Condo installation - professional installation required

[ESTinNYC]

Hi all,

I recently bought two Nest Learning thermostats and wanted to DIY them in the apt, as the initial compatibility check tool said these would work fine. It turns out that the wiring is a tad more complicated and I will need to book a pro (as told my the app).

Can anyone advise on this wiring and tell me if the Nest will actually work with my system? W1 / B/O label is not listed in the app. Also, note the jumper between RH and RC. Photos attached, and I am eternally grateful for any help & guidance. 

Sincerely!

Y1, G1, G3W1/B/O, C, RH and RC (jumper)

[CoolingWizard]

The Red wire in Rh is the power in from the step down thermostat. The white wire in C is the Common side of the step down transformer. The Jumper between Rh and Rc can be ignored. Now, there is a blue wire on W1/OB. Ot looks like you have a Heat Pump. The Y1 with the Yellow wire is the compressor control wire.  Then G1 is Blower Fan, the G3 is Blower Fan Speed 3.  You Nest compatibility checker will get Rc, Y1, C, O/B, G1, G3.  
Ken, The AC Cooling Wizard

[ESTinNYC]

Hi Ken, 

Thanks so much. I'm getting a "not compatible" from the Nest app. Is my dream of automating my home crushed before it ever started?

[EdwardT]

Hi folks,

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,

Edward

[CoolingWizard]

I do not think the Nest can handle more then 1 fan control.  As a test, make another compatibly test using the G2 and G1. 

Ken, The AC Cooling Wizard

[Jhonleanmel]

Hey folks, 

We appreciate your help here, @CoolingWizard.
@ESTinNYC, 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 concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,
Mel

[ESTinNYC]

Thank you all for following up. I have a professional installer coming tomorrow morning - apparently, this thermostat has been installed in other apartments in my condo, so I am keen to understand what limitations, if any, may be present. I'll provide an update after the installation - hopefully, this will be helpful for someone who has a similar setup to mine, which includes multiple fan speeds. 

Really appreciate everyone's help! 

[EdwardT]

Hi ESTinNYC,

Thanks for the update! Let us know once your Nest Thermostat is installed. Keep us posted.

Thanks,

Edward

[EdwardT]

Hi folks,

@CoolingWizard, thanks for the help!

@ESTinNYC, how's it going with your Nest Thermostat? Still need our help?

Thanks,

Edward

[CoolingWizard · Accepted solution]

Basically I am going to bet on the fact that the limitation in the compatibility test was the two wires hooked up to G1 and G3, I bet when they install it they’re going to disable G3 so there’s only gonna be a single speed on the fan.

Ken, The AC Cooling Wizard 

[ESTinNYC]

Thanks again, everyone, for your input! 

The thermostat was installed over the weekend. As @CoolingWizard suspected, the multiple fan speeds were not supported, so I was left with the high speed in the larger living area and the low speed in the bedroom (which gets the job done perfectly). 

For anyone who might be interested, this is what the new wiring looks like:

I sort of wish that Nest had been a bit more clear about the limitations around multiple fan speeds. This is not a deal-breaker for me, but I probably could have DIYd this myself rather than getting a professional install, as stated by the compatibility app. Happy with the outcome in any case! 

Have a great week, everyone!

[CoolingWizard]

As I explained it was for multiple speeds (G1, G2, G3) and other than manufacturers proprietary designed thermostat can do that. 100% of HVAC residential thermostat do not have multiple fan speed control connections.  Having said this, the fans that have multiple speeds are controlled by the control board located in the air handler/Furnace.  Those control boards are settable to have different speeds for heating and cooling.   The actual speed is set by the HVAC technician after evaluating the total static pressure measured in the duct system. The goal is to maintain 350 to 400 cubic feet per minute of airflow.  In very humid locations the air speed is set slightly slower during the cooling season to remove more moisture.   In dryer climates, the blower fan speed it set higher to increase the cooling capacity.  In the winter, the blower fan is set at medium-slow to increase the heat transfer.  Again, this is all performed automatically after the HVAC Technician sets the speed parameters on the control board.  

Ken, The AC Cooling Wizard

[CoolingWizard]

I would like to add that if you have a Nest Learning Thermostat 2nd or 3rd generation, and have a heat pump with auxiliary heat, the star (*) connector can be programed to operate an additional fan speed option. 

Ken, The AC Cooling Wizard

[EdwardT]

Hi ESTinNYC,

It's me again. I wanted to check back in to see if you have other questions and concerns. Feel free to let me know if you do.

Thanks,

Edward

[EdwardT]

Hi folks,

@CoolingWizard, thanks for the help!

@ESTinNYC, 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,

Edward

[CoolingWizard]

For the compatibility testing, set the two fan as Ghi and Glo. It will work for Nest Learning Thermostat 2nd and 3rd generations.

Ken, AC Cooling Wizard

[EdwardT]

Hey ESTinNYC,

I'm checking back in. Were you able to try the steps provided by CoolingWizard? Let us know if you still have questions and we'd be glad to assist you.

Thanks,

Edward

[EdwardT]

Hi ESTinNYC,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,

Edward