condensation on air diffuser!!!

[khongminhhason]

hello everyone,
my building is using VRVIII system, it have an air diffuser is condensated
RH of ambient ~90%
how to stop condensate on it??

[install monkey]

increase fan speed,ensure filters are clean-ensure windows are closed -few easy checks

[soleowner]

The supply air temperature is causing the metal diffuser to dip below the dew point. The diffuser is a wick (collection point) for moisture in the air collect and drip.

There are many facets to finding a answer(s). You can find the dew point on a given day by knowing the sensible (dry bulb) and latent (wet bulb) temperatures. Although 90%RH sounds high, there is a difference of moisture content (grains per pound of air) at different dry bulb temperatures. This science is called Psychrometric's.

At any rate, the higher end of a typical comfort cooling system's operating range are 115F ambient (outdoor), and return air temperatures (indoor) of 90FDB/75FWB = 50%RH.

If you system is receiving air at or beyond the max indoor air temperatures described above, there is nothing that can be done from a HVAC system stand point.

It really sounds like you should take a look at the building thermal envelop (insulation, windows, doors, cracks, etc.) Also you should check out the building pressurization and probable infiltration. The building should be slightly positive. If you have high infiltration, that is a major cause of discomfort.

[khongminhhason]

thank you very much!

[Makeit go Right]

If you have metal diffusers, try a plastic one (just one) to see if that helps.
Then, if successful, change the rest for plastic type.

[soleowner]

You could see if increasing the air flow would help and sealing up the duct system.