Research Project Information

Research Project Summary Information

Evaluation & Demonstration of Rinnai Combination Space Heating/Domestic Hot Water Systems in New York (23906)

Gas Technology Institute


Rinnai is in late-stage development of a combination system product using a 100,000 btu/hr hybrid water heater that is 90% thermally efficient and incorporates conventional storage and tankless water heater technologies. Conventional water heaters perform well with simultaneous demands because of their stored hot water. Nevertheless, , at times they run out of hot water during long draws because of the lower BTU input. Tankless technology performs well with long draws at steady flow rates. Still, due to the lack of storage, they struggle with simultaneous demand from multiple fixtures. The Rinnai hybrid combination system proposes to solve the shortfalls of the two technologies with the hybrid water heater. Rinnai expects the hybrid combination system to be available in the market by January 2012 and competitively priced in the low $2,000s. Rinnai is in an early-market stage with the wall-mounted condensing gas boiler. The boilers are 75,000 to 205,000 btu/hr and can be used as retrofit to replace traditional, less efficient boilers or provide simple, space-saving installation in new buildings with closed-loop heating systems. The condensing boiler is up to 96.5% AFUE efficiency and is typically used in closed-loop systems with an indirect tank for ASME certification.

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Project Description

Combo systems will be installed at 10 field test locations. At the end of a 12 month test period gas billing data will be analyzed and compared to the original baseline data on a heating degree basis. For the second part of the performance and savings analysis, three test sites will be instrumented with a detailed data collection package. This data collection package will be remotely monitored with the use of a cell modem allowing for constant analysis of the data along with the ability to look in on the live performance of the system.


Integrated systems reportedly can reduce energy consumption by more than 20 percent compared to separate water heating and space heating equipment. The technology identified for this project is roughly 90% to 95% efficient, compared to average nameplate efficiencies of installed equipment regionally of 81% for forced air furnaces and 57% for storage water heaters.

Project Results


Gas Technology Institute
39971 Treasury Center
Chicago, IL 60694

Principle Investigator

Tim Kingston

Universities Involved


Project Type:

Product Demonstration

Technologies Types:

Building Systems
Heating, Ventilation, & Air Conditioning

NYSERDA Contact Information

Gregory Pedrick


R&D -Transport & Power Systems

Contract Details

Start Date: 12/2/2011
Project Status: Active
Contract Number: 23906

Last Updated: 12/19/2013