SmartThings Community

ZOOZ Zen21 switch and whole house fan

(Brad Stevens) #1

I ordered a Zen21 switch to turn my whole house fan on and off, not for the high/low control, but now that I have the switch it says not to use with ceiling fans or heavy duty appliances. Did I order the wrong switch and if so can you make a recommendation for one you know will work. Here is a link to the fan that I bought.

(Dumb) #2

I been using Zen21 for months in fans… but how big is your fan?

Edit: big fan, not sure if zen21 will work, it works with my ceiling fans just fine

(Brad Stevens) #3

It a 24 inch whole house fan with a 2-speed, 1/3 HP motor. The link to the fan is in my original post.

(Dumb) #4

Deleted, looking for a better answer.


tagging @TheSmartestHouse

(JBrown) #6

Have you looked at the Zen15?

(Brad Stevens) #7

No, but mainly because I was thinking of the switch for on/off rather than the plug and wasn’t sure if the fan had a plug or was just spliced in to existing wiring for power.

(Brad Stevens) #8

I found some more specs for the Zen21 and it says it can handle a 1/2 HP motor so wouldn’t it work with a 1/3 HP motor?
Z-Wave Frequency: 908.42 MHz (US)
Power: 120 VAC, 60 Hz
Maximum Loads: 960W Incandescent, 150W LED and CFL bulbs, 1800W (15A) Resistive, ½ HP Motor
Z-Wave Range: Up to 100 feet line of sight between the Wireless Controller and the closest Z-Wave receiver module
Operating Temperature: 32-104° F (0-40° C)
Installation: Indoor use only


For a simple exhaust fan which only did on and off, sure. The problem is that you have a variable speed fan. The physics are different. There’s a reason why the manufacturer and the seller say in bold type in the instructions that it should not be used with a ceiling fan.

There are also people who have posted Amazon reviews saying that they tried it with fans and the switch burned out. That’s a fire hazard.

With fans it’s not just a matter of the total power being drawn, it’s the method of regulating that draw. This has been discussed in the past regarding a number of different devices and fans.

GE and Leviton both make variable speed fan control zwave switches which work with SmartThings. There is also a zigbee device which is popular. You would need to check the specs on those to see if they match your whole house fan.

Have you had a chance to look at the fan FAQ yet? (This is a clickable link.)

(Brad Stevens) #10

A dimmer switch won’t work. This whole house fan isn’t a ceiling fan. It has a separate switch that controls speed (high/low switch). Here is the wiring diagram from the fan.


The Zooz switches, like most other Z-Wave light switches rated for 15A won’t work with whole-house fans specifically because these are pretty powerful at 1/3hp or more. @JDRoberts summed it up well in his post above, your best bet would be to go with a dedicated fan control switch (like the GE) provided that all of the specs check out. Although the way the installation is wired now, the on off switch doesn’t control the motor at all so the whole set-up would have to be rewired so that your smart switch has the motor directly on load. We don’t carry GE switches anymore but from what we recall, even their 12730 fan switches were meant to be used with regular ceiling fans only and would malfunction with whole-house fans.

(Brad Stevens) #15

Ok, I kind of rambled as ideas came to me so I deleted those posts. Could I install an outlet, connect a Zen15, then rig a plug to the wires that lead to the fan switches. Leave the fan switch in the on position but set up my SmartHub to control the Zen15 to toggle the fan on and off? Am I making sense? @JDRoberts @TheSmartestHouse

Also, according to Home Depots website the ON/OFF switch that comes with this fan is a standard 15A. Does that change anything that you have said to this point?

I really appreciate any guidance you can provide.

(Tony) #16

I don’t believe the GE Fan Speed Control switch would be appropriate for this application; that’s for ceiling fans which are different from whole house fan motors which set their speed based on which set of windings is energized with a dedicated switch. You just want to control the power feed to your whole house fan’s 2 speed switch (that switch will route the hot wire to set the fan speed appropriately at the motor, as your diagram shows).

For my 1/3 hp whole house fan’s motor I’m using a Master Flow 2 speed fan control switch fed by a GE Z-Wave Plus 14291 In-wall Smart Switch . Its packaging seems to emphasize the light control aspect (and many shopping sites describe it as a ‘light control’) but if you look at the spec sheet it is not a dimmer; in addition to lights and resistive loads it can be used for switching pumps and fan motors up to 1/2 hp. It works great.

Why the Zen21 spec sheet specifies a max 1/2 hp motor load but also includes a ‘please read’ notice not to use with appliances or motors is baffling.


Thanks for sharing your solution @Burd!
The 1/2hp rating is there because the components of the switch (the relay) are rated for 1/2hp but from our experience servicing z-wave switches (be it GE, Zooz, or Aeotec), we found that the high inrush current in motors often kills the electronics in smart switches. The initial power draw of a motor or transformer can be 20 times as high as what it’s rated for. So fot a 1/3hp motor (which is still a very small motor for a whole-house fan, most of the ones we’ve seen are 1/2 or higher) a 15A smart switch just barely makes the cut. Which is to say that sooner or later it may still malfunction due to high inrush current. That’s why we don’t recommend using these switches in this application. Technically, you could, but we’ve serviced too many switches (especially from GE, the older generation though) to recommend using a regular 15A z-wave switch in this type of application.

(Brad Stevens) #18

What about my idea to use a Zen15?


I’m not feeling well today, you’re getting lots of good advice from others, and I usually leave rewiring discussions to the community’s electrical experts anyway (I’m good on device specs but my expertise ends at the workbench :wink: ), So I’m not going have much to add to the discussion at this point.

I did want to clarify that at no point did I ever recommend a dimmer device. The three that I mentioned are specifically for variable speed fan controls. Not dimmer switches. ( again the physics are different)

And you’re right, I did miss in the original discussion that this was a whole house fan, not a ceiling fan. My bad.

And, yeah, inrush current.

At this point hopefully @Navat604 or one of the other electricians in the community will have more to add. :sunglasses:

(Brad Stevens) #20

@JDRoberts thank you for the help you did provide.

@Navat604 and @TheSmartestHouse any thoughts on using the Zen15 prior to the standard switches that come with the whole house fan? Seems like the Zen15 is made for this type of application since it is designed for AC units, fridges and other large appliances.


Yeah, you can turn that on/off switch into a receptacle or just install a receptacle somewhere near and use a cord with a plug, something like that:

You’ll need to connect the wire coming from terminal 3 on that control switch to the black wire in the cord, then connect the white wire in the cord with the white from the motor and ground to ground (so wire from terminal 5 to green wire in the cord). Then plug the cord to ZEN15 in the outlet.

(Dave Hardin) #22

Goodness, if you have any problem with a whole house fan using a Zen21 (on/off only no dimmer) just install a contactor with a 120 volt coil that is rated for whatever current the fan motor requires. That way the only thing the Zen21 supplies power to is the coil for the contactor which is minimal. The current that supplies the fan is kept separate from the Zen21. Glad I could help.