Page 46
www.us-
tech.com Production
Setting the Correct Temperature of an Electrical Enclosure
By Jon LaPorta, V.P. of Marketing, Pfannenberg E
lectrical enclosures serve to protect electrical devices from adverse en- vironmental influences, such as dirt, other particulates, moisture, or chemicals that could damage components. Plus, by housing electrical
devices inside a secure enclosure or box, personnel are protected from electri- cal hazards such as electric shock, arc flash, and burns. However, electrical devices generate heat as a byproduct of their opera-
tion. When the heat load of the electrical devices within an enclosure exceeds the heat dissipation achieved through natural convection, the temperature in- side the enclosure will rise. Since the performance and lifespan of electrical devices will degrade as temperature increases, this excessive heat must be re- moved in order to keep the temperature within acceptable operating limits. The “rule of thumb” warns that for every 18°F (10°C) over their rated temper- ature limit, the life expectancy for electrical components gets cut in half. Cooling units can provide closed-loop cooling, using a refrigeration cycle
to move heat to the outside of a sealed enclosure while maintaining the enclo- sure’s mechanical isolation from the ambient environment. Excessive mois- ture condenses on the evaporator, located on the enclosure side of the closed loop, where it can be effectively removed to keep the humidity level down and electrical components dry. To avoid risking the safety and efficiency an enclosure is designed to en-
sure, operators must optimally set the temperature set point for any enclo- sure cooling unit. When unfavorable, high temperature ambient conditions exist and con-
vection alone cannot adequately maintain an acceptable operational temper- ature. In other words, if the temperature outside the box exceeds the target temperature intended inside the box, convection cooling is not going to work. In these cases, active cooling must be utilized.
Active Cooling Units The enclosure cooling unit is intended to keep electrical equipment in an
acceptable working environment, but this environment is not the same as the 72°F (22.2°C) comfort space that people prefer. A higher working environment temperature is acceptable, and in most instances desired for electrical equip- ment. The acceptable working environment temperature for most electrical devices exceeds 104°F (40°C) and excessive cooling can lead to several pitfalls. Energy consumption and efficiency are ongoing concerns for operation
managers and enclosure cooling units should not be exempt from scrutiny. Excessive cooling leads to wasted energy, increased costs, and unnecessary wear and tear on the cooling units themselves. The needless run time circulates more air through the cooling unit, re-
sulting in increased maintenance. This is particularly true in environments with airborne contaminants. Even highly efficient units with maintenance- free, filterless designs, such as the Pfannenberg DTS series side-mount cool- ing units, which are less susceptible to clogging, might suffer over time if the temperature is set too low. Heat energy is also a necessary component for the optimal performance
of the refrigeration cycle of the cooling unit. The evaporator is the heat ex- changer responsible for transferring the heat energy of the enclosure air to the refrigeration circuit where it can be exhausted to the ambient environ- ment at the condenser. This heat energy transfer increases as the tempera- ture difference between the surface temperature of the evaporator and the air temperature within the enclosure increases. Condensation forms on a surface when its temperature falls below the
dew point. It is common for the evaporator to be colder than the dew point, and Pfannenberg cooling units facilitate the management of condensation that forms on the evaporator through collection and drainage or burn off. An important performance characteristic to be aware of with enclosure
cooling units is the set point hysteresis (or dead band). The manufacturer could design the controller set point at the low-point of the dead band, the high-point, or the mid-point. Pfannenberg uses the mid-point technique with a ±3.6°F (±2°C) hysteresis and a factory default setting of 95°F (35°C). This means the refrigeration cycle will turn on at 98.6°F (37°C) and then will turn off at 91.4°F (33°C). This default setting is adequate for most applications; however, the user
has the ability to change the set point to suit specific circumstances and re- quirements. Cooling units, when properly set up, provide an excellent method for ac-
tive cooling of an electrical enclosure in order to keep electrical devices from exposure to temperatures that are beyond their acceptable operating limits. By using Pfannenberg cooling units, operators of enclosed electronics can pre-
serve the performance and extend the lifetime of their devices. Contact: Pfannenberg Sales America, LLC, 68 Ward Road, Lancaster,
NY 14086 % 716-685-6866 E-mail:
sales@pfannenbergusa.com Web:
www.pfannenbergusa.com r
August, 2019
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88
