St. Mary’s Janesville Hospital Benefits from Hybrid Boiler System Controlled by Cleaver-Brooks HSC

Case Study

  • Company: St. Mary’s Janesville Hospital
  • Industry: Commercial Heating
  • Location: Janesville, Wisconsin
  • Profile: St. Mary’s Janesville Hospital is a 50-bed community hospital that wanted a high-efficiency boiler room solution tailored for the healthcare facility whose demands require redundancy.
  • Challenge: The boiler control on the hydronic system was not operating to a reliable standard, frequently going off on high limit, causing the alarm to sound.
  • Solution: Replaced the third-party control system with a Cleaver-Brooks Hydronic System Control (HSC), which monitors supply, condensing return and non-condensing return. It also looks at the outlet temperature for each boiler to manage switchovers in order to optimize boiler operation.
  • Results: As a result of the new HSC control, the boiler system at St. Mary’s Janesville Hospital is running correctly and efficiently, reducing both fuel costs and the number of boiler alarms.

In 2011, SSM Health Care of Wisconsin built St. Mary’s Janesville Hospital, a 50-bed community hospital that spans 175,000 sq. ft., in Janesville, Wisc. The design of this state-of-the-art facility, engineered by Erdman Engineering, based in Madison, Wisc., required the use of both high-pressure steam and hydronic boilers. After careful consideration, Cleaver-Brooks, represented by PBBS Equipment Corporation, was selected to provide the equipment.

The high-pressure steam system at St. Mary’s Janesville Hospital consists of three Cleaver-Brooks ClearFire®-V (CFV) boilers, which are controlled by the built-in Cleaver-Brooks Falcon Lead/Lag System. The hospital uses these boilers for both sterilization and humidification. The hydronic system at St. Mary’s consists of two Cleaver-Brooks ClearFire-C (CFC) fully condensing boilers, two Cleaver-Brooks ClearFire-W (CFW) near-condensing boilers, and a standard hybrid system controller.  

The hydronic boilers are used for winter heat and summer reheat and are set up as a hybrid system, wherein the CFC boilers operate during spring, summer, fall and some of winter at higher efficiencies (88% to 99%), and the CFW boilers operate in winter at standard efficiencies (86% to 88%). 

Hybrid systems utilize both condensing and non-condensing boilers with outdoor reset. During spring, summer, fall and some of winter, the building heating loop may allow for cooler temperatures with return water below 140 degrees F. During these periods, a condensing boiler should be used to maximize efficiency. Warmer building loop temperatures may be required during winter, and a non-condensing boiler can be utilized, seeing as either a condensing or a non-condensing boiler would be around 86% to 88% efficient with the warmer return water temperatures. 

Both boiler systems at St. Mary’s were designed to have redundancy, operate year-round, and function dependably. It is essential to have redundancy in the healthcare industry because the boilers must be able to meet any demand at the time of an emergency, day or night. And since the boilers operate year-round it is important that they run efficiently to help reduce fuel costs and function dependably to ensure this performance.  

After the first year of operation, it was discovered that the standard hybrid system controller was not performing as required for modern hydronic systems. This standard controller was designed to change the set point by monitoring only the system and outdoor temperatures, which caused the boilers to shut down and alarm on high limit, allowed for undesirable condensing to occur in the CFW boilers and did not always provide dependable operation.  

It was decided that a more advanced controller was required for today’s sophisticated hydronic systems, which consist of ever-smaller condensing boilers, variable-frequency drives on pumps, heat recovery sub-loops, open/close isolation valves, etc. A more advanced controller would allow for the maximum efficiency to be obtained and improve reliability of the entire hybrid system.

Knowing that Cleaver-Brooks is continuously adapting to meet industry demands, Matt Van Vreede, engineer at PBBS Equipment, recommended that St. Mary’s replace the standard control with the Cleaver-Brooks Hydronic System Control (HSC). Van Vreede contacted Brent Sutherland, director of plant/environmental services for St. Mary’s Janesville Hospital, about replacing the control, and Sutherland welcomed the idea enthusiastically.  

Working together with St. Mary’s personnel, the design engineers at Erdman and PBBS Equipment, Cleaver-Brooks replaced the standard controller with the Cleaver-Brooks Hydronic System Control. The HSC is an exclusive hot water boiler system sequencing and modulating control developed by Cleaver-Brooks engineers. It was designed specifically to maximize the efficiency potential in hybrid hydronic systems. The HSC monitors the main supply, condensing header, and main return water temperatures as well as individual boiler temperatures. It also looks at the outdoor air temperature to perform outdoor reset of set point and to manage switchover between condensing and non-condensing groups in order to optimize boiler operation.

Van Vreede said, “The standard control was not designed to monitor certain points such as boiler inlet and outlet temperatures. When another boiler was called on during a transitional period, it had the potential to shut off on high limit. Because the HSC monitors inlet and outlet temperatures, it allows the boilers to back down before shutting off on high limit.”

Brian Huibregtse, product engineer at Cleaver-Brooks, added, “The HSC system has additional capabilities and monitors more points than a conventional hydronic controller. If the system requires operation of a non-condensing boiler, the HSC can make sure the return temperature is high enough, or it can be controlled to reach a high enough temperature in short order, thereby delivering the heat needed while protecting the non-condensing boilers.”

Due to the new HSC control, the boiler system at St. Mary’s Janesville Hospital is running efficiently and reliably, reducing both fuel costs and the number of boiler alarms. Sutherland has confidence in the new control and is pleased with the reliability of the boiler system.

Huibregtse emphasizes the importance of a good boiler room control. He said, “Boiler system performance is only as good as the control system that operates it. Boilers must be set to come online as needed and operate in their ‘sweet spots’ while minimizing short cycling, thereby maximizing efficiency and significantly reducing operating costs.”