The Airedale OptiChill™ FreeCool is a range of liquid screw chillers designed for cooling applications, with a nominal capacity range of 750kW to 1250kW. The chillers are available in Regular (R) or Extra Quiet (X) models and can be configured for High (H) or Medium (M) water temperatures, with Large (L) or Small (S) water temperature differentials (ΔT) to suit various applications. The range is optimized for energy efficiency, high output performance, and a minimal footprint, utilizing ozone-benign R134a refrigerant.
Function Description:
The OptiChill FreeCool chiller is designed to provide cooling by utilizing free cooling whenever ambient conditions allow, thereby optimizing energy efficiency. When free cooling alone cannot meet the required load, direct expansion (DX) cooling supplements the output. The unit's microprocessor controller manages both cooling modes, modulating fan speed and adjusting water valve position to maintain the set supply chilled water temperature. In high ambient temperatures where free cooling is not available, fan speed modulates to maintain an optimized head pressure. When the free cooling coil can satisfy the full cooling demand, condenser fans modulate between 25-100% of maximum airflow to maintain the supply water temperature. If the fan speed is reduced to a minimum, a 3-way valve controls the supply water temperature.
Important Technical Specifications:
- Capacity: Nominal capacity range from 750kW to 1250kW.
- Refrigerant: R134a, classified under COSHH regulations as an irritant.
- Compressors: Twin screw semi-hermetic compressors with electronic protection modules for motor, discharge gas, and oil monitoring, rotation direction protection, and phase failure protection. They feature low current Star/Delta Start, internal pressure relief, discharge non-return valve, oil separator, oil sight glass, oil heater, slide valve stepped capacity control, and suction gas motor cooling. Closed transition Star/Delta starting is an optional extra to avoid high transient changeover current peaks.
- Evaporator: Shell and tube heat exchangers constructed from a steel shell with internally enhanced copper tubes. Internal baffles optimize flow and minimize pressure drop. Insulated with Class O fire-rated, UV-resistant closed-cell polyurethane foam. Equipped with an immersion heater and thermostat for freeze protection down to -20°C.
- Free Cooling Coil: Manufactured from copper tubes and aluminum fins, designed for optimal energy efficiency.
- Condenser: Large surface area coils with refrigeration quality copper tubes and mechanically bonded aluminum fins. Copper tubes are internally rifled for improved heat transfer.
- Fans: Sickle bladed fan assemblies with integral long bellmouths and fingerproof grilles, incorporating external rotor AC motor technology for accurate speed control and vertical air discharge. Energy-efficient Electronically Commutated (EC) fans are available as an option, offering significant power reduction compared to standard AC fans at modulated speeds (15-100% modulation range for EC fans vs. 40-100% for AC fans).
- Electrical: Weatherproof electrical power and controls panel with individual mains power compartments, dedicated bus-bar chamber, emergency stop, and separate controls compartment. Circuit breakers protect major components. Mains supply is 3 phase, and a separate 230V permanent supply is required for controls and safety features (e.g., evaporator trace heating).
- Controls: AIRETronix microprocessor controller provides 8 stages of capacity control, with optional capabilities for Building Management Systems (BMS) and sequencing (Master/Slave and Run/Standby). Features an inbuilt display for operating status, parameter adjustments, and visual alarms. Electronic fan speed controllers modulate fan speed via voltage regulation to maintain optimized condensing pressure, allowing operation down to -20°C ambient.
- Pressure Relief: Dual maintainable pressure relief valve assembly (3-way dual shut-off valve with 2 relief valves per circuit) allows maintenance without refrigerant evacuation.
- Leak Detection: Factory-calibrated and fitted R134a leak detection system raises an alarm upon refrigerant gas detection.
- Water Connections: Grooved and clamped type pipe connections as standard, with optional flanged connections. Water inlet and outlet connections are designed to ensure minimum pressure loss and good oil circulation.
- Operating Limits: Minimum ambient air DB -20°C, maximum ambient air DB at full load 35°C, maximum ambient air DB at reduced load 40°C. Minimum leaving water temperature +5°C, maximum return water temperature +25°C. Minimum/maximum ΔT 4°K/8°K.
- ESEER Calculation: Based on unit performance at 20, 25, 30, and 35°C ambient temperatures for all loading stages, with a fixed 7°C supply temperature and 100% water.
Usage Features:
- Noise Variants: Available in Regular Quiet (R) and Extra Quiet (X) models to meet different noise level requirements.
- Water Temperature Options: High (H) or Medium (M) water temperatures, with Large (L) or Small (S) temperature differentials (ΔT).
- Energy Saving: The OptiChill FreeCool design emphasizes low energy consumption, with features like economiser circuits and electronically commutated (EC) fans contributing to significant energy savings, especially at part load and low ambient temperatures. Variable Supply Temperature control schemes further enhance energy savings.
- Remote Control: Unit remote ON/OFF and pump(s) remote ON/OFF functionality. Remote setback setpoint temperature switch for summer/winter or night setback conditions.
- Monitoring: The microprocessor monitors and displays various parameters including supply/return water temperature, evaporator differential water pressure, suction/liquid/discharge pressure and temperature, and superheat for each circuit.
- Alarm Handling: Logs and displays the last 100 conditions, detecting common alarms (low supply temperature, emergency stop, water flow, volt-free contact alarm indication) and individual circuit alarms (compressor trip, low/high suction/liquid pressure, low/high pressure switch, compressor overload, high compressor discharge temperature, circuit isolator status).
- Password Protection: Control system integrity is maintained with a password PIN number.
- BMS Interface: Optional BMS interface card for integration with most BMS protocols (ModBus/Jbus, Carel, SNMP, LonWorks, Metasys, BACnet, pCOWeb).
- Chiller Sequence Manager (Optional): For multiple units on a single site, this manager permits interlinked operation for optimum temperature control and minimum power consumption, sequencing up to 8 units.
- Energy Manager (Optional): Dedicated LCD display for monitoring system energy consumption and adjusting unit parameters to affect energy usage.
Maintenance Features:
- Warranty: Standard 12-month warranty on non-consumable parts, with variations available. Warranty is conditional on maintenance being carried out according to Airedale recommendations.
- Commissioning: Full commissioning services are available from Airedale.
- Spares: A spares list for 1, 3, and 5 years is supplied with each unit and available on request.
- Training: Airedale offers modular Refrigeration and Air Conditioning Training courses.
- Filter Driers: Equipped with replaceable cores for easy maintenance.
- Water Strainer: Optional water strainer with pressure drop curves provided for maintenance.
- Anti-Vibration Mounts (Optional): Spring or pad type mounts can be fitted on-site to reduce vibration transmission to the building structure.
- Discharge Air Plenum (Optional): Directs discharge air vertically, limiting re-circulation and providing acoustic reduction.
- R134a Leak Detection System (Optional): Raises an alarm if refrigerant gas is detected, aiding in early maintenance.
- Flow Switch (Optional): Protects the chiller against low water flow conditions.
- Pump Interlock (Optional): Ensures the chiller cannot operate without water flow.
- Storage Recommendations: Equipment should be stored in a heated warehouse (above 0°C), with all water drained, refrigerant line shut-off valves closed, and electronic expansion valves driven closed. Pre-start checks after extended storage include verifying compressor crankcase heaters, panel heaters, and electric trace heating are operational. Regular visual inspections during storage are recommended to prevent condensation.
- F-gas Inspection: Recommended to carry out an F-gas inspection to ensure no refrigerant leaks.
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