I have an Aprilaire 8145 ventilator that essentially runs X minutes every hour to bring fresh air into the house from outside. It is wired to my HVAC board so it will turn the fan on when it turns on. It is NOT controlled by my Tstat because my Tstat already has control of a dehumidifier and only allows 1 aux device. I am trying to see how I can control the ventilator wirelessly so that I can turn it off in times when I dont want it to run. An example would be, if there is a wildfire or smoke outside, i want to disable the ventilator from running so its not pumping smoke smell into the house. I can go into the attic and hit the button to turn it off but thats a hassle every time to turn it off and on.
I was thinking the simplest form would be to plug it into a smart outlet and just cut the power. I was hoping there was a way to not cut the power entirely but just interrupt the signal to run with a relay or something.
I would agree that cutting mains power could be an issue, and I would consider it a last resort. But I don’t think you’ll need it…
This might be the least-elegant solution, but buy a separate 24V transformer, run it through an appropriate smart relay, then hook the relay’s output to the incoming fan control on the ventilator to mimic current operation, but enabling the ability of a hard shutoff.
Variations:
Use the R & C wires from your current HVAC equipment. They should always be hot
There is an -NC variant of that ventilator that is intended to be used with a building automation system. My guess is yours can be similarly equipped*, and if so, the 24V signal goes straight to the board and you can bypass their controls and you can control directly from the relay.
*My guess is the board inside the ventilator is the same and you can bypass your existing control mounted to the ventilator.
Thank you for the reply. I have it wired like the diagram below to my furnace board from the control panel of the ventilator. If I was to wire it like you mentioned with the separate transformer, how would that look? I dont want to by pass the furnace wiring because when i do run the ventilator it runs the furnace fan directly. It would be great to be able to bypass the signal from the control board when it calls for ventilation. Almost like a "man in the middle". The control board calls for ventilation > Call is interrupted / not successful > Control board still thinks the call was successful and wont call again until the next 1hr period.
I missed that, my apologies, that would indeed be handy to have.
Scattershooting here (and the usual disclaimers: IANAAnything)...
Would it be acceptable for you to control the ventilator directly/completely and still send the fan signal back to the furnace? You could split the R & C from the furnace and send to the relay. The R&C relay outputs would go to the 'VENT' terminals on the ventilator to signal the ventilator, but you'd split the Red (+) output and send back to the G terminal on the furnace.
Alternatively, I wonder if you could drive the VENT terminal as described above, but leave just the GH -> G connection intact (removing the rest) and that may drive the furnace fan as it does today. Not sure, though. You'd probably also need to connect the C wire, too. I just don't know if that GH terminal is backdriven from the main control board, or if it is solely powered by the ventilation control. (I'd guess the ventilation control, making the whole paragraph moot, but it may be worth a shot.)
Have you tried reaching out to AprilAire tech support? They're big enough that the engineers probably aren't in the same room as support, but small enough that they may be just a room or two over.
I would think the ODT [outdoor thermostat} terminals would stop it if the outdoor temp got to cold. Possibly use a zigbee or zwave relay across it with a resistor to fake the thermistor reading. Also past the vent terminals is possibly the damper or fan that could be stopped with a relay. If I saw the entire wiring diagram I could probably help.
Sorry, I fixed the links. Now there are links to both the controller and ventilator. I dont have my furnace wiring but its wired just like the diagram I posted previously
So you are saying that you do not want to turn the fan on when the controller has it off, only to sometimes shut it off when the controller has it on?
If need just a cutoff relay, then, why not just put a relay in-line near the ventilation control? Power the relay from R - C, and put the relay before GH on the panel to cut the fan signal off when you need.
Wouldn't this do the trick? It will run off your existing 24VAC on the board. It even comes with a keychain remote. When you turn the relay on, it cuts the signal to the fan if it is put in-line on the GH wire, with the wires connected to COM and NC.
The ventilator is controlled by the controller on the ventilator (Aprilaire 8120x/8126x controller). What I want to do is interrupt the call for the ventilator to turn on in certain circumstances wirelessly. For example, say there is a wildfire nearby and the air quality is really bad outside. I would want to turn off the ventilator from running so that its not pulling in the bad smokey air into the house. Right now, I would have to go into the attic and click the button on the controller to turn off ventilation from running. Then go back into the attic and turn it back on when its better outside.
Like I said in the post, I could just plug the ventilator into a controlled outlet and cut power to the ventilator and turn power back on but I dont know if frequent power cycles are good or bad for the ventilator long term. If I could just interrupt the signal of the controller calling for the ventilator to turn on, the controller would think the ventilator is running for whatever time its set to run for, and the ventilator would remain powered but not pull in air until I say so.
I should note the ventilator is powered separately from the HVAC system. The only connection to the HVAC system is to allow the HVAC fan to turn on when the ventilator turns on.
Yes, that is exactly what I was saying. Use a relay to interrupt the signal that is keeping it on.
I'm assuming that signal is just a contact closing in the thermostat, which is most likely the case, just like for temperature. The thermostat is just closing a contact to call for heat or cool, so if you remove the heat or cool wire it will stop the signal, So, if you unhook the ventilator control wire coming from the thermostat at the controller, it should stop the fan, the same as the thermostat stopping the fan by opening the contact. Put a relay in that line to "unhook" the control wire when you want the fan to stay off.
Turning the relay back on resumes automatic control of the fan, allowing the signal wire to again be in contact to turn the fan back on, if the thermostat has the fan on.
This is a little more than a basic thermostat control. You need a dry SPDT contact to control GS, GH of the vent/furnace and another contact/switch to turn off the X-minute every hour fresh air fan.
Right now your thermostat is sending the fan control to your vent and the vent passes this signal to your furnace. Hence, both furnace and ventilation fans both run when your thermostat commands.
You cannot just interrupt this signal by leaving it open circuit or your furnace fan will not run. You need to somehow connect Thermostat G to Furnace G when you want to manually interrupt the Vent. You can accomplish this by having an STDP switch.
Now the second part is trying to stop the vent from having this X-times running every hour. One thing you can try with the ODT (outdoor temp sensor). Will the vent run when you remove the ODT? If it's not running, then a dry contact smart switch could be used.
The onboard controller for the ventilator has only two orange wires running from it to the internal of the ventilator. I took some photos of the ventilator control wiring. I also noticed that if I unplug the ventilator, the onboard controller does not power off. I assume this is because the controller is receiving power from the HVAC wires connected to it. I assumed the controller was receiving power from the ventilator and the two orange wires. I wonder if these orange wires are just the contact wires to call for the ventilator to turn on like you mentioned and then the ventilator turns on the HVAC fan.
Could I use something like the Zooz multirelay? If so, would I have one contact interrupting the controller signal and then one contact interrupting the HVAC fan connection?
What happens if the vent is running, and you pull the wire off of GS (when the furnace is heating) or GH (when it is hourly venting), based on the wires in the picture of your controller. Does the vent turn off?
That is what I was suggesting you try. If that works, you just need a two-channel dry contact Zigbee SPDT board, use this version of what I originally posted. Use the NC, Normally Closed, circuits. In Hubitat, you can use the parent device and both will open and close together, or use the child devices to control them separately.
I use a four-channel version of this to control my three zone valves on my furnace from Hubitat. I have four of these boards total, they work great with Hubitat.
