Enclosure Thermal Management: Sealing and Heat Are Opposites
Every vent you add to cool a cabinet is a hole in its IP rating. That is the whole problem, and it is why thermal management has to be decided at the drawing stage rather than solved with a fan drilled in afterwards. This page is about the trade-off, and about which cooling route suits which cabinet.
Fulei Metal builds the enclosure around your thermal requirement — wall thickness and material for conduction, vent and filter positions for natural convection, fan mounts and plenums for forced air, and the mounting for heat exchangers — in a 2,500 m² plant in Ningbo, China, since 2016.
Why the problem exists
Electronics make heat. Heat raises internal temperature, which shortens component life and eventually causes failure. The fix is to get the heat out. But an outdoor or washdown cabinet has to be sealed to keep water and dust out — and sealing stops the air movement that carries heat away.
So the design question is not “how do we cool it” but “how much heat has to leave, and what is the least sealing we can give up to let it.”
First: how much heat are we talking about
| Internal dissipation | Typical equipment | Usual route |
|---|---|---|
| Under ~50 W | Terminals, small PLC, a contactor or two | Natural conduction through the wall; no vent needed |
| 50–200 W | Mid-size control cabinet, drives, several breakers | Natural convection with a filtered vent, or a single fan |
| 200–600 W | Battery cabinets, inverter cabinets, dense device panels | Forced air with filtered intake, or a closed-loop heat exchanger |
| Over 600 W | High-density power equipment | Air conditioner or liquid cooling — outside what we build |
If you can give us the dissipation figure, the ambient temperature range and the target internal temperature, we can tell you which route the cabinet needs. If you cannot, send the device list and we will estimate it with you.
The four cooling routes
| Route | How it works | IP impact | Trade-off |
|---|---|---|---|
| Conduction | Heat travels through the wall to the outside surface | None — the cabinet stays sealed | Limited to low dissipation; aluminium conducts far better than steel |
| Natural convection | Warm air rises out of a high vent, cool air in low | Drops to IP54 unless the vents are filtered and labyrinthed | Filter needs cleaning; dust bypasses simple mesh |
| Forced air | Fan pushes air through, usually with a filtered intake | IP54 typical; IP55 achievable with a good filter | Fan is a wear item; positive pressure helps keep dust out |
| Closed-loop heat exchanger | Internal and external air circuits exchange heat through a core; no air crosses | IP rating preserved | Cost and mounting space; needs both internal and external airflow |
Choosing the route
| Situation | Recommendation | Why |
|---|---|---|
| Indoor control room, low dissipation | Conduction, or a louvred vent | No IP requirement to protect; simplest and cheapest |
| Outdoor, moderate dissipation | Forced air with a filtered intake, or a heat exchanger | Rain and dust have to stay out; a filter is the compromise |
| Outdoor, high dissipation, must hold IP66 | Closed-loop heat exchanger | The only route that keeps a high IP rating at high load |
| Battery or PCS cabinet | Forced ventilation, designed as a system | Battery off-gassing and thermal runaway make this a safety question, not a comfort one |
| Weight-sensitive | Aluminium body with conduction | Aluminium moves roughly five times the heat of steel for the same geometry |
Where the heat actually goes wrong
1. The vent is on the wrong wall. A vent low on a door in an outdoor cabinet collects rain. Intake low and outlet high works indoors; outdoors, the inlet needs to be shielded, baffled, or moved to a face that is not exposed.
2. The filter is forgotten in the drawing. A fan mount with no filter housing turns the cabinet into a dust collector within months. The filter needs a position, a retention method and a replacement route — all drawn.
3. Internal layout ignores convection. A device mounted low in a sealed box with no air path above it will cook regardless of the wall material. Component placement is a thermal decision, and it is usually made by whoever lays out the panel.
4. Solar gain on the roof. A dark roof in direct sun can add more heat than the electronics make. A light-coloured or reflective finish, a shade roof, or a double-skin roof with an air gap solves it, and it is a drawing decision.
What we build, and what we do not
| We build | We do not |
|---|---|
| Enclosure walls, roofs and doors to the thermal design | Formal thermal simulation reports |
| Vent openings, louvres, baffles and filter housings | Fan, heat exchanger or air conditioner supply |
| Fan mounts, plenums and airflow dividers | Component-level thermal design |
| Heat exchanger mounting frames and cutouts | Certification of the thermal performance |
| Material and finish selection for solar gain | — |
We do not issue thermal simulation or performance certification. What we do is build the mechanical envelope your thermal design specifies, with the openings, mounts and airflow paths in the right places, and hold the dimensions so the equipment you select fits.
What to put on the drawing
- Internal dissipation in watts, or the device list it comes from
- Ambient temperature range at the installation site, including solar exposure
- Target internal temperature, and whether it is a limit or a guideline
- Cooling route — conduction, vent, fan or heat exchanger — and the equipment model if known
- Filter specification and replacement route, if forced air is used
- IP rating, stated with the cooling route, because the two trade against each other
- Roof treatment — colour, shade, or double skin
Related reading
- Electrical enclosures and cabinets: the full selection guide
- IP66 enclosures: what the rating really means
- Weatherproof electrical enclosures
- Low voltage distribution cabinets
Frequently asked questions
Can you keep IP66 with a fan inside?
Not with a simple through-wall fan. A fan that moves air across the wall is an open path. The routes that hold IP66 are a closed-loop heat exchanger, or a sealed cabinet relying on conduction with enough external surface area. We will tell you which your dissipation figure needs.
Do you supply the heat exchanger or the fan?
No. We build the mounting frame, the cutouts and the airflow path to the model you specify. If you have not selected one yet, send the dissipation and ambient figures and we will tell you the class of equipment the cabinet needs to accommodate.
Aluminium or steel for a hot cabinet?
Aluminium, if weight and budget allow. It conducts heat away from the internals far better than steel, which matters most at low dissipation where you are relying on conduction rather than airflow. Steel is cheaper and stiffer, and works fine when you have forced air doing the work.
Can you tell us how hot the inside will get?
Not as a certified figure. We can tell you what the mechanical design supports — surface area, material, vent area, airflow path — and we will build to the thermal design you or your engineer specifies. Formal thermal analysis is outside what we do.
What lead times apply?
Simple samples 3–7 days. Complex first articles 15–20 days. Production batches 25–35 days, quoted after drawing review. Freight is quoted separately to your port.
Do you hold ISO 9001 certification?
Our quality system is documented to ISO 9001. We do not hold a third-party ISO 9001 certificate and do not claim one. Third-party audit evidence is available under NDA: TÜV Rheinland MIC-ASI243729 and Bureau Veritas MIC-ASR263630.
Send the heat figures
Send the internal dissipation, the ambient range and the IP rating you need. Those three decide the cooling route, and the cooling route decides the enclosure design. Getting them on the first enquiry saves a revision cycle later.