CH-03-07-1 (RP-1165) -- System Interactions in Forced-Air Heating and Cooling Systems, Part I: Equipment Efficiency Factors PDF

Computer simulations of residential heating and cooling systems in three climatic zones have been performed. The objective was to determine the functional forms of equipment efficiency factors (Fequip) in ASHRAE Standard 152P. Fequip is defined as a ratio of the space-conditioning equipment efficiency in the system under evaluation to the efficiency that the same equipment would have with a loss-free distribution system. It is one of the factors in the definition of distribution efficiency in Standard 152P. In the case of single-capacity equipment, the equipment efficiency is mainly affected by part-load ratio. Simulation results show that equipment efficiency factors are slightly larger than 1.0, which is the value used in the current Standard 152P. Variable-capacity equipment has a more complex relationship between capacity and power consumption. Equipment efficiency is not only dependent on coil output and part-load ratio but also on the ratio of building load to equipment capacity and operating range. For variable-capacity equipment, statistical analysis was performed based on simulation results. Fequip turned out to be a quadratic function of the product of delivery effectiveness and load factor, with coefficients that depended on the nominal equipment size relative to the load. These quadratic regression equations are recommended for use in the standard to calculate Fequip.

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