2021-414-E-AMS-Riggs-Harrod Builders, Inc-SHSC Roof & HVAC Replacement

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Southern Human Services Center Smith Sinnett /2020072 HVAC and Roof Renovations Orange County,North Carolina VAV PACKAGED DX RTU 23 74 00 - 5 8.Lead refrigeration circuit shall be provided with hot gas reheat coil,modulating valves, electronic controller,supply air temperature sensor and a control signal terminal which allow the unit to have a dehumidification mode of operation,which includes supply air temperature control to prevent supply air temperature swings and overcooling of the space. 9.Unit shall be configured as an air-source heat pump.Each refrigeration circuit shall be equipped with a factory installed liquid line filter drier with check valve,reversing valve, accumulator,and expansion valves on both the indoor and outdoor coils.Reversing valve shall energize during the heat pump cooling mode of operation. L.Condensers 1.Air-Cooled Condenser a.Condenser fans shall be a vertical discharge,axial flow,direct drive fans. b.Coils shall be designed for use with R-410A refrigerant.Coils shall be multi-pass and fabricated from aluminum microchannel tubes. c.Heat pump outdoor coil shall be constructed of copper tubes with aluminum fins mechanically bonded to the tubes and aluminum end casings.Fin design shall be sine wave rippled. d.Coils shall be designed for a minimum of 10°F of refrigerant sub-cooling. e.Coils shall be hydrogen or helium leak tested. f.Condenser coils shall include corrosion-resistant,electrostatically-applied coating rated for 5,000 hours in accordance with ASTM B117. g.Condenser fans shall be high efficiency electrically commutated motor driven with factory installed head pressure control module.Condenser airflow shall continuously modulate based on head pressure and cooling operation shall be allowed down to 35°F with adjustable compressor lockout. h.Condenser fans shall be VFD driven variable speed for condenser head pressure control. Factory provided and factory programmed VFDs shall continuously modulate the fan air flow to maintain head pressure at acceptable levels.Cooling operation shall be allowed down to 35°F with adjustable compressor lockouts. M.Filters 1.Outdoor air hood shall have a aluminum mesh filter section. 2.Unit shall include 2 inch thick,pleated panel filters with an ASHRAE efficiency of 30%and MERV rating of 13,upstream of the cooling coil. 3.Unit shall include 0-100%economizer consisting of a motor operated outside air damper and return air damper assembly constructed of extruded aluminum,hollow core,airfoil blades with rubber edge seals and aluminum end seals.Damper blades shall be gear driven and designed to have no more than 20 cfm of leakage per sq ft.at 4 in.w.g.air pressure differential across the damper.Low leakage dampers shall be Class 2 AMCA certified,in accordance with AMCA Standard 511.Damper assembly shall be controlled by spring return enthalpy activated fully modulating actuator.Unit shall include outside air opening bird screen,outside air hood,and barometric relief dampers. 4.Economizer shall be furnished with return air CO2 override. N.Controls 1.Factory Installed Controller a.The unit shall come with a factory programmed and supplied controller that provide all programming and functionality for the unit to operate,including internal safeties. b.All sensors required for the operation of the unit shall be factory furnished.This includes outside air temperature and humidity sensors,supply air temperature and humidity sensors,coil suction pressure and temperature sensors,space temperature and humidity sensors,preheat discharge temperature sensor,and other sensors as required to implement the sequence of operations.Refer to sequence on Drawings. O.Accessories 1.Unit shall be provided with a smoke detector in the supply of the unit,wired to shut off the unit’s control circuit. 2.03 CURBS A.Refer to Vibration and Isolation Section. DocuSign Envelope ID: 94E7997D-4F29-42F6-A9B4-0A160438D2A6