A few years ago, you would only find scroll compressors in special applications, including hospitals, vacuum pumps, and car superchargers. Scroll compressors are much more common today, so the big question is how to choose the perfect scroll compressor for your needs.
Although they’re now more common, scroll compressors still have niche applications. Before buying one, you need to have a clear picture of what you expect it to do and what features it needs to have.
The easiest way to do this is to answer these questions:
Whether you’re a technician, contractor, or building manager, this guide on choosing the best scroll compressor is for you.
Scroll or spiral compressors are a type of positive-displacement compressor, which means they trap fluid in a fixed volume and force it to move through mechanical means.
They use two spiral elements that trap fluid between them and compress it. One of these elements is fixed, while the second one orbits within the vanes of the fixed element.
You can see this scroll-like element in the Copeland Digital Scroll Compressor below.
The only moving parts in the compressor are the rotary scroll and motor. Emerson, the manufacturer of Copeland scroll compressors, estimates that it has 70% fewer moving parts compared to conventional models.
With so few moving parts, scroll compressors are much more reliable and quiet compared to reciprocating models. Scroll compressors can also run without lubrication, which reduces the chances of contaminating air or refrigerant with water or oil.
These benefits, paired with their small size, make scroll compressors perfect for sensitive applications. Common uses of scroll compressors include air conditioning, automobile superchargers, food and fruit refrigeration, vacuum pumps, and marine containers.
Scroll compressors use an orbital motion to compress crescent-shaped pockets of fluid caught between the vanes of the two scrolls.
Watch this outstanding video by Thomas Schwenke to see how this happens.
Due to the way they operate, scroll compressors don’t need a suction valve (although they usually have a special one-way discharge valve). Their design is simple but powerful, giving them a highly efficient compression process.
You will get smooth, reliable, and efficient compression with a scroll compressor. Learn more and explore various brands as you check out the latest prices.
The most important factor when choosing a scroll compressor is the type of work for which you need it. There are several reasons why this is necessary:
Scroll compressors are usually single-speed. That means they only operate at full capacity, but you can also buy units with variable capacity such as this Copeland Scroll Tandem Compressor.
If you’re replacing an air conditioner compressor, consider installing a model with variable capacity. These allow exceptional temperature and humidity, typically within +/- 0.5 °F. This ensures more comfort in homes and minimal food spoilage in refrigeration systems.
When replacing an existing unit, look for a unit with the same technical specifications.
The second most important factor is your air consumption. You need to determine the total airflow you need to power all your tools and equipment.
Check manufacturer specifications and pressure requirements for all your pneumatic tools/machinery. Your scroll compressor should be able to handle the highest PSI required for your equipment during peak operation.
For the airflow in cubic feet per minute (CFM), add up all the CFM requirements for all equipment that you will be running simultaneously. Add a 30% safety margin, and you will have a minimum CFM value for your scroll compressor.
If you’re buying a compressor for air conditioning, look for manufacturer guidelines on what compressor capacity to buy.
Scroll compressors come with a motor already mounted, so you don’t need to calculate horsepower figures. For example, the Danfoss H-Series Scroll Compressor below comes as a complete package with an internal motor and terminal box.
However, you need to figure out power supply requirements including voltage, current, circuit safety, and control features. Check manufacturer guidelines for these details and be careful to follow them to the letter, as scroll compressors can be sensitive to bad connections.
In fact, some of the most common causes of compressor failure include poor electrical connections and motor problems caused by electrical problems.
Scroll compressors have a big advantage because they can operate for extended periods without excessive wear. The best models only require a few minutes of downtime for an hour of continuous operation.
If you need a continuous supply of compressed air/refrigerant, make sure that the scroll compressor you choose has the right duty cycle. For example, the Danfoss 121L0386 Scroll Compressor below can handle 12 start/stop cycles and requires a 3-minute time-out per hour.
Turning a compressor on requires a large current draw from the mains and can cause increased equipment wear. If you have too many start/stop cycles, at some point it becomes more economical to run the unit continuously and eliminate the start/stop operations.
The rule of thumb is that you have to start and stop a compressor more than eight times an hour, consider installing a receiver tank or run it continuously.
Expert Tip: The compressor you choose must always be oversized for your particular applications. Better still, install a tank for your compressor so it doesn’t have to run all the time.
Scroll compressors are so quiet that you can install them close to the point of use. However, there are other installation considerations to think about.
The most obvious one is the electricity supply. Larger units often require three-phase power, while small ones operate off single-phase mains. Heat is also a major factor because scroll compressors generate a lot of heat and require some form of cooling.
Therefore, it’s worth taking the time to pick a scroll compressor that will run off the electrical supply you have. Also, check the space where you will be installing the unit. It needs to have good air circulation for cooling, and some manufacturers even recommend placing it near a fan or window for better cooling.
You should also think about what control system you need. For example, an automatic start/stop system based on air pressure levels will be necessary if you have a receiver tank.
Expert Tip: If you have to start and stop the compressor more than eight times an hour, it’s more economical to run the unit continuously to reduce the high current drawn at starting.
You can get a good single-speed scroll compressor for just under $800, while premium variable-speed models with sophisticated controls can reach $5,000 or more.
Apart from this, the prices of scroll compressors vary only slightly from brand to brand depending on performance factors such as flow and pressure.
The table below shows the average prices of four scroll compressor models we have at Industrial Stores.
|Product||Low Price||High Price||Average Price|
|Danfoss 121L1391 Scroll Compressor||$927.00||$1,330.00||$990.00|
|Trane COM13122 Scroll Compressor||$1,188.00||$1,667.00||$1,168.00|
|York 015-04920-104 Variable Speed Scroll Compressor||$6,292.00||$8,039.00||$6,543.00|
|Carrier HRM060U2LC6A Scroll Compressor||$1,100.00||$1,478.00||$1,382.00|
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The size of air compressor you need will depend on your airflow needs in cubic feet per minute (CFM), as well as the pressure ratings of your equipment. This information will be available for each piece of pneumatic equipment you are using in their user guide.
Sum up all the CFM flow requirements for all the equipment you will be operating simultaneously and add a 20 – 30% margin. Remember to use the higher CFM and PSI values for your equipment to make sure you can meet peak demand.
Scroll compressors are quieter, more efficient, and provide more consistent airflow than other types of compressors. However, this doesn’t mean they are the best since they also have a few shortcomings.
Each type of compressor has applications to which it is best suited depending on its features. The table below shows some important features of the four main types of compressors.
|Compression ratio/maximum PSI||Airflow in CFM||Contamination Levels|
|Scroll compressors||Relatively high, about 100-150 PSI for single-stage units||Relatively low, with most making up to 116 CFM||Oilless versions do not contaminate the air or fluid being compressed|
|Piston-type compressors||These can achieve high pressure, as high as 5,000 PSI or more||Relatively low—a typical 5 HP compressor provides about 18 CFM||Usually lubricated and tend to contaminate the compressed fluid|
|Rotary screw/reciprocating compressors||Can deliver up to 250 PSI for single-stage units or up to 600 PSI for two-stage units||Most large units can generate up to 2,500–3,000 CFM||They have minimal oil contamination, but not clean enough for sensitive applications|
|Centrifugal compressors||Relatively low||Very high, sometimes over 200,000 CFM||They can produce clean, oil-free compressed air|
|Axial compressors||Relatively low||Highest amount of airflow, from 8,000 to millions of CFM||Do not produce clean air, but this is fine for most of their applications|
Due to their design and working principle, scroll compressors are usually small in size. They tend to have leakages between the vanes of their scrolls, and larger units leak more and lose efficiency.
Also, large displacement scroll compressors require massive scroll elements, making them impractical.
Scroll compressors can be lubricated or oilless. They come in different designs, with somewhere the scrolls do not actually touch. This eliminates the need for flooding the compressor with oil or lubricant, providing clean air.
However, there are also lubricated and even oil-flooded scroll compressors, especially those that require a high compression ratio.
The way scroll compressors work is simply genius. The interlocking vanes can compress fluid with almost 100% efficiency and very little noise. Plus, they have very few moving parts and are extremely reliable and long-lasting.
That being said, scroll compressors have limited flow and pressure output. They are great for niche applications where clean air or refrigerant is required such as air conditioning, food processing, and medical laboratories, among others.
If you’re looking to buy a scroll compressor, you need to make sure that the one you choose will supply enough airflow at the right pressure for all your equipment. It also needs to meet your installation and performance needs.
Here at Industrial Stores, our expert staff are well-equipped to help you find the best scroll compressor for your needs. We will also source the right unit for you, get you reduced prices, and deliver the unit to you quickly and safely.
Shop for scroll compressors at Industrial Stores today to discover the best prices.
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