Fixed speed vs variable speed compressor

If you need an air compressor that offers reliable performance when dealing with varying air demands, a variable speed compressor (VSD) might be the way. The alternative is the more traditional fixed-speed compressor. However, you must make an informed decision before choosing your compressor unit as a VSD compressor might not be the best option for your requirements. Here, we explore the case for using variable speed compressors by comparing them to their fixed-speed counterpart to see which one comes out on top.

Variable speed compressor energy savings

The key benefit to using a variable speed air compressor is its ability to effectively meet fluctuating air demands by controlling speed. Because a variable speed air compressor system runs only at the required speed, this can present substantial energy-saving costs.

Variable speed compressors produce less because they rotate slowly, thus absorbing less energy. They can automatically slow down their rotation speed until the unit produces the precise amount of compressed air for the downstream equipment. As a result, variable speed compressors can save around 30% on average when compared to the energy costs of fixed-speed compressors.

Fixed speed energy savings vs variable speed compressors

Unless your application has either full load or no load requirements, the ability to save considerable costs on energy shouldn’t be ignored. As most applications tend to have a fluctuating air demand, this is one area where variable speed compressors have the edge over fixed speed compressors.

Additionally, if your business qualifies for energy-saving programmes then there may be an added incentive for using a variable speed compressor as it can help towards this.

What are the advantages of a variable speed compressor?

Aside from excellent energy savings, variable speed compressors are also able to stop and start under full system pressure. Because there is no need to unload, this can contribute towards an increase in productivity.

Additional benefits of variable speed compressors include:

• Quieter operation under lower RPM
• The ability to run on 100% airflow
• Minimised system leakages due to lower pressure
• Avoiding peak currents at compressor start-ups
• Soft motor starts
• Removing blow-off losses during operation
• Increased component lifetime
• Consistent plant pressure

 

Fixed speed benefits vs variable speed compressor benefits

A fixed speed compressor can provide a constant supply of compressed air around the clock, albeit one that is limited to a fixed RPM unless turned off manually. They are most efficient in applications with consistent compressed air demands, but not ones that might have peaks and troughs. Generally, they have a lower capital cost, lower maintenance and repair fees, and increased availability of air compressor spare parts.

It is important to note that despite their energy-saving potential, variable speed compressors are much more of an investment compared to fixed speed compressors, which are cheaper to purchase and do cost less to maintain.

How reliable is a variable speed air compressor?

Variable speed compressors are extremely reliable when it comes to addressing fluctuating air demand. Using variable speed drive technology, they can change the frequency that they supply to their motors. This means they can adjust the spin speed of their rotary screws.

Depending on the air pressure requirements at any one time, variable speed compressors are able to increase and decrease speed to address specific requirements without over-consumption.

Fixed speed reliability vs variable speed compressors

If your business operates 24 hours a day, seven days a week without any notable disruptions to production cycles, or has a consistent rate of energy consumption, fixed speed compressors can be just as reliable as their VSD counterparts. However, if your business has frequent changes in production outputs – whether they’re daily, weekly or even seasonal – a fixed speed compressor will use more energy than variable speed compressors.

Despite this, because variable speed compressors can change operational speeds, they are more prone to inconsistencies from their power source and are particularly sensitive to heat and moisture exposure.

Fixed speed vs variable speed compressor – a summary

​​The key differences between variable speed and fixed speed compressors are the way the motor is controlled, how much energy it can save, and how much they cost to maintain. While variable speed technology is superior for adapting to changing air demand and therefore saving considerable energy costs, they might not be worth the investment if they don’t match your requirements.

For example, if your business is prone to peaks in production cycles or fluctuations daily, then a variable speed compressor is a better choice, provided it won’t take too long to reap the energy-saving benefits. Alternatively, if your business experiences drop-offs or surges that can’t be controlled, a variable speed compressor might not be worth both the initial and the long-term cost.

Choosing an air compressor with Glaston

If you are unsure about whether your business requires a variable speed compressor or not, Glaston can offer a site and energy audit to assess which method of compressed air generation is most beneficial for your requirements.

With years of industry experience, our compressor engineers can provide the most comprehensive service available anywhere in the North West of England. Glaston has an extensive on-site stock of air compressor systems, including fixed speed compressors and variable speed drive compressors and we’re highly experienced in air compressor service and installation.

To arrange a site visit today, don’t hesitate to contact us on 01695 51010 or email info@glaston.com.