Cleanrooms typically have very specific demands and requirements. Obviously, that means there's no such thing as a "one-size fits all" approach to designing and installing an HVAC system for a cleanroom. However, even though the details will vary, there are some considerations to always keep in mind.
System vs. Unit
Many people confuse the HVAC unit with the HVAC system. Your HVAC unit or air-handling unit (AHU) is the enclosed equipment. This includes cooling coils and heating coils, as well as the humidifiers. Basically, all of the contained parts that are used to cool, heat, and humidify the air constitute the AHU. However, your HVAC system also includes your ductwork, your diffusers, the air return, and any control or monitoring systems. This distinction is important to keep in mind when designing an HVAC system for your cleanroom.
Conventional vs. Cleanroom
Conventional HVAC systems and cleanroom HVAC systems have a lot of areas where they overlap. They both control temperature and humidity, while maintaining a comfortable environment. However, there are many distinctions between the two. A cleanroom will have far more demanding specifications, especially when it comes to particulates and humidity. Additionally, air pressure, air supply, airflow patterns, and air changes per hour must all be considered. Most conventional HVAC systems accommodate air changes per hour of around 2 to 4. That's nothing when compared to a cleanroom. Most cleanrooms require anywhere from 15 to 250 or more. Clearly, maintaining the optimal environmental conditions for the cleanroom is the more demanding task. Pressurization is also tremendously important. The appropriate pressure differential must always be maintained. This prevents unclean air from escaping and traveling back to a cleaner zone. As you know, contamination must be avoided at all costs, and the pressure differential is key.
Estimated vs. Accurate
It's unfortunate, but there's no such thing as a shortcut when it comes to designing the perfect HVAC system for your cleanroom. There are many calculators available online, which you may be tempted to use. However, when you're looking to calculate the necessary airflow (often listed at CFM or cubic feet per minute) and air changes per hour (ACH), you won't want to rely on a simple Internet-based tool. Those estimates may get you in the ballpark of where your HVAC system should be, but it's not accurate enough for the engineering and design demands of your cleanroom. Your engineer will require far more information than that, and it can't simply be a good guess. If you want a cleanroom that fits your exacting specifications, the data must also be as precise as possible. One big issue is always the space requirements. This will be determined by the number of people, amount of equipment needed, and layout, as well as other factors. Your cleanroom class will obviously be essential information, but the number of rooms will also make a huge difference. Be sure to share any and all pertinent details, so your cleanroom HVAC
system can be as useful and efficient as possible.