Early Procurement Package Rotary-Screw Compressor Water Chiller Walker Complex HVAC and BAS Repairs (SCO ID# 25-29576-02B)

Walker HVAC & BAS Renovation- Early Procurement CD Bid
North Carolina Central University
1 SECTION 236426 - ROTARY-SCREW COMPRESSOR WATER CHILLERS
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3 PART 1 - GENERAL
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6 QUALITY ASSURANCE
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8 AHRI Compliance:
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10 Fabricate, test, and certify chillers to comply with AHRI Standard 550/590, Water-Chilling Packages Using
11 the Vapor Compression Cycle.
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13 Rate air-cooled chillers sound power levels according to AHRI 270, Sound Rating of Outdoor Unitary
14 Equipment, or AHRI 370, Sound Rating of Large Outdoor Refrigerating And Air-Conditioning Equipment, as
15 applicable.
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17 ASHRAE Compliance:
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19 Fabricate and install rotary water chillers to comply with ASHRAE 15, Safety Code for Mechanical
20 Refrigeration.
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22 Comply with ASHRAE 147 for refrigerant leaks, recovery, handling, and storage requirements.
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24 UL Compliance: Fabricate rotary water chillers to comply with UL 465, Central Cooling Air Conditioners.
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26 ASME Compliance: Fabricate and stamp rotary water chillers to comply with ASME Boiler and Pressure Vessel
27 Code, Section VIII, Division 1.
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29 North Carolina Building Code Compliance: Electric drive water chillers shall meet or exceed the minimum efficiency
30 rating required by the North Carolina State Building Code: Energy Conservation Code when tested, rated, and
31 certified in accordance with AHRI 550/590.
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33 Extended Warranty: The Contractor shall provide an extended parts and labor warranty on each refrigeration
34 compressor in addition to guarantees and warranties required under the General Conditions to the
35 Construction Contract.
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37 The parts portion of the warranty shall be directly from the manufacturer to the Owner.
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39 The labor portion of the warranty shall also be provided directly from the manufacturer to the Owner.
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41 Exception: Where a manufacturer labor warranty is not available, the Contractor shall provide a
42 labor warranty directly to the Owner.
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44 This warranty shall provide for repair or replacement of the covered compressor, including removal and/or
45 replacement of refrigerant, that becomes inoperative as a result of defects in materials or workmanship
46 within 4 years after the date ending the initial 1-year guarantee period for the Project.
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54 SUBMITTALS
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56 General: Submittals shall demonstrate compliance with technical requirements by reference to each subsection of
57 this specification. Where a submitted item does not comply fully with each and every requirement of the
58 Specifications, the submittal shall clearly indicate such deviations. Identification requirements for non-complying
59 features of items are very specific. See submittal appendix for exact requirements.
Rotary-Screw Compressor Water Chillers 236426-1

Walker HVAC & BAS Renovation- Early Procurement CD Bid
North Carolina Central University
1
2 Manufacturer's Data: Submit manufacturer's product data, including rated capacities, weights (shipping, installed,
3 and operating), furnished specialties and accessories, and installation and start-up instructions.
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5 Provide documentation of chiller compliance with Section 506.2.1(6) of the 2018 NC Energy Code.
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7 Provide documentation of chiller compliance with Section 503.4.7 of the 2018 NC Energy Code. Include in
8 documentation compressor staging/cycling and hot gas bypass control.
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12 PART 2 - PRODUCTS
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15 AIR-COOLED CHILLERS
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17 General: Provide factory-assembled and tested multi-compressor outdoor air-cooled liquid chillers as indicated,
18 consisting of at least two compressors, evaporator, condensers, thermal expansion valves, and control panels.
19 Provide capacity and electrical characteristics as scheduled.
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21 Refrigerant: Chiller shall utilize 513a
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23 Housing: Provide manufacturer's standard equipment housing construction, corrosion protection coating, and exterior
24 finish. Provide removable panels and/or access doors for inspection and access to internal parts and components.
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26 Rotary Screw Compressors:
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28 General: Provide multiple positive-displacement direct drive rotary twin screw compressors with
29 hermetically sealed casing, operating at not more than 3600 rpm. Maximum single compressor capacity
30 shall not exceed 50 tons.
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32 Each compressor shall be piped as an a separate and independent refrigerant circuit so that in the event of
33 failure of any one compressor, the remaining compressors shall continue to operate.
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35 Each circuit shall include a thermal-expansion valve, refrigerant charging connections, a hot-gas muffler,
36 compressor suction and discharge shutoff valves, a liquid-line shutoff valve, a replaceable-core filter-dryer, a
37 sight glass with moisture indicator, a liquid-line solenoid valve, and an insulated suction line.
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39 Provide each compressor with crankcase oil heater and suction strainer.
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41 Compressor motors shall be high-torque, two-pole induction type with inherent thermal-overload protection
42 on each phase, hermetically sealed and cooled by refrigerant suction gas.
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44 Provide full voltage, across the line starters in accordance with NEMA ICS 2, Class A, full voltage, non-
45 reversing. for each compressor.
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47 Mount individual compressors on vibration isolators.
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49 Construction:
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51 Casing shall be cast iron with gasket-sealed casing joints, machined to provide minimum, uniform
52 clearance for the rotors.
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54 Rotors shall be forged steel with asymmetric profiles.
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56 Provide sleeve or roller bearings in accordance with ABMA 9 or ABMA 11 to adequately contain
57 both radial and axial loadings and maintain accurate rotor positioning at all pressure ratios, with
58 L10 life rating of at least 200,000 hours.
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Rotary-Screw Compressor Water Chillers 236426-2

Walker HVAC & BAS Renovation- Early Procurement CD Bid
North Carolina Central University
1 Provide check valve on compressor discharge to prevent rotor backspin.
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3 Compressors shall be designed to provide access to compressor components for inspection,
4 maintenance, and repair.
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6 Open-Drive Shaft: For chillers with open drives, provide flexible disc with all-metal construction and no
7 wearing parts or need for lubrication. Provide spring loaded, precision carbon ring, high temperature
8 elastomer "O" ring static shaft seal, and stress-relieved, precision lapped collars. The entire shaft seal
9 cavity shall be at low pressure, and shall be vented to the oil drain from the compressor.
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11 Lubrication System: Provide oil separator on discharge of compressor to provide minimum 99% separation
12 prior to refrigerant entering condenser. Main oil reservoir shall be located so as to provide gravity lubrication
13 of rotor and rotor bearings during startup and coastdown; system differential pressure shall provide proper
14 oil flow during normal operation. Provide crankcase oil heater as required.
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16 Capacity Control: Achieve by use of compressor staging, for multi-compressor units, and individual
17 compressor slide valves, which shall provide fully modulating capacity control from 100% to 10% of full load.
18 Slide valves shall be actuated by oil pressure, controlled by external solenoid valves, via the chiller integral
19 controls.
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21 Lubrication System: Provide oil separator on discharge of compressor to provide minimum 99% separation
22 prior to refrigerant entering condenser. Main oil reservoir shall be located so as to provide gravity lubrication
23 of rotor and rotor bearings during startup and coastdown; system differential pressure shall provide proper
24 oil flow during normal operation.
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26 Capacity Control: Achieve by use of compressor staging and compressor slide valves, which shall provide
27 fully modulating capacity control from 100% to 10% of full load. The slide valve shall be actuated by oil
28 pressure, controlled by external solenoid valves via the chiller integral controls.
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30 Evaporator:
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32 Shell and Water Boxes: Fabricated from welded carbon steel plate. Provide 150 psig maximum working
33 pressure water boxes and nozzle connections. Provide vents, drains, and covers in water boxes to permit
34 tube cleaning within the space shown on the Drawings. Provide suitable tappings in the water boxes and
35 nozzles for control sensors, gages, and thermometers.
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37 Water Heads: Provide standard water boxes with grooved mechanical or flanged piping connections and
38 piping shall be arranged so that heat exchanger heads can be easily removed for maintenance.
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40 Tube Sheets: Fabricated of carbon steel sheets welded to the shell and drilled for tubes. Include
41 intermediate tube support sheets as required to prevent tube vibration.
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43 Tubes: Individually replaceable, finned, seamless copper tubes; removable from either end of the heat
44 exchanger without effecting strength and durability of the tube sheets and without causing leakage in
45 adjacent tubes. Expand ends of tubes in tube sheets and intermediate tube support sheets for tight fit to
46 prevent vibration of tubes. Provide suitable baffles or distributing plates in condenser tubes to evenly
47 distribute refrigerant discharge gas on heat transfer tubes.
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49 Pressure Limiting and Pressure Relief Devices: Manufacturer's standard complying with ASHRAE 15.
50 Provide refrigerant charging and transfer connections, pressure relief device on the evaporator to prevent
51 excessive pressure in refrigerant side, and means to sense refrigerant pressure or temperature. Pressure
52 relief valve shall close once pressure is reduced below setpoint pressure.
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54 Heater: Provide electrical resistance heater to protect evaporator to protect against freezing at -20 deg. F
55 ambient at no-flow condition.
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57 Evaporator Freeze Protection: Insulate evaporator as specified above with additional insulation and electric heat
58 tracing tape to protect the evaporator from freezing down to -20oF ambient temperature and zero wind velocity. Heat
59 tape power shall be supplied from integral chiller single point connection hereinafter specified. Wire the chilled water
Rotary-Screw Compressor Water Chillers 236426-3

Walker HVAC & BAS Renovation- Early Procurement CD Bid
North Carolina Central University
1 pump to start and initiate a freeze protection alarm whenever the chilled water temperature falls to 38oF or lower.
2 Provide 120v dry contact and interface the freeze protection alarm with building controls.
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4 Air-Cooled Condenser: Plate-fin coil with integral sub-cooling on each circuit, rated at 450 psig. Construct coils of
5 copper tubes mechanically bonded to aluminum fins, factory-coated with epoxy-phenolic after fabrication.
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7 Condenser Fans: Direct-drive propeller type with statically and dynamically balanced fan blades, arranged
8 for vertical air discharge.
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10 Fan Motors: Totally enclosed nonventilating (TENV) or totally enclosed air over (TEAO) enclosure, with
11 permanently lubricated bearings, and having built-in overcurrent- and thermal-overload protection.
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13 Provide condenser coils with louvers, baffles, or hoods to protect against hail damage.
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15 Pump-out System: Include compressor and drive, piping, wiring, motor starter, and manual isolation valves so that
16 entire refrigerant charge can be contained and isolated in the evaporator.
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18 Unit Controller: Provide BACnet compatible controller capable of interfacing with Building Automation System.
19 Provide (at minimum) control points as follows:
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25 Refrigerant Flow Control Devices: Provide refrigerant flow control devices between evaporator and condensers (and
26 elsewhere as required) to regulate refrigerant flow at volume and pressure required to maintain evaporator liquid
27 refrigerant at level sufficient to keep cooler heat transfer tubes adequately wetted through full range of chiller
28 operation.
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30 Design devices to permit chiller operation at scheduled conditions, and to allow condenser entering water
31 temperature to decrease to minimum permissible temperature or 1 deg. F above return chilled water temperature.
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33 Safety Controls:
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35 Design cutouts to operate independently and factory wire to control panel.
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37 Design controls to stop compressor motor in event of low refrigerant pressure or temperature in evaporator,
38 high condenser pressure, high compressor discharge temperature, low evaporator leaving water
39 temperature ("freezestat"), high motor temperature, high bearing temperature, low oil pressure, high oil
40 temperature, compressor motor overcurrent or over voltage, loss of phase, or power interruption.
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42 Design each cutout to require manual re-starting of compressor in event of safety failure but allowing
43 automatic restart after power interruption.
Rotary-Screw Compressor Water Chillers 236426-4

Walker HVAC & BAS Renovation- Early Procurement CD Bid
North Carolina Central University
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2 Provide anti-recycle timer for limiting compressor motor restarts at scheduled time intervals.
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4 Operational Controls: Provide controls to ensure that compressor will start only under unloaded condition.
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6 Provide sequencing controls to ensure lubrication of compressor motor bearings and seals (if any). Sequence as
7 follows:
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9 Run lubrication system oil pump so that compressor motor bearing is lubricated before start-up.
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11 Start compressor motor.
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13 Provide lubrication during coast-down after compressor motor shut-down.
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15 Design controls to automatically restart compressor after power failure interruptions, provided minimum time between
16 starts has been complied with.
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18 Manual Control and Display Panel: Factory-mounted and wired. Provide gages or meters to indicate low refrigerant
19 pressure in evaporator, high condenser pressure, and low oil pressure.
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21 Provide operator manual input functions designed to permit indicated operations including the following:
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23 Manual and automatic operation of oil pump.
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25 Manual and automatic operation of oil separator heater.
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27 Provide pilot lights or visual display for indicated operations and cutouts including the following:
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29 Oil pump operation
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31 Low chilled water temperature cutout
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33 Low evaporator refrigerant pressure or temperature cutout
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35 High condenser pressure cutout
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37 High motor winding temperature cutout
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39 Low oil pressure cutout
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41 Motor overload cutout
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43 Insulation: Insulate evaporators and all other cold surfaces to prevent condensation, with ambient humidity of 75
44 percent and dry-bulb temperature of 90 deg. F, no air movement.
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47 PART 3 - EXECUTION (NOT USED)
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Rotary-Screw Compressor Water Chillers 236426-5