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Connecting Nest to a Fan controller?

954 views 4 replies 4 participants last post by  stefuel 
#1 ·
I have a basic nest setup right now, that controls my AC compressor (on/off). I also have a fan that has a manual 3-setting switch on it (it's not a pull-down ceiling fan, just a wall switch controlling the on/off speed). The controller has 0/1/2/3 settings, 0 is off, 1-3 is fan speed control. I believe it's a 120V switch, but I haven't opened it up to check.


I'd like to connect them together, so when Nest starts the AC, for the Fan to automatically also start, and even (per tempreture) work at higher or lower settings.


What setup/switch/system do I need to make this happen? I also would like to connect the whole apartment (mostly dimmer switches), and whatever solution works with Nest and fan controller will dictate the rest of my system.


If there's no solution to work with Nest, which other smart thermostat may work instead (like Lutron with Honeywell?) , or else?


Thanks
 
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#2 ·
It can be done with the use of some 24 volt relays.

If you have a multi stage a/c then all you need to do is parallel in a relay for each speed of the fan in with your furnace fan. If your a/c is only single stage then you will still be able to hook the fan in but with only one speed (which ever one you choose).

You will need to do some fan re-wiring so you need to remember that there are certain electrical codes that must be followed on line level voltage systems (120/240 volt wiring and accessories) to stay legal (consult your local code book). There is no particular code to follow for your low voltage (24 volt) control lines.... other than common sense of course.
 
#3 ·
It can be done with the use of some 24 volt relays.

If you have a multi stage a/c then all you need to do is parallel in a relay for each speed of the fan in with your furnace fan. If your a/c is only single stage then you will still be able to hook the fan in but with only one speed (which ever one you choose).

You will need to do some fan re-wiring so you need to remember that there are certain electrical codes that must be followed on line level voltage systems (120/240 volt wiring and accessories) to stay legal (consult your local code book). There is no particular code to follow for your low voltage (24 volt) control lines.... other than common sense of course.
Thanks, but as this is a condo, wiring is not an option (I guess it could be, but very expensive). AC is single-stage, and I honestly don't care if I like only turn the fan on at speed 2, but I really need them to be in-sync.


I've called around, and literally no DYI kit has *conditional* commands! Insten, Lutron, WeMo, etc... The only option for conditional is C4, which is too expensive of an option, unless I did it via remote programming, etc...
 
#5 ·
Need to know more about what kind of fan it is you are trying to control. Also need to know what the A/C air handler is. Does your heat come from the same air handler (FWA heat) or do you have some other kind of heat. I suppose you could access 2 speeds of external fan control if the thermostat supports 2-stage heat or cooling even though your unit is single stage as the thermostat will control it.
It's really not rocket science. Pick up a 24 VAC relay with normally closed and normally open contacts. Send power to this relay from the 2nd stage contacts from the themostat (24 VAC) Connect the hot lead feeding the A/C fan to the com terminal on the relay. Plug the external fans low speed wire to the normally closed connection. Then connect a higher speed to the normally open contact. On a Y1 call the external fan will come on, on low speed. If for some reason Y2 is activated, 24 VAC will go to the relay. The normally closed contacts will open and the normally open will close bringing the fan on at a higher speed. Depending upon the thermostat, when a call for cooling is initiated, Y1 (stage 1) turns the A/C on. A couple of things (brand dependent) dictate Y2 (stage 2) If the spread between the "set temp" and the actual room temp are to far apart Y2 activates. Sometimes Y2 is called on if to much time has elapsed between the initiation for the call for cooling without the t-stat being satisfied. The same is true for 2 stage heat on W1 and W2.
 
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