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User Solutions
(Issue 3, 2005)
Controlling
Nature's Way of Cooling
Jennifer Gerborg,
Senior Editor
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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 alternative solution. A
roof mist sprinkling system from Sprinkool™ Systems International,
Inc. in Killen, AL, 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
turned on and off based on calculations by a program executed
in a DirectLOGIC 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 customer’s configuration.
The sprayheads, supports, and hydraulic tubing allow for a consistent,
low trajectory pattern and coverage of the water being misted.
The PLC is 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 analog inputs needed to profile the conditions on
the roof, as well as provide relay outputs 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 the expense of a service call. Says, Smith, "Prior
to the modem, if the customer wished to have the system parameters
changed, or if a sensor went bad, we would have to fly or drive
to the site and make the changes. We would normally plan to
be on site for a couple of days, requiring traveling time and
trip expenses. With systems located throughout the USA 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 LookoutDirect software, to provide customers with system
information, alarm notification, and to allow customers to modify
parameters without fear of altering the basic program. The text
panel displays numerical
information and allows input from the client, and the LookoutDirect
software shows customers a graphical view of the system operation.
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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