User`s guide

Hardware
Mitsubishi Electric, MA00758A 53
3.10.4 Ambient Temperature
The maximum ambient temperature for the operator panel is provided in the speci-
fications. The ambient temperature refers to the temperature in the device cabinet
which cools the panel’s electronics.
In most cases, the ambient temperature for the operator panel is significantly higher
than the device cabinet’s ambient temperature.
If the cabinet is tall and there are a number of heat-generating devices, the tempera-
ture at the top of the cabinet will be considerably higher than the theoretical temper-
ature increase that would be expected. All electronics are sensitive to heat. The
lifespan of an electrolytic capacitor is cut in half with an 8-10 ° increase in tempera-
ture. A 15-20 ° temperature increase results in a quarter of the lifespan etc.
Rittal has a good program for estimating the anticipated average temperature in the
cabinet as well as a large program for controlling the temperature in the device cabi-
net.
An enamel-coated steel cabinet has a radiant heat value of 5.5 W/m
2
and degrees C.
Installing a fan inside the cabinet will even out the temperature, while moving air
provides considerably better cooling than still air. A suitable fan is a 120 x 120 mm
axial fan, available in 24 V DC, 115 and 230 V AC.
Install the fan so that it sits in the cooler area and will blow cold air against the oper-
ator panel. If the fan is mounted at the top and sucks air upwards, the fan’s ambient
temperature will be higher = shorter lifespan.
A good fan with a ball-bearing mounting has an expected lifespan of at least 40,000
hours (not a guaranteed lifespan) at 40 °C. This corresponds to at least 4 years of con-
tinuous use. If a thermostat is installed, the fan only needs to come on when needed.
Large graphic terminals draw only one fifth of the current when the background
lighting is off. The loss effect drops from e.g. 25 W to only 5 W.
The operator panel’s loss effect = supply voltage x current. Virtually no power goes
to external users and no loss effects due to inputs.
5354
Top
50
° inside
Middle
45
° inside
Bottom
40
° inside
Operator
panel
30
°C outside
Power
Power
Power
Airflow
Axial fan
120x120 mm