Specifications - City of Montpelier, Vermont

Title:Montpelier District HeatingCity of Montpelier, VT15910 – Sequences of OperationsIssue Date:September 28, 2012Page #:8 of 112. Occupied, Hot Water System Offa. When the hot water system is off, operate the Unit Ventilator andadjust the position of the damper to maintain the space setpoint(ventilation cooling).3. Unoccupied, Hot Water System Offa. Disable the Unit Ventilator fan and close the damper.4. Occupied, Hot Water System Ona. Engage the fan motorb. Modulate the position of the outside air damper to maintain roomtemperature setpoint, keeping the hot water valve closed.c. If the damper reaches the minimum, occupied position, open thehot water control valve to maintain the room temperature setpoint.d. If the lowtemperature thermostat (freezestat) activates, signal analarm at the HMI, disable the fan motor, close the outside airdamper and open the heating control valve fully.5. Unoccupied, Hot Water System Ona. Disable the fan motorb. Close the outside air damperc. Adjust the hot water control valve to maintain space temperature(convective air currents across the hot water coil provide motiveforce for the air)d. If the space temperature falls 5 degrees below setpoint (adjustable)for one hour (adjustable) start the fan motor, keeping the outdoorair damper closed and operate with the hot water control valvefully open until the space temperature rises 5 degrees above thesetpoint (adjustable), then disable the fan and modulate the hotwater coil valve to maintain the space temperature setpointe. With the fan motor off monitor the mixed air temperature andcompare it with the room temperature. If the mixed air temperatureis 10 degrees (adjustable) lower than the room air temperature, it islikely outdoor air is leaking into the unit ventilator (damper stuckopen). Signal an alarm at the HMI and open the hot water valvefully until the alarm is reset by a human operator at the HMI.D. Unit Ventilators and Radiators1. Certain rooms have unit ventilators and hot water radiation forsupplemental heating.2. Occupied/Unoccupieda. Retain the existing occupied/unoccupied schedules and setpointsfor each unit ventilator3. Occupied, Hot Water System OffSEQUENCE OF OPERATION159108