Calculate Heat Loads from the Sun for Outdoor Control Panels

I am always happy to see the sun rise each morning. But, electrical panels that are exposed to the sun are not.  Solar heat adds significant BTU’s to the overall heat load in an electrical panel.

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A customer had a VFD to control a 300HP blower motor for a dust collection system. The VFD was getting an over-temp error and shutting down the system.  He contacted EXAIR to get a Cabinet Cooler to keep the VFD cool.  We went through our normal questions to determine the heat load, i.e. the size of the cabinet, the temperature inside, the temperature outside, the maximum external temperature and the desired temperature.  As we went through the questions, he stated that the cabinet was located outside.  This is not an issue for our Cabinet Coolers as EXAIR has NEMA 4 and 4X (IP66) Cabinet Coolers.  It did stem another question; was it under cover?  He mentioned that it was not.

NEMA 4 Cabinet Cooler
NEMA 4 Cabinet Cooler

Generally in calculating cooling capacities with our Cabinet Coolers, we size the units by adding the ambient heat load and the electrical heat load. With the panel exposed to the sun, this adds another component to the total heat load.  To get an estimation on the amount of solar heat, color becomes a big factor as the darker colors will draw more heat.  Here is a good approximation to follow:

Solar heating by color
Solar heating by color

In this application, the customer had a gray panel, a common color. With an exposed surface area of 16 ft^2 (1.47 M^2), we would have to increase the heat load by 16 ft^2 * 7 Watts/ft^2 = 112 Watts.  This equates to 112 Watts * 3.41 BTU/hr/Watt = 382 BTU/hr of added heat.  (Or 112 Watts * 0.86 Kcal/hr/Watts = 96 Kcal/hr).

If an electrical panel is outside and cannot be shaded from the sun, we can still protect the sensitive components inside.  With the proper sized Cabinet Cooler, your equipment will remain running cool.  If you need help to determine the correct Cabinet Cooler, inside or out, you can either contact an Application Engineers at 800-903-9247 or fill out our Cabinet Cooler Sizing Guide.

John Ball
Application Engineer
Email: mailto:johnball@exair.com
Twitter: @EXAIR_jb

 

“The sun” image courtesy of Lima Andruška, https://creativecommons.org/licenses/by-sa/2.0

More Cooling At A Kuwaiti Sewage Station

Overheating electrical enclosure at Kuwaiti sewage station
Overheating control panels for sewage pumps

Last week I wrote a blog about cooling sewage pumps at a facility in Kuwait.  The pumps in question were overheating and needed a way to cool the pump motors down to ambient temperatures.  And, fortunately, our Super Air Amplifiers proved to be a great fit.

On the other side of the same facility, there were control panels for 3.3kV pumps that were also experiencing an overheat condition.  But, the motors were operating properly, it was the electrical panels that were tripping due to excessive heat.

The overheating of the electrical panels would shut down the pump motors, bringing operations to a screeching halt.  What the end user needed was a way to regulate temperature within the electrical panels that was small, effective, and easy to use.

This application, and its requirements, were a perfect fit for our Cabinet Coolers.  Cabinet Coolers are small, effective, easy to install, require no maintenance, and are incredibly easy to use – once installed and setup, they regulate themselves.

By receiving a completed Cabinet Cooler Sizing Guide, EXAIR engineers are able to calculate heat load for an enclosure and recommend a suitable solution.

If you have an overheating cabinet or electrical panel, call an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

EXAIR Cabinet Cooler Systems Stabilize Relative Humidity

EXAIR Cabinet Cooler Systems are able to cool your electrical panels using only clean, dry compressed air. Other systems such as cooling fans or heat exchangers use ambient air full of dust and humidity. The temperature of ambient air also fluctuates with the seasons and will be very warm in the summer months, which degrades their ability to cool as the temperature rises. One of the myths about compressed air cooling is that humidity from the compressed air source will enter the cabinet. A water/dirt filter separator will prevent condensate from entering the cabinet and since relative humidity is carried away with the hot air exhaust, relative humidity will stabilize to 45%. This video shows how quickly EXAIR’s Cabinet Cooler Systems will have an effect on relative humidity.

Dave Woerner
Application Engineer
@EXAIR_DW
DaveWoerner@EXAIR.com

Powering Cabinet Coolers with Compressed Air

Dual CC outside
NEMA 4X Dual Cabinet Cooler

Not too long ago, I was contacted by one of our customers regarding the Cabinet Cooler Systems and the quality of the compressed air used to power them.

The specific questions were:

  1. What happens if the compressed air gets dirty with oil or other particles if sufficient filtration is not available at the facility where Cabinet Cooler is being used?
  2. Where does the oil particle go, into the cabinet or out through the hot exhaust or both?
  3. If it goes into the Cabinet Cooler, should one expect a spray or will it simply form small droplets?
  4. Is there a way to filter the cold air outlet?

Dirty, oil laden air would exhaust throughout the Cabinet cooler (both hot and cold flows) as well as into the inside of the attached cabinet if the air were contaminated and there was not any filter located up-stream of the Cabinet Cooler System. This is precisely why we always recommend the use of filter/separator and oil coalescing filters to clean up the compressed air before it goes into the Cabinet Cooler. In fact, we include a five micron, auto-drain, filter/separator with all our stock systems. If oil is a known contaminant in a customer’s system, we will also recommend use of an oil coalescing type filter which we can provide as well. Without a coalescing filter, you can expect any oil in the compressed air supply to be atomized into a vapor which then has possibility of settling on components inside the cabinet.

Filtering the compressed air while it is still in its compressed state and before it goes into the Cabinet Cooler is the only way to make sure that the air is properly cleaned before processing through the Cabinet Cooler System. Filtering the air after it has gone through the Cabinet Cooler System is not possible. Many filtration systems rely on the high velocity of the compressed air for their filtering capability. If it is no longer in its compressed state (a condition that exists at the cold outlet of the Cabinet Cooler), then the right conditions for proper treatment do not exist. Also, by the time the air exits the Cabinet Cooler, your primary need for it is going to be for cooling anyway. Attempting to add filtration to the cold air output will interfere with the cooling function, which negates the purpose for having the Cabinet Cooler.

As compressed air and the systems that produce it become more widely understood, filtering, drying and removing oil from the compressed air stream are tasks that are done on the production side of things.

The best way to proceed is to have the necessary filtration on the compressed air supply, at the point of use, even if the facility has filtered, clean, dry air. It would still be good to employ it just in case any up-stream equipment that is normally used to clean up the air, went down for some reason. I call it the belt and suspenders method. The redundancy is worth the investment.

Neal Raker, International Sales Manager
nealraker@exair.com