This report (Report A112) was presented by Harvey Sachs, Jacob Talbot and Nate Kaufman of the American Council For An Energy-Efficient Economy in October, 2011. For the full report please visit: ACEEE.org (click)
MULTIFAMILY BEST PRACTICES (an excerpt)
“Multifamily buildings are generally characterized by central tank heaters (or boilers) with recirculation loops.
There are approximately 16.7 million multifamily buildings in the United States.
Over 90% of the multifamily buildings use central hot water systems.
A “bad” hot water system delivers about 1/3 of the site energy to the hot water fixture, while a “good” one will deliver over 1/2.
The major strategies for improving efficiency in existing buildings [are]:
Implement improved control strategies that include using the smallest feasible water heater, circulating hot water at the lowest temperature that supports the instantaneous load, and using temperature-based demand control for the circulation pump.
Demand control of the circulation loop can reduce gas consumption by 15%, compared with savings in one studied building of a 9% for a single pump timer and 10% for a loop temperature modulation. A demand controlled pump will only run 1 – 2 hours per day while supporting 24 hour hot water service, and can save 17% of hot water energy. The pump control should allow the pump to run only when there is demand for hot water, or the hot water temperature is too cool.”
For the full report, click here: www.ACEEE.org