Specifications - City of Montpelier, Vermont

Montpelier District HeatingCity of Montpelier, VTIssue Date:September 28, 2012Title:15900 – Direct Digital Control SystemPage #:34 of 40g. When possible locate outside air temperature sensors on north side of thebuilding, away from exhaust hoods, air intakes and other areas that mayeffect temperature readings. Provide sun shields to protect outside airsensors from direct sunlight.h. Provide thermometers at locations indicated. Mount thermometers toallow readability when standing on the floor.i. Any room thermostats mounted on an exterior wall shall be mounted ona thermally insulated subbase.j. When specified provide guards on thermostats in entrance hallways,other public areas, or in locations where thermostat is subject to physicaldamage.k. Low Limit Thermostats (Freeze stats)1.) The freezestats used on fan shutdown control shall be wired so asto stop the fan in both the Auto and Hand positions of the HOAswitch.2.) Install low limit controls where indicated on the drawings or asspecified. Unless otherwise indicated, install sensing element onthe downstream side of heating coils.3.) Mount units using flanges and element holders. Provide ductcollars or bushings where sensing capillary passes throughsheetmetal housings or ductwork; seal this penetration toeliminate air leakage.4.) Distribute (serpentine) sensing element horizontally across thecoil to cover every square foot of coil; on larger coils this mayrequire more than one instrument. Install controls at accessiblelocation with mounting brackets and element duct collars whererequired. Freezestats shall be installed with capillaries supportedby nonmetallic standoffs. No part of the capillary shall otherwisetouch the coil or frame. Provide mounting support for thecapillary at least every 36 inches and at the capillary end within 6inches.5.) Freezestats capillary length shall be (by multiple Freezestat unitsif necessary to meet this requirement) one foot of capillary foreach four square feet of coil surface, but in all cases the coil faceshall be completely crossed from corner to corner with theFreezestat mounted at or equal to the highest capillary point so asto maintain calibration.2. Pressure Sensorsa. Install pressure sensing tips in locations to sense appropriate pressureconditions and at locations shown on the drawings.DIRECT DIGITAL CONTROL SYSTEMS1597234