Moisture ingress through structures

[HVAC68]

We have a positively pressurised building. It's an electrical switchgear room and has been kept positively pressurised to avoid ingress of dust and of course to prevent condensation.

However, we find that there is condensation on the electrical panels. Does moisture ingress through structures (block work or brick work walls and roofs) inspite of having the room positively pressurised ?

We have also taken steps to close out any openings like cable entry, etc. However, this doesn't seem to help.

Can somebody throw some light on this please.

Thanks

HVAC68

 

[friartuck]

Air pressure that you generate may only be a few pascals but the mechanism that 'moves' water vapour is linked to the vapour pressure of the air. This is usually much greater than the air pressure and will 'go against the flow' so to speak.

I must say however that usually the effect of pressurising the space usually does the trick.

Where are you getting your air from?

are you heating it?

Are the panels pushed up to the outside wall?

They would generate some heat and condensation would only form if the surface temp was lower than the dew point of the air.

What temp is the basement at.

have you taken any space temp/humidity readings?




Friar Tuck of Sherwood

 

[ChasBean1]

Completely bizarre...

Why? Because electrical panels generate variable quantities of heat and the panel surface temperature is always at or above the dew point of the room.

For condensation on the surface of a panel to occur, the surface temperature would have to be below the room dew point temperature, which would mean that the panel would somehow have to have a cooling source within. OR, there would have to be a DX cooling system serving the room that cycles on, cools surfaces, then cycles off (maintaining room temperature). The off cycle could bring in a rush of warm and humid air and cause condensation on surfaces that have been cooled...

I think we need more details about the HVAC system serving the space and about the condensation phenomena in order to help you further... -CB

 

[digitrex]

Do you remove the moisture from the outside air?

If you have 2 AHUs, one for internal circulation, the other for bringing in outside air, then you may need to check the temperature settings. I would think the outside air AHU needs to set at lower temperature to remove as much water as possible.

I also experienced some water condensations in my electrical substation and it took me some time on trials and errors to find out what would be the real problem. I am not so knowledgeable in aircon stuff, sometimes I learnt through in a hard way.

 

[walkes]

Does the room have a good vapour barrier?

You will still get some infiltration with a strong wind blowing.

 

[HVAC68]

Friends - sorry for not responding at all. Am having some other pressing issues to attend to and hence am not even able to log on these days.

Thanks for your questions - will revert shortly.

Regards

HVAC68