Humidity too low in summer

[ron3637]

I have the reverse problem of most. My house's humidity gets to low in the summer. It goes below the thermostat's set point. I have an infinity system. any suggestions thanks

[Shophound]

What exactly do you consider as being "too low"? Have you verified the humidity level with an independent instrument? Are you uncomfortable under this condition, or are just reacting to a number on an instrument?

[ron3637]

Just relying on the infinity thermostats reading.

[motoguy128]

If possible, you want to increase the blwoer speed to 400CFM or even 450CFM per ton. I think Carrier runs closer ot 350CFM per ton as "normal". on their VS systems.

Are you using "efficienc"y mode in the installer set-up menus? I think the other modes are "normal" and "Comfort".

Are you in a dry desert-like climate? It's pretty rare to have low humidity issues otherwise. Maybe you need more ventilation. Where do you live?

You can also try raising the indoor setpoint. The system won't run as long and therefore may not remove as much humidity.

Finally, you cna run the indoor an continously on low. that will reevaporate soem of hte moisture on the indoor coil and should increase indoor humidity.

Basically do everything opposite of what is recommended on this site to reduce humidity. Heck...maybe add some leaks to your house. :)

[beenthere]

Might want to have your contractor set it to efficiency if it is't already.

[Shophound]

Just relying on the infinity thermostats reading.

What are those readings?

Instruments that measure temperature and humidity can drift out of accuracy.

Again, are you experiencing discomfort issues in your house? Wooden furniture or floors or other items cracking?

Do you live in a dry climate, such as in or near a desert?

[Carnak]

Just run the fan all the time to filter the air, or set blower to run for say ten minutes after the cooling call ends

[ron3637]

I live in washington dc. Do you save on electricity in the efficiency mode?

[beenthere]

A little.
It speeds up the blower. So the unit reaches set temp a little quicker.

[motoguy128]

I live in washington dc. Do you save on electricity in the efficiency mode?

You should gain a little efficiency... BUT... if you have undersized ductwork creating high static pressure... above 0.9", you might actually lose some efficiency as the blower itself will consume more energy than the capacity you gain with the higher airflow.

Most liekely, at worst, it will be the same... but could be a little more efficienct. We're probbably talking like 2-5% at most from some numbers I've seen.

DC shouldn't be too dry... if not fairly humid in mid summer... it's only a few miles north of "The South".

[Shophound]

DC shouldn't be too dry... if not fairly humid in mid summer... it's only a few miles north of "The South".

A "design day" in Washington D.C. would be 91 degrees at 46% relative humidity. Kind of sticky. I wonder if the "too dry" complaint from the OP applies mainly for "shoulder season" weather, or on days like above?

[ron3637]

Good point! So far is happening on shoulder days this spring. Have to wait to the summer--new system. Thanks

[beenthere]

Besides its going below what you have the control set for.

What is the RH dropping to.

45? 40?

[motoguy128]

A "design day" in Washington D.C. would be 91 degrees at 46% relative humidity. Kind of sticky. I wonder if the "too dry" complaint from the OP applies mainly for "shoulder season" weather, or on days like above?

I would normally think the opposite. In shoulder season, overnight temps stay above 45F, keeping the dewpoint moderate, there's plenty of rain, but not enough heat load to run the A/C to remove moisture. I've struggled to keep the humidity below 55% the last few days with the latest weather system bringing in extra moisture and overnight temps over 50F.

[Shophound]

Good point! So far is happening on shoulder days this spring. Have to wait to the summer--new system. Thanks

Ah! That info is spot on. :)

Yes, I would wait to see how it performs over the summer. This time of year is a "flux time" when it comes to a/c peformance for temperature and humidity control. Most of us in humid climes struggle to keep indoor humidity low enough this time of year. If you still find your indoor conditions arid over this summer (which is hard to imagine, but possible), then some tweaking might be in order.

[Shophound]

I would normally think the opposite. In shoulder season, overnight temps stay above 45F, keeping the dewpoint moderate, there's plenty of rain, but not enough heat load to run the A/C to remove moisture. I've struggled to keep the humidity below 55% the last few days with the latest weather system bringing in extra moisture and overnight temps over 50F.

I don't really worry about my indoor climate being affected by outdoor humidity until outdoor dew points stay consistently above 55 degrees and nightly lows creep up toward the 70 degree mark.

Right now it is 79 degrees with 79% RH outside, meaning the dew point is 72 degrees. Definitely not open window weather. :D