Relative Humidity Vs Time

[WAYNE3298]

Wet bulb temperature is the total heat load (latent plus sensible). I agree calculations are done by calculating the sensible and latent heat loads but when added together their the same as the wet bulb. Sensible and latent heat loads are not constant and if the coil didn't satisfy the total load they wouldn't do a very good job a lot of the time. The loads can vary as long as combined they don't exceed the coil capability.
It doesn't matter where you reject the heat as long as you design for that condition. Heat rejection of cooling towers is no different than any other device but testing them is a lot more involved.

[stumpdigger]

The plain and simple is this: when the unit is running the evap is below condensing temp thus removing latent heat (moisture, humidity). When the unit is off it does not remove moisture from the air.

[ehsx]

Couple of considerations I may have missed reading thru. All units have a sensible/latent ratio based on air flow and coil temperature. Typical coils may take 5-7 minutes to build enough condensate to begin to drain outside of the cooling envelope. Short cycling may increase indoor humidity levels when the temp drops drawing moisture in without expelling the moisture. For a unit to be able to control humidity, run cycling must be limited.

Short cycling equipment, modulating controls, air flow, duct transitions, ref charge, expansion valves, coil selections, duct leakage, set points, internal loads, etc all can have an effect on humidity and indoor air quality.

[WAYNE3298]

The point of the original post was as long as the space is cooled completely to design temperature it doesn't matter how long it takes. A lot of good points have been brought up but none have made a case that the time it takes to cool the space impacts the RH at the time the space reaches set point.

The reason for the post is that oversizing a cooling system can be okay it just depends on how much it's oversized. It depends on a lot of factors most of which have been brought out here. One of the biggest factors is whether the fan runs continuously or cycles.

Cooling coil performance is by total heat. The coil doesn't know the difference between latent and sensible heat. A coil that delivers air at 55 F DB also has a WB temperature of 55 F which is 100% RH no matter the load distribution as long as it isn't overloaded. The difference is the quantity of condensate.

[ehsx]

I think if you would carefully read the responses you would see the answer(s).