How to turn furnace fan on and off by voice - and run indefinately

[AlStu]

I previously asked on this forum how to run the fan indefinately but did not get a good answer. Nest will run it only for fixed times, but [the royal] we want it to run all day. Can't do this through the Nest so it is done in hardware. Bit messy but works. BTW, otherwise the Nest is great.

Get a 5V relay such as this from 'zon and mount it inside the furnace (no, not the burners). Connect the NO (Normally Open) contacts between the furnace's G terminal and R terminal (use RC or RH if no R). Energizing the relay connects the G fan terminal to 24VAC and turns on the fan. Next, connect [small] wires to the relay coil and run it out of the furnace to near an AC outlet. Find a surplus 5V AC adaptor (AKA wall wart), strip the 5V wires and connect them to the relay coil, polarity does not matter with the above relay but your relay coil may be polarized. Finally, plug that wall wart into any smart plug and that into the AC outlet. Voilà, the fan can be turned an and off by voice and/or automation.

[zoeuvre]

Hi AlStu, 

Thanks for posting here In the Community forum. I understand that you've found a hardware solution to run your fan indefinitely using a relay and a smart plug connected to an AC outlet. It's worth mentioning that the Nest Thermostat's fan scheduling feature is designed to help regulate temperature and optimize energy efficiency. Running a fan continuously is probably going to cause high power consumption most of the time, which is unnecessary. However, if you prefer constant fan operation and have strict demands, you can opt for a hardware solution, as you suggested. This may be a good solution in your case, although rewiring the inside elements of your furnace or HVAC system could be very dangerous. As such, you should exercise caution and consult a professional HVAC technician before modifying your system. Check out our article, Fan control with a Nest Thermostat, for more details.

Also, Google offers a Smart Home skill to connect your Nest devices to Amazon's Alexa home control, where you can control some features on your Nest thermostat when you talk to an Alexa-enabled device, like an Amazon Echo Show or Dot. Check out more here in the Control Google Nest products with Amazon Alexa article.

Reach out if you have any questions in the future.

Best,

Zoe

[AlStu]

What Zoe says is all true. There should have been more emphasis on safety, which I had assumed but should be explicit. Unless you know exactly what you are doing with wiring, don't do it, don't be that person who has an emergency visit from the fire department.

As for power energy use, we are aware of that and willing to use the extra. More specifically, marital stability. Not mentioned but there is a timer so that the fan is on for 15 minutes and off for 15 minutes, marital compromise. BTW, our fan is BLDC (Brushless DC) and when on uses about 50W, acceptable. Running the fan does keep the temperature more constant throughout the house in the shoulder seasons when the furnace is not on often.

[zoeuvre]

Hi there, 

We'll take your feedback as an opportunity to learn and to be able to provide a better experience in the future. Please be assured that our product team is working non-stop with different partners to bring the best to the Google Nest devices and services. So, please let our product team know about it by sending feedback. Feel free to create a new thread if you have more questions or other concerns, and we'll be happy to help.

All the best,

Zoe