Project Delivery Method: Construction management @ risk (CM) with guaranteed maximum price (GMP)
Project Type: New construction and infrastructure (central cooling)
Owner Team: Data center owner, owner representative (consultant), project manager of capital projects, and facility manager
Project Delivery Team: CM project manager; mechanical-electrical coordinator; and HVAC, plumbing, electrical, structural, and security consultants
HVAC Project Team: HVAC project manager; automatic temperature control (ATC) technician subcontractor; building automation system (BAS) subcontractor; third-party commissioning consultant (CxC);, and third-party testing, adjusting, and balancing (TAB) Technician
Application 2019 ASHRAE Handbook: Chapter 20, “Data Centers and Telecommunication Facilities”
HVAC Systems and Equipment 2020 ASHRAE Handbook: Chapter 3, “Central Cooling and Heating Plants,” and Chapter 43, “Liquid-Chilling Systems”
References: 2019 ASHRAE Handbook – HVAC Applications, 2020 ASHRAE Handbook, HVAC Systems and Equipment; and Construction Management Association of America (CMAA)
Other References: ASHRAE Fundamentals of Design and Control of Central Chilled-Water Plants; ASHRAE Standard 202 (Commissioning Process for Buildings and Systems); ASHRAE Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems; and ASHRAE Guideline 22, Instrumentation for Monitoring Central Chilled-Water Plant Efficiency.
DESIGN INTENT DOCUMENT (DID)
- This optimum HVAC system selection and the project’s design intent is based on the analytical processed outlined in ASHRAE Handbook 2020, Chapter 1, “HVAC System Analysis and Selection” and includes the following:
- Owner’s project requirements (OPR), building program goals, and additional goals
- The finalized system selection shall be a remote outdoor central chiller plant and electrical generator to provide standby cooling and power to serve an existing data center
- Automatic controls shall include new system automatic controls interfaced with the existing BAS controls, equipment furnished controls, BACnet interface, internet interface, and populating new equipment data into the existing computerized maintenance management software (CMMS) system from in-house operation and maintenance (O&M) staff
- Functional Goals: (refer to Chapter 1, 2020 Handbook)
- Budget Goals: First cost and operating cost
- Timeline Goal(s): Installation due date and pre-purchased equipment date
- Management Goals: Data center management, in-house mechanical and electrical services, service contracts for new equipment, and capital projects management
BASIS OF DESIGN (BofD) DOCUMENT
- The HVAC BofD criteria shall be in sync with the project delivery method and owner’s project requirements.
- The utility shall consist of existing electrical 480-V power and natural gas service to serve the new gas-fired, 100-ton, standby liquid chiller and associated air-cooled condenser with a new 50-kW emergency generator to serve the new chiller installation. All new equipment shall be located outdoors adjacent to the existing chiller room and electrical room. Equipment shall be located on a 20-by-20-foot concrete pad. Chilled water pumps shall be existing VSD end-suction pump and standby pump connected inside the existing chiller room to the new outdoor standby plant.
- Standby Mode of Operation: The data center’s four chilled water-cooled, 25-ton computer room air conditioning (CRAC) units and their central chiller plant shall be backed up by a new standby chiller and emergency electrical power installation to provide emergency cooling should the existing, single chiller and/or associated cooling tower fail or are required to be shut down for central plant maintenance.
- Standby Chiller Installation: Existing chilled water valve with associated two-position diverting valves shall isolate the exiting central plant and open flow to the new standby chiller for chilled water supply to the data central CRAC units. The new chiller self-contained automatic controls shall be interfaced with the existing BAS system. Existing controls shall also include an interface with the building security system and electrical power distribution.
- The existing chilled water supply pump with variable flow to the four CRAC unit chilled water coils shall continue to operate in standby mode of operation with the new emergency generator operating to provide electrical power to the gas-fired chiller.
- The new pipe distribution shall be insulated and installed to serve the outdoor chiller and generator in their weather-tight enclosures. Propylene glycol antifreeze solution shall be added to the chilled water system to protect the outdoor piping installation.
- Conceptual/Schematic Phase General Notes:
- The HVAC design engineer shall provide system flow diagrams with the three documents (OPR, DID, and BofD) along with ATC sequences of operation that is integrated with the existing BAS control system and electrical one-line diagram.
- The HVAC design engineer shall include an electrical data sheet to coordinate with the electrical design engineer, a plumbing data sheet to coordinate with the plumbing design engineer, and equipment and distribution weights to coordinate with the structural design engineer and security consultant.
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