E19 wiring report Y2 wire without Y1 wire

[MikePage]

Spoiler

This is a new Google Nest Learning thermostat I am installing to replace an old thermostat.  There are only two wires going to the thermostat from the boiler: R and W.  The Nest is supposed to be compatible with this wiring.   So, the error makes little sense to me.  I also charged the Nest with a USB cable overnight, so should be fully charged.

Below are photos showing the error and wiring.  Any assistance in resolving this would be welcome.  Thanks.

Error messageWiring

[CoolingWizard]

Can you do us a favor and take the display off, and take a picture of the back plate with the wires attached?

AC Cooling Wizard

[MikePage]

I did include that picture along with two others in my post.  I think you may need to expand the post to see it all.

[thombre55]

Hello Mike,

Can you zoom in before you take pictures. The clarity is blurred. Thanks 

[MikePage]

[thombre55]

Thanks Mike,

Very good , pictures are legible 

[thombre55]

https://widgets.nest.com/nest-thermostat-troubleshooter/?hl=en#e89

[MikePage]

Unfortunately, the website says error codes e89 and e19 (codes I got) are not valid.  Not sure what to do about that.

[CoolingWizard]

E89 is The Nest Thermostat is physically detecting a Y2 wire but not a Y1 wire that is required for 2 stage conventional cooling systems or 2 stage heat pumps.

I do not have a listing either for the E 19 error

AC Cooling Wizard

[MikePage]

There is no wire connected to Y2.  I only have power (white) and heat (red).  This can be seen in the photos I posted.

[zoeuvre]

Hi MikePage, 
 

Thanks for posting here in Community forum, and I’m sorry to hear about the situation. Let’s sort this out. 
 

A few questions: What is the make and model of your HVAC system? Do you have a 2-stage furnace with a humidifier and/or dehumidifier, or do you have a 3-stage furnace? Also, please also help us with a photo of your thermostat wires connected to the control board. 

I’ll look forward to your response. 

All thanks for your help, @CoolingWizard and thombre55. 
 

Best,

Zoe

[thombre55]

Can you show a picture of reverse side of nest thermostat? There is wiring diagram please take photo and upload so I can understand?

[MikePage]

I did include that picture along with two others in my post. I think you may need to expand the post to see it all.

[CoolingWizard]

The simple answer is yes. Your two wires would be Rh and W1.  You have no common wire, so you might have to add a power adapter and a third wire attaching to C. By chance, can you take a moment and upload the picture of your old thermostat with the wires attach so I can see what it look like? Try this, on the Y1 and the Y2, push buttons, push it down and quickly release it like snap your finger nail off of it let it pop back up. What the nest back plate is telling the display is there is a wire inserted in Y1 and Y2. From the photo there’s clearly not but for some reason the push button underneath there is not making contact showing the display that there’s nothing there. Hopefully you can just flickered a couple times and straighten it up.

AC Cooling Wizard

[thombre55]

Can you tell me does the power adapter install at the boiler location? Will a third wire need to be pulled between boiler and thermostat?

[thombre55]

The third wire will connect to Y2, between power adapter and Nest thermostat? Can I use a blue wire for the common third wire?

[CoolingWizard]

@Patrick_Caezza is a PE on here that has a few examples that will show the wiring of the boiler and the addition of a transformer and and relay.  Perhaps he can share this with you. 

AC Cooling Wizard

[CoolingWizard]

@thombre55 , the tricky part is that some older boiler type furnaces, actually use a simple two terminal connection to turn on the boiler. It’ll be marked T & T. There is no common per se. So the answer is yes, we would need to pull a third wire, or what I would do would be to replace the current thermostat cable with a five or seven conductor cable. So if you find out that you need to have a common wire., you would have to put in a new thermostat cable, add a 24 V AC transformer, a relay. Then your thermostat would control the relay and when you sent a call for heating that would close the relay in the relay would connect the T to T and the boiler would start.

Truly understand your boiler I would need you to give me a picture of the boiler and the control system where the thermostat wires attached downstairs at the boiler so I can determine what might be able to be done easiest. It looks like you have a nest learning thermostat and that’s gonna have to have power to keep the lithium ion battery charged.

AC Cooling Wizard

[thombre55]

The three wires are power, heat, and cooling 

[thombre55]

I will pull back the existing two wire cable and replace with either a 5 or 7 conductor cable to feed the Nest thermostat. Thanks for your help

I will install 24vac xfmr along with relay at the boiler control box.

[thombre55]

I will feed the spst relay from load side of 24 vac transformer. The T terminal of boiler will feed through relay normally open contacts,  will close on demand from Nest thermostat, to cause boiler to turn on for heat. The same scenario will apply to cooling needing a second relay for cooling.

[Patrick_Caezza]

@MikePage 

It looks like I am late to the party.

Your system must have a C wire installed to work.

The best and easiest way is to use a Google Nest Power Connector and an external 24Vac transformer.

In one of your replies, I read that you plan on installing a new thermostat cable. Using the Power Connector will save you from having to do that.

If you still want to replace the thermostat cable you can just use an external 24Vac transformer and simple relay.

[MikePage]

Thanks Patrick.  I have contacted Google tech support, and they referred me to some resources on their website that suggested something similar.  The two options that I can determine might help are: 1) Nest Power Connector that you suggest, and 2) Connecting a 220 ohm 5 watt resistor at the boiler between the common (24 volts) and the thermostat power.  I have three Nest Thermostats that I just purchased, and at $75 ($25 / Nest Power Connector) I decided to first try option 2, which cost $7 for 10 resistors, and seems just as easy to implement.

My brother has the same boiler as I have, and 12 years ago added the first generation Nest Thermostat to his.  He also found that it also required a resistor to properly work.  Although he had other power related symptoms.

The resistors are scheduled to arrive today, and I will post about how they worked (or didn't)...

[Markjosephp]

Hello everyone,

I wanted to ensure that everything was covered here.
 

Thanks for lending your hand here, @Patrick_Caezza.

@MikePage, I'm checking in to see if you were able to install your new resistor. How's it going? Did that help? Please let us know, as we would be glad to know what the result would be.

Regards,

Mark

[MikePage]

Hi Mark,

Thanks for following up.

I installed the resistor, and the Nest Thermostat still thought a wire was connected to Y2.  So, I called my boiler service guy, and he called Energy Kinetics who makes my boiler (System 2000 model).  Apparently, they have something you can install at the boiler to fix this issue.  I am waiting for further information, so I can order the part.

Nothing hard is ever easy...

[zoeuvre]

Hey folks, 
 

Checking in — How's it going with your Nest Thermostat? In case you have an update, let us know and we'll be happy to help. 
 

On the other hand, we’ll keep this thread open but please be advised that as Community Specialists, we occasionally do a bit of housekeeping to keep the conversations in our community fresh and relevant. This includes locking threads after a period of inactivity.
 

Thanks for your help, Mark. 
 

Regards,

Zoe

[Dan_A]

Hey there,

I wanted to follow up and see if you still need 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.

Best regards,

Dan

[Dan_A]

Hi folks,

We haven't heard from you in a while so we'll be locking this thread if there is no update within 24 hours. If you need assistance or want to discuss topics, feel free to start a new thread.
 

Cheers,

Dan