Humidity inside - Ecobee vs. Hygro-Thermometer

I don’t think any thermostats do humidity readings well unfortunately. At least I’ve not come across any that do.

Do you have the hole behind the thermostat plugged with caulk or putty? If your tstat is pulling hot, humid air from the attic it can definitely influence your readings.

Otherwise, they should be fairly accurate. When I tested mine (after plugging hole), they were only off by maybe 1 degree on temp and 1-2% on humidity.

Ecobee also allows you to adjust your tstat readings to correct them if you have a way to measure. It’s within the settings menu.

So, unless you have inside unit that actually has Dehum terminal, all that wall stat is doing is telling you what it currently is. It can’t do anything about it.

With Carrier / Bryant, most of the mid to upper grade inside units have a Dehum terminal.
With that, whenever 24 volts is taken away from that Dehum terminal, the processor slows the blower down and runs a colder coil, which removes humidity quickly.

So, those thermostats that do humidity, usually has a set of contacts that you program to be either open or closed when humidity rises above desired set point. With Carrier / bryant, you program to open on rise of humidity.

Up in the attic, one of the contact wires goes on R, the other on Dehum.

You may find that your stat wire in the wall does not have enough strands
( colors ). Now you must get fancy and Fish another bundle down the wall.

There is a nice stat by Carrier that does it all with only 2 wires. The T6-prh.

Anybody buying new single stage system, at least get the inside unit that has the dehum terminal. It’s worth it in Louisiana.

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Do you have the hole behind the thermostat plugged with caulk or putty? If your tstat is pulling hot, humid air from the attic it can definitely influence your readings.

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I used to have Honeywell thermostats until I switched to Ecobee. This is what the base of the Honeywell looked like before I installed the Ecobees. I don't consider this too big of a hole, and I didn't want to caulk or putty in case I needed to access the thermostat wires.

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With Carrier / Bryant, most of the mid to upper grade inside units have a Dehum terminal.
With that, whenever 24 volts is taken away from that Dehum terminal, the processor slows the blower down and runs a colder coil, which removes humidity quickly

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I have two 15-year-old Rheem units (one is a 2.5-ton, and the other is a 4-ton). Both have been rock solid. I believe having a solid installation has made a difference in performance and longevity.

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True, and I agree with you. I can say adding a portable dehumidifier to my house has helped tremendously. Much cooler. The Hygro-Thermometer is reading around 50 to 52 % humidity when the portable dehumidifier is running. When the portable dehumidifier is off, I average about 60 % humidity in my house, which is considerably less than what the Ecobees report. A minor, but major annoyance to me.

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You kinda contradicted yourself.

And, you added a separate dehumidifier. Main central unit that has the aforementioned dehum feature, does that.