Three speed whole house fan

Ok I have the hardware worked out. Waiting on a large junction box to install it all. I went with the ZooZ S2 multi relay. It’s a 3 channel dry contact relay. Port 3 is rated for 240v 20amp so I’ll use that to directly the timer in QuietCool’s drawing above. The other two ports are rated at 240v 15 amp which is more than enough for the fan but they are only NO contacts on them. So I am going to wire those two ports over to a pair of SPDT relays. I found them on amazon soldered to a board with screw down terminals for like $7 so it was worth the time savings to go that path.

So recap: power will be controlled via relay 3. It will then feed into the SPDT relay wired to port 1 which will replaced the first speed switch in QuietCools drawing. NO contact will power high, NC will feed the input of the 2nd SPDT relay. It’s NO contact will feed the medium speed and the NC contact will feed the slow speed power. This way it’s electronically identical to the factory provided timer and speed switches and there is no way outside of one of the SPDT relays frying badly that I could power two of the inputs at the same time. While there is a risk for that it’s not much higher than the factory wall switch doing the same thing.

Next step is to work on the software side of things. My “Goal” is to build a virtual dimmer to control all of this.

If I set the dimmer to 0%/Off it turns relay 3 off
If I set the dimmer between 1%-33% it turns on relay 1, 2 & 3
If I set the dimmer between 34%-66% it turns on relay 2 & 3
Finally if I set the dimmer to 67%-100% it turns on relay 1.

It seems fairly straight forward but as I mentioned earlier I am a hack at best when it comes to programming so I am sure I’ll have plenty of questions when I get there. Thanks


Work got in the way but I got the first controller for my downstairs 3 speed quietcool built tonight. Right now it’s going to show up as 3 switches in ST but I’ll get started on the virtual switch setup once I get the hardware working.

How did this work out? It seems very complicated but I can’t find any good alternative. Basically we need a smart switch that has three mutually exclusive positions feeding three distinct load options. I’m using the Lutron Caseta system for my lighting and would love to find something simple - whether it integrates or not.

I highly doubt you are going to find something since you need a switch that feeds the 3 loads but cannot feed more than one at a time. That is why I ended up going down this route. So far its been working great for over a year on two fans (one into the lower attic and one into the upper attic). What I have not had time to do is mess with creating a virtual switch so it shows up in Smartthings as a single device. Right now I have the relay that controls on and off named “Upstairs house fan” or “downstairs house fan” and we just use alexa to turn it on or off since ST is integrated to Alexa. I also have those two relays set to auto turn off every day at 5am so it off before there is any chance of things warming out outside. To control speed I manually go into the ST app to change it but 95% of the time we just leave both on low as its plenty of airflow except on the hottest of days. If you have any other questions let me know.

I’m not real sure if this is what you have in mind, but since this topic popped up, I’ll offer an idea that I haven’t pursued yet.

What I’m thinking anyway is that with a regular “smart switch” i.e. SPST and one of the newer SPDT 2-channel smart relay options, this could be a two device solution.

Here’s the diagram that got me to thinking about it.

3-speed relay diagram

The SPDT being basically any smart switch, and the SPDTs being the 2-channel smart relay.

I sometimes get brain block with relay wiring, but unless I’ve just totally missed something, I think it’s viable.

edit: the only thing that stands out , is that diagram doesn’t reflect smart switch wiring and the relay would require it’s own seperate DC power to keep the board online, but the AC wiring betwenn switch and relays would remain essentially the same.

James, what 2 channel SPDT switch are you looking at. I ended up going with the Zooz 3 channel one (Zooz Z-Wave Plus S2 MultiRelay ZEN16 with 3 Dry Contact Relays (20A, 1 - The Smartest House ) which works great. It shows up as a single device with 3 child devices under it for reach relay. The problem is all 3 channels are SPDT. That works for channel 1 which is the “on/off” switch for the fan. For channels 2 & 3 to control the speed you need SPDT like you mentioned. For that I picked up a board that includes two SPDT relays. $7 for two of them. To power the Zooz zen16 I bought a small board mount 12 volt transformer. This powers the Zooz and the relays. This overall was the simplest way I could figure out to build this setup.

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Oh, yeah… I’ve been goin’ on about the MHCOZY Zigbee two-channel relay in other threads, as it solved some problems for me, especially with its interlock mode.

I’m thinking that some of the others like “curtain modules” etc, could be a nice option too, especially with the ability to wire momentary wall switches etc… Although, I know those can befuddle people, including myself.

Anyway, there are some decent explanations of the MHCOZY in the Amazon images, and there is also a 4-channel available.

Also, it works with the current ST Zigbee Multi Switch DTH, so I’m guessing it will continue with the Edge drivers.

Aliexpress has some other offerings, for the same relay, including a relay enclosure and an RF remote.

edit: And, yeah, the Zooz was also part of my thinking with the previous wiring diagram, I guess it has the momentary switch options too? I haven’t experimented with one.

** So, it might come down to changing the wiring with yours, or I’m missing something important here. I’ll think on this some more, especially regarding the Zen16, and see if I can manage some confidence with my logic.

Ok, I think I see what you mean with the Zen16, in that the single pole is static/fixed to all three relays. I think that is often the case with the curtain modules, as well.

I’d almost call the MHCOZY relay perfect if it had terminals for connecting external momentary switches, although, those could be added with a bit of soldering to the back of the individual relay buttons.

What you have seems to be doing essentially the same thing as the diagram would do with the Zigbee relay. And if it works, why fix it…

*If I get my hands on a three speed device, I’ll try to confirm if what I earlier proposed, does in fact work.

I know nothing about mhcozy or every even heard of them. Zooz has some great devices/firmware and has custom device handlers for each of their devices for a variety of home automation platforms including SmartThings. I try to stick with devices that are well supported as I have had some nightmares in the past with random devices doing things they are not supposed to.

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I totally get that

I wouldn’t have had any experience with MHCOZY if it weren’t for the application that I needed. name sounds a bit too feel-good, heheh…

But it’s been solid for several months, and has some notable differences, with it being Zigbee 3.0, with repeating capability, and the relay config options.

I can recommend it, for what that’s worth.

Good to know. I have like 3 zigbee devices and 40+ zwave devices so I have been trying to keep to zwave where I can. The Zooz also has a bunch of customization that sounds familiar to the one you are playing with. Once you have the custom device handler loaded all of these settings are available under the master device.

Very nice… It does have me interested to know what those “switch type” options do.

Zooz’s handlers are second to none. The Zen16 has been on my list to buy for a while, I’ve just been heavy on Zigbee lately. I’m sure it will swing back toward Z-wave at some point.

James, here is what the switch type settings look like.

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I have the quietcool setup that uses two separate physical fans. The top switch is on-off for the low-power fan, the bottom switch is low-high for the high-power fan.

We only really use low (LP fan off, HP fan on low) and high (LP fan on, HP fan on high). There are various settings available by mixing off low and high with the two fans, though. I was thinking of two separate on-off smart switches to power the LP fan (“low”) and the high side of the high-power fan (“med”), and that would turn them both on for high.

I have a lot of smart switches lying around needing jobs, and this seems like a pretty simple way of getting low, med and high.

I am not an electrician, and before reading this thread I was considering putting a dimmer on the high side of the high power fan, but now I’m guessing that is a bad idea?

I know this is an old thread, thanks for any and all input!

Correct. The physics for a dimmer that controls lighting is very different than the physics for a variable speed motor, and you can end up burning out the fan, the dimmer, or both. Instead, you need to use a switch which is specific to motors.

The following FAQ is old but still valid, because, well, physics. :wink:

Automating Fan Control--Don't Use a Light Dimmer!

I love this solution but I’m having trouble with the wiring between the SPDT and Zooz. I have a pretty good idea from the picture you posted but I’m not sure what’s going on left side of the SPDT and into the Zooz. Any chance you have a wiring diagram? Appreciate any help.

Timothy, Just saw this. Do you have two separate quiet cool fans or just on that is 2 or 3 speed? The 2 & 3 speed ones are a single fan motor that is multi speed and needs to be treated that way and only powered exactly how quietcool’s switch setup powers it. With how I have my Zooz & SPDT relays setup there is no physical way I can power it any different than how quietcool’s switch powers it. As for a dimmer, JDRoberts is right, do not run a dimmer or you are going to most likely burn up a very expensive fan motor. Good luck!

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If you go back to my posting of the quietcool wiring diagram I had early in this thread, you will see the two switches that ship with their 3 speed fans. I am using the two relays on that board to replace the two switches like for like for the quietcools switches that ship with their 3 speed fans. If you have a two speed this will be similar but a little simpler of a setup. The zooz has 3 on/off relays and to emulate the two single pole double throw switches (SPDT) I had to use those two external SPDT relays hooked to two of the zooz ports. I use R3 interface on the Zooz to replace the quietcool timer directly as that is just a single pole switch so that means my 120v that feeds into the relays is only on if R3 is turned on, exactly how the quietcool timer is wired. I then use R1 and R2 to control the two relays. The relays are low voltage and the Zooz needed a power source so in picture of my box in the lower left you will see a small DC transformer. I forgot right now if its 5vDC or 12vDC but what ever the Zooz needed I bought relays that used the same voltage. I then hard wired the DC negative to both relays and then ran the DC positive off the tranformer to one side of R1 and one side of R2 and then the other side of R1 and other side of R2 ran to the coil on each relay. The 120v side of the relays I wired exactly the same as the two quietcool switches. One other thing is that I was having reception issues with the Zooz in a steel enclosure so I ended up cutting a plastic cover for the top of the box and its been working great July of 2020. I have two seperate 3 speed quiet cool fans in the house, one for our upper attic and one for our lower attic and they are used almost every night from the middle of spring to the middle of fall and have been awesome. The wife and kids just use alexa to turn them on and off as needed but I also have an auto off setup in ST to turn them both off at 5:30am in case we leave them on all night. Please let me know if you have any other questions.

Awesome. I think I got it. Your details helped a ton on the DC side. Does this look right?

I was going to start on the virtual switch, but wanted to clarify if relay 3 needs to be on for the high setting?

If you turn on relay 3 (without changing the dimmer percentage) does the fan start on the last speed setting?

Good to know on the steel enclosure. Haven’t ordered one yet but will look for a plastic one.

I just had a quietkool house fan installed and it’s three speeds and is amazing.
I asked the installer why no smarthome connection?
He said it was a safety regulation as there were many people who used automation to turn the fans on but doors and windows were closed and the fireplace was on . apparently the fan sucked smoke and soot back into the house endangering the occupants.
He said so the quietkool folks made it manually operational only.
I’m also looking at the robotic fingers to press the buttons.