In the winter of 2013-14, NGRID carried pilot retrofit study of a single-pipe steam heating system converted into vacuum heating system. Study confirmed fuel gas savings for two different systems used to heat the same apartment – Table 1. Energy efficiency of the original single pipe steam system (~100 years old boiler, piping and radiators) was compared to the same boiler connected to new flat panel radiators by copper/plastic lines - Table1; the same comparison was carried later on new regular steam boiler. Up to 50% in savings was demonstrated by the retrofit into a vacuum heating system and in the winter of 2014 -15 results were confirmed. Infrared images of radiators are shown on Figure 1 for origonal steam system and after conversion into vacuum system

Report summary:

The Vacuum Steam Heating system, as designed and implemented by Applied Engineering Consulting, appears to save a significant amount of natural gas with only a minor electric penalty. The savings range from as little as 7.7% savings up to 50.2% savings, depending on what the test scenario was.The VSH system is theoretically infinitely scalable, with the only limiting factor being the size of the vacuum pump system required to hold the system at the required negative 24 inches of mercury.

Figure 1