How responsive is the humidity sensor in the On/Off switches? VZM30-SN

I recently purchased some Blue switches and fan canopy modules, and have them all set up and working with Home Assistant… But I have a question about the On/Off switch with integrated humidity sensor.

In one of the bathrooms, my previous set up was using an Everything Presence One that would trigger a light switch for occupancy and trigger the fan switch when the relative humidity raised above 60% to exhaust some of the moist air.

For this bathroom, I went with both a mmWave presence dimmer (VZM32-SN) and an on/off switch (VZM30-SN), figuring that I could simplify things a little by letting the switch itself control the lights, and use the built in humidity sensor in the on/off switch to trigger an automation through Home Assistant and move the EP1 elsewhere.

Here’s where I am struggling a little though… To test everything out, both to make sure the lights stay on when the shower is running and that it would turn on the fan, I turned the shower to the highest temp and watched my HA dashboard. The light stayed on the whole time, so that was a success, but the humidity sensor in the on/off switch never got above 40%, while the reading on my EP1 peaked at 85% before I manually triggered the fan and turned off the shower.

First, I checked to see that it was updating correctly, and it was, but was only changing by miniscule amounts, so I figure it has something to do with the sensor itself.

Am I doing something wrong? Am I expecting something more than what it is capable of offering? Is the switch working correctly?

It seems to more or less match the EP1 in the same room, although consistently about 3-5% lower… which in itself isn’t much of a problem, but when the entire room is steamy and the mirror is fogged up the sensor barely registered the extra humidity, and took quite awhile to even get to the max reading that I saw.

I see the same with my switches in Hubitat. There is not as much movement on the humidity level on those switches as there is on other humidity sensors.

What is the placement of the EP sensor compared to the on/off switch?

Wall switches are often just about the worst possible location for a bathroom humidity sensor – too far away and too low at that proximity.

Well, my EP1 is sitting on the same wall about 2.5ft higher (at the top of the door trim).

It seems like my expectations were just off then? If so, that’s fine, I just wanted to make sure that my experience wasn’t an outlier.

Guess it is really only intended as an ambient sensor and not responsive or sensitive enough for my use case due to its placement, whether that be the height it is mounted at or the fact it is built into a switch that is installed into an electrical box with its own air space.

Oh well, it isn’t like there was a premium on top of the regular switch price to play around with it.

I guess I’ll look into some battery powered sensors I can stick to the top of my mirror or something, as I was mainly looking to remove the USB charger and cord that the EP1 needs to operate.

Thanks everyone for taking the time to reply.

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