Technology
Rooms
Communications,
Technology Rooms Air Conditioning
Precision
environmental control requirements now reach far beyond the confines of the traditional
data centre or computer room to encompass a larger suite of applications, referred to as
"Technology Rooms".
Typical
technology room applications include:
1.
Medical equipment suites (MRI, CAT scan)
2.
Clean rooms
3.
Laboratories
4.
Printer/copier/CAD centres
5.
Server Rooms
6.
Hospital facilities (operating, isolation rooms)
7.
Telecommunications (switch gear rooms, cell sites)
Problems
Caused by the Wrong Environment
A
poorly maintained technology room environment will have a negative impact on data
processing and storage operations. The results can range from data corruption to complete
system shutdowns and failures. (The plastic buckets in the picture are to collect water dripping from the aircon unit positioned directly above the company's servers)
1-
High & Low Temperature
A
high or low ambient temperature or rapid temperature swings can corrupt data processing
and shut down an entire system. Temperature variations can alter the electrical and
physical characteristics of electronic chips and other board components, causing faulty
operation or failure. These problems may be transient or may last for days. Even transient
problems can be very difficult to diagnose and repair.
2-
High Humidity
High
humidity can result in tape and surface deterioration, head crashes, condensation, and
corrosion, paper handling problems, and gold and silver migration leading to component and
board failure.
3-
Low Humidity
Low
humidity greatly increases the possibility of static electric discharges. Such static
discharges can corrupt data and damage hardware.
Differences
Between Precision Air and Comfort Air Conditioning
Sensible
Heat Ratio
A
heat load has two separate components: sensible heat and latent heat. Sensible heat
removal or addition causes corresponding changes in air-dry bulb temperature. Latent heat
is associated with the increase or decrease in the moisture content of the air. The total
cooling capacity of an air conditioner is the sum of the sensible heat removed and the
latent heat removed.
Total
Cooling Capacity = Sensible Cooling + Latent Cooling
The
Sensible Heat Ratio is the fraction of the total cooling that is sensible.
Sensible
Heat Ratio (SHR) = Sensible Cooling
In
a technology server room, the cooling load is made up almost entirely of sensible heat
coming from IT hardware, lights, support equipment, and motors. There is very little
latent load since there are few people, limited outside air, and usually a vapour barrier.
The required SHR of an air conditioner to match this heat load profile is very high,
0.95-0.99. Precision air conditioning is designed to meet these very high sensible heat
ratios.
In
contrast, by sizing the air-cooling unit based on comfort cooling typical of a normal
office environment, comprising of a room occupied mainly by people and a few PC’s,
the SHR of 0.65-0.70, will provide too little sensible cooling and too much latent
cooling. The excess latent cooling means that too much moisture is continually being
removed from the air. In order to maintain the desirable 35-50% relative humidity band,
continuous humidification would be necessary, which by definition consumes large
quantities of energy.
Air
Quality
The
ideal room for technology equipment should have a high airflow rate per unit of heat
removed, generally, 160 CFM (76 Lps) per kW or greater. This high volumetric rate moves
more air through the space improving air distribution and reducing the chance of localized
hot spots. Modern technology equipment generally consumes around 160 CFM for each kW of
electrical power consumption, so it is important that this quantity of cool supply air be
available at the equipment inlet. If it is not, the equipment will obtain some of its air
from other areas of the room, often resulting in dangerously high inlet temperatures.
Design
Criteria
Load
Density
Due
to the high equipment concentration, the load density within a technology room can be five
times higher than that in a typical office. Systems must be designed to handle this
extremely high-density load. Sensible capacity and air distribution are very important.
Load
Density
Office
5 - 15 watts / sq. ft. (54 - 161 watts / sq. m)
Technology
Room 50 - 200 watts / sq. ft. (538 - 2,153 watts / sq. m)
Outside
Air Requirements
Technology
rooms tend to be sparsely populated and do not require much outside air for personnel.
Outside air should be minimized to limit the latent load brought into the room. A quantity
of 20 CFM (9.4 Lps) per person is currently sufficient to satisfy Indoor Air Quality
Redundancy
Redundancy
is achieved by operating additional equipment to provide 100% of the required cooling
capacity even after a unit shutdown or failure of one or more units. The cost of
redundancy should be weighed against the projected cost of technology room downtime.
Security
The
security of the air conditioners is as important as that of the technology room hardware
since the hardware cannot operate without them. The indoor units must be located within
the technology room and should be subject to the same restricted access as the IT
hardware. The outside heat rejection equipment should be placed on a roof or some other
secure area within the facility.
Summary
Today's
technology rooms require precise, stable environments in order for sensitive electronics
to operate optimally. Standard comfort air conditioning parameters are ill suited for
technology rooms, leading to system shutdowns and component failures.
Information
processing is the lifeblood of all critical operations. Therefore, your company's health
is dependent on the technology room reliability. IT hardware produces an unusual,
concentrated heat load, and at the same time, is very sensitive to changes in temperature
or humidity. A temperature and/or humidity swing can produce problems ranging from
processed "gibberish" to a complete system shutdown.
This
can create huge costs for an organization, depending on the length of the interruption and
the value of time and data lost. The calculations used to specify air conditioning for
offices and domestic applications are not the same to measure the heat load profile of
technology rooms, nor will they take account of the precise temperature and humidity set
point required for these applications. What is required is a level of flexibility and
redundancy necessary to keep the technology room up and running 24 hours a day.