2018-425-E AMS - Sasser Companies Annex upfit

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DocuSign Envelope ID: 9826C043- 4C32- 49CD- A4CC- DC28ABAB7CE7 SECTION 238147 — DEDICATED OUTDOOR AIR SYSTEM ant circuit from ambient condition of 0- -120 °F. Mechanical cooling shall be provided to 25° F. The motor shall include thermal overload protection and protect the motor in the case of excessive motor temperatures. The motor shall have phase failure protection and prevent the motor from operation in the event of a loss of phase. D. The condenser fan shall be low noise blade design. Fan blade design shall be a dynamic profile for low tip speed. Fan blade shall be of a composite material. E. The unit shall have scroll compressors. One of the compressors shall be an inverter compressor providing proportional control. The unit controller shall control the speed of the compressor to main- tain the discharge air temperature. The inverter compressor shall have a separate oil pump and an oil separator for each compressor that routes oil back to the compressor instead of through the dis- charge line. F. Pressure transducers shall be provided for the suction pressure and head pressure. Temperature sensor shall be provided for the suction temperature and the refrigerant discharge temperature of the compressors. All of the above devices shall be an input to the unit controller and the values be dis- played at the unit controller. G. Refrigerant circuit shall have a bypass valve between the suction and discharge refrigerant lines for low head pressure compressor starting and increased compressor reliability. When there is a call for mechanical cooling the bypass valve shall open to equalizing the suction and discharge pres- sures. When pressures are equalized the bypass valve shall close and the compressor shall be al- lowed to start. H. Each circuit shall be dehydrated and factory charged with R-41 OA Refrigerant and oil. 2.014 ELECTRICAL A. Unit wiring shall comply with NEC requirements and with all applicable UL standards. All electrical components shall be UL recognized where applicable. All wiring and electrical components provided with the unit shall be number and color -coded and labeled according to the electrical diagram pro- vided for easy identification. The unit shall be provided with a factory wired weatherproof control panel. Unit shall have a single point power terminal block for main power connection. A terminal board shall be provided for low voltage control wiring. Branch short circuit protection, 115 -volt control circuit transformer and fuse, system switches, and a high temperature sensor shall also be provided with the unit. Each compressor and condenser fan motor shall be furnished with contactors and in- herent thermal overload protection. Supply fan motors shall have contactors and external overload protection. Knockouts shall be provided in the bottom of the main control panels for field wiring en- trance. B. A single non -fused disconnect switch shall be provided for disconnecting electrical power at the unit. Disconnect switches shall be mounted internally to the control panel and operated by an exter- nally mounted handle. 2.015 CONTROLS A. Provide a complete integrated microprocessor based Direct Digital Control (DDC) system to con- trol all unit functions including temperature control, scheduling, monitoring, unit safety protection, in- cluding compressor minimum run and minimum off times, and diagnostics. This system shall consist of all required temperature sensors, pressure sensors, controller and keypad /display operator inter- face, programming / sequence, etc.. All MCBs and sensors shall be factory mounted, wired and test- ed. B. The stand -alone DDC controllers shall not be dependent on communications with any on -site or remote PC or master control panel for proper unit operation. The microprocessor shall maintain ex- isting set points and operate stand alone if the unit loses either direct connect or network communi- cations. The microprocessor memory shall be protected from voltage fluctuations as well as any ex- tended power failures. All factory and user set schedules and control points shall be maintained in nonvolatile memory. No settings shall be lost, even during extended power shutdowns. C. The DDC control system shall permit starting and stopping of the unit locally or remotely. The control system shall be capable of providing a remote alarm indication. The unit control system shall provide for outside air damper actuation, emergency shutdown, remote heat enable /disable, remote cool enable /disable, heat indication, cool indication, and fan operation. Reece, Noland & McElrath, Inc. 238147-6 Orange County Board of Elections Orange Co., NC 05/04/18