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Would I benefit from a Variable Speed Drive Screw Compressor?

If your current compressor is oversized or you have a process where the air demand varies, then considerable savings could be made by installing a VSD compressor. In some case’s this may be a standalone single compressor system or part of a system where a number of compressors are all supplying air to the same network. Usually only one VSD compressor is required, with the fixed speed machines providing the base load and the VSD compressor acting as the ‘top up’ machine.

The simplest way to see the energy saving benefits is to compare your running hours with the load hours. If for example the annual run hours are 8000 hours and the load hours are 4000 your compressor is spending half of it’s time consuming energy but without making any air! These off load costs can be around 20-30% of your compressor motors full power!

To find out how much an SCR Variable Speed Screw Compressor could save, please see our online energy saving calculator

You only have to input the following details to see how much you could save….

  • Motor size in kW – This can usually be found on the data plate on the side of the compressor. This data can also be found on the motor nameplate.

  • Annual Running Hours – This data can be found either on an a mechanical hours run counter or by accessing the data on your digital compressor controller. If your machine is for example 5 years old, simply divide the total run hours by the number of years the compressor has been operating to arrive at your annual operating hours.

  • Annual Off Load hours – As with the annual running hours, this figure can be taken from the on load hours counter or by accessing the on load hours figure on your digital compressor controller. Alternatively, count the number of times the compressor unloads over a 15 minute period during production hours.

  • kWh rate. This is the current cost of your electricity. If you have a different day & night rate and the compressor runs continuously then you can use an average figure. If you don’t know your current cost, you can use the default value of 0.10p.

  • Purchase cost of the compressor – Simply click on the link to the oil flooded DV range of compressors and select a compressor of the same kW rating. If you are unsure then please contact us for help and advice, providing the make and model number of your existing compressor if possible. Enter the cost of the new compressor and the calculator will display your payback period, which is the time it will take to recover the cost of the new compressor in saved energy. There are two versions of SCR VSD compressors listed, 30%-100% speed range and 60%-100%. The compressor with the lowest speed turn down will offer enhanced savings but for simplicity we have taken an average of the two models.

  • There are two savings shown on the calculator once the data has been entered. Unloaded energy savings along with the additional savings that would be gained by tighter pressure control. Please see our Variable Speed overview brochure for further information.

This tool is designed to help estimate the potential savings. All compressed air systems are different. If you would like detailed site survey including energy and flow monitoring then please contact us.

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