SF-98-29-2 -- Electronic Equipment Heat Gains in Buildings

Heat gain from equipment is an important factor in determining the overall cooling load of a space or building. The results of extensive measurements indicate that the actual heat gain from equipment is significantly less than that indicated on equipment nameplates. Measurements at panels that serve large areas of office buildings allowed for the analysis of equipment diversity factors. Results indicated that engineers who rely on nameplate data alone will grossly oversize HVAC systems. This study evaluated over 270,000 ft² of space in five different buildings. On the average, if nameplate data were used, the equipment load factor would have been 3.5 W/ft². When the factor was adjusted to account for the disparity between nameplate data and the measured maximum for each individual piece of equipment, the equipment load factor would be expected to be 1.75 W/ft². Measurements at the panels, which served all equipment, gave the sum total of the peak power to all equipment as 0.8 W/ft². This indicates that both factors, nameplate disparity and usage diversity, have a significant impact on the actual heat gain and cooling load. Usage diversity averaged 47% but ranged from 22% to 98%. If the total area considered in this study (270,000 ft²) was considered as a single building and designed based on nameplate data, it would have been designed with 170 tons of unneeded chiller capacity. Air delivery systems would have also been designed with 0.47 cfm/ft² of unneeded airflow.

Units: I-P