What would be considered the optimum humidity level coming from the vents when the a/c is running? My upstairs unit throws off 55% humidity and the downstairs is 75%. The rooms overall humidity once the cold air and room air mingle is 45 to 50%.

What, if anything, should be done if the range is not the norm? Thanks

 

Theorectically the air coming off the cooling coil should be 100% humidity. By the time it gets to the vents it drops, but is still higher then what a comfortable humidity level in the house is.

If the overall humidity in the house is too much that is a different issue, but if you are asking just about coming out of the vents don't worry about it.

Which is it?

 

There is no such thing as an optimal humidity level for airconditioned supply air.
The main thing that determines the humidity level in your home is the size of the unit compared to the cooling load.
An a/c unit will supply a fairly constant temperature but the humidity will drop according to the run time of your unit.
If your unit is being serviced properly and the humidity is too high then there is a possibility your unit is oversized.
An indication of an oversized unit is if the a/c unit runs for only a short while to satisfy the load and then shuts off.

If the outside temp is 90 degF/90% humidity and it's 74 degF/50% inside you wouldn't be doing too bad.

Do you have a comfort issue?

 

Thank you for the input. The humidity level in the rooms is between 45 to 50%, that is with 80 to 90% humidity outdoors in 90 degree plus temperatures.

I will pay closer attention as to how long the unit runs to cool properly but how long is the norm to get it down a couple of degrees?

If it isn't long enough, can the unit be adjusted to take longer to cool? Thank you.

 

You don't say what indoor and outdoor temps you are getting.
You cannot really have a decent discussion about humidity levels without them.
To say that if the a/c brings down the temp too quickly and shuts off, no moisture would be removed because of being oversized.
Or, the unit runs continuously and doesn't bring down the humidity AND the temperature, would be because of being undersized.

With a simple home airconditioner the capacity of the unit is the single major thing that controls what humidity you wind up with.
Well, yes there is something that you can do but removing insulation and installing cheaper windows is counter productive.
I have not seen it myself but have heard that some have had problems with central air after doing a major upgrade to insulation and windows.
Because the cooling load affects the run time of the unit people were experiencing a lack of moisture removal.

So, unless you want to do something major, as shank said, "don't worry about it".