Standard Plumbing Heating Controls Corporation of Spokane, WA, recently designed a new heating and domestic hot water system for the Dominican Center, which was constructed in 1969 to house the Dominican Sisters, who work with charity organizations worldwide to help troubled women and victims of abuse and addiction.
Originally designed with a separate boiler room located 150 ft away from the main building, the heating plant housed a 3 million Btuh firetube boiler. The steam was piped underground from the boiler room across the entire length of the building to a steam-to-water converter located 350 ft away, where water was heated at 120°F to 180° to heat the building. The building that housed the boiler room also produced domestic hot water for the center, which was stored and maintained at 150° in a 546-gal tank before being piped to the main building.
Lukewarm instead of cold“While the equipment had been well maintained and the piping was in good condition, a significant amount of heat was being lost in many unwanted areas, causing the cold water to run lukewarm and the crawl spaces and storage areas to become unbearably hot,” explained Dave Ressa, the center’s the facilities manager. “We estimated that the steam boiler was running at an efficiency of 60%, so for each one million Btu of natural gas, the boiler used only 600,000 Btuh to make steam and the other 400,000 Btuh was lost to venting, piping, or the air in the boiler room.”
Designer Don Smet chose two Lochinvar KNIGHT Boilers with 500,000 Btuh and 95% thermal efficiency to heat the building; in addition, he selected a Lochinvar ARMOR Water Heater with 399,000 Btuh and up to 98% efficiency and a new ASME 100-gal insulated storage tank to supply domestic hot water for the entire building and kitchen.
As Smet explained, “We accessed the existing four-in. water heating loop by welding two closely spaced two-and-a-half-in. tees and valves behind the boilers using a primary/secondary configuration. The two boilers were then piped in cleanly and easily, utilizing their own circulating pumps.”
The direct venting was accomplished by running the PVC piping up through the ceiling of the basement to the main floor, into the attic, and then out above the architectural roof. The Standard team took advantage of the KNIGHT’s built-in cascading sequencer by simply wiring the two new boilers with a two wire pair and then completing the quick and easy set up of the controls and burners.
Piping for the ARMOR domestic water heater and tank was simple and straightforward. The new piping was run to the existing hot and cold water pipes located in the building’s basement. Since the water softener had been piped to the heating system in the old boiler room 150 ft away, it had to be relocated and piped in next to the ARMOR.
The cold water line coming into the building remained the same, but the hot water line had to be cut and isolated from the old boiler room. The lead installer for the project, Dan Sem, then converted the old hot water line, which had been cut in the tunnel leaving the center, to a hot water recirculation line for the new system by coupling the newly cut end to a three-quarter-in. PEX line and running it all the way back to the ARMOR water heater with a mini pump.
A long wait for cold waterOnce this isolation and recirculation line was complete, the ARMOR was fired up and the new domestic hot water system was running beautifully. The Smart System control on both the KNIGHT and ARMOR made the set up of the cascade, outdoor reset, night setback, and heating and domestic water setpoints and controls a quick and painless endeavor.
For the first time since 1969, the Dominican Sisters have access to cold rather than lukewarm water, as well as nearly instantaneous hot water in all of their dorm rooms and the kitchen. The 100 gal of stored domestic hot water is now maintained at 140°, and the building’s water heating setpoint is controlled solely on the cascade modulation of the boilers and the outdoor temperature.
The new system is dramatically more stable and efficient than the previous system. With an investment of $65,500, the center can expect a minimum of 35% fuel savings; and with the local utility company’s 30% reimbursement, a three- to four-year payback will easily be achieved. ES