HVAC Retrofit Increases Efficiency
Published by Lisa Hickey
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Those seeking comfort will find it at Assisi Heights in Rochester, Minnesota. For many years, that wasn’t the case. The Sisters of St. Francis of Rochester and others who lived, worked, and taught at the historical convent, did so without air conditioning and a very outdated steam heating system. Many of the pneumatic actuators throughout the steam system were in disrepair.
The Mayo Clinic agreed to fund the HVAC improvements at Assisi Heights in exchange for classroom and education space at the facility. Selected for the repairs was Control Services of Minnesota, Inc. They were to provide and install a new Direct Digital Control system and rework the entire control system for the steam and new chilled water system to serve these areas. Belimo, with its long-standing relationship with the Mayo Clinic, was chosen to provide the valves and actuators for the new fan coils, VAVs, and AHUs.
Making It Fit
Space can be a challenge in any retrofit, especially in an older, historical building like Assisi Heights. Built in 1952 to resemble the famed Basilica of St. Francis of Assisi in Italy, the facility is a structural fortress with thick walls throughout and no vertical risers to accommodate a modern piping or control system. As a result, the 110 fan coil units had to be installed in the minimal space above the ceiling in the hallway of the sister’s residence. Although compact in size, these units had the capability of full-size AHUs. Internal components included steam radiation valves, hot water reheat valves, and chilled water valves. All this jammed into one 2’ X 2’ casing; there was no room for bulky valves or actuators. Belimo’s VS and VSS Series ball valves with dual-mounted on/off spring return actuators was an important space-saving strategy. These stainless steel ball valves, designed especially for tight spaces, provide on/off (or modulating) control of hot water, chilled water, and saturated steam. Because of their size, the Belimo valves allowed Control Services of Minnesota to complete the installation while minimizing any structural alteration to the historical home of the Sisters of St. Francis. “We had a very small footprint to work with,” remarked Brian Ulrich, project manager for Control Services of Minnesota. “The radiation housing would not fit any other valve.”
There were other advantages multiple outputs were required for full communication between the various valve actuators and the Andover DDC system. Control Services used 2-10 VDC, floating point, and on/off control. The overall renovation was challenging but is a success. The outdated, inefficient pneumatic control system is replaced, and the residents at Assisi Clinic now enjoy comfortable spaces year-round. They can better focus on the community outreach and healthcare ministries for which the Sisters of Saint Francis of Rochester are legendary.