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Options and unit configurations are indicated in Red and/or brackets [ ] which indicate required choices to be made.

This Engineering Specification is intended for the use of an Engineer when creating an HVAC guide specification that is applicable to a specific project. User should delete any portions of text or descriptions that are not applicable to the specific project. It shall be the responsibility of the Engineer to meet any components or configurations required for applicable building codes, industry standards and system commissioning. Engineer shall coordinate with other product specifications along with any applicable drawings.

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OmegaAir

Indoor Horizontal

Dedicated Outside Air System (DOAS)

ENGINEERING GUIDE SPECIFICATION

WATER-COOLED UNITS

Part 1 –General

1.01 Related Documents

A. Drawings and general provisions of the contract, including General and Supplementary Conditions and other Division 1 specification sections, apply to this section.

1.1General Description

A. Furnish and install an indoor horizontaldedicated outside airsystem (DOAS)designed to control outside air temperature and humidity levels introduced into the conditioned space. It shall have the performance, electrical characteristics, and air path configurations as defined in the product schedule for the space to be conditioned.

B. The unit(s) shall be anOmegaAir water-cooled model manufactured by United CoolAir, York, Pennsylvania.

C. The unit(s) shall be installed as a ceiling mountedsingle packagesystem[coupled] [decoupled] with the space air conditioner system.

D. All systems shall be shipped with a full factory refrigerant charge and be ready to wire once the unit has been placed on site.

E. A wiring diagram shall be affixed to each unit. A printed Installation, Operation and Maintenance Manual shall be provided with each unit. All units shall be suitably labeled for safety purposes and for access.

1.2Quality Assurance

  1. Unit and refrigeration system(s) shall comply with ASHRAE 15, Safety Standard for Mechanical Refrigeration.
  2. Unit shall be certified in accordance with UL Standard 1995/CSA C22.2

No. 236-11, safety Standard for Heating and Cooling Equipment.

  1. Unit shall be factory evacuated, charged with refrigerant R-410A, leak tested, and functionally tested prior to shipment.

1.3Submittals

  1. Literature shall be provided that indicates unit dimensions, applicable clearances, unit operating weights, capacities, blower performance, filter information, factory supplied options, electrical characteristics, and connection requirements.
  2. Installation, Operation, and Maintenance manual shall be provided.

1.4Delivery, Storage, and Handling

  1. Unit(s) shall be shipped with all access panels in place and suitably affixed to prevent damage during transportation and thereafter while in storage either offsite or on the jobsite.
  2. Unit(s) shall be stored in a clean, dry place protected from construction traffic and the natural elements.
  3. Installing contractor shall follow industry accepted practices and instructions in the Installation, Operation and Maintenance manual for moving unit(s) where required.
  4. Unit or any portion of the unit shall not be disassembled in the field, except as designed for, in order to facilitate placement into the building or mechanical space. Any disassembly of the unit or unit sections not incorporated into the basic design would act to void the unit warranty and reduce the factory quality assurance process.

1.5Warranty

  1. Manufacturer shall provide a “parts only” limited warranty for a period of 12 months from the date of equipment start-up or 18 months from date of shipment from the factory, whichever is less.
  2. Manufacturer shall provide a “compressor parts only” limited warranty for a period of 60 months from the date of equipment start-up or 66 months from date of shipment from the factory, whichever is less.
  3. Manufacturer’s limited warranty shall be for parts only. Labor is not included.

Part 2 – Products

2.1 Cabinet

  1. Cabinet shall beunpainted, non-weatherized and constructed of scratch resistant heavy duty galvanized G90 steel.
  1. [Cabinet shall be painted non-weatherized and constructed of scratch resistant heavy duty galvanized G90 steel. All structural members and access panels shall be electrostatically sprayed, powder-coated with a polyester wrinkle finish textured coating designed to function as both a decorative and a protective finish. Film thickness shall be in the range of 2.5 – 4.0 mils and be cured at 375 deg. F. for a minimum of 10 minutes.

Finish shall have a Salt Spray Resistance of 1500+ hours – 1/8” vertical scribe, in accordance with ASTM B117.

Color shall be Rohm & Haas, Corvel 244-0253 Stormy Gray or approved equal.]

  1. Cabinet shall be shipped as a self-contained unit on a single skid from the manufacturer. Cabinet shall be assembled using zinc plated fasteners.
  2. Unit shall be provided with integral support rails and integral hanging brackets which eliminate the need for external, field-supplied brackets. Brackets shall accommodate the unit being ceiling mounted using hanging rods or slab mounted.
  3. Cabinet access panels shall fit into recessed pockets within the cabinetstructure and held in place with screws. Recessed areas will be lined with flexiblegasket to minimize air leakage. Access panels shall have inserts to easily facilitate panel removal.
  4. Panels shall allow sideaccess to key internal components to facilitateinstallation, maintenance and servicing of the unit.
  5. Cabinet shall be constructed so that thermal bridging does not occur.
  6. Duct flanges shall be factory-installed prior to shipment for front or top supply air configurations. Duct flange for bottom supply air configuration shall be shipped loose for field attachment.
  7. The back of the cabinet shall have an inlet for the outdoor air stream. The supply air duct location shall be [front discharge] [top discharge] [bottom discharge]. The cabinet shall be suitable for installation adjacent to an exterior wall.
  8. Cabinet and removable panels shall be lined with 2”, R-8fiberglassthermal/acoustic insulation having an approximate density of 1.9 lbs. / ft3which meets NFPA 90A and90B/ASTM-C1071, Type 1/ ASTM E 84 / CAN/ULC S102-M88 / CAN CGSB-51.11 requirements. Insulation shall be a dual density fiberglass, comprised of a 1.2 lbs. / ft3 flexible core and a 4.0 lbs. / ft3 density, 1/8” face. Insulation shall be certified to meet The GREENGUARD Environmental Institute air quality standards and product emission standards for VOC’s. Insulation shall not promote or support the growth of fungi or bacteria. Insulation shall include an acrylic polymer coating to help guard against the incursion of dust and dirt into the substrate.
  9. Cabinet and removable panels in the evaporator section shall be lined with 2”, R-8 flexible, closed cell elastomeric sheet insulation. Insulation material shall be manufactured without the use of CFC’s, HFC’s of HCFC’s. It shall also be formaldehyde free, low VOC’s, fiber free, dust free and resist mold and mildew. Insulation shall have a flame spread index of less than 25 and a smoke-developed index of less than 50 when tested in accordance with ASTM E 84, latest revision. Insulation shall have a maximum thermal conductivity of 0.27 Btu-in./h-ft2-°Fat a 75° F mean temperature when tested in accordance with ASTM C 177 or ASTM C 518, latest revisions. Insulation shall have a maximum water vapor transmission of 0.08 perm-inches when tested in accordance with ASTM E 96, Procedure A, latest revision.
  1. Double Wall with Perforated Liner - Cabinet and removable panels shall be double-wall construction with interior panels consisting ofperforated galvanized metal with 1/8” holes spaced on 3/16” staggered centers.
  1. Double Wall with Solid Liner - Cabinet and removable panels shall be double-wall construction with interior panels consisting ofsolid galvanized metal.

2.2 Refrigerant Circuit

A. Each refrigerant circuit shall be provided with high and low-side Schrader access valves, sight glass with integral moisture indicator, filter-drier, maximum operating pressure (MOP) expansion valve with external equalizer line, manual reset high and auto-reset low pressure safety switches.

B. Each refrigerant circuit will be factory leak tested, evacuated, and charged with R-410A refrigerant prior to shipment. No field piping, brazing, evacuation or refrigerant charging shall be required.

C. Hot gas bypass shall be included in each refrigerant circuit. Discharge gas shall be diverted into the hot gas inlet port of the evaporator distributor.Each refrigerant circuit shall include a manual shutoff valve on hot gas bypass line to be used for isolation of the hot gas bypass capability during unit start-up, testing, or maintenance.

D. Single-circuit units and the lead circuit on dual-circuited units shall contain a fully modulating, balanced port, 3-way hot gas reheat diverting valve, a 1-row reheat coil and a receiver tank for refrigerant management. The reheat coil shall be constructed of one row of copper tubing mechanically expanded into aluminum fins. The fin spacing shall be 12 fins per inch. The reheat coil shall be vertically mounteda minimum of 8” after the evaporator coil for ease of cleaning and to prevent re-hydration of the condensate from the evaporator coil. The reheat coil shall have the manifold outlet located at the bottom of the coil to assure that no oil logging occurs. All refrigerant passing through the reheat coil shall be routed back to the condenser coil to assure full refrigerant condensing.

2.3Compressors

  1. Refrigerant circuits 1-1/2 ton and smaller shall utilize a single reciprocating compressor. Reciprocating compressors shall be mounted on vibration isolators to ensure quiet operation. Each reciprocating compressor shall be protected internally from overheating.
  2. Refrigerant circuits 2 ton and larger shall incorporate a high-efficiency, heavy duty, single-speed, suction-cooled hermetic scroll type compressor, operating at 3450 RPM on 60Hz. The compressor shall contain internal overload protection and solid-state motor overload protection.
  3. Scroll compressors shall utilize internal spring vibration isolators and external rubber in shear (RIS) mounting to minimize sound and vibration transmission.
  4. Compressors shall be mounted outside the air stream in an insulated compartment.
  5. Each compressor circuit shall be protected with a high and low pressure safety switch.
  6. Units with multiple compressors shall have separate independent refrigerant circuits.
  7. Lead compressor shall be a digital scroll type.

2.4 Evaporator Coil Section

A. The direct expansion evaporator coil shall be configured for draw-thru airflow design for uniform air distribution across the coil face. It shall be made with heavy wall seamless copper tubes mechanically expanded into tempered aluminum fins with drawn self-spacing collars. Coil end sheets shall be hot-dipped galvanized.Coils shall be 6 rows deep with no more than 10 FPI, for uniform performance and optimum part load and humidity operation. All coils shall be factory leak checked under pressure. Dual circuit units shall utilize interlaced evaporator coils.

B. All systems shall incorporate an independent refrigerant circuit for each compressor. The evaporator coil shall utilize a distributor with suitable porting for hot gas bypass. Maximum Operating Pressure (MOP) externally adjustable thermostatic expansion valves, externally equalized, shall feed each circuit in the evaporator coil.

C. Evaporator coil section shall be equipped with a double sloped304 stainless steel drain pan with 7/8” OD condensate drain connection located on the right hand side of the cabinet. Drain pan shall extend to the entire length and width of the evaporator coil.

  1. Evaporator section air path shall be as shown on project drawings.

2.5 Water-Cooled Condensing Section

A. Thewater / glycol condenser coil shall be co-axial counter-flow refrigerant type. The condenser(s) shall be selected to maintain low refrigerant operating pressure, while using a minimum quantity of water / glycol. Maximum working pressures shall not exceed 450 psig water side, 650 psig refrigerant side.

B. Condensers shall be provided for each independent refrigerant circuit.

C. A single water supply connection and single water return connection shall be provided on the front side of the cabinet. Water connections shall be female pipe thread type.

D. Each circuit shall utilize a factory installed water regulating valve. Valve shall modulate fluid flow based on the refrigerant circuit pressure. Valve(s) shall be [2-way, 150 Psig] [2-way, 350 Psig] [2-way, 150 Psig valve with NO solenoid valve] [3-way, 150 psig] [3-way, 350 psig].

2.6 Blower / Motor Assembly

  1. The evaporatorcentrifugal blower assemblyshall be belt driven with double width, double inlet housing and forward-curvedblades mounted on a solid keyed shaft. The hub shall be precision machined and incorporate a keyway and a locking screw.
  2. The shaft shall be hardened steel,precision ground and polished. Shafts shall include a keyway for the wheel hub and the pulley.
  3. Bearings shall be mounted in a rubber inter-liner fitted into a spider bracket. These bearings shall be permanently lubricated and sealed.
  4. All wheels are to be balanced, both statically and dynamically.
  5. The motor shall have an adjustable base for tensioning of belts and a locking mechanism to prevent the motor from shifting.
  6. The blower fixed pulley shall be cast iron, keyed to the shaft, and the motor sheave shall have an adjustable pitch in order to allow for field adjustment of blower speed in order to match the system airflow requirements.
  7. Blower motor shall be open drip proof. Motor shall have internal overload protection and permanently lubricated ball bearings. Motor shall be rigidly mounted to an adjustable motor frame.
  8. Unit shall include a factory-installed, pressure differential type loss of air flow proving switch that is set to read pressure drop across the evaporator blower section. Upon loss of air flow, this control shall terminate system operation.

2.7 Electrical System

A. The electrical system shall conform to National Electric Code (NEC) requirements.

B. Unit shall have a single isolated electrical control panel located out of the air stream. Access to the control panel shall be from the right side of the unit. A single point power connection shall be provided through theright side of the cabinet. Power shall be connected to factory installed terminal blocks. Ground lug shall be affixed in the control panel.

C. All electrical components (blower motor, compressor(s), etc.) shall have individual definite purpose contactors.

D. A low-voltage transformer, with protection, shall be providedto supply 24 VAC to the control circuit.

E. Terminal strips and blocks shall be factory installed internal to the control box and be clearly labeled for control wiring connections.External control wires shall enter the cabinet through the right side of the cabinet.

F. Terminal blocks shall be factory provided for a Remote On / Off switch capability. Controls shall be suitably wired and enabled to accept a signal from a field supplied Remote On / Off switch.

G. Terminal blocks shall be factory provided for a Fire / Smoke Detector sensor interface. Controls shall be suitably wired and enabled to accept a signal from a Fire / Smoke Detector.

H. Each component shall be safety agency listed as required. All electrical components shall be labeled to co-ordinate with the unit wiring diagram provided.

  1. The unit shall contain the OA3 self-contained programmable microprocessor controller. The factory mounted controller shall include the following:
  2. An 8 line by 22 character white backlit LCD wall mounted screen display shipped loose for field mounting.[An 8 line by 22 character white backlit LCD unit mounted screen display shall be factory installed.]
  3. English Text
  4. System Status Display
  5. Active Temperature Display
  6. 6 Button Navigation / Submenu
  7. Manual control from the controller keypad.
  8. Password protection (Optional)
  9. Automatic restart from a loss of power
  10. Real Time Clock (back up of clock during power outage)
  11. 7 Day Occupied / Unoccupied Period Programmability
  12. Wall Mounted Temperature / Humidity Sensor
  13. Duct Mounted Temperature Sensor
  14. Duct Mounted Temperature / Humidity Sensor
  15. High & Low Refrigerant Pressure Safety Switch Inputs
  16. Anti-short Cycle Protection
  17. 4 MB Flash memory
  18. 8 Analog inputs
  19. 14 Digital inputs
  20. 3 Analog outputs
  21. 14 Digital outputs
  22. Plastic housing shall be DIN Rail mounted
  23. Plug-In Screw Down Type connectors
  24. Alarm history (Up to 50 alarms)
  25. System Enables Menu
  26. Time Clock Menu
  27. Alarm Set Point Menu
  28. Equipment Run Hours Menu
  29. Set Point Menu
  30. Technician Menu
  31. Factory Menu
  32. Unit shall include 100’[150’] [200’] [250’] 300’] [400’] [500’] of cable for connection of wall display to unit mounted microprocessor.
  33. pLAN Network capability
  34. Microprocessor shall include [BACnet™] [ModBus] [LonWorks®] BMS Interface
  35. The unit shall provide the following visual and audible alarms:
  36. High Refrigerant Pressure (each compressor)
  37. Low Refrigerant Pressure (each compressor)
  38. Loss of Air Flow
  39. Evaporator Motor Overload
  40. High Supply Air Temperature
  41. Low Supply Air Temperature
  42. High Inlet Air Temperature
  43. Low Inlet Air Temperature
  44. Sensor Failure
  45. Dirty Filter (Optional)
  46. Drain Pan Overflow (Optional)
  47. Freezestat (Optional)
  48. Smoke Detector (Optional)
  49. Firestat (Optional)
  50. Damper End Switch (Optional)
  51. [OA3 controller shall be set up to provide room neutral air supply.] [OA3 controller shall be set up to provide space conditioning air supply]
  52. OA3 controller shall provide a flush cycle for the hot gas reheat circuit.
  53. OA3 controller shall provide space dew point set point reset.
  54. The OA3 controller shall provide the following operating modes:
  55. Dehumidification (Hot Gas Reheat to function as required)
  56. Cooling Mode (Mechanical Cooling or Smart Cooling)
  57. Heating Mode (Mechanical Heating or Smart Heating)
  58. Ventilation Mode
  59. Occupied and Unoccupied Modes (Unoccupied override)

2.8 Evaporator Air Filtration

A. The filter rack shall be factory mounted directly to the unit cabinet and shall be accessible from either side. Slide shall be provided within the filter rack for easy removal of all the filters. Filter rack shall have flanges that are suitable for field attachment of field supplied duct work.