Quick answer: A dehumidifier in a battery cabinet only works if its water leaves the enclosure every time. Plan the whole path: tray → drain connection → hose → sealed wall penetration → outside termination. Make it fall continuously (no rises or sags), keep the hose from kinking, seal the penetration to the enclosure's IP rating, protect the outside end against freezing, insects and backflow, and discharge where water can't run back toward cable entries or foundations. Use a pump only where gravity is impossible, and alarm it. Test the drain with water before handover.
Quick answer
- Continuous fall from tray to outlet; no rises.
- Sealed penetration; protected outlet (freezing, insects, backflow).
- Test with water; add alarms where failure would wet equipment.
How much water
| Unit type | Typical rated removal | Average flow |
|---|---|---|
| Peltier cabinet unit | 0.5–1 L/day | 20–40 mL/h |
| Compressor cabinet unit | 4–10 L/day | 0.2–0.4 L/h |
| Container or room unit | Tens to hundreds of L/day | Varies |
Ratings are at stated test conditions. Peaks come after door openings and during the first dry-down, when the unit removes water stored in the enclosure. If drains are shared, add other equipment such as HVAC condensate.
Gravity drainage
- Continuous fall, typically at least 1–2 % (follow the manufacturer).
- No loops or rises; support the hose so it can't sag.
- Short and direct; use a rigid pipe outside the enclosure if exposed.
- Diameter at least the unit's outlet.
Traps, pressure and backflow
- If the enclosure is pressurised or under negative pressure (fans, HVAC), a dry outlet can pull or push air. A trap with a water seal, or a check valve, stops that air path.
- Traps can dry out in long dry periods; a dry trap is an open air path.
- Make sure the outside end can't be submerged in rain or snow.
Pumped drainage
Use only where gravity is impossible. Choose a pump rated for the flow and head, with a high-level alarm or a float switch that stops the dehumidifier. Plan for service access.
Seal the enclosure penetration
- Use a gland or bulkhead fitting rated to the enclosure's IP class.
- Place it away from cables and busbars, below the tray outlet.
- Avoid routes over electrical equipment inside.
Freezing
- In cold climates, outdoor sections freeze and block.
- Keep outdoor runs short and steep, insulate them, or add heat trace.
- Make sure a frozen drain stops or alarms the unit rather than overflowing inside.
Discharge location
- Away from cable entries, foundations, walkways and other equipment.
- Onto gravel, into a drain or a soakaway, per site rules.
- Visible enough to check during maintenance.
Installation and commissioning checklist
- [ ] Tray level; unit installed as specified
- [ ] Continuous fall, no rises; hose supported
- [ ] Penetration sealed to IP rating
- [ ] Trap or check valve if pressure differences exist
- [ ] Freeze protection where needed
- [ ] Outlet protected and discharges safely
- [ ] Pour a measured volume into the tray; confirm it all exits, with no leaks
- [ ] Pump and alarms tested (if used)
See the BESS commissioning checklist.
Maintenance
- Inspect the outlet for blockage, insects and ice.
- Flush the tray and hose periodically.
- Check traps for water seal.
- Check for stains near the drain path inside.
Our energy storage dehumidifiers and electrical cabinet dehumidifiers include drain connection details in their installation manuals.
FAQ
Frequently asked questions
Where should a battery cabinet dehumidifier drain?
Outside the enclosure through a sealed penetration, with continuous fall, to a location away from cable entries and foundations.
Does a cabinet dehumidifier need a trap?
Where the enclosure has pressure differences from fans or HVAC, a trap or check valve stops air flowing through the drain.
What happens if the drain freezes?
Water can back up into the enclosure; insulate or heat-trace outdoor sections and alarm the unit.
Sources
- IEC 60529, Degrees of protection provided by enclosures (IP code).
