Case Studies

Heating Case Studies: Navien Combi Boiler/On-Demand Water Heater Installation in Newark, NY

Tuesday, February 25th, 2014 by Matthew Crandall


Due to high energy costs and comfort issues, these Newark, NY homeowners were using their existing boiler to only heat the 1st floor of their home on regular basis.


We took out an existing 80% induced-draft 120K natural gas boiler that had three massive single-speed 1/12 HP Bell and Gossett circulator pumps – one for each zone.  The pumps were of such an industrial size that they required 62 watts each of electricity to operate, as well as routine oiling on a regular basis (as evidenced from the oil spots on the floor below each of them).

The home is a geodesic style (spherical) with a very high ceiling.  Conventionally, they only operated one zone of the system (1st floor) because operating the upper 2nd floor zone would make the living space uncomfortably warm (180F-200F supply water).  The basement is fully finished with extensive décor throughout, but was only heated when entertaining in an attempt to save money.  All three zones are finned tube, conventional baseboard which they were able to keep with no modifications.

For domestic water, they used a separate on-demand style water heater for a three person household.

The new pre-fabricated modulating/condensing combination Navien boiler with on-demand domestic water heating capability that we installed with a hydraulic separator, zone valve-style distribution, and single alpha variable-speed pressure-regulated circulator (running at a cool 24 watts with all zones operating simultaneously) fits this and almost every other conventional hydronic application in existence to date.

By utilizing a return water setting (120F or less) and an outdoor temperature reset control, we were not only able to cut their operating costs (both electrical and fuel consumption) dynamically in half, but we were able to allow them to run all three zones at a comfortable level for a comparably less cost to the single zone they were utilizing in the previous system design.  To top off this massive improvement to the home, they are now able to run space heating and domestic hot water through a single wall mounted appliance with common piping, providing them with additional storage space in their mechanical room.

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