A Too much cooling air? (Power supply failures due to condensation)

AI Thread Summary
The discussion centers on the failure of AC to DC power supplies due to moisture, with condensation forming inside the enclosure despite seemingly favorable environmental conditions of 30C and 45% relative humidity. The use of clear plexiglass instead of a metal cover revealed condensation, raising concerns about the effects of negative pressure created by large cooling fans pulling air out of the cabinet. Participants question whether this airflow could lower the dew point and lead to moisture condensation. Suggestions include assessing the conditioning of the room and considering relocating the cooling fans to blow air into the cabinet instead. The issue highlights the complex interplay between thermodynamics, airflow, and humidity in equipment reliability.
powerelect
Messages
1
Reaction score
0
TL;DR Summary
condensation and dew point in electrical cabinet with high velocity air
I have a situation that I cannot explain so I need the assistance of someone with a good understanding of thermodynamics.

I have 36 AC to DC power supplies located in an equipment rack. These power supplies are failing after some time. The failures appear to be moisture related. We put moisture indicating labels in the power supply and their color changed indicating the presence of moisture.

We replaced the metal cover on the power supply with clear plexiglass and we also saw condensation form inside the enclosure after a number of hours. The environmental conditions were 30C and 45%RH. The dew point should be far below room temperature under these conditions. This was installed at a location close to sea level. There are large cooling fans on the cabinet door pulling air out of the cabinet.

So, the pressure inside the cabinet is negative. Could this large amount of airflow pulling through the unit cause the moisture in the air to condense? Could the negative pressure cause the dew point to drop? Can someone explain this? I have been designing power electronics for decades and have never seen this before.
 
Last edited by a moderator:
Science news on Phys.org
Welcome, @powerelect ! :smile:

Is the room containing the panel conditioned?
If so, at what temperature?
Could you relocate the cooling fans to be blowing into the cabinet?
 

Thread 'Condensate rate of water for an air conditioning cooling coil'

I need to calculate the amount of water condensed from a DX cooling coil per hour given the size of the expansion coil (the total condensing surface area), the incoming air temperature, the amount of air flow from the fan, the BTU capacity of the compressor and the incoming air humidity. There are lots of condenser calculators around but they all need the air flow and incoming and outgoing humidity and then give a total volume of condensed water but I need more than that. The size of the...
View full post »
Thread 'Why work is PdV and not (P+dP)dV in an isothermal process?'

Thread 'Why work is PdV and not (P+dP)dV in an isothermal process?'

Let's say we have a cylinder of volume V1 with a frictionless movable piston and some gas trapped inside with pressure P1 and temperature T1. On top of the piston lay some small pebbles that add weight and essentially create the pressure P1. Also the system is inside a reservoir of water that keeps its temperature constant at T1. The system is in equilibrium at V1, P1, T1. Now let's say i put another very small pebble on top of the piston (0,00001kg) and after some seconds the system...
View full post »

Similar threads

Thermodynamics is air ducts, dew point
Replies
2
Views
2K
Preventing Condensation in Outdoor Enclosure
Replies
2
Views
3K
Calculating saturation and dew point given pressure and temperature
Replies
4
Views
5K
How to reduce RH of air from evaporative cooler?
Replies
5
Views
7K
Atmospheric humidity for water production.
Replies
3
Views
3K
Dyson bladeless fan/turbine compressor building air cooling?
Replies
6
Views
9K
Are Isotopes in Ice Cores Indicators of Temperature or Precipitation?
Replies
1
Views
4K
Strong negative feedback in Climate
Replies
1
Views
6K
B How Does an IEC Fusion Reactor Work?
Replies
19
Views
5K
Solaculture: A novel biological approach for low cost energy?
Replies
3
Views
4K

Hot Threads

Recent Insights

Back
Top