Project Delivery Team: CM project manager; mechanical-electrical coordinator; and architect, HVAC, plumbing, electrical, structural, fire protection, and security consultants.

HVAC Project Team: The 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.

Owner’s Building Program: Application 2019 ASHRAE Handbook, “Retail Facilities,” Chapter 2, and “Commercial and Public Buildings,” Chapter 3. Systems and Equipment 2020 ASHRAE Handbook, “Central Cooling and Heating Plants,” Chapter 3, and “Boilers and Hydronic Heating and Cooling,” Chapter 13.

Project Type: New construction and infrastructure (central heating).

References: 2019 ASHRAE Handbook, HVAC Applications; 2020 ASHRAE Handbook, HVAC Systems and Equipment; ASHRAE GreenGuide: Design, Construction, and Operation of Sustainable Buildings; ASHRAE Practical Guide to Seismic Restraints; ASHRAE Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems; ASHRAE Standard 202 (Commissioning Process for Buildings and Systems); and Construction Management Association of America (CMAA).

DESIGN INTENT DOCUMENT (DID)

The HVAC system selection and design intent is based on the processed outlined in ASHRAE Handbook 2020, Chapter 1, “HVAC System Analysis and Selection,” and includes the owner’s building program and additional goals; a finalized system selection that shall consider a central plant heating versus decentralized heating plants; specialized systems that shall include general exhaust, boiler flue exhaust, and boiler plant ventilation; and automatic controls, including a new BAS, temperature controls, furnished equipment controls, a BACnet interface, an internet interface, and a new computerized maintenance management software (CMMS) system from an outsourced operations and maintenance firm.

Program and Project Goals: For the functional goals, refer to Chapter 1 of the 2020 ASHRAE Handbook. Budget goals include first cost and operating cost; the timeline goals include the occupancy due date, pre-purchased equipment date, and phased construction dates; and management goals include property management, out-sourced mechanical and electrical services, service contract(s), and capital projects management.

Available utilities include new natural gas service, electrical service, emergency power, central plant hot water heating, and a BAS.

The heating system will include firetube, gas-fired boilers; two lead-lag boilers; and one summer boiler. 

Boiler Plant Ventilation System: 100% outside air with a VAV control will maintain 0.1-inch positive building pressure. The pre-filter and final filter will be MERV filters. The system will include an outdoor air barometric damper. 

The system will include low-velocity sheet metal (galvanized), boiler breeching (black iron with welded cleanouts), and an outside air louver. The pumps include split case, horizontal, closed-loop, and parallel pumping with secondary pumps in each new building and each pump with a variable frequency drive (VFD).

DESIGN CRITERIA DOCUMENT

• The HVAC design criteria shall be in sync with the project delivery method and owner’s project requirements.
   
• The utility shall be natural gas to serve the new central boiler plant that shall include two firetube hot water boilers and one condensing boiler.
   
• Heating season boilers shall be lead-lag control at 800 boiler horsepower (BHP), each sized at 60% of load and one summer boiler at 200 BHP. The automatic controls furnished with each boiler shall be interfaced with the new BAS.
   
• The new central plant hot water system shall be primary pumps serving the three boilers furnished with VFDs. The pipe distribution shall be installed underground to the new commercial office buildings and connect to new individual pump and stand-by pump, each with VFDs. 
   
• A 100% outdoor air system within the boiler plant shall maintain 65°F in the winter and ventilation in the air conditioning season via a single-duct, single-zone, VAV system. This system shall provide ventilation air, combustion air, and maintain a positive building pressure of 0.1 inch gage.
   
• Filters shall be MERV-8 pre-filter and MERV-14 final filter.  
   
• The air-handling unit’s heating coil shall be an integral, vertical face, and bypass preheat hot water coil.  
   
• Regarding the conceptual/schematic phase, the HVAC design engineer shall provide system flow diagrams with these three documents (OPR, DID, and BOD) along with ATC sequences of operation. 

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