Warmer temperatures are quickly approaching, which may seem like a welcome change for personal reasons, but in a processing line, the increased temperatures can wreak havoc on sensitive components found in an electrical control panel.
EXAIR Corporation will be hosting a FREE webinar titled “Intelligent Solutions for Electrical Enclosure Cooling” on May 23, 2018 at 2:00 PM EDT.
By attending this interactive session, you will learn the difference between the 3 most common NEMA ratings for electrical control panels found in an industrial setting, NEMA Type 12, 4 and 4X. We’ll provide examples of traditional, yet unreliable, methods of cooling and the concerns associated with using these types of devices.
Next we will explain how ignoring heat related issues can cause machines to shut down due to failed electrical components, resulting in lost production and increased maintenance costs, negatively affecting a company’s bottom line.
In closing, we’ll show how using an engineered, compressed air operated solution can reduce downtime by providing a low cost, maintenance-free way to cool and purge control panels with no moving parts.
As you may have seen in our most recent E-NEWS Special Bulletin, or experienced in real life (depending on where you’re located,) most of the eastern United States is seeing a pretty significant heat wave for early summer…or, as we call it at EXAIR, “Cabinet Cooler Season.” And this year is kicking it off with a bang, for sure.
On Tuesday, when the E-NEWS email went out, I was on the phone, processing an order for a Model 4340 NEMA 12, 2,800 Btu/hr, Thermostat Controlled Cabinet Cooler System, to ship overnight to a user who wanted to protect the new drive they were replacing because theirs overheated. They were up and running before noon on Wednesday.
On Wednesday, four local customers placed “will call” orders for Cabinet Cooler Systems. I had the pleasure of talking with one of them, who was installing one for the very first time. As he was looking over the Installation & Operation Guide before he left our building, he just wanted to make sure that hooking it up was as simple as it sounded…and it is. We pulled the parts from the box and went over exactly how each step is performed, and he left feeling confident that he’d have it installed pretty quickly. Just in case, I also got his email address and sent him a link to our NEMA 4 Cabinet Cooler System Installation Video Blog:
I don’t know what the rest of the summer holds in store, but I know this: if you have concerns about protecting sensitive, critical, and/or expensive electrical & electronic enclosures, EXAIR Cabinet Cooler Systems are the solution you’re looking for. Easy to install. Maintenance free operation. Durable, UL Listed, and CE Compliant. If you’d like to discuss your application and get one for yourself, call me; let’s talk.
When an electrical device mounted inside a control panel goes offline due to an overheating condition, it can be difficult to determine which component in the panel is the root cause. There may be an intermittent heat load from a variable frequency drive that isn’t present when troubleshooting, making things appear to be OK. Or, the overheating condition may only happen during peak operation on days with high ambient temperatures.
Fortunately, no matter the root cause, an EXAIR Cabinet Cooler can maintain temperature within the enclosure at a desired set-point, eliminating overheating conditions and lost throughput due to downtime.
When calculating heat load, EXAIR Application Engineers consider the components within the control panel. We inquire with our customers regarding devices such as VFD’s, which may lead to temperature spikes, or fans, which actively remove heat (albeit that they often force dirt and debris into the enclosures they’re designed to be cooling).
Fans can be particularly important, because with the installation of any EXAIR Cabinet Cooler, all external fans will need to be removed, and their openings will need to be sealed (internal fans can remain in place). So, this means we have to account for any heat the fans may already be removing from the application, even if it isn’t enough to keep the enclosure cool.
In order to determine the amount of heat a fan is removing from an application, we consider the diameter of the fan, which corresponds to a typical air flow volume in CFM (cubic feet per minute). We then consider that 1 BTU/hr. is the amount of heat required to raise the temperature of one pound of water by 1 degree Fahrenheit, and it is also the amount of heat needed to raise/lower the temperature of one cubic foot of air by 1 degree Fahrenheit in one minute. This means that for every CFM the fan is moving, we are reducing the temperature of the air by 1°F . To put it another way, we remove 1 BTU/hr. for every °F * every CFM the fan is moving.
As an example, a 3″ fan will move 22 CFM. In an enclosure with a current temperature differential of 15 degrees Fahrenheit, this fan is removing 330 BTU/hr.
15°F * 22 CFM = 330°F*CFM
The fans holes should be covered up with sheet metal using rivets, caulk/sealant, duct tape or other ingenious methods you know of. But please cover and seal the cabinet as well as you can.
Using the Cabinet Cooler Sizing Guide and the experience of the EXAIR Application Engineers, we can accurately calculate heat load of an overheating electrical control panel. When you need help with determining which Cabinet Cooler to use, contact an EXAIR Application Engineer. We’re here to help.
My previous blog post was about how Vortex Tubes react when there is back pressure due to a restriction on either the hot or cold discharge of the Vortex Tube. In it I mentioned that there is a formula to calculate what the cooling capacity (Btu/Hr) will be if there is no way to avoid operating the Vortex Tube without back pressure on the discharge. That is the calculation focus of this blog – calculating Btu/hr of a Vortex Tube with back pressure.
To continue with the same example, the calculations from the previous blog are shown below. Last time the example Vortex Tube was operating at 100 psig inlet pressure, 50% cold fraction, and 10 psi of back pressure. We will need some additional information to determine the Btu/Hr capacity. The additional information needed is the temperature of the supplied compressed air as well as the ambient air temperature desired to maintain. For the example the inlet compressed air will be 70°F and desired ambient air temperature to maintain will be 90°F.
(100 psig + 14.7 psia) / (10 psig + 14.7 psia) = X / 14.7 psia
4.6437 = X / 14.7
X= 14.7 * 4.6437
X = 68.2628
(Values have been rounded for display purposes)
The calculation above gives the compensated operating pressure (X = 68.2628) which will be needed for the BTU/hr calculation. The rated air consumption value of the Vortex Tube will also need to be known. A 30 SCFM rated generator will be used for this example, the normal BTU capacity of a Vortex Tube with a 30 SCFM generator is 2,000 BTU/hr.
First, determine the new consumption rate by establishing a ratio of the compensated pressure (68.2628 psi) against the rated pressure (100 psi) at absolute conditions (14.7 psia).
Second, the volumetric flow of cold air at the previously mentioned cold fraction (50%) will be calculated. To do this multiply the cold fraction setting (50%) of the Vortex Tube by the compensated input consumption (21.7 SCFM) of the Vortex Tube.
50% cold fraction x 21.7 SCFM input = 10.85 SCFM of cold air flow
Third, the temperature of air that will be produced by the Vortex Tube will need to be calculated. For this consult the Vortex Tube performance chart which is shown below. To simplify the example the compensated operating pressure (68.2628 psi) will be rounded to 70 psig and to obtain the 70 psig value the mean between 80 psig and 60 psig performance from the chart will be used.
For the example: A 70 psig inlet pressure at 50% cold fraction will produce approximately an 88°F drop.
Fourth, subtract the temperature drop (88°F) from the temperature of the supplied compressed air temperature (70°F).
70°F Supply air – 88°F drop = -18°F Output Air Temperature
Fifth, determine the difference between the temperature of the air being produced by the Vortex Tube (-18°F) and the ambient air temperature that is desired (90°F).
90°F ambient – -18°F air generated = 108°F difference.
The sixth and final step in the calculation is to apply the answers obtained above into a refrigeration formula to calculate BTU/hr.
1.0746 (BTU/hr. constant for air) x 10.85 SCFM of cold air flow x 108°F ΔT = 1,259 BTU/hr.
In summary, if a 2,000 BTU/hr. Vortex tube is operated at 100 psig inlet pressure, 50% cold fraction, 70°F inlet air to maintain a 90°F ambient condition with 10 psi of back pressure on the outlets of the Vortex Tube the cooling capacity will be de-rated to 1,259 BTU/hr. That is a 37% reduction in performance. If a back pressure cannot be avoided and the cooling capacity needed is known then it is possible to compensate and ensure the cooling capacity can still be achieved. The ideal scenario for a Vortex Tube to remain at optimal performance is to operate with no back pressure on the cold or hot outlet.