Need House Thermostat To Trigger 120V Outlet

Hi. (Long post, sorry) Here’s the situation: I (wife) have a whole-house air freshener (“scent machine”) that can pump aroma directly into HVAC, to make the entire house “smell pretty”. If you hook directly into a/c ductwork, you can’t have it run when the a/c is off, only while a/c fan is running. Fragrance oil will pool up inside the plenum (?) and start to grow bacteria, etc. So I have two choices and I want choice number #2. 1) run the a/c fan constantly, and let the machine cycle on/off throughout the day as it does by default. Easy, but costly on the electric bill plus wear/tear on air handler. 2) rig a 120v receptacle to be “tripped” or energized only when the a/c fan turns on and off. The unit will still cycle on off, but only when only the a/c fan is running. Hard, but so much better. I figure the thermostat is 24v (?) so a 24v to 120v relay connected where thermostat connects to air handler.   Then run a simple pigtail female plug or receptacle mounted inside HVAC closet; 120v power would come from another receptacle in the adjoining bedroom. Relay? “Contactor”? Here’s what a local electrician told me along with his estimate of $400-$450! “there are multiple types of relays to accomplish this, depending upon the load the relay has to handle. Being I do not know the load created by this machine you wish to operation, I would do it with a contactor, verse a relay, so it does not stand a chance to be overloaded.“ The scent machine only pulls 14w, so I don’t think there’s an overload concern. Any words of advice?? Thanks. // Radar //RadarContact

I don't have specifics on your unit, but if it were me, I would tap into the feed for the fan itself, not the thermostat. When the fan gets power, a separate contactor can energize and allow your scent machine to operate.My ex once told me I have a perfect face for radio.

I’ll have to research contactors, I’m not familiar. But that’s an interesting approach… need to pull the HVAC schematics and take a look!RadarContact

The thermostat connects to a board inside the unit but it doesn't determine when the fan is running. That's why you're best bet is to use the motor hot lead to control a contactor.My ex once told me I have a perfect face for radio.

Understood. Great point. I researched contactors and that seems like overkill as the unit only draws 14w total. So, I will try to figure out which relay to use based on that info. (From www.engineerfix.com: “ The load capacity of relays is mostly used for applications that carry 10A or less. Any applications that use 10A or more normally use contactors.”RadarContact

Yeah, it's definitely overkill. You could use a solid state relay to do the same thing.My ex once told me I have a perfect face for radio.

Sweet. I’ll try to find one and then I’ll come back for a thumbs-up! Lol!RadarContact