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Energy-efficient Modular Variable Speed Drive for HVAC Systems

e Siemens Building Technologies Division has just introduced the G120P variable speed drive for HVAC systems. The device has a modular structure, which makes individual components easy to replace.

Various user-friendly functions ensure high energy efficiency and safety while keeping operating costs low. Thanks to protection classes IP54 and IP55, the G120P variable speed drive can also be used under harsh environmental conditions.

The Siemens G120P variable speed drive is suitable for applications that require an economical, energy-efficient and easy-to-operate drive for pumps or fans. It operates in a power range from 0.37 to 90 kilowatts (kW). The device has a modular structure, consisting of a control unit, the power module and an operating panel (basic operating panel BOP-2, or intelligent operating panel IOP) or a blanking cover. This design enables individual components to be exchanged without having to replace the entire drive. For example, a power module can be exchanged without reconfiguring the entire device or rewiring the signal and bus cables.

A high protection class, either IP55 (with the BOP-2 or blanking cover) or IP54 (with IOP), allows the variable speed drive to be used under harsh environmental conditions at temperatures up to 60°C, for example for controlling the speed of fans and recirculation pumps in heating and cooling systems. The new variable speed drives replace the Siemens SED2 devices.

The G120P variable speed drive is tailored to the needs of pump installations and ventilation systems and therefore offers numerous safety features. The device can routinely detect different events (such as overloaded motors, pumps that are blocked or have run dry, blocked fans, cracked belts, etc.) and respond to them immediately, for example by shutting down the pump or fan, triggering an alarm or starting a predefined process. When used in ventilation systems, the G120P automatically switches to emergency mode in the event of a fire. As a result, the overpressure generated by the ventilation is retained as long as possible, and the escape routes remain smoke free.

The G120P has various functions that improve energy efficiency for operating HVAC applications and systems economically. For example, the device is characterized by very low apparent power. The integrated hibernation function supports an energy-efficient and wear-reducing idle mode, depending on the current requirements. Because the drive automatically switches to mains operation at nominal speeds, it can cut energy consumption by as much as three percent. In addition, the variable speed drive has a low impact on the power grid and meets the IEC/EN 61000-3-12:2011 standard without additional components such as line reactors. A comprehensive fan, filter and motor monitoring system is integrated into the device to avoid loss of HVAC plant and rising operating costs. Flow optimization in U/f mode and during vector control adapts the motor magnetization to the partial load of the pump or fan. This helps increase motor efficiency under partial load, which substantially increases the efficiency of the overall system.

Plug connections for motor and power cables on the power modules up to frame size C and screwless terminals on the control unit permit easy installation of the G120P variable speed drive. The Starter software, which comes with several application wizards, is available to facilitate commissioning. The variable speed drive also has an integrated MMC (Micro Memory Card) slot for commissioning and diagnosis. This makes it possible to preconfigure the parameters for entire series of variable speed drives and to back up the settings.

The I/O and field bus interfaces, such as Modbus RTU, USS and BacNet MS/TP, are customized to the special requirements of HVAC. This allows the variable speed drive to be integrated easily into building management systems such as Siemens Desigo.

The G120P models with protection classes IP54 and IP55 are available now, and a device with the lower protection class IP20, which is suitable for panel mounting, will follow later this year.


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