Are you worried about your air conditioning systems performance on days like today? With temperatures in the single-digits many IT managers may be concerned about the ability of their cooling system to provide capacity.
Thankfully if you are the owner of Liebert precision cooling equipment you don’t have to worry.
All Liebert cooling systems use some form of controlling the cooling circuit to maintain the operating refrigeration pressure at an acceptable level. This ensures the systems is capable of providing rated cooling capacity. All Liebert air-cooled systems will use some form of low ambient temperature control. The most common method used is condenser fan speed control. This system will slow the speed down or even turn off the outdoor condenser fan(s) to ensure the refrigerant pressure is high enough to circulate thru the entire circuit. If you see your condenser fans off, this is likely the reason. Fan speed systems have been tested down to ambient temperatures of -20 degF.
Some installations in our area may be fitted with a heated refrigerant receiver system called Lee-Temp. In lieu of staging the condenser fans, a heated refrigerant receiver is used to collect the refrigerant being pumped to the condenser. This system is the standard for northern climates where temperatures routinely get to where we are today. If you have this type of system you may also find your condenser fans off.
If you operate water-cooled or glycol-cooled systems the low ambient operation is different. These fluid-cooled systems will rely on a percentage glycol concentration to ensure freezing does not occur. In the Delaware Valley it is common to see the circuit be 30% by volume.
Operators of glycol systems will be glad to see days like today. Certainly the ambient temperature is cold enough to allow the pumped glycol to be cooled to a low enough temperature to provide all the cooling your server room requires. The energy savings on days like today will be quite noticeable.
Conventional cooling systems – such as roof-top mounted units or wall-mounted systems unfortunately are not designed to provide cooling during temperatures this low. It is one of the drawbacks in applying this type of air conditioning to a server room application. If you have one of these systems you will likely see the cooling circuit (compressor) stop working due the inability to keep the refrigerant pressure high enough to operate.
If you are interested in more information on this issue, please download Emerson’s White Paper entitled: "Precision versus Comfort Cooling, Choosing a Cooling System to Support Business-Critical IT Environments"
