PWS Appendix D - CRAH Units.pdf

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APPENDIX D:

COMPUTER ROOM AIR Handling UNITS

HAW RM 191 CRAH REPLACEMENT

EFFECTIVE DATE: 02 JULY 2019

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PART 1 GENERAL

1.1 SCOPE

This specification details the salient features for computer room air handling (CRAH) units.

PART 2 PRODUCTS

2.1 EQUIPMENT

2.1.1 Computer Room Air Handling (CRAH) Units

The contractor shall procure and install two self-contained units, designed, factory assembled, and factory tested. Each unit must have a cooling capacity of 140 kW, listed in UL Elec Equip Dir or ETL DLP for computer room application. Equipment must have a minimum sensible coefficient of performance (SCOP-127) as defined by ASHRAE STD 90.1 IP Section 6 and ASHRAE STD 127.

Contractor must coordinate with unit manufacturer to provide units with sequential serial numbers.

Units shall be rated for marine environment.

2.1.1.1 Cabinet and Frame

2.1.1.1.1 Unit Cabinet

Unit frame must be minimum 16 gauge welded steel tubes or steel angles and mill-galvanized or coated with an epoxy finish, or an approved manufacturer's standard finish, if equivalent. The contractor is responsible for moving each unit into computer room 191, the height of the lowest doorway is 82 inches.

Exterior panels must be furniture grade steel sheet, minimum of 20 gauge, with a powder-coated or corrosion-inhibiting epoxy finish. Finish color must be a manufacturer’s standard color and approved by the Government if multiple standard color options are available.

Each unit shall have removable panel for access to controls without interrupting airflow. Panels must be gasketed to prevent air leakage under system operating pressure and removable for service access using simple, commonly available tools. Proprietary tools are not acceptable. Condensate pans shall be assembled using a stainless steel, non-corroding, double-sloped, and removable.

Manufacturer’s standard cabinet materials and finishes will be acceptable if considered equivalent to the above requirements by the Government.

2.1.1.1.2 Cabinet Interiors Sound Attenuation

The cabinet shall have a factory-installed sound attenuation system on the interior of the unit cabinet.

The cabinet shall have 1/2 inch of 2 pound per cubic foot high density sound and thermal insulation on interior of cabinet panels. Insulation shall be attached using 100% adhesive coverage and both the insulation and the adhesive must conform to NFPA 90A.

Manufacturer’s standard interior cabinet sound attenuation materials and finished will be acceptable if considered equivalent to the above requirements by the Government.

2.1.1.2 Fan Section

The fans must meet the following requirements:

• Plenum type.

• Single inlet.

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• Dynamically balanced.

• Direct drive, electronically commutated.

• Variable speed.

• Located to draw air over the entire coil and ensure even air distribution and maximum coil performance.

• Speed modulates to maintain under floor pressure.

2.1.1.3 Cooling Coil

The coils shall be assembled of seamless copper tubes with aluminum fins, and slope for drainage for more moisture removal. Condensate drain pan shall be stainless steel with nonferrous connections and internal trap.

2.1.1.4 Condensate Pump

Cooling Coil Condensate Pump Unit must be a packaged unit including a corrosion-resistant pump and automatic controls. Include factory installed check valve and integral float switch. Pump must have a minimum capacity flow rate and net positive suction head to prevent overflow of the condensate drain pan.

2.1.1.5 Electric Reheat

Each CRAH unit shall include electric reheat for dehumidification.

2.1.1.6 Filters

Filters shall be UL listed, 2 inches thick deep pleated fiberglass throwaway type filters with a Minimum Efficiency Reporting Value (MERV) of 8 as determined by ASHRAE 52.2.

2.1.1.7 Chilled Water Control Valve

The water circuit must include a 2-way modulating valve to maintain a 55°F (adjustable) coil leaving air temperature.

2.1.1.8 Insulation

All internal piping, fittings, valves, and appurtenances associated with the piping loop must be insulated during unit fabrication by the manufacturer. Insulation must be secured with contact adhesive.

2.1.1.9 Unit Temperature and Pressure Control

Cooling coil control valve must modulate to satisfy cooling coil leaving air temperature of 55°F (adjustable).

Maximum allowable dead band is 5°F (adjustable).

Provide temperature and humidity sensors at both the unit return air inlet and supply air outlet.

Fan speed must have a variable operation to satisfy underfloor plenum differential air pressure setpoint of

0.02 inch w.g., minimum (adjustable). Each unit must have a differential pressure sensor, the pressure sensor settings must allow the fans to operate between 30-100%. Unit controls must be capable of modulating fan speed to a minimum speed to prevent air from cycling through the unit due to underfloor static pressure greater than room level static pressure.

Units must be capable of operating using zone pressure controls in the computer room. Both units must operate to maintain pressure setpoint.

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2.1.1.10 Control Panel

Each CRAH shall have a control panel with the following features:

a. Color display viewable while the front panel is open or closed.

b. Menu-driven controls including user menus for active alarms, event log, graphic data, unit view/status overview (including the monitoring of room conditions, operational status in percentage of each function, date and time), total run hours, various sensors, display setup and service contacts.

c. Service menus, including setpoints, standby settings (lead/lag), timers/sleep mode, alarm setup, sensor calibration, maintenance/wellness settings, options setup, system/network setup, auxiliary boards and diagnostics/service mode.

d. Password required to make system changes. Coordinate changing default password from factory settings with the Government.

e. Factory installed emergency power off/remote shutdown connection.

f. All wiring over 50 VAC enclosed with a separate hinged cover inside the control panel to provide energized access to control wiring without exposing the higher voltage electrical components.

2.1.1.11 Space Temperature Control System

Each CRAH shall have an integral microprocessor control system including electronic control center, control valves, sensors, wiring, and other appurtenances for workable system. Provide access panel or door in front of unit. Control system must be capable of accepting the following remote sensor connections at a minimum: temperature, pressure, and humidity.

The electronic control center shall be isolated from conditioned airstream to allow service while system is in operation. Control sensors shall be provided in unit for cooling and dehumidifying. High-voltage circuits in system must have individual leg overload protection. Control starters, contactors and relays by 24 volt control circuit.

High-voltage circuit components shall be protected by safety lock, dead-front panel. Mount nonautomatic, molded-case circuit breaker in high-voltage section of electrical panel. Operating mechanism must prevent access to high-voltage electrical components until switched to "OFF" position.

Include the following control capabilities:

a. Capable of changing the setpoints and sensitivity of the space and humidity along with their low and high alarm points.

b. Logging capability of the last 10 alarms and run time.

c. Diagnostics

2.1.1.12 Alarm System

All unit alarms must be annunciated through both audio and visual cues. System must monitor high and low space temperature, high and low space humidity, dirty filters, loss of power, loss of airflow, water flow and humidifier problems. Provide smoke sensor and underfloor water leak-detection cable loop matching the unit footprint. Provide field accessible local audible alarm with silence pushbutton. Provide push-to-test lamps or all-lamp test pushbutton. Provide local signal devices for remote audible and visual alarming capability for the above specified alarm conditions through BACnet or Modbus TCP/IP communication.

2.1.1.13 Alarm and Temperature Control Systems Requirements

Each CRAH shall have the appropriate communication card or hardware to support connecting systems to the site building automation system. The communication protocol must be BACnet or Modbus TCP/IP, in accordance with site requirements. The communication must occur without additional gateways or proprietary software. The unit must not have wifi, web servers or web interfaces installed or available to

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UNCLASSIFIED Page 4 of 5 allow for connection to the building automation system or a separate network. Each unit must have capacity for the addition of end-user readable and writable adjustable setpoints.

Modbus registers must be capable of providing the ability for the building automation system to read and write to all unit setpoint registers and read only to all other registers. At a minimum, provide 31 registers with the following points: Local Off Alarm, Loss of Airflow Alarm, Change Filters Alarm, High Temperature Alarm, Low Temperature Alarm, High Humidity Alarm, Low Humidity Alarm, Man Fan Overload Alarm, Smoke Detected Alarm, Loss of Water Alarm, Humidity Setpoint, Temperature Setpoint, Unit On/Off, Fan Motor Run Hours, High Humidity Alarm Setpoint, High Temperature Alarm Setpoint, Humidity Setpoint, Low Humidity Alarm Setpoint, Low Temperature Alarm Setpoint, Temperature Setpoint, Temperature Tolerance Setpoint, % Capacity Status, Cooling Status, Dehumidification Status, Humidity Status, Temperature Status, Unit Status.

2.1.1.14 Building Automation System Interface

Provide units with communication cards, switches, and other BAS connections that are IPV6 compliant.

Additionally the CRAH shall be configured with MODBUS TCP or MODBUS RTU(485) communication cards.

2.1.1.15 Air Return and Delivery Orientation

Provide units with downflow discharge, top return, draw-thru cooling coil, and which discharge air into a raised floor plenum with an acoustically-lined multiple turning vane elbow provided to direct the flow of air away from the back of the unit.

2.1.1.16 Floorstand

Each CRAH shall be provided with an elevating floorstand for freestanding installation on the main building floor. Floorstand must elevate the unit to the height of the new raised access floor (approximately 18 inches) and allow for leveling and locking at the desired height, and have adjustable legs with vibration isolation pads. Unit must be fully gasketed (rubber or neoprene) to prevent air leakage at the raised floor penetration. Floor stand shall include a turning vane.

2.1.2 Electrical

2.1.2.1 Electrical Motors, Controllers, Contactors, and Disconnects

Each CRAH unit shall be provided with the following respective pieces of equipment: motors, controllers, contactors, and disconnects conforming to all current national and local codes. Controllers and contactors shall be provided with control circuits not to exceed unit input voltage or utility power voltage, and auxiliary contacts for use with controls provided. Motors must be variable-frequency.

2.1.2.2 Disconnect Switch

Each CRAH unit shall be provided with a factory-installed lockable disconnect switch to disrupt the flow of power to the unit for each power source.

2.1.2.3 Dual Power Source

Each CRAH unit shall be provided with a factory-installed, automatic, dual power source connection. Dual power source connection must automatically and safely transfer power source from utility power to emergency backup source.

2.1.2.4 ISC Rating

Equipment and installation must comply with NFPA 70 Articles 110.9 and 110.10.

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2.2 ACCESSORIES

2.2.1 Nameplates

Nameplates must be stainless steel and include at the minimum the following information:

a. Project name.

b. Customer order number

c. Equipment designation

d. Manufacturer’s name

e. Manufacturer’s address

f. Date manufactured

g. Type and Style

h. Model, catalog (if applicable) and serial numbers

PART 3 EXECUTION

Not used.

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