Avera St. Luke’s Hospital Upgrades Air Handler with FANWALL TECHNOLOGY

For over 100 years Avera St. Luke's Hospital has served the community of Aberdeen in eastern South Dakota. The East addition of the hospital, which was built in 1991, is served by air handlers in a central mechanical room. One of those air handlers serves the dialysis, endoscopy, outpatient services, and same-day surgery departments at the hospital. In summer months, the areas served by this air handler experience excessive humidity. Moisture carryover from the cooling coil waterlogged the final filters and dripped into the supply ductwork. Corrosion attacked the ducts as a result of water pooling, and in some cases, water had damaged ceiling areas. According to Jeff Gorham, Plant Operations Manager at the facility, these high summer humidity levels also interfered with basic maintenance operations, such as drying carpets after cleaning. Analysis indicated that this air handler was experiencing moisture carryover from the cooling coil due to its close proximity to the final filter bank and the face velocities being too high for this blow through fan unit. Instead of trickling down into the drain pan, some of the condensate was being blown through the airstream, saturating the downstream final air filter which further reduced the effectiveness of the air handler, increased humidity levels, and caused odors. A second concern was the reliance on a single belt ribbon fan and motor for these critical patient service areas.

With advice from Huntair, they decided to convert the air handler from a blow-through to a draw-through design and to replace the single fan with a four unit FANWALL array. This project would involve not only replacement of the fan but also relocation of the heating and cooling coils within the air handler cabinet. Note how the two coils were to be relocated upstream in the airflow to make room for the new draw-through fan system. Smooth airflow from the fan wall array would eliminate moisture carry through and multiple fans would add much needed redundancy. Also, to get a better mix of outdoor air and return air to the unit, an air blender or air turbulator section was envisioned.

Workers from various building trades began work on Friday evening, pipe insulation, chilled water piping and condensate drain lines were removed. Electrical power and control wiring was disconnected. Air handler doors and doorframes as well as one of the wall panels and support struts were removed and will be reused. For a 16 year old air handler, the components had held up well, which was a testament to Temtrol's welded framed construction. By Friday evening, the existing single plenum fan was disassembled. The 30 horsepower motor was removed and put into storage as backup for other air handlers. The fan wheel, fan shroud, and support structure were removed to be scrapped. Existing heating and cooling coils were disconnected. In converting the unit from a flow-through to a draw-through configuration, the coil section was moved to where the supply fan existed and the supply fan section was moved to where the coil section once stood. Flooring and supports were installed over the condensate pan section to support the new FANWALL section. By this time, the entire side of the air handler was open, allowing the team to begin installing the FANWALL retrofit cells.

Because of the manageable size of the individual FANWALL units, they could be rolled into and through the building on a hand cart, taken to the second floor on a standard elevator, and rolled right up to the work site. One by one, the four cells were brought into the air handler and lifted into place to form a two-wide by two-high configuration. The units were simply bolted together to form a rigid fan array, and sound absorbing insulation was inserted around each cell.

By 10 A.M on Saturday morning, the old fan had been removed and the new FANWALL array installed. And by noon, the electrical connections were completed. The entire fan section retrofit was completed in only eight hours.

Meanwhile, work on relocating the coils on the drain pan was completed and these were reconnected to chilled water and condensate drain piping. The sidewall struts on the air handler were re-welded and in some cases relocated to simplify service access in the future.

While the air handler structure was being reassembled, electricians extended electrical service and control wiring to the units. The units themselves were pre-wired, simplifying this task. Electrical conduit was installed atop the air handler and dropped down to the four units.

The amount of space required downstream and upstream of the FANWALL cells is often dictated by what's necessary for service access. A new air blender section was added to the unit upstream of the coil bank, to help mix the entering outdoor and return airstreams before they enter the coil bank. The space needed for the air blender or air turbulator section was made possible due to the small footprint of the FANWALL array.

The final stages of the installation involved testing the water lines, electrical connections, and control circuits. The variable speed fan control was integrated with the building automation system. Motors in a FANWALL array can run above 60 hertz, and the design point for this unit was 89 hertz. The restructured air handler was started up and tested while the worksite was cleaned up. By 6 p.m. on Sunday, the installation was complete and operating. By doing the work over a weekend, it was not necessary to interrupt hospital service or comfort to patients or employees.

FANWALL TECHNOLOGY: great for business, great for the environment. Consider upgrading now.