Although many electrical enclosures are naturally ventilated, there are a number of sound technical reasons for using sealed electrical enclosures. These include keeping components clean, dry, and preventing ingress of corrosive materials and dust. However, modern electrical and electronic equipment generates a significant amount of heat that must be removed from the enclosure, and sealed electrical enclosures cannot rely on traditional ventilation or fans for cooling. Thus, closed loop cooling is needed to ensure internal temperatures are maintained at safe levels.
Although you’ve typically purchased the enclosure cooling system and enclosure from separate manufacturers, it is possible to speed up planning time by purchasing as a package.
Here are six tips to help you choose the right enclosure and cooling package:
Sealing Quality of the Enclosure
Firstly, it’s wise to clarify the degree to which an enclosure is sealed as this impacts on the protection of internal components, and to an extent, on the efficiency of the enclosure cooling system.
At the very least, you should select an enclosure that has protection against windblown dust such as a NEMA 12 enclosure, but bear in mind this does allow limited dust ingress. If you require total protection, select a NEMA 4 rated enclosure. If corrosive chemicals, weathering, or a polluted environment are an issue, choose a NEMA 4X stainless steel enclosure. NEMA 4 and 4X ratings also provide protection against strong water jets and are ideal in outdoor locations.
Enclosures may be floor mounted or free standing. Select an enclosure that is adequately sized for your application, and allow for the possibility that it may require upgrading or be subject to alteration at some stage in the future.
Allow For Heat Load
As the enclosure is sealed, it’s important to carefully calculate the heat load. Sources of heat include the components in the enclosure, the effect of solar radiation, and any localized heat sources near the enclosure. Take note of the ambient temperature where the enclosure is to be located as this determines the cooling options available. Don’t neglect to account for the heating effect of high currents in power distribution enclosures.
Select Air Conditioner Capacity
When calculating the size of the enclosure air conditioner, avoid the temptation to oversize the unit. Although the air conditioner may have adequate capacity, it will cycle frequently, be less efficient, and the frequent cycling may lead to early failure. Conversely, if the air conditioner is too small, the enclosure temperatures will be too high. The best method is to use an online calculator to size the air conditioner and, if there are any special factors that the calculator does not make adequate allowance for, to seek technical advice.
During the layout designing of the electrical enclosure, allow for the required air conditioner cut-outs and the position of the enclosure air conditioner. Is there space for the electrical enclosure and adequate air circulation? Also, check that the required air conditioner will physically fit the enclosure.
Useful Extra Features
Before finalizing your selection, consider including some options that will enhance the reliability of your package.
Door kill switch: This switches the air conditioner off when the enclosure door is opened, thus preventing continuous operation during panel maintenance.
Remote monitoring: Although enclosure cooling systems are extremely reliable, it’s good practice to install some form of remote monitoring; failure of the cooling system could lead to equipment damage and plant downtime within a short period of time.