The Settings - FAQ
First you must set up a “Humidity Derivative Sensor”. On how to do this Click Here
Humidity Derivative Sensor
This is the sensor that will be used as the trigger.
This is the fan you would like to turn ON. Lights can also be added. It is normal used when you have a niche in the shower that has a LED’s strip lighting and you would like to turn them ON when showering and OFF when finished automaticity.
Fan Speed - Switch Off Option
Sometimes you need to select a different entity to turn the fan OFF. This is normally used when having a fan that has different speeds and one of the speeds is OFF. You normally have to turn ON the switch to turn the fan OFF. If you have this scenario then select your OFF speed entity here. If you do not have this, then please leave it blank.
Input - Bathroom Humidity Sensor (Optional)
Select your bathroom humidity sensor. Your bathroom humidity sensor is the actual humidity sensor located in your bathroom. This will be the reference sensor if you have chosen to use “The Maximum Humidity Option” below. It applies to default and winter mode settings.
Rising Humidity & Falling Humidity Settings
Once you have your “Humidity Derivative Sensor” set up in HA the best way to find your settings is to add your exhaust fan, humidity sensor and your humidity derivative sensor into a dashboard. To do this, go into a “Dashboard” then top right 3 dots click “Edit dashboard”, then click “+ ADD CARD”, click on “History Graph” in the entity field add your exhaust fan, humidity sensor and your humidity derivative sensor entities, then show “2” hours (you can change this any time), click save & “DONE”. You will now see something like this.
The above image shows humidity changes throughout the day in a 2 hour window. You can see the “Humidity Derivative Sensor” + & - values of around + 0.75 & - 0.48. Yours can be higher as it all depends on your site and the location of your sensor.
The below image is what happens when we have a shower. The image shows 2 showers data. You can see the first shower goes to + 10.0 then when finished around - 7.0. The next shower goes to + 14.0 then when finished around - 7.5. If you move your mouse over your graph in HA a pop up window will show more accurate figures.
Because we can see what is happening, we can now adjust our setting. Looking at the Rising Humidity Derivative %. The first shower jump is just below + 5.0 and the ending is just above -5.0. The second shower first jump is around + 7.0 and the ending is just above -5.0. Note: These reading are with a working exhaust fan so you may need to set + 1.0 & - 1.0 first then adjust and readjust your settings to get it right.
I have my sensor at the highest point right next to the fan inlet so my reading are high. Your reading could be lower but the working principle is the same.
I have monitored my site for some time now and I know my readings during the day never go above + 2.3 & - 1.5. Having the sensor up high next to the fan always has a similar results when showering as the above graph. It is good to keep your setting a low as possible as it will react faster but at the same time we don’t want to have false trigger turning ON the fan all the time, especially at night. I have set my “Rising Humidity %” to + 3.0 & “Falling Humidity %” to - 3.1. Your setting will depend on your site, where you live and your climate but being able to monitor your settings will help you work it out. If you get false trigger turning ON the fan consider raising your + value as this is what turns your fan ON. The - value is what triggers the automation to start the “Time Delay”. Then just monitor what happens and adjust as necessary.
This is important. It really depends on the fan you have, location of your humidity sensor, etc. It is a good idea to monitor it so the fan brings down the humidity before turning it OFF. See the above image how the humidity returns to around the starting value after a shower. Then just monitor what happens and adjust as necessary. Try starting with 10 min and adjust as necessary. I have my “Time Delay” set to 3.5 in summer (hot climate) and 8.0 min in winter (cold climate).
Safe Guard - Maximum Run Time Setting
Think of the longest shower anyone will have and add some time. It is really a safe guard and should never really be needed if your settings are correct. I have set mine to 25 min.
Use The Maximum Humidity Option (Optional)
Sometimes after a shower the humidity can take longer to fall back to its normal level. This can cause a lower rising % when having another shower before the humidity has time to return to its normal level, thus not triggering the automation. Enabling this option will allow the fan to be turned ON when the humidity rises above the set value.
NOTE - You must input your “Bathroom Humidity Sensor” in “Input - Bathroom Humidity Sensor” for this option to work. Your bathroom humidity sensor is the actual humidity sensor located in your bathroom.
This is where you set your maximum humidity %. When using this option, it is recommended to set this value as high as possible to stop false triggers. If you would like a lower % value and the slider will not allow it then just type the number value you would like in, and click save.
Use The Winter Mode Option (Optional)
This is where you can add another set of settings for the winter months (colder months). The settings are the same as above but you will need to select the months you would like to apply the winter mode settings to.
Humidity Derivative Sensor By-pass
This will allow you to By-pass the humidity derivative sensor and make your fan function as normal. The entity cannot be included in the “Fan Switch” and or “Fan Speed - Off Switch Option” selection. Please see our FAQ on how to set this up without having a physical switch.
Safe Guard - Use The HA Restart Option
If Home Assistant restarts for any reason, and the fan is ON, the fan will stay ON until the trigger is triggered again and the automation runs. In this scenario the fan could stay ON for a very long time. Enabling this option will allow you to turn the fan OFF in a set time delay, providing a safe guard option. I decided if someone just started in the shower and the fan was ON. If I restarted Home Assistant (HA) for any reason at that time, then for us the normal maximum fan time when someone had a shower was around 10 min, so I have set my “HA Restart Time Delay” to 10 min. Then no one would know anything happened, it would look like a normal shower took place if I restart HA.
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