566.5 7764 

571.8 8057 

602.6 10587 

609.1 10761 

602.8 10603 

602.6 10587 

2275 

2361 

3103 

3154 

Table B.6: Unit 2. data #1 

6.102 572.555 3.974 13.560 

5.504 577.327 4.090 13.955 

5.485 608.098 5.1 02 17.41 1 

7.338 61 6.41 3 5.1 16 17.458 

I Description 1 Filename 

3103 

31 71 

3064 

3135 

I Coolina Tests I 

5.485 608.098 5.1 02 f 7.41 1 

5.880 609.278 5.203 17.756 

5.843 61 3.991 4.989 17.026 

5.479 624.064 5.023 17.140 

I IS0 Standard ReDeat bV010614A 

I 

F010427C 603.4 

FO10430A 608.1 

I IS0 +20% GPM tVr/lO614B 

10818 

10454 

IS0 -20% GPM 

ARI Standard 350scfml ODT 

Heating Tests 

IS0 Standard 300cfm 

IS0 300cfm +20% GPM 

IS0 300cfm -20% GPM 

ARI Standard 300cfm 

84.9 I 29.4 I 80.4 I 26.9 I 60.3 115.7 

hOl0614C 

W010620A 

W 01 061 2A 

W010612B 

W010612C 

W 010611A 

Air-DT 

FI C 

Filename 

W010614A 

W010614B 

W010614C 

W010620A 

W010612A 

W010612B 

W010612C 

W010611A 

20.94 11 1.63 

in H20 Pa Psid Pa 

Air-DP Air-DP Water-DP Water-DP Air-cfm Air-Us 

0.01 1 2.740 3.1 58 21 773.6 331.81 156.59 

0.01 1 2.740 4.436 30585.1 333.21 157.25 

0.01 5 3.736 2.089 14403.1 335.41 158.29 

0.01 2.491 2.845 1 961 5.5 345.14 162.88 

0.094 23.41 4 4.01 4 27675.5 309.74 146.1 8 

0.095 23.663 5.667 39072.5 309.95 146.27 

0.096 23.91 3 2.693 18567.5 309.74 146.1 8 

0.093 23.165 3.597 24800.4 31 1.54 147.02 

Table B.7: Unit 2, data #2 

I I 

' Water-DT 

C 

10.45 I 5.81 

30 
Latent Capacity SHR Total Capacity 

W010614A 1348.7 611.7 2.69 0.170 8275 2425 2191 642 0.791 10466 3067 

W010614B 1618.1 734.0 3.23 0.204 8280 2427 2093 613 0.798 10373 3040 

W010614C 1076.2 488.1 2.15 0.136 8345 2446 1922 563 0.813, 10266 3009 

W010620A 1267.0 574.7 2.53 0.160 8046 2358 2481 727 0.764 ~10528 3085 ' 

W010612A 1449.1 657.3 2.90 0.183 14121 4139 0 0 1 14121 4139 

W010612B 1764.4 800.3 3.52 0.222.14272 4183 0 0 1 14272 4183 

W010612C 1145.7 519.7 2.29 0.144 13883 4069 0 0 1 13883 4069 

W010611A 1380.5 626.2 2.76 0.174 14357 4208 0 0 1 14357 4208 

Water Mass Water Volume Sensible 

Filename Flow Flow Capacity 

lb/h kgh GPM LIS Btuh W Btuh W Btu/h W 

Table B.9: Unit 2, data #4 

Water-Side 

Btdh W 

10357 3035 

10391 3045 

10277 3012 

10686 3132 

14612 4282 

14796 4336 

14373 4212 

14777 4331 

Ca 

Pump 

Power 

Adjustment 

Averaged Total Uncorrected Uncorrected Corrected Corrected Corrected 

Capacity Total Power EER2 COP 

Btdh W W Btu/Wh WnnJ W W Btu/Wh WIW 

W010614A 10412 3051 752 13.85 4.06 12.3 764 13.63 3.99 

W010614B 10382 3043 739 14.05 4.1 2 20.8 760 13.66 4.00 

W010614C 10272 3010 769 13.36 3.92 6.5 775 13.25 3.88 

W010620A 10607 3109 742 14.18 4.1 6 10.4 753 14.09 4.13 

W010612A 14367 4210 972 14.78 4.33 16.8 989 14.53 4.26 

W010612B 14534 4259 973 14.94 4.38 29.0 1002 14.51 4.25 

W010612C 14128 4140 960 14.72 4.32 8.9 968 14.59 4.28 

W010611A 14567 4269 1010 14.22 4.1 7 14.4 1024 14.22 4.17 

Power EERl Filename 

31 
Appendix C: Summary of Manufacturer and NIST Test Data 

Cooling Values 

The two units tested at NIST were selected for this study from the pool of fifteen watersource heat pumps tested by their respective manufactures according to the ARI and IS0 

test procedures. Test results obtained by these manufacturers were submitted to DOE by 

ARI in support of ARI’s comments on the DOE’S proposed rule making regarding test 

procedures and efficiency standards for commercial air conditioners and heat pumps 

(DOE- 1999). The tables in this appendix present manufacturers’ test results and 

comparison of manufacturers’ and NIST relative ratings obtained by the two test 

methods. On average, the disparity between the ARI and IS0 ratings obtained by NIST 

is smaller than that obtained by the two manufacturers. The designation of the heat 

pumps tested (Unit 1 and Unit 2) is consistent with that used in the main body of this 

report. 

Using IS0 13256- 1 : 

Uncorrected Capacity, W (Btuh) 

Uncorrected Total Power, W 

Uncorrected EER 

~~ ~ ~ 

2149 (7333) 

NA 

11.75 

32 
Manufacturer 

Capacity Capacity EER EER 

% % 

Difference Difference 

320 320 

ARI 320 2181 NA 12.0 NA 

W wrt ARI wrt ARI 

(7443) 4 

IS0 Raw 2149 -1.5 11.7 -2.4 

(7333) 5 

IS0 2195 0.6 12.8 6.6 

Corrected (7489) 4 

NIST Capacity 

% Difference wrt Manufacturer 

NIST 

Capacity Capacity EER EER 

% % 

Difference Difference 

W from ARI wrt ARI 

(BtA) 320 320 

2352 13.21 NA 

(8024) 

2316 -1.5 12.89 -1.5 

(7902) 

2353 0.04 13.79 5.3 

(8028) 

NIST EER 

% Difference wrt Manufacturer 

Table C.3: Manufacturer heating; test results for Unit I 

IS0 Raw 

IS0 

Corrected 

I Heating I Values I 

7.8 9.8 

7.2 7.5 

Using IS0 13256-1 : 

Uncorrected Capacity, W (Btu/h) 

Uncorrected Total Power, W 

Uncorrected COP 

Water Flow, Us (gpm) 

Water Coil Temp Change, "C (OF) 

Water Pressure Drop, Pa (psid) 

Air Flow, Us (cfm) 

Air Static. Pa (in H70) 

I I IS0 Capacitv Adjustment: 

For Fan Heat. W (Btuk) I 45 (153) 

2890 (9860) 

NA 

4.6 

0.119 (1.89) 

5.56 (10.0) 

1 1376 (1.65) 

139 (294) 

97 (0.39) 

I IS0 Power Adjustment: I For Fan Power. W I 45 

I For PumD Power. W I 5 I 

2845 (9706) 

Corrected COP 

Using ARI 320 

Total Power, W 

2942 (10037) 

COP 4.52 

33 
Table C.4: Manufacturer and NIST heating test results for Unit 1 

Using IS0 13256- 1 : 

Uncorrected Capacity, W (Btu/h) 

Uncorrected Total Power. W 

Manufacturer 

Difference Difference 

from ARI from ARI 

3177 (10839) 

NA 

ARI320 2942 NA 4.52 NA 

IS0 Raw 2890 -1.8 4.6 1.8 

IS0 2845 -3.3 4.84 7.1 

(1 0037) 

(9860) 

Corrected (9706) 

NIST Capacity 

% Difference wrt Manufacturer 

ARI 320 10.04 

IS0 Raw 10.72 

10.86 IS0 

Corrected 

Uncorrected EER 

Water Flow, L/s (gpm) 

Water Coil Temp Change, "C (OF) 

Water Pressure Drop, Pa (psid) 

Difference Difference 

from ARI from ARI 

12.8 1 

0.196 (3.1) 

4.99 (8.99) 

22717 (3.29) 

(BtW 320 320 

3237 NA 4.85 NA 

(1 1045) 

3200 -1.15 4.90 1.01 

(109 17) 

3153 - 1 -44 5.14 6.05 

Air Flow, Us (cfm) 

Air Static. Pa (in H30) 

(10760) I I I 

1 60 (340) 

0 

NIST COP 

% Difference wrt Manufacturer 

IS0 CaDacity Adiustment: 

For Fan Heat, W (Btuh) 

IS0 Power Adiustment: 

0 

For Fan Power, W 0 

For Pump Power, W 15 3 

Corrected Capacity, W (Btu/h) 

Using ARI 320 

Total Power, W NA 

3177 (10839) 

r Corrected EER 12.58 

Capacity, W (Btu/h) 3341 (11399) 

EER 13 -67 

7.3 1 ~~ 

6.52 

6.28 

Table C.5: Manufacturer cooling: test results for Unit 2 

Cooling 1 Values I I 

34 
ARI 320 

IS0 Raw 

IS0 

Corrected 

ARI 320 

IS0 Raw 

-4.0 

Manufacturer 

% % 

Difference Difference 

W from ARI from ARI 

320 320 

3341 NA 13.67 NA 

Capacity Capacity EER EER 

(11399) 

( 10839) 

(10839) 

3177 -4.9 12.8 1 -6.3 

3177 -4.9 12.58 -8.0 

NIST Capacity 

% Difference wrt Manufacturer 

-7.7 

I -4.0 

oling test results for Unit 2 

For Pump Power, W 

Corrected Capacity, W (Btuh) 

Difference Difference 

W from ARI from ARI 

f 

18 

4572 (15599) 

(BtW 320 320 

3085 NA 14.18 NA 

(10528) 

305 1 -1.1 13.85 -2.3 

Using ARI 320 

Capacity, W (Btuh) 

Total Power. W 

(10412) 

(10412) 

305 1 -1.1 13.63 -3.9 

4641 (15837) 

NA 

NIST EER 

% Difference wrt Manufacturer 

3.7 

8.3 

Table C.7: Manufacturer heating: test results for Unit 2 

I Heating 1 Values I 

I Using IS0 13256- 1 : I Uncorrected Caoacitv. W (Btu/h) I 4572 (15599) 

I Uncorrected Total Power. W I NA I 

Uncorrected COP 

I Air Static. Pa (in H70) I 0 I 

I I IS0 Capacity Adjustment: 

For Fan Heat. W (Btu/h) lo 

I I IS0 Power Adiustment: 

For Fan Power. W Io 

I Corrected COP I 4.59 I 

I COP I 4.59 I 

35 
Table C.8: Manufacturer and NIST heating test results for Unit 2 

Capacity 

~ 

w 

Capacity 

% 

Difference 

from ARI 

Manufacturer 

Difference 

from ARI 

COP COP 

% 

Difference 

from ARI 

~ ~ 

COP 

% 

Difference 

from ARI 

ARI320 

Capacity 

(Btum 320 320 

IT 

(Btfi) 

4641 NA 4.59 NA 4668 

320 

NA 

320 

4.94 NA 

IS0 Raw 

I Corrected I (15599) I I I I (15469) 

(15837) ( 15927) 

4572 -1.5 4.67 I .7 4534 

NIST 

I (15599) 

IS0 I 4572 

( 15469) 

-1.5 4.59 0.0 4534 

ARI 320 

IS0 Raw 

IS0 

-2.9 1 4.87 1 -1.4 

0.6 7.6 

-0.8 6.6 

NIST Capacity NIST COP 

% Difference wrt Manufacturer I 96 Difference wrt Manufacturer 

-0.8 Corrected I 6.1 

36