Multifamily Pilot Project Single Pipe Stream Balancing Hot Water Outdoor Reset

In the fall of 1984 the Energy Office initiated the Multi-family Pilot Project (MFPP) to test a delivery mechanism and to refine the technology for conservation retrofits in single pipe steam (SPS) and multizone hot water (MZHW) apartment buildings.

The major cause of energy waste in SPS buildings is uneven heating. The temperature is usually set to satisfy the coolest apartment which overheats other apartments and wastes energy. This paper summarizes balancing strategies including: controlling the boiler cycle, installing main line and radiator air vents, conducting a tenant survey to identify remaining problems, and using thermostatic air vents and other techniques to fine-tune the systems.

Installations were completed on 25 buildings. Energy savings averaged 9.3, the average cost was about $1400, and the median simple payback was 1.4 years. Field and laboratory tests were conducted on main line and radiator air vents which showed significant differences in venting rates and the importance of these differences in achieving even heating.

The most cost effective retrofit for MZHW apartment buildings is the outdoor reset of boiler water temperature. The MFPP tested a delivery mechanism for the retrofit. Installations were completed on 18 buildings. Energy savings averaged 9.1%, the average cost was $615, and the median simple payback was 1.9 years. A computer simulation was done to determine how large of a performance degradation is incurred when the reset ratio used varies from the ideal. As much as 50% of the potential savings can be lost with the use of the wrong reset ratio.

Full report (PDF)
Multifamily Pilot Project Single Pipe Stream Balancing Hot Water Outdoor Reset