Salient_Characteristics__Data_Center_CRAC__Chiller_Replacement.pdf

Salient Characteristics for Data

Center CRAC & Chiller Replacement

1. General Scope This document outlines the salient characteristics and minimum requirements for the procurement, delivery, and installation of replacement Computer Room Air

Conditioning (CRAC) units and the supporting outdoor Air-Cooled Chillers for the

Data Center. The new equipment must meet or exceed the performance, capacity, footprint, and efficiency metrics of the legacy equipment as detailed in the facility’s as-built schedules.

The systems operate as an integrated chilled water loop where the outdoor chillers supply chilled water directly to the indoor CRAC units to maintain precise environmental conditions within the critical data center whitespace.

2. CRAC Equipment Overview The indoor mechanical replacement includes six (6) downflow Chilled Water (CHW)

CRAC units currently servicing the data center.

• Equipment Tags: CRAC-01, CRAC-02, CRAC-03, CRAC-04, CRAC-05, and CRAC-

• Cooling Method: Chilled Water (CHILL WTR)

• Airflow Configuration: Downflow (for raised-floor distribution)

• Location: Indoor Data Center

2.1. CRAC Mechanical & Fan Specifications

• Fan Type: Air Foil Plug Fan (or modern equivalent high-efficiency, direct-drive

Electronically Commutated [EC] fans)

• Drive Type: Direct Drive (to minimize maintenance and belt-shedding particulates in the white space)

• Motor Capacity: Up to 15.00 HP (must match or exceed legacy CFM and static pressure requirements)

• External Static Pressure (ESP): Designed for a minimum of 0.75 in. w.g.

2.2. CRAC Cooling & Performance Capacities

Replacement CRAC units must support the varying airflow and cooling load profiles defined by the existing design baseline:

Unit Designation

Total Airflow

(CFM)

Entering Air Temp

(DB / WB /

RH)

Chilled Water Flow

(GPM)

Min. Total Capacity

(MBH)

Min.

Sensible Capacity

(MBH)

CRAC-01 17,500 72°F / 60°F

/ 50%

75.0 352.0 310.8

CRAC-02 19,500 72°F / 60°F

/ 50%

75.0 352.0 310.8

CRAC-03 16,000 72°F / 60°F

/ 50%

75.0 352.0 310.8

CRAC-04 17,500 72°F / 60°F

/ 50%

75.0 352.0 310.8

CRAC-05 9,000 67.4°F /

57.8°F / 50%

15.0 214.8 90.0

CRAC-06 9,000 67.4°F /

57.8°F / 50%

15.0 214.8 90.0

Chilled Water Coil Performance (Baseline):

• Entering Chilled Water Temperature: Ranging from 44.0°F to 54.4°F

(depending on loop conditions)

• Maximum Air Pressure Drop Across Coil: 0.4 in. w.g.

2.3. CRAC Filtration Requirements

• Filter Type: High-capacity Pleated

• Efficiency Rating: MERV 8 minimum (providing at least 70% dust spot efficiency)

• Maximum Initial Pressure Drop: 0.23 in. w.g. @ 500 FPM

3. Chiller Equipment Overview The outdoor utility replacement includes two (2) high-efficiency, air-cooled, packaged scroll chillers operating in a parallel N+1 redundant configuration to supply the indoor CRAC loop.

• Equipment Tags: CH-1 and CH-2

• Cooling Method: Air-Cooled Condenser Coils (utilizing environmentally friendly approved low-GWP refrigerants)

• Compressor Type: Hermetic Scroll (featuring multiple compressors per unit or digital scroll unloading to match partial load swings)

• Location: Outdoor Ground Pad / Chiller Yard

3.1. Chiller Performance & Capacity Specs

Each chiller must meet or exceed the performance capabilities of the legacy 115-Ton baseline units:

• Minimum Capacity (Tons): 115Tons at design ambient conditions

• Design Outdoor Ambient Temperature: 110.0°F

• Chilled Water Flow Rate (GPM): 233.3 GPM per chiller

• Leaving Chilled Water Temperature (LVT): 44.0°F

• Entering Chilled Water Temperature (ENT): ~51.7°F to 52.0°F (yielding a design Delta T of approx. 7.7°F)

• Maximum Evaporator Pressure Drop: 21.2 ft wg (approx. 9.2 psi)

• Minimum Part-Load Efficiency (IPLV): 15.3 EER or better

3.2. Chiller Mechanical & Condenser Specifications

• Condenser Coils: All-aluminum microchannel (MCHX) technology to reduce overall refrigerant charge and operating weight. Coils must feature protective corrosion-resistant e-coat encapsulation to ensure durability in outdoor environments.

• Condenser Fans: Direct-drive, low-sound composite AeroAcoustic vertical discharge fans with protective wire safety guards.

• Low-Ambient Operation: Standard operation down to –20°F ambient

(requiring integrated head-pressure fan controls and factory-installed wind baffles) to support winter-time data center cooling loads.

• Evaporator: Single-pass, brazed plate direct expansion heat exchanger constructed of ANSI 316 stainless steel, insulated with 3/4-in. closed-cell foam and wrapped with factory freeze protection heaters down to -20°F.

4. Electrical Requirements (All Equipment) All indoor and outdoor mechanical systems must be fully compatible with the facility's existing electrical infrastructure:

• Operating Voltage: 460 V AC

• Phase/Frequency: 3 Phase / 60 Hz

• Power Connection: Single-point electrical connection at each unit-mounted terminal block or integrated non-fused disconnect switch.

• Chiller Safety Locks: Electrical components must have high short-circuit current ratings (minimum SCCR of 65 kA) to protect internal motor circuits.

5. Piping, Hydronics & Loop Infrastructure The mechanical contractor must align replacement piping and accessories with the parallel N+1 as-built hydraulic schematic:

• Common Chilled Water Header Flow: Sized for a combined maximum design flow of 466.0 GPM.

• Piping Material: Type-L seamless copper tubing or schedule 40 carbon steel piping with Victaulic-style mechanical couplings to isolate structural vibrations.

• Air Separator: Inline centrifugal-type air separator with automatic air vents installed at the system's highest and warmest return points to prevent loop cavitation.

• Expansion Tank: Diaphragm-type expansion tank, pre-charged and rated for a maximum system working pressure of 150 psig, located on the suction side of the pumps.

• Water Filtration: A 40-mesh Y-strainer with an integrated blow-down ball valve must be installed at each chiller's evaporator inlet.

6. Controls & BMS Integration Both the chillers and the CRAC units must have robust, open-protocol communication cards to integrate seamlessly with the existing Building

Management System (BMS):

• Protocols Supported: Native BACnet MS/TP or BACnet/IP over Ethernet.

• Chiller Plant Automation: The chillers must feature an integrated master/slave parallel control algorithm. The controller must automatically equalize compressor run hours, manage lag chiller staging based on loop temperature reset metrics, and immediately switch leads in the event of a primary circuit fault.

• CRAC Controls: Local microprocessor screens displaying entering/leaving water temperatures, air temperatures, fan status, and alarm history (up to the last 20 alarm logs).

• BMS Control Points Required:

• Entering/Leaving Chilled Water Temperature.

• Compressor and Pump run hours / start count.

• Flow switch verification alarm.

• Water pressure drop calculations (via factory-installed pressure transducers).

• Dynamic demand-limiting status (load shedding).

7. Footprint & Site Coordination

• Indoor Footprint Constraints: CRAC replacement units must fit entirely within the structural limits of the existing Bravo 2000 floor grid (24" x 24" floor panel dimensions, 18" raised floor height).

• Outdoor Pad Clearances: Chillers must fit on the existing concrete equipment pad while maintaining National Electrical Code (NEC) clearances (minimum 4.0 ft clearance on electrical panel doors and 3.5 ft to 6.0 ft airflow clearance around condenser coils).