Waterside Economizer Flow Control Units equipped with a waterside economizer can be set from the human interface panel for variable or constant water flow.
• Constant Water Flow
Two-way modulating control shutoff valves are wired, controlled, and installed in the unit. One valve is located in the economizer’s water inlet, and the other is in the condenser bypass water inlet. When the waterside economizer enables, the two-way valve modulates to maintain the discharge air temperature setpoint. As the economizer valve opens, the condenser bypass valve closes, and vice versa. Full water flow is always maintained through the condensers. Both valves will close in the event of a power failure.
• Variable Water Flow
Two-way modulating control shutoff valves are wired, controlled, and installed in the unit. One valve is located in the economizer’s water inlet, and the other is in the condenser bypass water inlet. When the economizer valve is active, the condenser bypass valve closes. The economizer valve modulates, thus water flow through the unit modulates. If the water is cool enough for economizing, but mechanical cooling is also required, the economizer valve fully opens to establish full water flow through the condensers. Whenever the water is too warm for economizing and there is a call for cooling, the economizer valve fully closes and the bypass valve fully opens, establishing full water flow through the condensers. Full water flow is always maintained through the condensers when mechanical cooling is required. Both valves close whenever cooling is not required and in the event of a power failure.
Water Flow Switch
A water flow switch is factory installed in the condenser water pipe within the unit. Whenever the flow switch detects a water flow loss prior to or during mechanical cooling, compressor operation locks out and a diagnostic code displays. If water flow is restored, the compressor operation automatically restores.
Service Valves
Service valves are factory installed on each circuit before and after the compressor to allow compressor isolation for servicing.
Heating Coils
• Electric Heat
A single stage electric heating coil and controls are factory installed inside the unit casing at the fan discharge. An open construction type coil is provided. Power to the electric heater is factory wired to the unit’s single-point power connection.
• Hot Water
The hot water heating assembly includes the coil and filter section and is factory installed on the unit’s inlet. A three-way modulating valve, actuator, manifold piping, and automatic air vent are also factory installed.The coil is aTrane type WC, constructed of 5/8-inch (16 mm) OD copper tubes arranged in a parallel pattern. The copper tubes are expanded into aluminum fins positioned continuously across the entire coil width, not exceeding 12 fins per inch. The coil casing is 16-gauge steel. Coil performance is rated at a maximum working pressure of 200 psig in accordance with ARI Standard 410. Supply and return water header connections are female tapered NPT and are accessed from the unit’s left side.
• Steam
The steam heating assembly includes the coil and filter section, factory installed on the unit’s inlet. A two-way modulating valve, actuator, and manifold piping are also factory installed. Also, connections are provided for field installing a vacuum breaker.The coil is aTrane type NS, constructed of one inch (25 mm) OD copper tubes arranged in a parallel pattern. The copper tubes are expanded into aluminum fins positioned continuously across the entire coil width, not exceeding 42 fins per foot. The coil casing is 16-gauge steel. Coil performance is rated at a maximum working pressure of 100 psig in accordance with ARI Standard 410. Supply and return steam header connections are female tapered NPT and are accessed from the unit’s left side.
Factory provided controls limit the steam coil leaving air temperature to no more than 105 F (41 C) at all operating conditions.
Single Stage Electric Heat Interface
A heat control module will be factory installed and wired for customer supplied and powered electric heat. This module will allow the unit to stage the customer- provided electric heat. Single stage electric heat control will be accomplished with one dry binary output rated at one amp for 115 VAC.
Hydronic Heating Control Interface A heat control module will be factory installed and wired for customer supplied hydronic heating. This control will be accomplished with a dry binary output, 0- 10 VDC analog control signal.
Time Clock
A factory-installed programmable time clock is wired to the unoccupied mode binary input to provide on/off control. The timer is accessible without opening the control panel door, and is a seven-day type with a maximum of four operations per day. A permanent built-in rechargeable battery pack is provided.
Low Entering Air Temperature Protection Device
A thermostat limit switch is factory mounted on the unit’s entering air side with a capillary tube serpentine across the coil face. If the temperature falls below 35 F (2 C), the fan shuts down and the waterside economizer and/or hydronic heat valve option opens to allow full water flow.The heat output also energizes. A manual reset is required. Note: this option is standard on units with
awaterside economizer or hydronic heat.
Non-fused Disconnect Switch
The unit has a factory mounted non-fused disconnect switch accessible without opening the control panel door.
Dual Point Power Terminal Blocks
Two separate power terminal blocks are available to bring power to the unit; one terminal block provides power to the compressors and the other provides power to the fan motor and controls. Note: a single point power terminal block is standard.
