A sealed box that overheats has three main cooling options: filter fans, an air-to-air heat exchanger, or an enclosure air conditioner. Filter fans exchange outside air; the other two can keep the air circuits separate. A fourth option, thermoelectric cooling, needs careful capacity and heat-rejection checks. Choose by ambient temperature, allowable internal temperature and heat load—not a universal wattage cutoff. Use the enclosure sizing guide for the space and clearance fundamentals.
Compare the cooling methods
The first decision is whether outside air can enter the enclosure. The second is whether that air is cool enough to carry away the heat.
| Decision point | Filter fan | Air-to-air heat exchanger | Enclosure air conditioner |
|---|---|---|---|
| Cooling mechanism | Replaces warm internal air with outside air | Transfers heat between separate air circuits | Uses refrigeration to move heat outside |
| Outside air enters electrical space | Yes | No, with an intact separating core and seals | No, with properly separated air circuits |
| Can cool below ambient | No | No | Yes, within its operating limits |
| Capacity selection basis | Installed airflow and allowable temperature rise | Heat-transfer capacity in W/°C and temperature difference | Cooling capacity at actual internal and ambient temperatures |
| Main environmental limitation | Dust, humidity, oil mist and water exposure | Ambient must remain below the required internal temperature | Ambient operating range, external contamination and condensate management |
| Routine maintenance | Filters, fans and airflow paths | Fans and heat-transfer surfaces | Condenser, filters where fitted, fans and condensate system |
| Mounting needs | Intake and exhaust openings | Separate internal and external airflow paths | Cutout, structural support, airflow clearances and condensate provisions |
Our enclosures are rated NEMA 4X / IP66 by the manufacturer; not UL listed. Adding a cooling device changes the assembly. Its installed rating depends on the device, opening, gasket, mounting arrangement and installation instructions. The NEMA 4, 4X and IP66 guide explains the rating fundamentals.
Where a filter fan wins
A filter fan suits clean, dry indoor locations when the allowable internal temperature exceeds the worst-case ambient temperature. It can remove substantial heat without refrigeration, provided the installed airflow is sufficient.
For a screening calculation near room temperature and sea-level pressure, heat removal is approximately:
Heat removed in W = 0.57 × airflow in cfm × temperature rise in °C.
For example, removing 300 W with a 10°C air-temperature rise requires approximately 53 cfm [90 m³/h]. That is the theoretical airflow through the enclosure, not the fan's unrestricted airflow rating. Filters, grilles, ducts and internal obstructions reduce actual flow. Select from the fan's performance data at the installed resistance, including the expected filter condition.
Arrange intake and exhaust paths to sweep the heat-producing equipment. Avoid placing them so close together that cool air leaves without crossing the panel. Internal circulation fans can reduce hot spots, but they do not independently remove heat from a sealed box.
An ordinary filter fan is not the default choice for hose-down areas. Filters also do not reliably remove water vapor or corrosive gases. Do not assume a weather hood makes an open fan assembly suitable for the required enclosure rating.
Where an air-to-air heat exchanger wins
An air-to-air heat exchanger suits applications that need separated air circuits and can tolerate an internal temperature above ambient. It avoids bringing surrounding dust and moisture directly into the electrical space.
Its capacity depends strongly on temperature difference. As an illustrative selection, consider a unit rated at 30 W/°C under its stated operating conditions. With 45°C internal air and 35°C ambient air, the 10°C difference gives approximately 300 W of heat transfer.
If ambient rises to 40°C while the internal limit remains 45°C, that estimate falls to 150 W. At equal internal and external temperatures, there is no temperature difference to drive useful heat rejection. Use the selected unit's performance curves rather than extending this simple calculation beyond their stated conditions.
This means a heat exchanger is not automatically a low-load solution. A sufficiently large unit can handle higher loads when enough temperature difference is available. Conversely, even a modest load can require refrigeration when ambient approaches the equipment's temperature limit.
Keep both air circuits clear. External fins and passages still collect dirt, even though outside air does not enter the electrical compartment.
Where an enclosure air conditioner wins
An enclosure air conditioner wins when ambient air is too warm for ventilation or an air-to-air exchanger. It also suits applications requiring an internal setpoint below ambient.
Select its cooling capacity at the actual design temperatures. A nominal capacity measured under different conditions may overstate what the unit delivers on a hot installation. Confirm the permitted ambient range, startup conditions, supply voltage and installation orientation.
The surrounding space must accept the rejected heat. For example, a cooler removing 500 W while consuming 300 W rejects approximately 800 W outside the enclosure. A small equipment room can therefore become hotter after refrigeration is added.
Cooling below the internal air's dew point produces condensate. Follow the cooler's collection, drainage or evaporation instructions, including any stated capacity limits. Do not add an improvised drain opening through the enclosure wall.
Avoid choosing an unnecessarily low setpoint. It increases the cooling duty and can increase condensation risk when humid air enters through an open door. Leave the specified clearances around the condenser and keep its discharge away from nearby cooler intakes.
Where thermoelectric cooling fits
Thermoelectric, or Peltier, cooling can suit compact assemblies with limited heat loads. It has no compressor, but the complete installation still needs heat sinks, airflow, controls and sealing.
The module's maximum cooling figure is not its useful installed capacity at every temperature difference. Capacity depends on cold-side temperature, hot-side temperature and electrical operating point. A hot external heat sink reduces the heat the module can move.
The hot side must reject both the extracted heat and the module's electrical input. Adding modules also adds heat-rejection demand; it does not remove that requirement.
Use the complete cooler's performance curves at your design conditions. There is no universal 200 W or 1000 W boundary separating thermoelectric cooling, heat exchangers and refrigeration. Compare installed capacity, power consumption, available mounting area and maintenance needs.
Choose by the environment
For a clean indoor panel, start with ventilation if the required temperature rise and installed rating permit it. Include filter access in the layout, not just enough space to fit the fan.
For dusty, oily or humid surroundings, separated air circuits usually provide a better starting point. Choose an exchanger only if the hottest ambient leaves enough temperature difference. Otherwise, evaluate an air conditioner rated for those conditions.
For washdown, specify the cooling assembly's required installed protection and compatible exposed materials. A stainless enclosure does not protect a cooler with unsuitable seals, coatings or external components.
For outdoor service, include solar gain and the hottest local ambient in the thermal calculation. Check cold-weather operation as well. A summer cooling solution does not automatically control nighttime condensation or provide winter heating.
The available wall-mount enclosures provide the enclosure starting point. Cooler suitability still requires a separate thermal and mechanical review.
Confirm the load before selecting capacity
Count the heat released inside the electrical compartment, rather than adding every connected motor's nameplate output. Motor power delivered to equipment outside the enclosure does not all become heat inside the control box.
Use device dissipation data for drives, power supplies, transformers and other components. For example, a supply delivering 500 W at 95% efficiency dissipates approximately 26 W internally: 500 divided by 0.95, minus 500.
Include internal accessories and evaluate the relevant operating duty. Account for solar gain and heat transfer through the walls without counting either contribution twice. If the enclosure contains the entire machine, define that larger thermal boundary separately.
Check equipment inlet temperatures and local hot spots, not only the average enclosure temperature. The backplate and DIN rail layout guide covers the layout fundamentals. Keep cooler discharge paths clear of wiring duct and provide the equipment clearances required by its manufacturer.
After commissioning, record ambient and internal temperatures during representative maximum operation. Confirm that the system reaches a stable temperature with the doors closed. Set maintenance intervals around the actual contamination rate.
What to specify before ordering
Select the cooler before approving the enclosure cutout drawing. A cooling-capacity match does not prove that the unit fits the available wall or door.
For example, the 20 x 16 x 8 in wall-mount enclosure has those outside dimensions in H × W × D order. The 24 x 20 x 8 in wall-mount enclosure offers a larger mounting envelope, but both require a cooler-specific fit check. Neither dimension set establishes cooling capacity.
Send these requirements with the enclosure drawing:
- Maximum ambient temperature, desired internal temperature and calculated heat load in W.
- Water, dust, oil, chemical and sunlight exposure, plus the required installed enclosure rating.
- Selected cooler model, capacity curves, supply requirements and installation instructions.
- Cutout template, mounting-hole locations, gasket footprint and required flat sealing area.
- Cooler weight, support requirements, internal projection and external service clearances.
- Door swing, hinge loading, cable routing and condensate provisions where applicable.
Use the cutouts, glands and HMI windows guide for penetration details. A factory cutout improves coordination, but does not independently establish the finished assembly's rating. Any later modification requires review against the enclosure and cooler instructions.
For custom enclosures, we build to your specified material, width, height, depth and cutout layout. Approve the drawing only after the thermal selection, cooler mounting and panel layout agree.
Enclosures in this article
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 20 × 16 × 8 in | 304 stainless | 20 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 24 × 20 × 8 in | 304 stainless | 24 x 20 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Can Peltier modules cool a sealed enclosure?
Yes, when the complete cooler provides enough capacity at the actual temperature difference. Select from its performance curves, not the bare module's maximum cooling figure. The hot side must reject both the heat removed from the enclosure and the module's electrical input. There is no universal wattage cutoff that applies to every thermoelectric installation.
Does an enclosure fan break a NEMA 4X rating?
An ordinary open fan-filter kit cannot be assumed to preserve the enclosure's original rating. The finished assembly depends on the fan system, openings, seals and installation instructions. Internal circulation fans do not create outside-air openings, but they also do not independently remove heat. Factory and field cutouts both require a reviewed installation design.
How much heat can an air-to-air heat exchanger move?
Capacity depends on the selected unit and the temperature difference between its air circuits. For example, a unit rated at 30 W per degree Celsius transfers approximately 300 W at a 10°C difference under its stated conditions. It cannot cool below ambient. Use its performance curves at the hottest design ambient.
How do I know the heat load before choosing a cooler?
Add the dissipation released inside the electrical compartment using equipment loss data and the relevant operating duty. Include power supply losses, drive losses and internal accessories. Do not count motor output delivered outside the box as internal heat. Account separately for solar gain and wall heat transfer, using a clearly defined thermal boundary.
What cutout does a cooler need in the enclosure wall?
Use the selected cooler's mounting template rather than a generic opening size. Confirm mounting holes, gasket footprint, flat sealing area, internal projection, weight and service clearances. Send that drawing before the enclosure is built. Field modifications require review against the enclosure and cooler instructions; a factory cutout alone does not establish the finished assembly's rating.
