Drives raise efficiency in HVAC applications

Recognising the enormous energy savings that variable speed drives can deliver when applied to fans, pumps and compressors, Danfoss has developed a new range of high efficiency drives.

With rapidly rising energy costs and the spectre of global warming, energy saving has become an imperative in industry and commerce.

Recognising the enormous energy savings that variable speed drives can deliver when applied to fans, pumps and compressors, Danfoss has developed a new range of high efficiency drives dedicated specifically to those applications.

The new VLT HVAC drive range is designed to be an intelligent part of the intelligent building, gives the lowest cost of ownership and makes HVAC operation pure child's play.

The VLT HVAC drive, in ratings up to 450kW, broaches the 98% efficiency barrier for the first time.

This reduction in losses, mostly manifested in heat, is highly significant in terms of the thousands of kilowatt-hours saved over a drive's lifetime, the corresponding reduction in carbon emissions and also in the reduction in time required to justify the initial investment.

A 150kW drive for example, based on continuous operation in an air conditioning application, will yield a benefit of over 25,000kWh and over 10 tonnes of carbon saving per annum and the improvement in payback period is equivalent to that yielded by the Enhanced Capital Allowance tax break.

The heat emission reduction along with a 50C ambient specification, also enables the drives to be installed in more compact enclosures and enables Danfoss to offer an IP66 version as standard.

The VLT HVAC drive also improves motor efficiency with automatic energy optimisation (AEO), whereby flux levels in the driven motor are continuously monitored and the drive output varied to maintain ideal motor magnetisation for load conditions.

This feature can improve motor efficiency by 5-15% at partial load, the most common operating conditions for fans, pumps and compressors.

It is made more user friendly with the automatic motor adaptation (AMA) feature which "tunes" the inverter to the chosen motor, leaving the customer freedom of choice on motor selection and ensuring optimum efficiency on retrofitting to existing motors.

The efficiency benefit of this feature alone would justify the replacement of older, less efficient inverters.

Applying the VLT HVAC drive has been made absolute child's play by the development of software suites and features dedicated to fan, pump and compressor operation.

The award winning local control panel allows access to a quick setup menu which in turn allows the user into an HVAC application menu and an HVAC function menu.

Additionally, for the more savvy user, there is a 'personal' menu that can be fully customised.

Dual-layer password protection means that an OEM can set the drive up to the design criteria demanded by the equipment, as well as allowing the end user access to program the drive to local conditions.

All the most common BMS network protocols are offered and the drive offers 27 language programming including Mandarin and Cantonese.

A host of features developed in conjunction with Danfoss' global fan, pump and compressor OEMs greatly simplify application of the drives.

The built-in smart logic controller and four auto-tune PID controllers simplify the control of air handling functions like fan volume, valves and dampers, releasing valuable data points on any building management systems (BMS).

The integral I/Os are equally available as remote I/O to extend the BMS' capacity.

Room temperature sensors, for example, can be connected directly to the drive.

Other intelligent air handling unit (AHU) functionality enables highly flexible control to be achieved.

Workday and weekend operating conditions can be programmed; cascaded P-PI temperature control is simplified; multi-zone pressure control is facilitated and flow balancing between fresh and outlet air is programmable.

The drives' ability to detect changes in current relative to speed enable the drive to automatically detect a drive belt malfunction, bring up an alarm and stop the motor, without the need for dedicated air flow monitors, reducing first cost and down-time.

The Fire override and Stairwell pressurisation features ensure that the drive will continue in operation, until self destruction if necessary in the event of a fire and maintain higher levels of pressurisation in stairwells and escape routes, ensuring smoke free conditions for longer.

For pump applications, the most sophisticated pump cascade controller in the market can be fully integrated as standard.

This invaluable feature shares running hours evenly across a multiple pump system, minimising wear on any one pump.

Vital water supply control keeps the pumps running in the event of a rupture or a severe leak and dry pump (end of curve) protection detects a dry well or leak conditions and enables the user to preprogram the action to be taken.

In sleep mode, the drive detects low or no flow, boosts system pressure then goes to energy saving sleep mode and wakes up again if pressure falls below the set-point.

Compressors have different needs.

Scroll, screw and centrifugal compressors have varying requirements and the VLT HVAC Drive can be set to meet their varying characteristics while optimising cooling capacity with constant temperature and pressure levels, typical compressor applications in the HVAC sector.

The intelligence in the drive enables it to calculate the temperature in a room from the pressure of the cooling media and refine compressor operation accordingly, eliminating the need for additional sensors, software or controllers.

This means the temperature set-point can be set at the control panel rather than by a pressure value.

The control flexibility of the drive means that a more cost effective large single compressor can be used over a wider operating range, rather than a cascade of smaller compressors, without compromising control accuracy.

The drive also features a quick start feature whereby the drive controls a bypass valve, enabling the compressor to be started offload, lengthening compressor life.

The VLT HVAC drive sets a completely new standard in energy saving drives across the industrial and commercial sectors, not just in the HVAC market.

It further reinforces Danfoss' position as global market leader in HVAC drives and raises the bar another notch in the quest for meaningful energy savings.

In fact, one year's production of advanced power electronic drives saves energy equivalent to the output of a major nuclear power station.

If UK industry and commerce were collectively to apply VLT drives on all applicable fans, pumps and compressors, our Kyoto commitments would be met quickly and cost-effectively with room to spare.

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