Question about 2 stage and fan speeds

[Skidrc]

I recently installed a Nest Gen3 on my Lennox 2 stage system that is about 15 years old. The issue I am having is on the old thermostat the system fan would run 24/7 on a low speed,  a medium speed on stage 1, and a high speed when stage 2 kicked in.  Now that I have the nest the fan still runs at a low speed 24/7 all the time when no air is called for, but at a high speed even when stage 2 isn't being called for. I think the issue is how my system was wired. I have no G wire and when I go down to the controller in the air handler there is a G connection available but it is jumpered to the R on the controller in the air handler. I'm assuming that jumper is how my fan runs 24/7 at low speed. If I remove that jumper from the R to the G on the controller and connect the green wire that is not being used to the G at the controller and the G at the thermostat would that resolve my issue? Would the Nest be able to understand how to handle the fan speeds and run at medium on stage 1 and high on stage 2 or is the Nest simply not compatible with my system and the fan speeds are controlled internally within my system and the Nest can't help me? Here is a link showing my wiring: https://photos.app.goo.gl/nAF75fuP6UGwv3Wb8 

Thanks for any advice,

Brad

[CoolingWizard]

Skidrc, the fan speed is actually controlled by the control board in the air handler.  And yes, the Jumper between R and G did indeed keep the blower fan running all the time. I cannot think any reason to do that.  

The Nest Learning Thermostat, 3rd Generation, can be set up for up to  3-stages (W1, W2, Aux) of heat and 2-stages (Y1, Y2) of cooling. I would Remove the Jumper on R and G, put a wire on the G in the air handler and connect that wire to the G on the nest.  Your nest wall plate is wired correctly.

Can you post the Model Number from the outdoor unit? I want look up the cooling stages.  

[Skidrc]

Here is the link to the photos you requested. I couldn't get a photo of the model and S/N off the unit outside as the sticker is faded so bad that it's not legible. But, I did have the manuals so I took a photo of those. I also included a picture of how the thermostat was wired. https://photos.app.goo.gl/Q1YLGZfzqhpvYkVE8

Thanks,

Brad

[CoolingWizard]

You have a very efficient HVAC system. Your outdoor condensing unit is rated as 19 SEER.  Awsome dude.  The Furnace/Air handler is also high efficiency with ultra low NOX.  It is capable to handle the air flow for both stages of heat and cooling.  You should add the G wire so you can turn I the blower if you simply want to circulate the air with the AC or Heat is not active.  

The furnace uses and ECM motor and the IFCB has pregamed values to control the speed to attain a specified volume of airflow for given heating or cooling demands.  It is the thermostat that controls Stage 1 or stage 2 for heating and cooling.  

[Skidrc]

So if my system doesn't support the AC current that the Nest supplies is there another smart thermostat you could recommend? Would an Ecobee work? Or something else I don't know of you would recommend?

[CoolingWizard]

Your system is a standard operating system that is, it operates on a 24 V AC control system power. The Nest thermostat is fully compatible with that. What I was suggesting was you do not need to have the blower running continuously as it is being done with the  jumper between R and G in your air handler.  Your system can control and the blower speed 100% of the time.  

on your air handler, I suggest removing the red wire that is jumping between R and G. Take the unused green conducting wire from your thermostat cable in your air handler, and connect it to the G terminal of the control board.  Install the Nest wall plate and connect the wires adding Green wire to G of the nest. 

[Ryan_G]

Hi Skidrc,

Thanks for reaching out here in the Google Nest Community.

I'd like to jump in here and check if you've seen CoolingWizard's response. Let us know if you've tried the suggested wiring on your system.

Thanks for your help, CoolingWizard.

Best regards,

Ryan

[aatienza]

Hey Skidrc,

I wanted to follow up and see if you are still in need of any help? Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.

Thanks,

Archie

[aatienza]

Hey Skidrc,

Just checking in to make sure that you've seen our responses. Please let me know if you have other questions or concerns as I will be locking this in 24 hours if I won't hear back from you again. Feel free to start a new thread and we'll be happy to help.

Thanks,

Archie