Wiring an Emerson Sensei WIFI Smart thermostat with a De-humidistat control for Air Conditioning

[SamMonaco]

I have a home in hot humid Florida. As is typical in Florida, our AC was controlled by a traditional thermostat but also has a separate "de-humidistat" control wired "in series" with the thermostat. By de-humidisat, I mean a control that allows you to set the desired humidity. By having it wired in series (vs parallel), both the thermostat set point and the de-humidistat set point must be exceeded for the AC to be turned on. When you are at home, the de-humidistat is set to "ON" and the AC is full under control of the thermostat. When away from the home, the de-humidistat is set to 50 or 55% and the AC to 80 degrees. This allows the AC to only run when the humidity goes above 50 or 55% to avoid mold. My question is this: Recently I installed an Emerson Sensei "smart thermostat" in order to be able monitor both temperature and humidity on my iphone while away from the home. I followed the instructions from Emerson as to how to wire the Sensi based on the wires connected to the original thermostat which did NOT have a connection to the 24v power wire from the AC unit. The thermostat functioned fine with the de-humidistat set to ON (eg. only the thermostat controls the AC.) The wifi also worked fine and I was able to see temp and humidity on my iphone as well as change the set temperature remotely. However, I then found out with further research that the wifi was operating only on the Sensei's 2 AA batteries. Given that I am gone several weeks at a time, the batteries would go dead. However, you can attach the 24v power line from the AC blower unit to the Sesei and have the wifi powered by that such that the batteries are only for back-up. The 24v wire was in the wire bundle so I connected to the AC blower unit and to the Sesei per the instructions. Again, the thermostat including the wifi connection worked fine with the de-humidistat set to ON. However, upon leaving the home, I entered my usual "away settings" of 80 for the thermostat and 55% for the de-humidistat. What I failed to realize until after I was gone is that both the AC AND the WIFI connection work only when the temperature AND the humidity are above the set points. Therefore, I am not able to see the temperature and humidity on my iphone remotely (and change the temperature setting if I wanted to) when the AC unit is actually running (ie both the temp and humidity set points have been exceeded. Kind of defeats the whole reason for have the wifi thermostat. I contacted Emerson and asked if the Sesei could be wired to function with a de-humidistat in series and I was told NO. Not sure they really understood what I was asking. I suspect there is a way to do it but I am not sure how. Has anyone out there done this successfully and can tell me how? Many Thanks

 

[Sandford]

I have a non-programmable 4-wire thermostat and a 2-wire Humidistat.
Can I connect both to the Sensi WiFi Stat ?
If so, to where do the 2-Humidistat wires connect in the Sensi install ?
Also, there is an unused blue wire (C ?) that is available, if required for this setup.

 

[Dirtmechanic]

I want my dehumidifier to work independently of my temperature control. Maybe this is in part why that system won't work in series? Not that they thought of me, but that the systems are separate and therefore systems are designed that way?