Only emergency heat works after my nest thermostat was installed

[mnman]

My nest thermostat was installed and the heat doesn't turn on but the fan blows.  I have a trane furnace.  It does work when I tell it to use emergency heat.  I reset furnace.  I'll show my set up as well.  Both current and the old wiring. 

[CoolingWizard]

Perhaps you actually have a Heat Pump? in which case the White wire was attached to the O/B and not actually W for heat.  If as you say you have a Trane gas furnace, then the white wire is indeed W and gas heating. Did you set the system type to Forced Air, Gas Heating?

Also, I see the old thermostat did not have a blue wire attached, however, you attached a blue wire to the C terminal. 

[EdwardT]

Hi there,

@CoolingWizard, thanks for the help!

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

Thanks,

Edward

[EdwardT]

Hi mnman,

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

[mnman]

I was not able to get it to work, I was only able to get it to work for emergency heat.  I know I have a trane gas furnace but I am not seeing anything on my home inspection about a heat pump.  

Is there an issue because my R and RC wire are connected on the old installation?

[CoolingWizard]

Older thermostats were not that intelligent, so they had to “assume” that sometimes there are separate heating systems for AC Cooling systems. In that case, each would have it own power transformer. In system where they are combined, the heating functions are powered by Rh, so, a jumper is needed to get the Rc power to the Rh.  The Nest Learning Thermostat 3rd Generation is pretty flexible, it knows the wires connected to it and it can determine if the power systems are the same or not.  It programs the base plate to make the required logical connections for proper operation. 
However, when you have only a heating system, it expects to see incoming power on Rh. when you have both a Cooling System and an gas furnace that is integrated to the air handler, then the incoming power should be on Rc since both the AC and the Furnace control board are using the same power transformer. 

Can you go outside and get me a picture of the outdoor unit manufacturer label showing the model number? 

I hope that this explanation helps.  

Ken, The AC Cooling Wizard

[mnman]

So what did I screw up that the wires are only turning on the fan when heat is on, but actual heat comes out when I switch it to emergency heat?  How should my wires be connected to the nest based off the previous one?

[CoolingWizard]

Help me understand how you “switch it to emergency heat” since you have no wire on Aux/E.  Wake up your Nest Thermostat and go to Settings, rotate the ring to EQUIPMENT and select it.  Take a picture of the screen.  Let’s see what the Nest Thermostat is detecting.

Ken, The AC Cooling Wizard

[mnman]

 here is my current set up and the readings

[CoolingWizard]

Clearly the thermostat does not sense the wires but now we need to figure out why it’s not sensing the wires. I can see from the wire clamps they are depressed slightly which tells me they are making contact with the wires, but it does not see the actual wires for some reason or it does not sense the power on the R. 

Did you purchase this Nest as a new product or used product?  Can you turn the thermostat display over and get me a picture of the back of the display please?

Ken, The AC Cooling Wizard

[mnman]

I purchased it new, I installed one at my previous home and had zero issues so I'm very perplexed!

[CoolingWizard]

I can tell you that I am as perplexed about it as you are. It makes no sense that it’s not picking up the signals. That implies to me that either the thermostat or the base plate is not properly manufactured or something like that. By chance do you happen to have a volt ohm meter and a couple of metal paper clips?

Ken, The AC Cooling Wizard

[mnman]

Alright I had a technician come over, he said it was because I didn't have a common wire.  So we repurposed the blue wire (which was disconnected at both ends) and now it works.  I then redid the set up.

[EdwardT]

Hi folks,

@CoolingWizard, thanks for the help as always!

@mnman, thanks for the update. I'm glad to hear that you were able to get it working. Please observe it for now and let us know if anything comes up.

Thanks,

Edward

[EdwardT]

Hi mnman,

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

[Jhonleanmel]

Hi everyone,

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,
Mel