How does condensation happen?
Condensation is caused by warm moist air coming into contact with a surface that is colder than the air’s dew point. So what happens in an electrical enclosure?
In humid conditions the warmer air is the more water vapour it holds. When warm air inside an enclosure comes into contact with the enclosure’s colder casing, it cools. And it may chill to a point where it can no longer hold water vapour. The vapour, suspended as a gas, turns into water. The air has reached its “dew” point and condensation occurs.
Outdoor equipment is particularly prone to condensation, especially when it is not thermally insulated. That is due to the change in temperature as daytime warmth turns into the chill of night.
And with the extreme weather and wild temperature swings of recent years, outdoor enclosures are even more highly exposed to the risks of condensation.
Condensation may also form in indoor enclosures, of course, when humidity levels are too high and temperatures swing sharply.
Why is condensation dangerous?
When condensation gathers on the inside surface of an enclosure, the risks of malfunction are high.
It causes premature ageing, rusting, short circuits, and breakdowns in electric and electronic equipment that is housed in enclosures.
The consequences can be serious in for, example, critical outdoor applications like wind turbines and solar power installations.
How can condensation be prevented?
You can design humidity control into your enclosure. Enclosures that are tightly sealed and large enough to allow airflow reduce the risk of condensation.
Essentially, however, you prevent condensation by keeping relative humidity below 60% and controlling sudden temperature variations.
Its the amount of water in the air at a given temperature expressed as a percentage of the amount of water the air could hold.
What can you do when condensation does occur?
The most effective solution combines heaters with control devices like hygrostats, thermostats or hygrotherms.
Thermostats trigger heaters when temperatures fall below a set point. Hygrostats, however, turn heaters on when humidity rises above a given threshold. Hygrotherms do both.
Using hygrostats to control your heater is considered more energy efficient. However, they are much more expensive to buy than thermostats, so compare the solutions carefully before you choose.
When would you use a hygrotherm?
In some parts of the world, temperatures fall so low in winter that they are below the operating temperatures of control panel components. Similarly, in summer, dew points occur at high humidity levels.
This is where hygrotherms come into their own. With hygrotherms, both low ambient temperatures and high relative humidity levels trigger the heater.
Why are some heaters so slim?
Because small is beautiful. Electronic and electric parts are getting ever smaller. So, too, are enclosures. Yet, as we mentioned, enclosures should also be airy enough to stop condensation forming.
The answer is ultraslim resistance heaters – some are only just over 1.5 mm thick. These slimfit devices kick in at low temperatures and can be mounted any way up.
What do you think is the most effective condensation solution? Please share. Or maybe you’d just like to know more?