I have a pair of new Daikin systems. My Honeywell smart thermostats show indoor humidity. The level has been 60% or so for a few weeks. This seems high to me.

The system has two stages, with controls designed to run at low and high capacity depending on conditions. It is believed that the system would run on low capacity settings to avoid overcooling. It also has variable speed air handler fan.

I am restricted by SWMBO regulations from decreasing the temperature below 73 F. I did try while she was at work, moving the temperature to 68 F, and the humidity did not reduce.

The system was thoroughly checked by the installation company on Friday. Nothing was incorrect. They (a)slowed down the maximum fan speed on the air handler, to in theory give air molecules more time on the coil to shed moisture and (b)increased the temperature at which two attic exhaust fans turn on, to reduce any interior suction.

The humidity is still high. Anyone with informed opinion care to offer guidance?

I needed to lower the temp a couple degrees. went from 60 to less than 50

Usually that is a sign of the AC system not being sized correctly having significantly too much cooling capacity for the environment as in it is cooling too quickly thereby not running long enough to dehumidify properly. Hope you get it sorted out.

Fan speed may also be too high. You can usually change your Heat and Cool fan speeds if that is the issue.

yep,

We had the same problem with our mini-splits and an engineer suggested turning down the fan speed....

Did they do a load calculation?

Is it uncomfortable? Meaning, does it feel any different then BEFORE the new systems?

It is incredibly wonderful here in the castle. I can achieve 68 F indoors at 98 F outdoors. Who can complain about capacity?

It is just a bit more humid than I'd like. I suppose I am oversensitive and being an engineer, with a readout on the thermostat, I can complain.

We'll see if the turned down fan speed suffices.

Just a thought... might not be relevant but perhaps you need to address the source of the humidity rather than trying to remove it. Vents for showers, cooking?
My daughters house was very humid until I put vapor barrier down in the crawl space. That alone took the indoor humidity from 60+ to less than 50.
I'm remodeling a small bath now for another daughter and I am considering adding a vent with humidistat so it turns on automatically if the humidity (from shower) gets too high. I find lots of people forget to turn them on manually.

Crawlspace renovation makes sense! Thanks for the idea.

quote:

Originally posted by 4MUL8R:
Crawlspace renovation makes sense! Thanks for the idea.

I should have mentioned... I have a couple times put my wireless outdoor thermometer with humidity readout in a crawl space for a few days to easily see and monitor the humidity under floor, just to see if it might be an issue.

quote:

Originally posted by cparktd:
Just a thought... might not be relevant but perhaps you need to address the source of the humidity rather than trying to remove it. Vents for showers, cooking?
My daughters house was very humid until I put vapor barrier down in the crawl space. That alone took the indoor humidity from 60+ to less than 50.
I'm remodeling a small bath now for another daughter and I am considering adding a vent with humidistat so it turns on automatically if the humidity (from shower) gets too high. I find lots of people forget to turn them on manually.

Panasonic whisper fans can be had with this feature, and I would recommend them. Also, venting to the outside is not just a great idea, it's code.

I assume the HVAC is in unconditioned space? If a recent install, modern insulated duct and sealing would have been in order. If a new unit just gets attached to existing ducting, tht ducting can be leaky and have no or inadequate insulation.

I would evaluate the areas where the equipment and ducting is run and look to improve.

Too large a system, not running long enough.

quote:

Originally posted by grumpy1:
Usually that is a sign of the AC system not being sized correctly having significantly too much cooling capacity for the environment as in it is cooling too quickly thereby not running long enough to dehumidify properly. Hope you get it sorted out.

This^^^

If the AC cools too fast it does not run long enough to dehumidify.

I went one size bigger on my new AC unit and experience this do a degree.

Mine is not that bad though, when it gets humid in the house I just go 2 degrees lower than I normally would for a few hours and it will reduce the humidity and usually maintain it.

.

Your drain may also be clogged up and the condensation is not draining off.

quote:

Originally posted by 4MUL8R:
It is incredibly wonderful here in the castle. I can achieve 68 F indoors at 98 F outdoors. Who can complain about capacity?

The guy with the humid house?

You could buy a dehumidifier.

This could be. Also, once I left my A/C fan on all the time in the Summer and it made my house really humid. Turned it to Auto and solved the problem.

quote:

Originally posted by 41:
Your drain may also be clogged up and the condensation is not draining off.

quote:

Originally posted by bubbatime:
Too large a system, not running long enough.

Thats exactly what my HVAC guy told me when I replaced my system in Fla. It simply has to run long enough to reduce the humidity.

You might want to get independent contractor out to do a through analysis of your system and see if if matches the size of your unit.

quote:

Originally posted by arcwelder76:
Also, venting to the outside is not just a great idea, it's code.

Disclaimer:I am not an HVAC expert.

But, just because fresh air make up is code doesn't mean it always a great idea. If you have a super airtight home well then, maybe you need it. If your home is not really all that air tight then not so much.Kids or dogs constanly in/out puts a lot of fresh air in a house.
I use to have to run 2 portable dehumidifiers to help lower humidity while the AC ran. I'm talking during extremely high humid weather.
I capped off my 6" fresh air makeup several years ago and have no regrets. The AC handles the humidity the vast majority of the time. Only during the most extreme weather do I run a portable dehumidifier.

Also helps in the winter, was having to run humidifier more because of the dry air being sucked in the fresh air makeup.
When I

the tiny town barber has the same problem ,in his shop.

he claims that they put way too much machine in and that
a pro told him that it takes much longer to lower the humidity , than it does to cool the cubic feet of air,

so yes his shop gets cool, but it air works more
than it should because the humidity does not drop much at all