Controlling Nature's Way of Cooling
When conventional air conditioning systems were no longer adequate to cool General Tool Company's (GTC) facility in Cincinnati, OH, the company began looking for an alternate solution. What they found was a system that cooled from the outside of the building instead of blowing cool air through the building. GTC had learned of a roof mist sprinkling system from Sprinkool T Systems International, Inc. in Killen , AL , that would provide evaporative cooling of the roof and ceiling zone of the plant to reduce heat build-up and the radiant heat load of the roof.
Since 1981, Sprinkool has manufactured roof mist cooling systems that intermittently mist a very small amount of water on and above the surface of the roof to cool and maintain the roof's surface temperature as close to the ambient wet bulb temperature as possible. With controllers designed and programmed specifically for roof cooling, and with temperature sensors mounted on the roof, the system calculates and mists just the amount of water that can be evaporated on the roof at that particular moment of the day. All of the water is evaporated almost instantaneously, so there is no runoff or wasted water. As the water evaporates from the roof's surface, it absorbs and carries away into the atmosphere over 8600 BTUs for each gallon misted. The system cools the exterior surface of the roof and virtually eliminates the transfer of radiant heat from the roof into the building's interior, without raising the humidity within the building.
The Sprinkool system can be used to reduce the temperature in buildings with or without air-conditioning, and can also supplement aging or marginally-performing A/C equipment. The systems also help reduce electrical power and maintenance costs of existing A/C equipment, and to displace or reduce requirements for mechanical A/C equipment and insulation in new construction.
The system installed at GTC consists of a network of hydraulic piping mounted on the roof's exterior. The network is essentially a supply line, which branches into a number of fields activated by low voltage solenoid valves. Each field contains sprayheads specifically designed for roof mist cooling. The fields are activated on and off based upon the calculations determined by a program running in a Direct LOGIC DL205 PLC system with a D2-240 CPU, using information provided by three analog temperature sensors located on the roof. Each Sprinkool system has a unique program specifically written for the customers' configuration.
The sprayheads, supports, and hydraulic tubing allow for a consistent, low trajectory pattern and coverage of the water being misted. The PLC and its performance are critical to a properly operating system. In the past, Sprinkool had tested many different brands of PLCs and finally settled on AutomationDirect DirectLOGIC PLCs, including the DL06, DL205 and the DL405 series. According to Sean Smith, VP of Technical Services at Sprinkool, "We chose AutomationDirect for ease of use, reliability and durability of the controllers, quick shipping time, and the superior technical support provided by AutomationDirect."
"With systems cooling industrial, commercial and educational facilities, from 8,000 square feet to in excess of 17 acres in size, the flexibility of the PLC and the ease to remotely connect multiple controllers is vital. The PLC must be able to accept the required number of analog inputs needed to profile the conditions on the roof, as well as to provide the number of relay outputs necessary to activate the fields on the roof. "
Another important feature of the Sprinkool system at GTS is the use of a modem. The modem allows for communication with the controller from any location to permit program monitoring, troubleshooting and modification when necessary, without the need for travel and the expense of a service call. Says, Smith, "Prior to the modem, if the customer wished to have the system mist more or mist less frequently, or if a sensor went bad, we would have to fly or drive to the site and make the changes. Since the system is mounted on the roof and weather being what it is, we would normally plan to be on site for a couple of days. This would of course require traveling time for our personnel, as well as the expenses such trips require. Since our systems are located throughout and outside the USA , this cost could prove to be prohibitive. Now all of Sprinkool's roof misting systems are installed with a modem, which is especially helpful for customers in remote locations."
Sprinkool also offers the option of incorporating an HMI interface between the PLC and the customer with the use of EZText displays and Lookout Direct software, to provide customers with system information, alarm notification, and to allow customers to modify parameters without fear of altering the basic program. The EZText displays numerical information and allows for input from the client, and the Lookout Direct software allows customers to have a graphical view of the system and its operations.
In addition to cooling the facility at GTS, the Sprinkool system provides the added benefit of extending the life of the roof surface by keeping it at a lower temperature. The heat load has also been reduced sufficiently so that the facility's original air conditioning system has been adequate to cool the interior of the building. And, most importantly, the system requires very little maintenance, an important factor for both GTS and Sprinkool.
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