krisys,

I have recently designed an enclosure for installation on an offshore oil rig. The customer had a very, very detailed design guide. Perhaps your customer has one too. Trial and error is the wrong way to learn safety.

You can buy breather desiccators. I have used these on otherwise sealed airborne systems.

You need a heater at 50°C?

--
JHG

Condensation is often caused by the thermal lag of enclosed components.
When the RH is high, a rise in ambient temperature may leave the temperature of internal components below the dew point.
This will cause instant condensation, even at high temperatures.
The core iron of halted motors and generators is particularly susceptible, even at elevated temperatures

Bill
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"Why not the best?"
Jimmy Carter

The simplest and most reliable setup IMHO is a mass of desiccant. But that requires periodic recharging that may be unacceptable per your maintenance plan. Another solution, though less reliable, is a plain old wound resistor you can generate heat with by running current through it. The current would have to be controlled with a controller CCA with an onboard humidity sensor and dry bulb temperature sensor so you can calculate the dew point temperature and control the internal temperature accordingly. Of course if it's feasible, you could just keep heating the box all the time. That way you would not need the sensor CCA. A fan may be needed to mix the air but I supposed it depends on how well sealed the box is.

ElectroMechanical Product Development
(aka Electronic Packaging)
UMD 1984
UCF 1993