Quick answer: An anti-condensation heater keeps surfaces above the dew point but leaves the water in the enclosure. A cabinet dehumidifier removes the water and drains it out. Use a heater for a well-sealed enclosure with little moisture getting in. Use a dehumidifier when moisture keeps entering (doors opened often, humid or coastal sites, washdown areas, outdoor cabinets with large day–night swings), or when you cannot add heat. Vents and desiccant bags suit only small, predictable loads.
Quick answer
- Heater: warms surfaces, removes no water, runs whenever it is cold.
- Dehumidifier: removes water, works with the door closed, needs a drain.
- Vent: dries only when outside air is drier than inside air.
- Desiccant bag: holds a fixed amount of water, then must be replaced.
Why enclosures condense
Water condenses on any surface colder than the dew point of the air inside the enclosure.
Example: air inside a cabinet at 25 °C and 70 % RH has a dew point of about 19 °C. At night the door and roof cool to 15 °C, and water forms on them and drips onto terminals. Two ways to stop it:
- Keep the surface above 19 °C — that is what a heater does.
- Lower the dew point of the air, for example to 10 °C by taking water out — that is what a dehumidifier does.
The four methods compared
| Method | How it works | Removes water? | Works best when | Fails when |
|---|---|---|---|---|
| Anti-condensation heater | Raises inside temperature a few kelvin above ambient | No | Enclosure is well sealed; only small temperature drops | Moisture keeps entering; heat is unwelcome (drives, batteries, electronics near limits); large swings |
| Vent or breather (with membrane) | Exchanges inside and outside air | Only if outside air is drier | Mild, dry climates; enclosures already designed with an air path | Outside air is the moisture source: humid, coastal, tropical sites |
| Desiccant bag | Absorbs a fixed amount of water | Yes, until full | Sealed boxes in transport or short storage | The enclosure leaks or is opened; bags are not replaced |
| Cabinet dehumidifier (Peltier or compressor) | Cools a surface below dew point, condenses water and drains it outside | Yes, continuously | Humid sites, frequent door openings, washdown areas, outdoor cabinets | No drain route; capacity too small for the leakage |
Often the answer is a combination: seal the enclosure, add a dehumidifier for the moisture load, and keep a small heater for cold-start protection.
How to size an anti-condensation heater
The heat needed to hold the inside a few kelvin above the outside is roughly:
P (W) = A × k × ΔT
- A = free surface area of the enclosure, m² (exclude a side mounted against a wall)
- k = heat transfer coefficient; about 5.5 W/m²·K is a typical value used for painted sheet steel in still air
- ΔT = temperature rise wanted, K
Example: a wall-mounted cabinet 1.0 × 0.8 × 0.3 m has about 1.9 m² of free surface. To hold it 5 K above ambient: 1.9 × 5.5 × 5 ≈ 52 W, running whenever it is cold, about 1.25 kWh per day in winter.
A 5 K rise protects against small night-time drops. It does not stop condensation if humid air keeps coming in, and it adds heat that may push drives, PLCs or batteries closer to their temperature limit in summer, so control it with a thermostat or hygrostat.
How to tell which one you need
| Question | If yes |
|---|---|
| Is water getting in through doors, glands, rain, washdown or leakage? | Fix the leaks first; then a dehumidifier, because a heater cannot remove incoming water |
| Is the site humid (coastal, tropical, wastewater, food plant, underground)? | Dehumidifier; vents will bring moisture in |
| Does condensation appear only on cold nights or at start-up? | A heater may be enough in a sealed enclosure |
| Is the equipment heat-sensitive (batteries, drives, electronics)? | Dehumidifier; avoid adding heat |
| Is there no maintenance access for months? | Avoid desiccant bags; use a dehumidifier with a drain or a heater |
Peltier or compressor cabinet dehumidifier?
| Peltier (thermoelectric) | Compressor | |
|---|---|---|
| Best for | Small enclosures with small moisture loads | Larger cabinets, battery and energy-storage enclosures, high loads |
| Capacity | Hundreds of millilitres a day | Several litres a day |
| Moving parts | Fan only | Compressor and fan |
Our ANTIS cabinet range covers both:
| Model | Type | Rated capacity | Rating condition |
|---|---|---|---|
| ADS-500ML | Peltier | 500 mL/day | 35 °C / 85 % RH |
| ADS-1000ML | Peltier | 1,000 mL/day | 35 °C / 85 % RH |
| ADS-100WB-01 | Compressor | 4 L/day | 30 °C / 80 % RH |
| ADS-100WB-06 | Compressor | 6 L/day | 30 °C / 80 % RH |
| ADS-10D / ADS-10DW2 | Compressor | 10 L/day | 30 °C / 80 % RH |
Peltier and compressor models are rated at different conditions, so compare them only within each type. See Peltier vs compressor cabinet dehumidifiers and our electrical cabinet dehumidifiers.
Installation points for a cabinet dehumidifier
- Mount it where enclosure air circulates past it, not in a dead corner.
- Run the drain tube outside the enclosure with a fall, and seal the entry.
- Keep it clear of components that are heat- or moisture-sensitive.
- Seal glands and doors first; a dehumidifier sized for a sealed cabinet cannot keep up with an open one.
- Use a humidity setpoint or hygrostat so it runs only when needed.
FAQ
Frequently asked questions
Is an enclosure heater or a dehumidifier better?
A dehumidifier, when moisture keeps entering or the equipment cannot take extra heat. A heater, when the enclosure is sealed and the problem is only cold surfaces on cold nights.
Do anti-condensation heaters remove moisture?
No. They raise the temperature so water stays in the air instead of condensing. The water remains in the enclosure.
Can I use a heater and a dehumidifier together?
Yes. A common arrangement is a dehumidifier for the moisture load and a small thermostat-controlled heater for very cold starts.
Do vents stop condensation in electrical panels?
Only when the outside air is drier than the air inside. In humid or coastal sites, vents bring moisture in.
How often do desiccant bags need replacing?
It depends on how much water gets in. In a leaking or frequently opened enclosure they can saturate quickly, which is why they suit sealed transport and storage better than permanent installations.
Sources
- ASHRAE Handbook—Fundamentals, Psychrometrics (dew point).
- IEC TR 60890, Method of temperature-rise verification for low-voltage switchgear and controlgear assemblies.
