Case study: Hydronic heating system

A new heating hot water system was included in the design of a water treatment plant

By Ian Marchant and April Ricketts September 21, 2020

To provide space heating to process spaces at a new water treatment plant, a hydronic heating system comprised of two 960 thousand Btu/hour (MBH) capacity natural gas-fired water-tube boilers and base mounted centrifugal pumps was selected.

The primary looped heating system distributes hot water to unit heaters located at filter rooms, chemical storage spaces, process treatment areas, pipe galleries and utility tunnels. The boiler and related equipment are housed in a mechanical room located away from the corrosive chemical areas and piping. Hangers and accessories running through corrosive spaces were required to include protective coatings suitable for the unique environments.

Combustion air enters the boiler room through two louvers, one located 12 inches above the floor and one located 12 inches below the ceiling; each louver includes a motorized damper to only open when the heating system is in use. A unit heater is located near the louvers to temper the incoming combustion air.

Boiler controls operated one boiler at a time and alternates between the lead and lag boiler at regular intervals. As required by the local boiler code (which references ASME CSD-1 Section CE-110), an emergency boiler shutdown switch is located just outside of exit door of the mechanical room to shut off the boiler in an emergency situation.

Author Bio: Ian Marchant is a senior mechanical engineer at CDM Smith. He has more than 30 years of experience in the building system and energy fields. April Ricketts is a senior mechanical engineer at CDM Smith. She has 24 years of experience in the design of building mechanical and plumbing systems.