Specifications - City of Montpelier, Vermont

Montpelier District HeatingCity of Montpelier, VTIssue Date:September 28, 2012Title:15900 – Direct Digital Control SystemPage #:30 of 40b. Twoway valves position versus flow relation shall be equal percentagefor water flow control.c. Maximum pressure drop through valve:1.) Modulating water flow control, greater of 10 feet of water or thepressure drop through the apparatus, unless otherwise indicatedor scheduled in the contract documents.N. Miscellaneous Output Devices1. Electronic Signal Isolation Transducersa. Whenever an analog output signal from the Control System is to beconnected to an external control system as an input (such as a chillercontrol panel), or is to receive as an input a signal from a remote system,provide a signal isolation transducer.b. Signal isolation transducer shall provide ground plane isolation betweensystems.c. Signals shall provide optical isolation between systems.2. Line Voltage Thermostats:a. Use single or two pole as required, with minimum rating equal toelectrical load of device being controlled. Provide integral manualOn/Off/Auto selector switch, maximum dead band of 2/F, concealedtemperature adjustment, and locking cover.3. Remote Bulb Thermostats:a. One or twopipe, proportioning, direct or reverse acting to match devicebeing controlled. Thermostat to have adjustable setpoint and throttlingrange. Capillary to remote bulb shall be armored.4. Immersion Type Thermostat Sensors:a. Rod and tube type with linear output. Provide separable wells with heatconductive fluid for installation in pipeline. Units shall be factorycalibrated.PART 3 EXECUTION3.1 INSTALLATIONA. Identification1. All I/O field devices (except space sensors) that are not mounted within fieldinstalled panels (FIPs) shall be identified with name plates.2. All I/O field devices inside FIPs shall be labeled.3. The identification shall match all documentation and identify the function (i.e.mixed air temperature sensor).4. Calibration settings shall be marked with paint or indelible ink.5. Each terminal strip termination shall be tagged with an identification thatmatches the control drawings.6. The outside of each FIP shall be identified with a bakelite label matching theidentification name shown on the drawings.DIRECT DIGITAL CONTROL SYSTEMS1597230