DOE Appliance Program

Refrigerator Instrumented for Testing

Linear fit rating procedure

Water-cooled condensing unit. Finned Tube Heat Exchanger Heat Exchanger Test Rig

NIST has been involved with the U.S. Department of Energy appliance rating program since the 1970’s. Over the years, the Group has developed various rating procedures for residential air conditioners and heat pumps (cooling efficiency - SEER and heating efficiency – HSPF), rating procedures for variable-speed equipment, and alternative rating methods for systems combining indoor and outdoor units from different manufacturers (mixed systems).

In FY06, we formalized a linear-fit method of rating mixed systems in the cooling mode. This simplified method gives indoor coil manufacturers a method of determining the ARI A-Test cooling capacity (Q(95) and SEER for their indoor coils when paired with different manufacturers’ outdoor units. This method was made possible by the original equipment manufacturers releasing cooling capacity and power linear fits for their equipment and publishing this data through the Air Conditioning and Refrigeration Institute.

The goal of the proposed 2008 NIST effort is to bring a complete solution to the mixed system rating problem. NIST will expand the cooling mode method from single-speed to multi-speed systems. Based on the experience gained from the work performed so far on the single-speed cooling-mode procedure, the most effective path to follow will be formulating multi-speed procedures first, discussing them with the stakeholders (condensing unit and coil manufacturers), and performing experimental validation of the modified procedure at the end of the development effort.

Some of our efforts have been focused on the following:

1. Upper limits on HSPF and Q(47) ratings for mixed systems
2. Linear-fit-based rating procedure for the heating mode  
3. Cooling mode rating procedure for mixed two-speed and variable speed systems
4. Evaluation of alternative rating procedures
5. Participation in ASHRAE SPC 16/58, “MOTR Room ACs and Packaged Terminal ACs”
6. Air velocity distribution patterns in evaporator coil installations

NIST also works closely with domestic and multinational standards bodies, manufacturers, and trade organizations on rating procedures for residential refrigerating appliances.  In recent years, refrigerators and freezers have become smarter and more functional.  On occasion, new features require some units to be rated under slightly different conditions.  NIST works with DOE, manufacturers, and trade organizations to ensure that all units are rated properly and that fair credit is assigned to energy saving technologies.

At least five refrigerator rating procedures are used throughout the world, which presents a substantial burden for international trade.  In 2006, a global effort was started to develop a uniform test method under the International Electrotechnical Commission (IEC) for all countries that require energy rating of domestic appliances.  NIST has been involved in the new rating method development effort since it began..

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

Linear fit cooling mode procedure illustration