Specifications - City of Montpelier, Vermont

Montpelier District HeatingCity of Montpelier, VTIssue Date:September 28, 2012Title:15900 – Direct Digital Control SystemPage #:35 of 40b. Install high pressure side of the differential switch between pumpdischarge and check valve.c. Install snubbers and isolation valves on steam pressure sensingapplications.3. Signal Transmission System Equipmenta. General: Install all system components in accordance with the NationalElectrical Code and other applicable codes as necessary in accordancewith the manufacturers’ recommendations.b. Splices: Splices in shielded and coaxial cables shall consist ofterminations and the use of shielded cable couplers. Terminations shallbe in accessible locations. Cables shall be harnessed with cable ties.c. Equipment: Fit all equipment contained in cabinets or panels withservice loops, each loop being at least 12 inches long. Equipment forfiber optics system shall be rack mounted, as applicable, in ventilated,selfsupporting, code gauge steel enclosure. Cables shall be supportedfor minimum sag.4. Control Valvesa. Valve operators shall be installed directly above the controlled valvewhenever possible unless rotation is needed to permit maintenanceaccess. However, in no case shall the operator be rotated beyond 80°from the vertical centerline of the valve.3.2 DAMPER AND VALVE ACTUATOR APPLICATIONSA. All valve and damper actuators for VAV, ECV, reheat coils, and perimeter heating shallbe electronic.B. Damper and valves actuators for AHU and other large equipment shall be electronic.3.3 CONTROL SCHEMATICS COORDINATIONA. The control schematics on the engineered drawings imply minimum functionalexpectations and may require enhancement and expansion by the Contractor to meet allspecifications.3.4 PROGRAMMINGA. Point Naming. Name points as shown on the equipment points list provided with eachsequence of operation. See Section 15910 Sequences of Operation. Where multiplepoints with the same name reside in the same controller, each point name may becustomized with its associated Program Object number. For example, "Zone Temp 1"for Zone 1, "Zone Temp 2" for Zone 2. In general, provide plainlanguage names forpoints that reference the equipment or the geometric space served.B. Software Programming. Programming shall provide actions for each possible situation.Graphic or parameterbased programs shall be documented. Textbased programs shallbe modular, structured, and commented to clearly describe each section of the program.DIRECT DIGITAL CONTROL SYSTEMS1597235