So I have a whole home humidifier attached to my forced air furnace (full hvac) and my thought process is to put a remote outlet on the humidifier and have the main humidity read by my thermostat (go control) be turned on when lets say it dips below 35. Would this be the proper way to execute this or should I get a zigbee/zwave humidistat?

I have a 6 zone system. I used an ESP32 with a relay. The Arduino code gets info from the ecobee thermostats, outside temp, etc. The Arduino takes the humidity level and calculates the appropriate humidity level depending on outside temp (and some other things). I have an app that feeds info to the ESP32. This total bypassed the humidity controller from Aprilaire and it works for all zones with respect to humidity levels.

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For my whole house humidifer I have a smart switch that provides the power to the humidifier motor that triggers on and off (on below 40% per Ecobee), but also have wired in a current sensing relay (White Rodgers A50) around the power lead for the blower motor heating circuit.

So, it has to be less than 40% humidity per Ecobee, but the furnace also has to be in heating mode with the fan running for the humidifier to run.

Also have a smart switch powering this tiny USB pump I found on Amazon... It turns on once a day for 4 seconds to pump bacteriostat into the humidifier reservoir to keep the water from getting funky.

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Do you use any kind of special rule or simply "if sensor >40% then switch on" but the humidifier won't run till the relay is tripped by normal heating regardless of the rule?

Right, that other relay is not 'smart' and is just wired in series with the power to the humidifier motor from my smart outlet. HVAC guy was here once for a burner repair and clued me in on their existence, and it seemed like a good idea to keep it from running when the blower was off, or when it was in AC mode.

I just have the smart outlet set to come on if the humidity is less than 40%.

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I have a simple two stage goodman hvac system with a Go Control thermostat. Will probably set mine up like that then. Thank you!

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Was just double checking, and I see my Simple Automation Rule has an offset for turning the outlet back off at 45% to try to prevent it from cycling on/off right at the setpoint...

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Yeah, I figured I'd have to do that.

Depending upon where you live or how efficient your windows are, 40% can be high.

Pittsburgh. Honestly even without it running it hovers around 40 percent, but once feb gets here it will drop to around 25

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You also may need to think about what the temp is outside and the dew point. If you have a the humidity to high in your house and the dewpoint is very very low outside you can start to build up water in your exterior walls and that can lead to big issues. I have a smartapp that manages my humidifier and it does some calculations and adjustments based out outside temp. As the temp drops it adjusts the allowed humidity inside.

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Yeah - NJ here, and the humidifier is only run in the winter. I have seen it drop into the 20% range in the dead of winter before it was installed, and anything under 35ish and my family will complain of dry hands / mouths. It is typically between 45%-55% on this ecobee. But, it also used to go too high and seeing 65%+ would happen and make me worried.

Heh, originally from Princeton.... So yeah, I know about dry winters in NJ...LOL

That's pretty high, unless your weather is a lot warmer than mine. I live in northern Illinois. 45% is typically recommended above 50 degrees. I wrote a routine to calculate the ideal humidity setting. Ecobee uses one too. Their calc allows for a factor based upon window efficiency - essential it bumps it up or down depending.

I thought all the things I used to read said 40%-60% was good. Just doing a quick double check now and I find...

ASHRAE Standards specify ideal comfort ranges of 68ยบ to 74ยบ at 40% to 60% relative humidity in the winter months and 73ยบ to 79ยบ at 40% to 60% relative humidity in the summer months.

That defines my indoor, winter conditions perfectly, and I don't control humidity in the other three seasons. I have the switch set at 40%, but it goes higher since the humidity is impacted by other things in the house and outside, as it is supposedly 35 degrees and 70% humidity outside right now. All in all, this approach and setpoint works well for us in terms of personal and home health, and the high/low excursions are under control.

The problem is that what seems good for personal and home health may not actually work 100% of the time. Especially in extremely cold weather. What you have to remember is that your house is always breathing to some extent. Not everyone's house breaths the exact same, but they all breath. This is why outdoor weather can effect our indoor temps and humidity.

When the air gets colder is can hold less water. So air outside at 35 degree's at 70% humidity hold considerably less water then what the air in your house at lets say 65 degrees. The problem is when the air inside with 55% humidity starts to breath through your walls and starts to cool down. As it cools down it's ability to continue to hold the water vapor drops. Once it drops to the Dew point if the amount of water vapor in the air would create 100% humidity you would have water condensation in the walls possibly. The key is to let it drop to the outside temp and never let it reach the dew point so the water never condenses.

It is unfortunately a balancing act which only gets worse the colder the weather gets. The humidity you want inside when it is in the teens would normally not be a good thing, but may be needed to prevent other problems. I haven't seen a perfect answer to this in a algorithm yet. I am sure the one I use isn't right most of the time either.

I am from Florida and learned some of this the hard way as my family had a bunch of issues after moving to SC a few years back. It doesn't get to cold here, but the first winter i was here was unusually cold for the area. I did allot of research on it so we could get our issues under control. I totally understand low humidity is a really crappy thing to deal with after that experience. On top of that everything you read says you should be between 45-60% humidity. I completely agree with it to a point. My dehumidifier keeps inside humidity around 55% during the summer and I have two humidifiers that try to maintain 45% under normal circumstances. One of them will adjust down since it is controlled by hubitat (use to be Smartthings) as the air gets colder outside.

two things.

  1. humidifiers that run without the heat or fan on i have found to be basically useless/ineffective.
    that is why i use the honeywell steam humidifier with a furnace that can have the fan run independent of the heat/ie when the humidifier is on. the solution above with a switch cannot mimic this.

  2. the steam humidifier has settings to mitigate the above problem with it being too cold.. it will back off on the humidity based on outdoor temp.

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Not from the documents that I've read. I know the ecobee humidity code does not set the humidity that high in the winter. If it works for you, then that's all that matters. :slight_smile:

i never said it did if you note i was talking about the honeywell steam humidifier

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I was not replying to you.

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