HVAC Retrofitting – Small Changes Can Make a Difference

Facilities professionals often choose not to invest in energy-efficiency upgrades because of perceived high upfront costs. But if armed with the right information, they can see that energy savings can make a retrofit project a more worthwhile investment.

Example: William Pecor, Assistant Supervisor of UCONN's building operations, had problems on hand with the pneumatic actuators that controlled the movement of fan blades to circulate air. The current pneumatic actuators were expensive to repair and replace, along with the process would be extremely time consuming and labor-intensive.

Fan

The chemistry building management system at UCONN either calls for heating or cooling and when it does, it needs the air quickly and at variable speed and volume. The chemistry building mechanical room consists of four large Air Handling Units (AHU) that are approximately ten feet high by forty feet long. Each AHU has two chambers consisting of large guide vein fans with variable angle blades, which controls the air velocity by Cubic Feet per Minute (CFM). A pneumatic linear actuator currently controls these blades. The arm attaches to the actuator to pull or push to increase or decrease the blades' angle. The arm moves approximately two inches in total in either direction and is controlled by the Building Management System (BMS). The critical part of the application is not the precision of movement, but the unit's downtime if the fan fails. If both fans were to fail at the same time, this would cause a handicap to the building's access to fresh air and air across the coils.

Uconn Fan

In front of these fans is a large 8' x 8' damper section that is pneumatically controlled. When the fan is on, the dampers open to allow more air to the coils. The entire building runs most of its HVAC devices off pneumatic actuators. The units have two chamber sides for redundancy, with only one fan running at any given time. The fans are manufactured by Joy Fan Company, a division of Howden, a world leader in fans and rotary heat exchangers.

Tower Equipment Co., with guidance from the Belimo retrofit team, was able to create a retrofit solution. The design included two fabricated UFSP0014 linkages utilizing an SY4-120MFT, non-spring return actuator with a crank arm. Calculations determined the SY4-120MFT with 3560 in-lbs of torque would move the arm of the fan at full speed. The SY would work off a 2-10 VDC control signal and would have a speed of 15 seconds. The MFT software would be utilized to limit the rotation to only 40 degrees for a 2" movement of the blade.

The SY actuator's linkage cost outweighed the cost UCONN would have had to pay for replacing and repairing the pneumatic actuator unit. To purchase and restore the pneumatic was approximately $3000 to $4000 net with weeks of dangerous downtime. The Belimo fabricated retrofit linkages and SY actuator solutions were installed in less than one week for less than $2000.00. Pecor was amazed and excited that a retrofit solution could be created that met his needs, kept within the specifications, and carried a 2-year warranty. Since the install of the first two units, UCONN has moved forward with the installation of the next four fan units.

Pecor saved money, reduce downtime, and kept the chemistry department running. The cost savings associated with switching to electronics also benefit UCONN in energy savings and a reduction in replacements. The speed of repair and installation was critical, with only one fan and no additional backup.

HVAC retrofit involves any project aiming to improve the efficiency of the system. HVAC upgrades can range from installing continuous environmental management systems to replacing or retrofitting individual components of a system (valves, actuators, heat pump, air-side economizers, etc.). Belimo offers a retrofit technical documentation book for Valves, Actuators, and air economizer HVAC. This book can be downloaded for free or request your free copy.

HVAC Guide to Retrofitting
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