Fault Detection and Diagnostics of a Residential Split-System Heat Pump

An increasing emphasis on energy conservation and the environment requires that air conditioners and heat pumps should be of high efficiency and operate refrigerant leak-free. To this end, a few government initiatives have already been undertaken. For example, the ENERGY STAR initiative, a program formulated by the EPA and DOE promotes products that offer energy efficiency gains and pollution reduction. Directly affecting residential equipment, a DOE regulation imposed a 30 % increase in the minimum seasonal energy efficiency ratio (SEER) of central air conditioners from 10.0 to 13.0 beginning January 23, 2006. In response, manufacturers have undertaken significant design, optimization, and laboratory efforts to improve the SEER of their products.

To assure that HVAC equipment operates in the field at its design efficiency, good equipment installation practices and performance monitoring must parallel the efforts exerted by equipment manufacturers to improve their equipment efficiency. To this end, the HVAC&R Equipment Performance Group carries out a research project to develop fault detection and diagnostic (FDD) methods for a residential heat pump. The six common faults studied are: improper refrigerant charge, improper indoor airflow, improper outdoor airflow, flow restriction in the refrigerant liquid line, non-condensable gases in the refrigerant, and reversing valve or compressor valve refrigerant leakage/bypassing.

The experimental phase of the project investigating fault-free and faulty performance characteristics in the cooling and heating modes has been completed. The current effort is focused on the development the FDD methodologies applicable to the heating and cooling modes. The issues of future interest include FDD-assisted system commissioning, detection of sensor failure, and accounting for performance degradation due to system aging.

Recent Project Results:

Kim, M., Payne, W.V., Domanski, P.A., Hermes, C.J.L., 2006. ”Performance of a Residential Heat Pump Operating in the Cooling Mode With Single Faults Imposed”, NISTIR 7350, National Institute of Standards and Technology, Gaithersburg, MD.

Minsung Kim, Seok Ho Yoon, W. Vance Payne, and Piotr A. Domanski, 2007. “Design of a Steady-State Detector for Fault Detection and Diagnosis of a Residential Air Conditioner”, accepted for publication by Inter. J. Refrig.

Contact:
Vance Payne
HVAC&R Equipment Performance Group
(301) 975-6663
vance.payne@nist.gov