From Commercial Ground-Source Heat Pump Systems


The project began with modifications to an existing 3-ton (10.6 kW) variable-speed air-to-air heat pump. The machine has an ARI 210/240 rating of SEER=15.2 (COP=4.5) and an HSPF=8.75 (COP=2.6) (ARI 1992). Table 1 lists the performance data at various conditions.

Table 1: Performance Data of Variable-Speed Air Heat Pump Before Modification to Ground-Source (TC 1990)

COOLING @ 80 /67 F (27 /19 C) EAT

Low Speed

High Speed

Capacity @ 95 F


12.6 MBtuh

37.5 MBtuh



3.70 kW

11.0 kW

EER @ 95 F OAT



COP @ 35 F OAT



[*] Capacities and COPs do not include defrost penalty.

HEATING @ 70 F (21 C) [*]

Low Speed

High Speed

Capacity @ 47 F


11.8 MBtuh

34.6 MBtuh

8 C


3.46 kW

10.1 kW

@ 17 F


6.5 MBtuh

19.3 MBtuh

1.9 kW

5.7 kW

COP @ 47 F

(8 C)



@ 17 F

(-8 C)



[*] Capacities and COPs do not include defrost penalty.

The heat pump was installed as recommended by the manufacturer and tested at a variety of indoor and outdoor air conditions. The unit operated between 3% and 7% below published performance.

The compressor and power electronics were removed from the outdoor coil and installed in a cabinet indoors. A nominal 48 MBtuh (14.1 kW) coaxial water-to-refrigerant coil replaced the outdoor coil, and a vented 24 MBtuh (7.0 kW) water-to-refrigerant coil was placed at the compressor discharge. These coils, the heating mode thermostatic expansion valve (TEV), and the reversing valve are also...

Copyright American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 1995 under license agreement with Books24x7

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TEST RESULTS FIRST STAGE Testing was performed in a psychrometric room. All temperatures were measured with 1000 ohm platinum RTDs. Airflow was measured with a 12-by 8-in. (30 by 20 cm) venturi.

At the time this article was written, Stephen P. Kavanaugh and Joey K. Parker were associate professors in the mechanical engineering department at the University of Alabama, Tuscaloosa. Robert S.

At the time this article was written, Bernard E. Woller was director of facilities and special projects at Buckeye Power, Inc., Columbus, OH. Reprinted from ASHRAE Transactions 1994, Vol. 100, Part 1.

These conversions are for those units most commonly encountered in cold-air distribution design. Additional information and conversions for other units are given in the ASHRAE publication, SI for...

List of Symbols and Units [1] A Heat transfer area (m 2) C P Specific heat capacity (kJ/kgK) COP p Coefficient of performance for a heat pump (-) COP r Coefficient of performance for a...

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