Specifications - City of Montpelier, Vermont

Montpelier District HeatingCity of Montpelier, VTIssue Date:September 28, 2012Title:15900 – Direct Digital Control SystemPage #:33 of 40c. Wiring otherwise protected by a metallic enclose or approved installationmethod such as permitted cable tray, channel or similar.18. Install in wireway all trunk communication wiring between the Operator Stationand the controllers and between the controllers. Open wiring is not permittedunless specifically accepted.19. Wireway runs shall be parallel or perpendicular to walls, pipes and sides ofopenings. Right angle turns shall be used and passage ways for access andservicing shall not be blocked.20. All trunk or LAN cables shall be 100 percent backed up with spare conductors.21. All conductors shall be identified with typed or machine lettered labels, Bradleyor approved equal. Tag numbers shall agree with wire numbers assigned onwiring diagrams and the installation drawings.D. Open Wiringa. Not PermittedE. Control Device Installation1. Temperature Sensorsa. Wall mounted temperature sensors shall be mounted on electrical boxesand all wire penetrations shall be caulked to prevent thermal convection.b. Sensors installed for outside air measurement and pressurization shall belocated to optimize the accuracy of the measurement.c. Temperature sensors shall be readily accessible and adaptable to eachtype of application in such a manner as to permit quick, easyreplacement and servicing without special tools or skills. Calibratesensors to accuracy specified. In no case will sensors designed for oneapplication be installed for another application such as replacing a ductsensor with a room sensor. Room temperature sensor should not bemounted on exterior walls when other locations are available. Mountcenter line of room sensor at (5 feet) above finished floor.d. Mount duct sensors in locations to sense the correct temperature of theair only, within the vibration and velocity limits of the sensing element.Mount extended surface element, when used, securely within the ductand position to measure the best average temperature. Do not locatesensors in dead air spaces or positions obstructed by ducts or equipment.Thermally isolate elements from brackets and supports to respond to airtemperature only. Surely seal duct penetrations.e. String duct averaging sensors between two rigid supports in a serpentineposition to sense average conditions. Thermally isolate the sensingelements from supports.f. Locate freeze protection sensors in appropriate locations to sense lowesttemperatures, to avoid potential problems with air stratification.DIRECT DIGITAL CONTROL SYSTEMS1597233