Optimizing the Conversion of Heating Systems from Two Pipe Steam to Hot Water

Converting older low-rise buildings from steam to hot water heat has been shown in previous research to produce savings of 13 to 39% and result in a more even and easily controlled heating system. Conversion to hot water is most practical for Two Pipe Steam (TPS) heating systems which require minimal changes to existing distribution pipes and radiation.

Based on investigations in three multifamily buildings, options for reducing costs and optimizing performance of TPS conversion were considered. A variety of boiler retrofit options, zoning techniques and control strategies were studied. Boiler options included: converting the steam boiler to hot water, replacing the boiler, installing a steam to hot water convertor and adding a front-end boiler. Zoning options included zoning at branches, radiators, risers or apartments. Control options were outdoor resets or thermostats.

This report discusses the mechanical performance of each option as well as the costs. The advantages and disadvantages of various types of products are described. In addition, guidelines for estimating conversion costs and choosing the best option package are suggested, for use by auditors in the field. When compared with contractor's bids on the three investigated buildings, and used to specify a steam to hot water conversion for a fourth building, these estimates were close to contractors' actual bids for converting the buildings.

Full report (PDF)
Optimizing the Conversion of Heating Systems from Two Pipe Steam to Hot Water