Avoiding Adverse Environmental Conditions - Parker H Series Installation & Service Instructions Manual

Safety Guidelines for the Application, Installation and Maintenance of Solid State Control

3.6 Avoiding Adverse Environmental Conditions

3.6.1 Temperature
Solid state devices should only be operated within the
temperature ranges specified by the manufacturer. Because
such devices generate heat, care should be taken to see
that the ambient temperature at the device does not exceed
the temperature range specified by the manufacturer.
The main source of heat in a solid state system is the
energy dissipated in the power devices. Since the life of
the equipment can be increased by reducing operating
temperature, it is important to observe the manufacturer's
"maximum/minimum ambient temperature" guidelines,
where ambient refers to the temperature of the air
providing the cooling. The solid state equipment must be
allowed to stabilize to within the manufacturer's
recommended operating temperature range before
energizing control functions.
When evaluating a system design, other sources of heat
in the enclosure which might raise the ambient temperature
should not be overlooked. For example, power supplies,
transformers, radiated heat, sunlight, furnaces,
incandescent lamps, and so forth should be evaluated.
In instances where a system will have to exist in a very
hot ambient environment, special cooling methods may
have to be employed. Techniques that are employed
include cooling fans (with adequate filtering), vortex
coolers, heat exchanges, and air conditioned rooms.
Over-temperature sensors are recommended for systems
where special cooling is employed. Use of air conditioning
should include means for prevention of condensing moisture.
C.3.6.1 Temperature
Operation above the maximum rated temperature will
usually result in many failures in a short time. Nuisance
type malfunctions can also be encountered as a result of
elevated ambient temperature. These malfunctions, when
they occur, are usually temporary and normal operation
resumes when temperatures are lowered.
Some solid state devices temporarily cease to function
when ambient temperature is below their minimum rated
operating temperature. Operation in cold environments
should be avoided or heaters should be installed in the
equipment enclosures to bring the system up to the
minimum specified operating temperature before applying
power to the system.
Air circulating in a non-ventilated enclosure with equipment
operating will be at a higher temperature than the room in
which it is installed. A temperature differential of 10 to 20
degrees Celsius can be expected in a typical industrial
installation.
Also see section 2.1.
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