I am looking to add a Aprilaire E100 dehumidifier to my system and want to control it with my T40K. I am looking for information on how to wire it to the T40K given it requires two wires to call for dehumidify. I have seen hints that a relay may be required, but I am unclear how that relay would be wired into the existing system.
Yes, with a 2-wire dehumidifier you would use an isolation relay so the dehumidifier is powered by its own power source and not the thermostat. From ADC’s guide on installation, see the instructions below:
Thanks for that information. Are you able to provide a complete copy of that installation guide? It seems much more detailed than the one that came with the thermostat.
That is the entirety of the section relevant to your installation, the rest is for different humidifier installation or using the AC to dehumidify. It is from a humidity control install guide.
That would be a good addition to our how to guides here on the support site though, I’ve put in a ticket to get it added to our #how-to section soon.
I have gotten the dehumidifier installed but the thermostat does not seem to be calling for dehumidify like I would expect.
Is there a way to set the thermostat to only run the dehumidifier when the air conditioning is not also running? Currently the thermostat only runs the dehumidifier when the air conditioning is running or the system mode is set to off.
I can live with the dehumidifier running at the same time as the air conditioning but I definitely need it to continue running after the air conditioning stops. My house is frequently above the humidity set point while being below the temperature set point.
Is there a way to set the thermostat to only run the dehumidifier when the air conditioning is not also running? Currently the thermostat only runs the dehumidifier when the air conditioning is running or the system mode is set to off.
The dehumidifier will run on either AC calls or while the the tstat is off. This is expected. You cannot limit it to when it is off only. For clarity though, it sounds like you may be specifically saying that when the tstat is in cooling mode, unless the the Tstat is actively cooling the dehumidifier is not running, is that correct?
I can live with the dehumidifier running at the same time as the air conditioning but I definitely need it to continue running after the air conditioning stops. My house is frequently above the humidity set point while being below the temperature set point.
This should already occur. The Z-terminal dehumidifier option will run when the Tstat is set to cool or off, and will run based on the humidity level and differential.
The fan should be called along with the Z terminal dehumidifier whether there is a call for cooling or not - if the humidity level is above the threshold.
If you do not have a configured dehumidifier then dehumidification can only be performed via the cooling stage, so that would only run when cooling is active.
It looks like you have two thermostats. Just to be sure we are clear, which one should currently have the Z-terminal dehumidifier and humidity rules?
Are you also running Circulate fan rules? Try turning the circulate off.
Yes that’s correct. Regardless of the humidity level the thermostat does not call for dehumidify unless it is also calling for AC.
The dehumidifier is connected to the Z1 terminal of the “Upstairs” thermostat.
Yeah I did have circulate enabled. I’ve tried turning it off but the behavior was unchanged.
Can you confirm the humidity reading when this next occurs? When the dehumidifier turns off, check the humidity reading and let me know, please?
I can forward that to ADC to investigate if your account is following the Smart Humidity controls as though no dehumidifier was installed.
It stopped just now when the temperature reached the set point. The humidity reading was 60% and the set point is 40%. I’ve included pictures of the various screens if that helps.
If I lower the temperature set point such that cooling is called for or change the system mode to off, the dehumidifier immediately turns on.
Not running when should be based on settings:
correctly dehumidifying when HVAC mode is OFF:
humidity settings:
Thank you, I’ll forward this and see if a bug is occurring. (I am assuming it is a bug) They may have purposely set it to dehumidify using the AC only when cool is enabled, though that does not make sense to me, as the dehumidifier would do this more effectively.
One additional data point I noticed this morning: The thermostat will call for dehumidify in cool/auto mode without a corresponding call for cooling when it is first powered on but after the first call for cool it reverts back to the (hopefully) buggy behavior.
Thanks, yeah this is not how it should behave. There is still the advanced setting option to dehumidify only when cooling, but it is disabled for you. It seems that rule may be bugged for you.
ADC has asked if we can test the humidity differential setting to see if the dehumidifier continues until the differential is reached or if it stops as soon as the cool set point is reached.
Would you mind setting that differential to the default 3 degrees and test that? This can help identify where the bug is.
Much to my surprise setting the differential to 3 degrees seems to fix the issue.
Cooling still stops at the temperature set point (rather than up to 3 degrees below it like differential would allow) but now dehumidification continues by itself until the humidity set point is reached. I can also confirm that dehumidification resumes on its own if the humidity set point is exceeded independently of the temperature set point.
Well, that’s good news. If the bug is actually dependent on that differential setting we can avoid it.
Yes this makes things much more manageable.
In the mean time I would like to submit a feature request to ADC to allow not running the dehumidifier during a call for cool. When they are ducted together it doesn’t make sense for them to run at the same time.
Yes, we will forward that request.
Unfortunately this seems to have only been a temporary fix. The original buggy behavior is back even with the differential setting now.
Interesting, did anything else change between then and now? Did you turn on schedules again or otherwise make changes?
Yeah I turned the schedule back on in the app yesterday evening. As far as I’m aware it was working fine until this morning.
My morning setback is greater than the differential so maybe that has something to do with it? However, when it was working these previous couple of days I was able to make manual adjustments to the temperature setpoint that were greater than the differential without issue.
Unfortunately it has not resumed calling for dehumidify even after the temperature has risen to be within the differential.
My morning setback is greater than the differential so maybe that has something to do with it?
You mean the change from night to the morning temp is more than 3 degrees? It would be good to test especially if the dehumidifier stopped around then. Making manual changes does not include all the same automation code so it is possible the bug is triggered by schedules initially.
If you turn the schedule off, turn the mode off, does the dehumidifier resume?
If so, let’s test this by setting the humidity differential to be more than the change you described. Then you can re-enable the schedule and test.