Enclosure Air Conditioners, Fans, & Heaters Technical Specifications
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With wide spread use of micro-electronics in today's control systems, temperature mangement takes on a new priority in order to ensure steady and reliable performance. The maintenance of a correct operating temperature may combine both cooling and/or heating inside an enclosure which can protect against costly down time and system failures. Before selecting an air conditioner, fan, or heater it is necessary to understand the cooling or heating capacity that your enclosure requires.
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Click here to download for either cooling or heating of electrical/electronic enclosures.
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Click here for a cooling calculation guide.
Click here for a heater calculation guide.
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- Thermal Management - General Selection Consideration
- Thermal Management - Glossary of Thermal Management Terminology
- Thermal Management - Sizing an Air Conditioner
- Thermal Management - General Specifications of Blowers and Fans
- Thermal Management - Sizing Blowers and Fans
- Thermal Management - General Information on Heating Products
- Thermal Management - Heater Sizing Information
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Cooling |
| Conditions |
Solution |
Advantages |
Disadvantages |
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| Maximum desired enclosure temperature is 10°F or 5°C above maximum outside ambient. |
| Oversize the enclosure. |
Easy to implement, no maintenance. Maintains NEMA rating of the enclosure. |
Dissipates small amount of heat. Larger enclosure size takes up more space. |
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| Install ventillation louvers. |
Economical solution, very little maintenance, easy to implement. |
Dissipates small amount of heat. Larger enclosure size takes up more space. |
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| Install filter fans. |
Easy to implement, no maintenance. Maintains NEMA rating of the enclosure. |
Dissipates small amount of heat. Larger enclosure size takes up more space. |
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| Use an air/air heat exchanger. |
Easy to implement, no maintenance. Maintains NEMA rating of the enclosure. |
Dissipates small amount of heat. Larger enclosure size takes up more space. |
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| Maximum desired enclosure temperature lower than maximum outside ambient. |
Use an air conditioner. |
Easy to install. Temperature control via factory installed thermostat. Removes large amounts of heat. Maintains NEMA rating of enclosure, dehumidifies enclosure air. |
Must maintain filter. Generally not to be used when outside temperature is below 59°F (15°C) or above 130°F (52°C). |
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Circulation |
| Conditions |
Solution |
Advantages |
Disadvantages |
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| Localized heat or 'hot spots'. |
Install circulation fans in the enclosure. |
Economical solution, no maintenance, easy to install, Maintains NEMA rating of the enclosure. |
Dissipates small amount of heat. |
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Heating |
| Conditions |
Solution |
Advantages |
Disadvantages |
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| Outside temperature is below minimum allowable equipment operation range. |
Heat with radiant heater. |
Economical power consumption. Reliable, can be temperature controlled. |
Consumes energy, takes up internal panel space. |
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| Condensation occurs. |
Heat with radiant heater to maintain temperature above the dew point. |
Economical power consmpution. Reliable, humidity can be controlled. |
Consumes energy, takes up internal panel space. |
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Construction: Outer shell of sheet steel.
Closed Loop Cooling: Ambient outside air is never mixed with clean dry enclosure air.
Operating Temperature: Minimum +46°F (+8°C). Maximum +125°F (+52°C).
Gasketing: Is provided and/or installed on all units to maintain NEMA ratings specified.
Templates: Provided on all units for easy layout of cutouts and mounting.
Power: Available in 115 V 60 Hz, 110 V 50 Hz and 230 V, 460 50/60Hz 3 phase.
Filter: Removable filter mat made from synthetic fibers are reusable and can be rinsed clean.
Refrigerants: All models use environmentally friendly R134a.
Fans: All blower motors are thermal protected and sealed with permanent lubricants.
Condensate Disposal: Built in condensate evaporators are standard on most models. All units feature a condensate drain fitting complete with hose attachment.
Insulation: Cold components, lines and evaporator compartment insulated for maximum efficiency and protection against condensation.
Quality Assurance: Prior to charging, the refrigeration system is hermetically sealed with all joints brazed under protection gas atmosphere to exclude any internal scale. After a thorough leak test every unit undergoes safety and function checks, then is serialized and packed into sturdy boxes prior to shipment.
Installation Manuals: Included with all models are detail drawings, mounting, schematic and wiring diagrams, a trouble shooting checklist and warranty information.
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The proper selection of an air conditioner is determined by the following steps:
Step 1 - Internal heat load quoted as Watts that must be dissipated.
Step 2 - The exposed surface area of the enclosure.
Step 3 - Temperature differential required between maximum inside temperature and maximum outside ambient.
Step 4 - Final calculation of the above.
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Step One
1 Watt = 3.413 BTU/H
Determine the internal heat load (in Watts) that must be dissipated. |
Step Two
1 m² = 10.76 ft²
Calculate the exposed surface area of the enclosure:
[2(h"xw") + 2(h"xd") + (w"xd")]*(1/144) = Area (ft²)
(Example for freestanding enclosure)
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Step Three
1°C or 1°KΔT=1.8°FΔT
Determine the temperature differential by subtracting the maximum allowable temperature inside the enclosure (Ti) from the maximum ambient temperature outside the enclosure (To).
To-Ti = DT |
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Step Four
(Watts x 3.413) + [1.25 x Area (ft²) x DT (°F)] = BTU/HCapacity Required BTU/H (Capacity Rating of Air Conditioner)
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The DTS/DTT offering is available in the most popular selection of cooling capacities, sizes, voltages, and mounting configurations. Available capacities range form 1,200 to 12,000 BTU/H in both side mounting and top mounting models. All models use powerful radial fans for maximum air circulation inside the enclosure in ambient temperature of 125°F (+52°C). Models from 2,000 BTU/H capacity are equipped with thermal expansion valves for optimal use of the evaporator heat exchange surface under all operating conditions. For additional protection of the compressor motor, these valves are supplied as standard with Maximum Operating Pressure control devices (MOP). For energy conservation, the use of hot gas bypass valves is limited to the unload starting and control of large compressors from 8,000 BTU/H upwards.
All air conditioners were developed, designed, and subject to final inspections in accordance with international standards.
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Blowers and fans use forced convection cooling, which means ambient air flows through a filter into the enclosure to cool heated components. Both blowers and fans are sized in CFM (cubic feet per minute).
It is recommended that an exhaust filter be used in combination with the blower or filter fan to act both as an exhaust point for the hot internal air plus aid in the pressurization of the enclosure, reducing the chance of unfiltered air entering the enclosure. Whenever possible, the blower or filter fan should be located in the bottom third of the enclosure and the filtered exhaust grill placed as high as possible on the opposing side. Performance levels can be further increased by adding a second exhaust filter. |
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To determine the CFM (cubic feet per minute) required in any standard situation, use the following calculation, (non-standard situations would consist of high air density - significantly more then 0.075 lbs per cubic feet).
Note: The calculation above is exact, but adding an additional 25% to the CFM level is a standard safety factor.
If the air density is high (significantly more then 0.075 lbs per cubic foot), use the number calculated above in the following formula:
Note: Ambient Temperature must be lower than maximum internal temperature for fan/blower to be effective.
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Heating products protect electronic and electrical components from temperature problems that are below acceptable tolerances. There are obvious circumstances when extremely low ambient (outside cabinet) temperatures would require a heater, but there are also less apparent times that a heater should be considered. For example, a system may run all day having its components generate heat, but once the system shuts down for the night, the quick drop in temperature could cause condensation and possibly corrosion - a heater could maintain a safe, constant temperature.
Some components today are sensitive enough that both cooling and heating could be required in the same enclosure. When designing your system, be aware of the need to maintain a relatively constant temperature inside the enclosure as ambient temperatures swing from cool to very hot. Hammond thermostats (one for heaters and one for cooling products) can control both systems automatically.
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PH = Total power required for this Application (W)
PV = Existing power from components (W)
DT = Temperature differential (Kelvin) ambient to cabinet interior (1°Kelvin = 1°C = 1.8°F)
A = Free-standing cabinet surface area (ft²)
k = Heat transmission coefficient (W/ft²K) convection in quiet air:
- Painted Steel - approx. 0.51 W/ft²K
- Aluminum - approx. 1.115 W/ft²K
- Plastic - approx. 0.325 W/ft²
- Stainless Steel - approx. 0.344 W/ft²K
Formula
PH = (DT x k x A) - PV
If enclosure located outside, use x 2 (DT x k x A)
Sample with Solution
DT = 5 Kelvin
k = 0.51 W/ft²K (Painted Steel)
A = 50 ft²
PV = 50 Watts
PH = F(5 x 0.51 x 50) - 50
= 127.5 - 50
= 77.5 Watts
Recommendation: 80 Watt Capacity Heater
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