Cooling Surveillance SystemsBy Ben Wood, Published Jan 29, 2012, 12:00am EST
An IPVM survey and discussion addressed the topic of “How often, if ever, do you add additional cooling measures to rack/ equipment rooms?” The survey results show that 70% of the respondents replied “0-20% of installs” indicating that it is not something generally addressed or provided by security integrators. However, a recent IPVM update on hard drive failures shows that integrators are experiencing a significant number of hard drive failures due to heat. In this update, we’ll take a look at why cooling is important, determining when additional cooling measures may to needed, and what cooling measures can be added to racks to reduce equipment failures.
Why is cooling important?
Heat is the number one killer of electronic equipment such as CPU’s and hard drives. Rack equipment manufacturers cite studies by BCC and the Uptime Institute that show an estimated 55% of electronic failures were due to heat [link no longer available], and that for every 10% rise over 85 degrees digital equipment’s lifespan is reduced by up to 40% [link no longer available]. As a design goal, the equipment in the rack should be kept at or below 85 degrees for maximum performance and lifespan of rack mounted electronic equipment.
Why is cooling important for surveillance?
As more equipment with greater processing power is installed in the same amount of rack space, heat buildup is inevitable and should be a significant concern. Increases in manufacturing technology of video servers and storage appliances have made them smaller and more powerful, allowing more equipment to be installed within a single rack. A video server that used to take up 2 rack units coupled with a RAID storage array that took up 3 rack units just a few years ago is now frequently combined into single server/storage video appliance in a 2 rack unit form factor, more than doubling the video processing and storage capacity per rack unit. The logical approach is to maximize rack space and install as many units as possible in a rack, but rack cooling often gets overlooked leading to equipment failures.
Advances in technology are reducing the amount of floor space required. Communications rooms in new facilities are now becoming smaller, many times becoming a closet instead of a room. In existing facilities, many small storage rooms are converted to network equipment closets for network and video equipment. As more equipment is being installed in smaller rooms, heat buildup becomes even more of an issue if adequate air conditioning and rack cooling measures are not provided.
When should installing rack cooling equipment be considered?
The two primary factors to be considered are equipment and environment:
Equipment: What equipment are you installing in the rack? A good rule of thumb is “more power equals more heat” - the more power that is required for the equipment, the more heat it will generate.
- Equipment racks consisting mostly of low or no power equipment such as patch panels and network switches generally will not require additional cooling.
- A rack mounted 16-camera system with a single DVR and network switch does not use a significant amount of power and will most likely not require any additional cooling, unless it is being added to an existing rack with other equipment.
- A larger system of 100+ cameras with multiple network video appliances will likely require additional cooling depending on the heat output of the equipment, ambient temperature, and air handling characteristics of the equipment room.
Environment: What is the ambient temperature of the room where is the rack being installed? Does the room have its own dedicated thermostatically controlled air handling system or are air ducts branched in from a central air handling system serving adjacent areas. What effect will adding the equipment rack have on the temperature of the room?
Rack equipment manufacturers such as Middle Atlantic and others have thermal calculators on their websites which are extremely useful tools to determine if additional rack cooling is required. The thermal calculators will ask for the waste heat output of the equipment in BTU/hr., current draw of other equipment in the rack, and the ambient temperature of the room. This information can usually be found on manufacturers’ equipment data sheets.
Let’s look at a real world example of a head-end rack consisting of video recording appliances for a 200 camera system using Middle Atlantic’s Thermal Calculator [link no longer available]. This calculator determines how much additional rack cooling may be required to keep the equipment temperature in the rack at 85 degrees.
This example installation will have 2 Cisco 48-port PoE network switches and 5 NVR appliances installed in a single rack. We will assume that UPS power is fed to the rack from separate source. Looking at data sheets, we can determine: each NVR appliance: 2600 BTU/hr x 6 units = 13,000 BTU/hr. (Note: The specified rate should always be used for these calculations.) The Cisco network switch data sheet does not indicate a thermal specification, but the amperage draw is listed at 5A, x 2 units for a total of 10A.
Using the Middle Atlantic thermal calculator for this example, at a 73 degree ambient temperature, this rack will require an additional 1,312 CFM of airflow to keep the rack equipment at 85 degrees.
How does rack cooling work?
Most rack cooling systems consist of a either a top mount fan kit or ventilated rear door kit with a multiple cooling fans that pull cool air from the bottom of the rack and exhaust it to the top toward the air handler’s return grille. More extreme cases may require separating equipment into multiple racks, or the use of rack-mounted heat exchangers. Middle Atlantic offers a very detailed white paper on various rack cooling methods and the proper installation methods on their website at: http://www.middleatlantic.com/pdf/ThermalManagement.pdf [link no longer available]. It is extremely important to install the rack cooling devices properly or they will be ineffective.
In our example case, assuming we were using a Middle Atlantic rack, by simply adding a high CFM split rear door kit would provide 1,320 CFM of airflow and would keep our rack equipment at 85 degrees.
What effect does the room’s ambient temperature play?
The cooler the ambient temperature of the room, the less additional cooling is required, and vice versa. In our example, if the room’s ambient temperature was 70 degrees instead of 73, only 1,050 CFM of additional cooling would be required. If the ambient room temperature was 77 degrees, it would require 1,968 CFM. A few degrees in either direction significantly impacts additional cooling requirements. This is why it is important for the room temperature to remain as constant as possible.
For our example, it would be impractical to install this equipment in a room that did not have a thermostat to keep the room temperature constant, as adding this amount of equipment to a small room without a thermostat will increase the ambient temperature and require more rack cooling. If a dedicated air handler is not available, consideration must be given to installing one such as a wall-mounted ductless unit by an air-conditioning contractor. Without proper air conditioning, rack mounted cooling devices by themselves may not be enough to reduce heat buildup.
For extremely large applications with multiple racks of servers, it will often require the services of an HVAC engineer to perform more advanced room thermal calculations and properly design the air handling system to protect the equipment.
By performing a simple thermal calculation prior to installation, a consultant or integrator can determine when additional rack cooling may be required. When additional rack cooling measures are required, addressed and installed properly they will increase the uptime, performance and lifespan of video surveillance system head-end hardware, as well as reduce CPU and hard drive failures. Taking a proactive approach to equipment cooling with the customer also shows a commitment to providing a system that will perform better, last longer and bring added value as a consultant or integrator.
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