HVAC Fan/Pump Control Systems
UNICO’s fan/pump control systems are available as stand-alone components or turn-key packages. Packaged systems, which incorporate selected options with a variable-speed drive inside an enclosure, accommodate the majority of applications. Custom integration is also available for special requirements.
UNICO’s 1100 family of AC drives provides flux vector or variable-frequency (V/Hz) motor control from a single- or three-phase 230 or 460 V AC or three-phase 575 V AC input. Drives are available from 11/2 to 500 hp and are UL and C-UL listed.
There are two basic option configurations. The Disconnect Package provides an AC input circuit breaker and operator, 115 V control transformer, and Hand/Off/Auto selector switch. The Bypass Package provides an AC input circuit breaker and operator, 115 V control transformer, Hand/Off/Auto selector switch, drive input and output contactors, bypass contactor, Drive/Off/Bypass selector, motor overload protector, keyed drive Test/Off selector, and bypass mode pilot light. Each of these components is described below.
A step-down transformer converts the high-voltage line supply to 115 V AC for supplying the control circuits. Both the primary and secondary sides are fused.
An input circuit breaker or fused disconnect interrupts the power to both the drive and bypass circuit. The breaker provides short-circuit protection when the motor is running across the line.
A three-position switch selects either local or remote operation. When set to hand, the user can start, stop, and adjust the speed of the motor from the drive’s keypad. In auto, the drive is controlled externally through contacts and gets its speed reference from a remote source or through the keypad. When set to off, the drive will not run.
A three-position selector switch controls a bypass contactor and drive input and output contactors. When set to drive, the input and output contactors are closed and the bypass contactor opened for normal operation. When bypass is selected, the motor is connected directly to line power and runs at full speed. The input and output contactors are opened to electrically isolated the drive so that it can be serviced without interrupting operation. A pilot light indicates when the system is in bypass mode.
A keyed switch permits testing of the drive while the motor is in bypass mode. The switch closes the drive input contactor to provide power to the drive while it is disconnected from the motor.
Motor Overload Protector
A thermal motor overload relay protects the motor while in bypass mode.
Systems can be packaged in NEMA 1, 4, 3R, or 12 enclosures to accommodate any indoor or outdoor application. NEMA 4 packages can be placed in wash-down areas or on rooftops. NEMA 12 packages can be placed in mechanical rooms that serve as the plenum. Customization is available for special environmental requirements. All work is done in a UL-certified panel shop.Enclosures for systems with bypass control feature mechanical isolation between the drive and the bypass to ensure electrical safety.
A terminal block provides easy connection for freeze, fire, smoke, start/stop, and other external safety interlocks. This allows a building automation system to shut the motor down at any time by opening the 115 V circuit.
Motor Selection Contactors
Using motor selection contactors, two motors can be interchangeably operated by the same drive, such as for switching between primary and backup pumps. A Local/Off/Remote selector switch specifies whether the motor is selected locally using the Motor 1/Off/Motor 2 selector switch or remotely using contacts from a building automation system. Timers prevent a newly selected motor from being connected to the output of the drive until the drive has come to a stop. Pilot lights indicate the selected motor.
The system can automatically enter bypass mode in the event of a drive failure.
A Remote/Off/Local Run selector switch selects the mode of bypass operation when the Drive/Off/Bypass selector is set to bypass. When set to remote, a contact must be closed to start the drive remotely in bypass. When local run is selected, the motor runs in bypass. If set to off, the drive will not run.
Various options are available for conditioning the incoming line, including an AC line reactors, isolation transformers, twelve-pulse transformers, or harmonic filters.