Trying to add power connector

[es114]

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  Adding nest thermostat to a two wire newer Burnham boiler x-205.  Thermostat wires are easy to identify at boiler.  But they go into a fully loaded crimped wire connector attached to the circuit board. Also cannot identify where common is.  

[CoolingWizard]

The transformer power arrives to the controller on P4. Normally there is pink wire and a brown. I noticed that your thermostat cable has a blue conductor and a green conductor wrapped around the outside of the cable sheath. You can locate the common of the two wires in P4 using a Volt Meter. Normally the Blue wires are the common side of the transformer.  Using voltmeter set the setting to AC voltage, place, one lead in the pink connector of P4, and put the other one in the blue connector on P5 which is left of P4 and where two yellow thermostat wires connect. If you measure 24 V AC +/-5 V you found the common and it will be the blue wire. Now  unwrap the blue conductor on your thermostat cable, and attach it to blue wire on the boiler control and at the thermostat attach the blue wire to the C and your Nest thermostat will now have a Common.  

The AC Cooling Wizard. 

[es114]

Thanks for your reply.  I believe the blue and green wires wrapped around the thermostat cable have been cut somewhere in the run to the thermostat.  I will check to confirm.  Also is there a common on P9 terminal 3?  If I use the nest power connector,  would the gray r and w go to P9 terminal 1 and 2?

[CoolingWizard]

The P9 connector is for the EnviraCOM communications. Typically Pin 1 is the communications line, Pin2 and Pin3 are 24 Volts. I am not sure if pin 2 or pin 3 is a Common.

Ken, The AC Cooling Wizard

[es114]

So could could terminal 2 or 3 be used as a common?

[CoolingWizard]

I am not sure, you need to test it with a Volt Ohm Meter, as I stated, if a multimeter show 24 VAC +/- 5, between pin 2 and pin 3 then yes, one of those is going to be a common.  

The AC Cooling Wizard

[es114]

If I find approx 24 volts, how do I determine which terminal is the common?

[CoolingWizard]

Sometimes they tie the common side to the metal chassis. Try going between bare metal of the cabinet and each of those wires and see which one showed you the 24 V. The one that shows your 24 V will be the R and the other one will be the common

[es114]

Your suggestion worked.  Found that the common was terminal 3.  Installed the power connector following the heat only instructions and everything is working normally.   Thanks for your help.  

[CoolingWizard]

es114,

glad to hear that it’s all working for you now.

The AC Cooling Wizard

[CoolingWizard]

I edited this adding colors to help you see the connections.  

[es114]

Thermostat working fine but just got an email from google indicating I need a power connector to avoid battery drain.  Did a power test: vin 32.090v, Lin 385 (W), PS 385, WP 25. All on blue characters. Wiring info: connected W (P)-R. Power Status - Nest Power Connector detected.  What could be wrong?  

[Jenelyn_O]

Hi es114,

Thanks for reaching out. I'm sorry for the delay and for the confusions. Could you please try updating your Nest Thermostat software? Go to your thermostat Settings then choose Version and select Update. Let me know how it goes. 

I appreciate your help, @CoolingWizard.

Best,
Jenelyn

[es114]

Finished installing with power connector.  Are these numbers good?  Power test: vin 32.090 Lin 385(W) PS 385 WP 25 wiring info W(P)-R. Power connector detected. 

[Jenelyn_O]

Hi es114,

Thanks for posting in the Google Nest Community forum. There are no power readings that will tell how good your Nest Power Connector is. If your Nest Thermostat says that your Nest Power Connector detected, that means it's properly installed and it's good to go.

Best,

Jenelyn

[es114]

Then why am I getting sporadic n260 messages?  I have spoken with a Burnham furnace technician who says my power connector install is correct including the common?

[Jenelyn_O]

Hi es114,

We’ve duplicated your thread to the main one here. You’ll receive all updates on this issue on the main thread and we recommend updating and checking this thread when needed.

Thanks,

Jenelyn

[CoolingWizard]

The N260 indicates that the COMMON wire is getting interrupted.  That is, the Common connection is is apparently a switched common. Might Need a dedicated common. 

Ken, The AC Cooling Wizard

[es114]

Not according to technician at Burnham furnace.

[es114]

Burnham states that terminal 3 on enviracom port is dedicated common.  Getting n260 error message often a week apart. 

[es114]

Next is up to date. 

[es114]

Keep getting above message which indicates I need a nest power connector.   But power connector is installed in heat only system with common wire connected to terminal 3 of envirocom port on burnham x-205 furnace. Multimeter indicates power is term 2 and common term 3.  Is there another common I could use or are these false messages?  

[es114]

Tried installing a separate transformer.  Followed the pro manual with transformer wires to common on power connector and bunch with r wires.  Removed the jumper and no power.  Checked the transformer wires while connected and got 27 vac.  Removed the transformer and reconnected the common to term 3 on enviracom block put back jumper on power connector and got normal values with no error messages on thermostat.  Why won’t anybody help?

[es114]

Spoke to Burnham Furnace technical support.  Confirmed that enviracom terminal 3 is common on my furnace.  So what I’ve done to install the power connector is right.  So why am I getting an n260 error message?

[Jenelyn_O]

Hi there,

We’ve duplicated your thread to the main one here. You’ll receive all updates on this issue on the main thread and we recommend updating and checking this thread when needed.

Best,

Jenelyn

[CoolingWizard]

ES114, 

sometimes some controllers when they switch modes, or if they receive a signal to heat, and then the signal for heating is dropped or satisfied, sometimes the control boards reset. When they reset, they disable the output signals, and then you will get an error. 

here’s what you can try, on the P9 connector one of those wires is the common and you can splice onto that wire. Now how do we find it? Use a voltmeter put one lead on the environ con terminal two and then use the other one to probe the backside of the pink or the brown wire. When you get a voltage of 24 V AC, you have found the common. 

P9 is straight from the transformer which means that power will never go away unless the main power is turned off. That’s the most ideal location to grab your comment from.

The AC Cooling Wizard

[es114]

Disconnected from terminal 3 on envirocom block.  Found gray wire to be common after testing with terminal 2.  Spliced wires together and powered up.  Getting normal readings as before.  Hopefully no more “system issue” messages.  

[CoolingWizard]

I am sorry, I misstated the connector. The transformer goes to P4.  That is where the Pink and the brown wire are.  Again sorry. 

The AC Cooling Wizard

[es114]

Yes I know it is P4 from the wiring diagram above.  The gray/brown wire is the common. 

[Jenelyn_O]

Hi folks,

Checking in — were you able to install your separate transformer? How's it going? 

I appreciate your help, @CoolingWizard.

Thanks,
Jenelyn

[es114]

No I did not install a separate transformer.  I tapped into the common wire of the existing transformer.  Need another few days to determine if the error messages have finally stopped. 

[CoolingWizard]

Your system will not work properly if you install a separate transformer. This is because the main control board is using that primary transformer to power the R wire and the other control systems and components. This is why I was suggesting that you connected to the P4 connector.

The AC Cooling Wizard

[Markjosephp]

Hello folks,

Thanks for the continued support here, @CoolingWizard.

@es114, I'm checking back in — how's it going? Still need our help?

Regards,

Mark

[es114]

The Nest is working normally now without any error messages.  Thanks for the follow up.

[Markjosephp]

Hello es114,

Sounds great! I'm glad to hear that it's up and running. It looks like we can consider this one complete, so I will lock the thread within 24 hours unless I can help out with anything else.

Regards,

Mark