Project Quick Facts

• Catoctin High School
• Owner: Frederick County Public Schools
• Type of project: Systemic Replacement
• Location: Thurmont, MD

Project Details

The scope of this project included 2 phases.

Phase 1:

This project included the one for one systemic replacement of six (6) original (1969) multizone split type air handling units and associated air cooled condensing units serving areas A, B, and F. The units are packaged rooftop type for service and accessibility reasons. The rooftop units are high efficiency variable air volume type utilizing a heat recovery device for pretreating outdoor air. Ductwork is extended from the proposed AHU’s into the building where thermostatically controlled Variable Air Volume (VAV) terminal units (i.e. VAV box) with electric heating coils were provided for each preexisting thermostatically controlled duct zone. The VAV box discharge duct connects to the preexisting supply air duct serving the occupied space(s). A return air duct extends from the air handling unit to the preexisting return air system.

Rooftop units are located on steel dunnage on flat roof areas adjacent to the spaces currently housing the preexisting indoor air handling units.

Additionally, two (2) small rooftop units located in the same proximity were replaced.

Work includes exterior steel platforms for rooftop units, internal catwalk systems to access VAV boxes and associated electrical work, as indicated on the contract drawings to support the mechanical scope of work in a fully turnkey fashion.

Phase 2:

This project included the one for one systemic replacement of five (5) original (1969) single zone, electric heat, air handling units and associated air cooled condensing units located in area F. The preexisting units were located above the ceiling in a very limited space for maintenance and connected by catwalk system that included climbing over/under preexisting ductwork and preexisting roof structure. The units are packaged rooftop type to allow for service and accessibility reasons. The rooftop units are high efficiency, single zone variable flow type utilizing a heat recovery device for pretreating outdoor air. Ductwork is extended from the proposed AHU’s into the building ceiling space and connected to preexisting supply and return air ductwork. Additionally ERU-1, a 2 pipe roof mounted DOAS unit serving the office space was replaced to accommodate all the new rooftop units located on a common steel platform above the preexisting roof well. Based on the extent of work in this area, the preexisting flat roof was replaced as part of the project. All preexisting duct mounted electric reheat coils were replaced in kind. All unit and coil control were interlocked to the preexisting Johnson controls energy managements system.

The rooftop units are located on steel dunnage on flat roof areas above the space previously housing the preexisting indoor air handling units.

Two (2) Direct Expansion (DX) cooling coils were installed in the supply air ducts for the Gym served by preexisting Air Handling units ERU #7 and ERU #8. Remote Air Cooled Condensing Units (ACCU’s) were mounted at grade on a concrete pad with refrigerant piping extended to the duct mounted cooling coils. Cooling Coils were sized to cool the air down to 55f based on 45f SST. Coils and condensing units were matched based on capacity. The preexisting Gym supply air ductwork is externally insulated and motors were replaced and equipped with variable speed drive.

Work includes exterior steel platforms for rooftop units, roofing and associated electrical work as indicated on the contract drawings to support the mechanical scope of work in a fully turnkey fashion.