N260 error with voltage at 15.5

[edstefanski]

I replaced my Honeywell Z-Wave stat with an entry level  "Nest" stat (not the "E" or learning one) because I no longer have or use the Z-wave system and wanted my stat accessible through the internet. It has  Y,W,R,G, and C (blue) wires. I connected the wires to the corresponding Nest connections but get the "Note: N260 code" coming up. The stat is functioning properly but has this code. I checked the voltage with my tester by connecting to the R and C wires and get 15.5VAC but in the setup process the software does not sense a wire in the C terminal.. 

What do I need to do if anything?

[CoolingWizard]

exstefanski,

the HVAC control system requires 24V AC power.  If you are reading 15.5VAC that is below the acceptable level for the system and Nest or operate.  The 24VAC step down transformer is typically relates for 40Volt Amps. This is sufficient to operate the control board, compressor contactor, fan relay, and blower fan and few other things. 
Ken, The AC Cooling Wizard

[edstefanski]

Understood but system is working fine. Heat and AC and blower working fine along with Wifi control with my Android phone. Just keep getting the error code. I know its supposed to have 24V and it is only 15.5VAC so what is the harm if all is working? Since there is 15.5V why does the setup not even recognize a wire connected at the "C" terminal when there definitely is one there yet everything is running OK? 

[CoolingWizard]

The system will not be damaged by low voltage it’ll get to the point if it if the transformers going bad it’ll get to a point where else simply just quit working. You should open your nest thermostat go to the menu then turn the dial to equipment and then it will show you a picture of the back plate in the wires that it’s recognizing. If you go to the pro set up below that you could have it test the wires again and verify that it recognizes are working. If the thermostat is not recognizing any power coming in between the R and C then there is a possibly a problem with the wire itself. 

[edstefanski]

I don't have a "Pro" just the basic "Nest". That said, It does not "see" the wire at the "C" terminal, however putting a tester on the C and R terminals gives me 15.5V, so why does it not see the wire connected if there is 15.5V? Will it not see it unless there is 24V minimum? All function of the system are working including access with my phone. The only thing not working is that it does not light up when I am near it and yes I set it up to recognize someone nearby and even tried turning on recognition of my phone.

[CoolingWizard]

Edstefanski, let me see if I can explain this.  Imagine that there are devices in your HVAC control has electrical devices that have coils inside used to create a magnetic force to close the contact and cause power to go to a motor. That coil has the power in on one side and Common on the other.  So the wire you have on C was not on C in your old thermostat or is not connected to the Common side of the transformer.  The voltage you measure is the common on the the other side of the coil your wire is connected to.  Can you post the picture your took of  the old thermostat before your disconnected the wires?

Ken, The AC Cooling Wizard. 

[edstefanski]

I didn't take a picture of the original connection because it was pretty simple, R, Y, W, G, and C . All wire colors corresponded to the ID on the stat except "C" which is blue. They were all connected on  the original Honeywell Z-Wave stat  and I connected them to the Ring stat the same. After getting the "C not connected" note from the ring I checked my wire and connection of the Blue wire on the C terminal several times (properly stripped and inserted) but no change. That's when I checked the voltage with my meter to see if there was any power there at all and got the 15.5 VAC. 

[CoolingWizard · Accepted solution]

Do you have access to the Furnace? You will the brown cable with the thermostat wire going into the Furnace on one of the sides.  You can remove that cover and and check the wires and see if the Blue wire is attached to the common side of the transformer.  

Ken, The AC Cooling Wizard 

[Jeran]

Thank you so much for helping out on this thread, CoolingWizard!

Hey there edstefanski,

I'm just checking up on this thread, do you have any more questions or need any additional help? 

Best regards,
Jeran
 

[edstefanski]

The Blue Common wire was not hooked up at the furnace, so I hooked it up and now getting 28V so it seems that all is A-OK. I am curious where the 15.5Vac was coming from if the common blue wire was not hooked up a the furnace.

[Markjosephp]

Hi edstefanski,

Thanks for getting back to us and for keeping us in the loop on what you've done to have your concern rectified.

It looks like we have come to a solution, so I'm going to lock this thread after 24 hours. If you have any other concerns or questions, please feel free to create a new post.

Bet regards,

Mark