Creating and maintaining precise conditions is a complex process - but an essential one in mission critical environments like data centres and server rooms, as well as many other settings such as laboratories, hospitals and pharmaceutical manufacturing plants.
That’s where close control cooling comes in - or precision cooling as you may sometimes hear it referred to. But what exactly is this system of temperature control? And how does it differ from comfort cooling?
In short, comfort cooling is designed to create ideal conditions for people, whereas close control is designed to create ideal conditions for equipment.
To understand this in greater detail, we first need to look at the two forms of heat relevant to air conditioning.
Sensible heat - this refers to a change in temperature only. Heat is added or removed to increase or decrease the temperature of an object without affecting its state.
Latent heat - this refers to heat that causes a change in state without affecting temperature (think water turning to vapour or ice turning to water).
Understanding this is key to understanding sensible and latent cooling - the first is used to remove heat, while the second is used to remove moisture.
Now we’ve explained this, we can explain more about the differences between close control and comfort cooling.
Close control systems focus on precise temperature, humidity and airflow control along with specified levels of air filtration, and are specifically designed for environments with sensible cooling requirements.
In a data centre, for example, an excessive amount of sensible heat is generated by equipment - far greater than the heat generated in a space occupied by people. This heat needs to be removed to protect from equipment failure.
At the same time, data centres are closed off - unlike an office, say, where doors are continually opened and closed - and have minimal human presence, so there is little need for the removal of moisture, because little moisture is present.
Close control systems have a sensible heat ratio of 0.80 to 1.0, meaning 80 to 100% of effort is focused on heat removal. By contrast, comfort systems have a sensible heat ratio of 0.60 to 0.70, so between 60 and 70% of effort is focused on heat removal, and the other 30 to 40% focused on lowering absolute humidity.
Because close control systems are far more capable of sensible cooling, they are the most appropriate solution for maintaining the integrity of mission critical environments.
Beyond this, there are other key differences between close control and comfort cooling systems:
Close control systems are designed to handle high density heat loads - they move significantly larger volumes of air compared to comfort cooling systems.
Close control systems provide control of relative humidity - data centres have very specific relative humidity requirements. Too high and condensation and corrosion can occur, too low results in an increase in static electricity. Close control systems are designed to provide an accurate ratio of cooling, humidification and dehumidification to meet these needs, whereas comfort cooling systems generally offer no control over relative humidity.
Close control systems offer greater filtration - equipment housed in data centres is highly sensitive to dust and other particulates. As such, close control systems use much higher grade filters than their comfort cooling counterparts.
Close control systems are designed for continual operation - as cooling is a constant requirement in mission critical environments, they’re capable of running 24/7 year round, unlike comfort systems which are designed for limited daily use in the summer months.
To summarise:
Close control systems are designed to handle high density heat loads. They have a higher sensible heat ratio, and are used on a constant basis for close control of temperature and relative humidity.
Comfort air conditioning is designed for both sensible and latent cooling at low density heat loads. It is made for intermittent use to create comfortable conditions for people.
If you’re looking for more advice on close control cooling solutions, we’re happy to help. We have years of experience in the design, installation and maintenance of systems for close control applications.
