Quick answer: For most electrical and battery enclosures, choose demand control with dew-point sensing. Demand control switches drying on when dew point or RH approaches a limit and off with a deadband. Use continuous drying only where the load is steady and high or the risk of condensation is unacceptable.
In an electrical or battery enclosure, "continuous" usually means the unit’s fan and sensing run all the time while the drying stage (compressor or Peltier) runs only when needed. True continuous drying is rarely required. Demand control uses less energy and causes less wear, but it depends on a sensor in the right place and on the unit responding fast enough when moisture surges, such as after a door opens.
Quick answer
- Ask "continuous what?": fan, sensing, or drying.
- Demand control: drying on below a margin to dew point, off with a deadband.
- Check that recovery after a door opening is fast enough.
What runs, and when
| Function | Continuous mode | Demand mode |
|---|---|---|
| Fan / air circulation | On | On, or on with drying |
| Sensing and monitoring | On | On |
| Drying stage (compressor or Peltier) | On | On only when needed |
| Energy use | Highest | Lower |
| Wear | Highest | Lower |
| Risk | Lowest response delay | Depends on sensor and deadband |
Read "standby" and "continuous" carefully in specifications. Ask which component each run-time counter refers to.
Setting up demand control
- Control variable: dew point is best (compared with the coldest surface); RH at a stated temperature is acceptable.
- Setpoint: dew point a margin below the coldest internal surface (e.g. cooling plates).
- Deadband: wide enough to avoid rapid cycling; narrow enough to keep the margin.
- Sensor location: representative air, not dehumidifier discharge.
- Override: drying on after a door-open signal or a high-humidity alarm.
- Communication loss: a defined fallback, usually local control at the setpoint.
When continuous drying makes sense
- Steady high ingress (ventilated enclosures in humid climates).
- Very cold internal surfaces with a small dew-point margin.
- No reliable sensor or control signal available.
- Short-term after commissioning or service to pull moisture down.
Compare energy on the same task
A unit that runs less isn't automatically cheaper if it can't hold the target. Compare energy over the same period for the same moisture removed, including fans and controls. For desiccant units, include reactivation heat.
See multi-cabinet controls and alarms, the BESS commissioning checklist and our electrical cabinet dehumidifiers.
FAQ
Frequently asked questions
Should an enclosure dehumidifier run all the time?
Usually the fan and monitoring do, and drying runs on demand; continuous drying is needed only for high, steady loads.
What should demand control be based on?
Dew point relative to the coldest internal surface, or RH at a stated temperature.
Does demand control save energy?
Yes, when it holds the same target; compare energy for the same moisture removed.
Sources
- ASHRAE Handbook—Fundamentals, Psychrometrics.
