November 22, 2024 www.p2sinc.com

USGS WFRC – Room D109 Cooling Study Mechanical Narrative

USGS WFRC – Room D109 Cooling Upgrade Mechanical Narrative

TABLE OF CONTENTS

1.0 PROJECT BACKGROUND

2.0 SCOPE OF WORK

2.1 Existing Condition

2.2 Recommended Solution

1.0 PROJECT BACKGROUND

At the US Geology Survey (USGS) Western Fisheries Research Center (WFRC) Building in Magnuson Park, Room D109 cannot maintain a comfortable temperature due to the heat rejection from the 13 freezers.

The freezers emit an approximate combined heat load of 31,000 Btu/hr. The existing variable air volume

(VAV) box serving the room is undersized for the amount of heat gain from the freezers.

2.0 SCOPE OF WORK

2.1 Existing Condition

Room D109, a 30’ x 15’ x 12’ freezer room, is currently served by a 400 CFM Titus VAV box (CR2) located in the mechanical room on the floor above. This VAV box is served by a 36,000 CFM air handling unit

(AHU-1), located in the same mechanical room. AHU-1 provides 100% outside air with a cooling set point between 54 and 61 degrees F based on trend data. The cooling set point during the site visit was

61 degrees. The building HVAC system uses Siemens controls. A six-inch duct extends from AHU-1 to the

CR2 VAV box. Downstream of the VAV box, a 10” x 14” duct routes directly into the ceiling, discharging into a single diffuser on the south side of the room. On the opposite side of the room, there is a return air grille sized for 450 CFM.

There are 13 large freezers in Room D109 with an approximate combined heat rejection of 31,000 Btu/hr.

During the site visit the room was in full cooing mode, and although both doors to the room were open and two floor-set fans running, the room was 75 degrees F with a setpoint of 72 degrees F.

2.2 Recommended Solution

P2S performed a load calculation using Trane Trace modeling software. Given the freezer’s total heat rejection of 31,000 Btu/hr, a cooling airflow rate of 1,500 CFM at a supply air temperature of

55 degrees F is required to cool the space. P2S recommends replacing the CR2 VAV box with a larger VAV box to meet this requirement.

The existing CR2 VAV box and the six-inch duct serving it from AHU-1 will be demolished. The Siemens controller will be retained for re-installation. The existing diffuser, as well as the 10” x 14” duct between the VAV box and the diffuser, will be demolished. The return grille and associated duct leading to the

17-inch duct above Room D111 will be demolished. The 17-inch duct will be capped at the existing connection.

A new 1,500 CFM Titus DESV VAV box with a 12-inch inlet will be provided and connected to AHU-1.

Downstream of the VAV box, a 14”x 18” duct will be installed and routed through the floor of the mechanical room to the Room D109 ceiling. The concrete floor opening will need to be increased to fit the new duct.

Two 750 CFM supply diffusers will be installed to accommodate the increased airflow. Four return grilles sized for 325 CFM each will be installed above the freezers, allowing heat to be transferred directly up and out of the room. A new 18-inch return duct will connect the return air grilles and route to the mechanical room above. The 18-inch duct will connect to the existing 32” x 26” duct in the ceiling of the mechanical room.

The existing air handling unit has 36,000 CFM capacity. The proposed increase in airflow to the freezer room will likely be acceptable to the overall air handling unit load due to the diversity in the system.