In 1969, the Dominican Center was constructed in Spokane, Wash., to house the Dominican Sisters, a religious order dedicated to helping troubled women, victims of abuse and addiction, and single mothers.
Located 150 ft away, the heating plant initially housed a 3-million-Btu firetube boiler. Later, an additional boiler was installed to heat a second dormitory. Steam was piped underground from the boiler room to a steam-to-water converter 350 ft away, where 120°F to 180°F water was produced.
An evaluation of the heating system revealed that a significant amount of heat was being lost in many areas. Because the main steam line was buried underground, heat was being transferred to the earth and domestic-water pipes, which also were buried. As a result, cold water was lukewarm whenever the steam boiler ran, and the center's crawlspaces and storage areas were unbearably hot.
The heating plant also produced domestic hot water, which was stored at 150°F in a 546-gal. tank.
The steam boiler was estimated to be running at an efficiency of 60 percent, meaning that for every 1 million Btu of natural gas, only 600,000 Btu was used to make steam. The other 400,000 Btu was lost to venting, piping, or the air in the boiler room.
A PLAN FOR IMPROVEMENT
After learning that the steam boiler was operating so inefficiently, the center decided to install a new heating and domestic-hot-water system. The local utility company, Avista Utilities, agreed to provide incentives and gas credits that would be determined upon completion of the installation.
Standard Plumbing Heating Controls Corp. of Spokane worked with the center, Avista Utilities, and local building and code personnel to design a new heating and domestic-hot-water system. Standard recommended installing new highly efficient equipment in the center's basement and eliminating the use of steam.
To heat the building, designer Don Smet chose two 500,000-Btu, 95-percent thermally efficient Lochinvar Knight boilers. To supply domestic hot water, he chose a 399,000-Btu, up-to-98-percent efficient Lochinvar Armor water heater and a new ASME 100-gal., insulated storage tank.
STEPS TO SUCCESS
Installation began in March 2007. Work progressed smoothly throughout spring and summer, as demand for heating decreased. The steam system had to be shut down only three times, for less than six hours at a time.
The Standard team accessed the existing 4-in. water-heating loop by welding two closely spaced 2½-in. tees and valves behind the boilers using a primary/secondary configuration. The two boilers then were piped in cleanly and easily, utilizing their own circulating pumps.
Direct venting was accomplished by running PVC pipe through the ceiling of the basement, to the main floor, into the attic, and then out above the architectural roof.
With the building's electrical panel located only 20 ft away in the same room, electrical installation of the boilers and pumps was simple. The Standard team took advantage of the Knight's built-in cascading sequencer by wiring the two new boilers with a two-wire pair and then completing the setup of the controls and burners. At that point, the steam boiler was shut down, and the new heating plant was up and running smoothly and efficiently.
“Straight out of the box, the Knight can do anything I need it to do without any third-party controls,” Smet said.
New piping was run to the existing hot- and cold-water pipes located in the basement. Because 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, Dan Sem of Standard, then converted the old hot-water line, which had been cut in the tunnel leaving the center, to a hot-water recirculation line by coupling the newly cut end to a ¾-in. PEX line and running it all of the way back to the Armor with a mini pump. Once this was done, the Armor was fired up, and the new domestic-hot-water system was running smoothly. A Lochinvar Smart System control on both the Knights and Armor made the setup of the cascade, outdoor-reset, night-setback, and heating- and domestic-water set points and controls quick and painless.
The Dominican Sisters now have cold, rather than lukewarm, water, as well as nearly instantaneous hot water, in each of their dorm rooms and the kitchen.
Without modification, the new heating plant is ready for a direct-digital-control building-management system. What's more, the 100 gal. of stored domestic hot water is maintained at 140°F, and the building's water-heating set point is controlled solely on the cascade modulation of the boilers and the outdoor temperature.
With an investment of $65,500, as well as 30-percent reimbursement from Avista Utilities, the center can expect fuel savings of at least 35 percent and a payback of three to four years.
Information and photographs courtesy of Lochinvar Corp.