It can be a daunting task for any plant manager or engineer to make the right decision. You make the wrong one and there can be big problems for your plant and for your job outlook. Let’s discuss some of the choices you have at hand.
The first part of your buying process is to decide whether you need an water cooled or air cooled chiller. Now if you are simply replacing or upgrading an older piece of equipment, you will likely replace that unit with the same type of chiller. But if you are handling a new installation, you need to look at your options.
The two most popular types of chillers are Air Cooled or Water Cooled. The “Air” or “Water” cooled designation refers to the type of condenser the chiller is utilizing to cool the refrigerant.
Air Cooled Chiller
Air cooled is the most commonly used chiller system because it is a self-contained system. No additional outside components are needed. These systems are less efficient than water cooled chillers but since they are self-contained, they are much more appealing. An air cooled chiller is relatively easy to install and start-up.
Water cooled chillers require an external cooling tower and cooling tower supply pump to cool the water cooled condenser. If you already have an existing cooling tower at your plant with excess capacity available, then this is your best option to consider.
Once you have made your decision of air cooled or water cooled chiller, you now have to make some harder decisions.
Water Cooled Chiller
If you are looking for a relatively small chiller (under 30 tons), you will have to purchase a scroll chiller. If your cooling requirement is over 30 tons, you have a decision to make. Do you go with the scroll or a screw compressor. There are several things to consider when making this decision.
Scroll compressors are limited in size. Although technology is continuously improving and increasing their size, the current largest scroll compressor you can buy is 40HP. So if you require a larger cooling load, you will need multiple compressors. While that can be a benefit, you need to insure that you do not get multiple compressors on a single circuit.
Screw compressors have their own limitations. The smallest screw compressor is 30HP. That is, however, where their limitations end. On the high end, we have screw compressors in excess of 500HP. At that size, we don’t even have an air cooled condenser big enough to accommodate it. (It would only be installed on a water cooled chiller). Screw compressors are commonly looked as being a true industrial process option. “The right tool for the job.”
Flooded Type Screw Type Chiller
Scroll compressors fit a good niche market. They are excellent for smaller process applications – specifically when the operating time is more sporadic (< 24hrs/day). We classify our scroll units as medium duty process chillers. Scroll chillers can handle longer run times depending on the environment.
If you are planning on running your unit 24/7 and fit the load requirement (over 30 tons), we will always recommend the screw chiller over the scroll system. Screw compressor systems offer better capacity control options, are fully serviceable, and have a wider operating range.