For the longest time we have been using this form on EXAIR.com to get the information we needed to manually calculate the internal and external heat loads and ultimately make a recommendation on which Cabinet Cooler System would be best for that application! Typically it would take thirty minuets to an hour to get a email back from a application Engineer!
While the manual Cabinet Cooler Sizing Guide worked great (and we will still reply within 24 hours), we have been racking our heads over here to better that process and get you a solution faster than ever! Now you type in your information and you have a recommendation and a link to that product on the website where you can learn more or place an order! So you can go from form to order in less than 5 Minuets!!!! Check it Out HERE!!
By providing certain information like size of the enclosure, NEMA rating needed, and environmental conditions, this new calculator will sort through our large selection of ready-to-ship Cabinet Cooler® Systems and provide instant feedback on the best model number for any applicable electrical enclosure. Taking the guess work out of the equation, EXAIR’s Calculator ensures the customer that they can be confident in selecting the correct product for their unique specifications. You can even Print the form for your records!
EXAIR’s complete line of Cabinet Cooler systems include 120V AC, 240V AC and 24V DC thermostat voltage, continuous operation, type 316 stainless steel and high temperature models – all of which are selectable with the new calculator. Find this new tool on the website EXAIR.com, in the Knowledge Base Calculators, along with many other resources, such as the CAD Library and Application Database, which also help customers choose a perfect solution. Cabinet Cooler systems start at $534. https://www.exair.com/knowledgebase/calculator-library/cabinet-cooler-system-calculator.html
Pressure drops, incorrect plumbing, undersized piping, insufficient flow; if you hear these terms from tech support of your point of use compressed air products or from your maintenance staff when explaining why a process isn’t working then you may be a victim of improper compressed air piping selection. Often time this is due to a continued expansion of an existing system that was designed around a decade old plan. It could also come from a simple misunderstanding of what size of piping is needed and so to save some costs, smaller was used. Nonetheless, if you can understand a small number of variables and what your system is going to be used for, you can ensure the correct piping is used. The variables that you will want to consider when selecting a piping size that will suit your need and give the ability to expand if needed are shown below.
Minimum Operating Pressure Allowed (psig) – Lowest pressure permitted by any demand side point of use product.
System Pressure (psig) – Safe operating pressure that will account for pressure drops.
Flow Rate (SCFM) of demand side (products needing the supplied compressed air)
Total Length of Piping System (feet)
Piping Cost ($)
Installation Cost ($)
Operational Hours ( hr.)
Electical Costs ($/kwh)
Project Life (years) – Is there a planned expansion?
An equation can be used to calculate the diameter of pipe required for a known flow rate and allowable pressure drop. The equation is shown below.
A = (144 x Q x Pa) / (V x 60 x (Pd + Pa) Where: A = Cross-Sectional are of the pipe bore. (sq. in.). Q = Flow rate (cubic ft. / min of free air) Pa = Prevailing atmospheric absolute pressure (psia) Pd = Compressor discharge gauge pressure (psig) V = Design pipe velocity ( ft/sec)
If all of these variables are not known, there are also reference charts which will eliminate the variables needed to total flow rate required for the system, as well as the total length of the piping. The chart shown below was taken from EXAIR’s Knowledge Base.
Once the piping size is selected to meet the needs of the system the future potential of expansion should be taken into account and anticipated for. If no expansion is planned, simply take your length of pipe and start looking at your cost per foot and installation costs. If expansions are planned and known, consider supplying the equipment now and accounting for it if the additional capital expenditure is acceptable at this point.
The benefits to having properly sized compressed air lines for the entire facility and for the long-term expansion goals makes life easier. When production is increased, or when new machinery is added there is not a need to re-engineer the entire system in order to get enough capacity to that last machine. If the main compressed air system is undersized then optimal performance for the facility will never be achieved. By not taking the above variables into consideration or just using what is cheapest is simply setting the system up for failure and inefficiencies. All of these considerations lead to an optimized compressed air system which leads to a sustainable utility.
Is your electrical cabinet overheating and causing expensive shut downs? As spring and summer approach, did your enclosures have seasonal overheating problems last year? Is your electrical cabinets AC Unit failing and breaking down? Then it may be time to consider EXAIR Cabinet Coolers Systems. These systems are compressed air powered cooling units designed to keep your cabinet cool in hot environments. Major benefits include no moving parts to wear out, UL listed to maintain the NEMA integrity of your enclosure (also CE compliant), they are simple and quick to install and they reliably turn on and off as needed (perfect for solving seasonal overheating).
Just one question then; how do you pick which Cabinet Cooler is best for your application? It’s time to bust out ye ole trusty calculator and crunch some numbers. Keep in mind that the following calculations use baselines of an Inlet air pressure of 100 psig (6.9 bar), compressed air temperature of 70F (22C), and a desired internal temp of 95F (35C). Changes in these values will change the outcome, but rest assured a Cabinet Cooler system will generally operate just fine with changes to these baselines.
Before we dig right into the math, keep in mind you can submit the following parameters to EXAIR and we will do the math for you. You can use our online Cabinet Cooler Sizing Guide and receive a recommendation within 24 hours.
There are two areas where we want to find the amount of heat that is being generated in the environment; this would be the internal heat and the external heat. First, calculate the square feet exposed to the air while ignoring the top. This is just a simple surface are calculation that ignores one side.
(Height x Width x 2) + (Height x Depth x 2) + (Depth x Width) = Surface Area Exposed
Next, determine the maximum temperature differential between the maximum surrounding temperature (max external temp) and the desired Internal temperature. Majority of cases the industrial standard for optimal operation of electronics will work, this value is 95F (35C).
Max External Temp – Max Internal Temp Desired = Delta T of External Temp
Now that we have the difference between how hot the outside can get and the max, we want the inside to be, we can look at the Temperature Conversion Table which is below and also provided in EXAIR’s Cabinet Cooler System catalog section for you. If your Temperature Differential falls between two values on the table simply plug the values into the interpolation formula.
Once you have the conversion factor for either Btu/hr/ft2, multiply the Surface Area Exposed by the conversion factor to get the amount of heat being generated for the max external temperature. Keep this value as it will be used later.
Surface Area Exposed x Conversion Factor = External Heat Load
Now we will be looking at the heat generated by the internal components. If you already know the entire Watts lost for the internal components simply take the total sum and multiply by the conversion factor to get the heat generated. This conversion factor will be 3.41 which converts Watts to Btu/hr. If you do not know your watts lost simply use the current external temperature and the current internal temperature to find out. Calculating the Internal Heat Load is the same process as calculating your External Heat Load just using different numbers. Don’t forget if the value for your Delta T does not fall on the Temperature conversion chart use simple Interpolation.
Current Internal Temp – Current External Temp = Delta T of Internal Temperature Surface Area Exposed x Conversion Factor = Internal Heat Load
Having determined both the Internal Heat Load and the External Heat Load simply add them together to get your Total Heat Load. At This point if fans are present or solar loading is present add in those cooling and heating values as well. Now, with the Total Heat Load match the value to the closet cooling capacity in the NEMA rating and kit that you want. If the external temperature is between 125F to 200F you will be looking at our High Temperature models denoted by an “HT” at the start of the part number.
If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.
Cody Biehle Application Engineer EXAIR Corporation Visit us on the Web Follow me on Twitter Like us on Facebook
One of the free services we offer to customers here at EXAIR is our Efficiency Lab. In case you are not familiar here is a brief synopsis. Speak with an Application Engineer about your existing compressed air blowoff/point of use product and that you would like to know how much air it consumes. Fill out the brief survey and send the product you use in to our facility. Let us perform tests on calibrated test equipment to determine the force, flow, and noise level. We will then issue you a report that states what the EXAIR model would best be suited (if applicable) as well as how much compressed air you will be able to save. Order the recommendation and start saving money.
To do these evaluations, we have to have calibrated equipment that is reliable and capable of handling vast range of products we may receive in. For this, we could use a Digital Flowmeter, in some cases that is what has to be done due to large flow rates. For the majority of these though we go old school. We utilize a piece of equipment called a rotameter.
This is a device that is designed to measure the flow rate of a fluid within a closed tube. The inside diameter of the tube is varied which causes the float within the meter to raise or lower. They are calibrated for a specific gas at a given pressure and temperature, most are calibrated for atmospheric conditions, 14.7 psi (1.014 Bar). The meter must be mounted vertically and this is not always best suited for industrial environments.
When testing products the compressed air within the meter is pressurized which means we have to correct the reading for the given pressure, if the temperature is outside of the calibration temp then we must also perform that correction. We do this using a table provided by the manufacturer of the meter or by using the calculations shown to get exact values that may be in between the pressures in the table.
This will allow us to then multiply the Correction Factor by the meter reading and calculate our corrected flow for the point of use device at a given operating pressure and temperature.
Knowing where the values that are measured and calculated come from add validity to the reports and understanding all of the variables that go into reading like this helps to better validate the cost savings that can be seen.
In a pinch, for a field estimation, we can also use these Correction Factors and determine an approximate consumption rate of a device that has been measured at a pressure such as our cataloged 80 psig (5.5 Bar). This can often be done on the fly to help determine the flowrates currently on a system. This can be helpful when troubleshooting, giving estimated simple ROIs, and help justify results and reasons for future purchases of engineered solutions.