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Install Nest Thermostat with Nest Power Connector and Honeywell Zone Valve

lordofthering
Community Member

Hello,

I am trying to connect Nest Thermostat with Nest Power Connector in Hydraunic Gas Heating System and I am getting no Power Error.

I have wired Thermostat, Power Connector, External 24V transformer and Honeywell zone valve as shown in attached image.

Before Nest Thermostat and Power Connector Wiring:

Before_PowerConnector.jpg

 

After Nest Thermostat Installation with Nest Power Connector:

After_PowerConnector.jpg

Below are the exact model of product users.

Nest Thermostat:

https://store.google.com/product/nest_thermostat_specs?hl=en-US

Nest Power Connector:

https://store.google.com/product/nest_power_connector?hl=en-US

Honeywell V8043E1012 Zone valve

https://www.supplyhouse.com/Honeywell-Home-Resideo-V8043E10############-Sweat-Zone-Valve-Connection-...

 

Thanks

1 ACCEPTED SOLUTION

dhx227
Silver Product Expert
Silver Product Expert

So, normally in order to do this, you need a device on either end: one to inject the DC current, and then one on the other end to pull the DC current off and clean the AC back to normal (non-biased).

In the case of the Nest couple with the Google Power Connector, these two devices would be working together to accomplish that.

Also, whether or not that is what is happening is purely a guess (I do not have a Power Connector and have not tested what it is doing myself).  It would be a reasonable engineering solution.  However, there are also other engineering solutions like switching to a pure DC solution with low-level signaling between the Nest and the Power Connector whereby the Nest gets power and then signals to the Power Connector to operate the 24VAC relay connected to the furnace.   The Nest would then look at the R/W pair and see what kind of voltage/signal is present and then operate in the appropriate mode.  If it senses there is 24VAC present, then it operates in regular thermostat mode, if instead is senses something like 3VDC, then it might send a low-level coded signal to the other end to check if it's connected to a Power Connector.

If you are up to experimenting, what you could do is with a basic voltmeter and the Power Connector wired in, check the AC voltage between Power Connector's R wire going to the Nest and the transformer (C)ommon.   If it does read 24VAC, then it's likely there is a DC bias...   You can then switch the voltmeter into DC mode and see if it shows a DC voltage between the R and W wires from the Power Connector to the Nest (and depending on which wires you randomly tested +/- with the voltmeter, it may read a + or - voltage).

If instead, you read no AC voltage (or very minimal < 1V), but you do read a DC voltage, then it's more likely the Power Connector is sending DC power and communicating with a low-level signaling protocol.

I would be very curious to know what you find on this.

View solution in original post

30 REPLIES 30

dhx227
Silver Product Expert
Silver Product Expert

Two possibilities:

  1. have you made sure the Nest has F/W 1.1 or greater.  Apparently that is a pre-requisite for the Nest Power Connector.
  2. Depending on how your thermostat is wired (the block you have drawn for "Thermostat" is not super clear about what wires (colors) have been wired to what terminals.   It's entirely possible you have it backwards.  When it was just a normal thermostat, the thermostat merely acts as a switch, so polarity is not relevant.  However, with the Power Connector it is likely very important as that is how it is feeding power to the Nest.  The Power Connector is sending a baseline DC current over the wires that the 24VAC then floats on top of when switched on/off - this is the same principal that PoE (Power over Ethernet) uses.   If you have those wires backwards, it may not sense the power.

Thank you for your reply

Actually my wiring diagram is correct and it is working as expected, during testing, I had loose wire in Thermostat which caused this issue. It would be nice if google post well drawn wiring diagram on how to use nest power connector in Hydronic system with multiple zone valve. I could not find such diagram anywhere, not even in there manual.

dhx227
Silver Product Expert
Silver Product Expert

The DC power thing is a trick you can do with AC.   The Nest internally operates on 3VDC, so that's the power requirement it needs from somewhere.   You can push a DC current over a AC line without disrupting the AC.   As an example, that's how PoE works without disrupting the ethernet signal (which is effectively an AC-like signal).   That's just techy stuff and more/less irrelevant to your problem, especially given that it was a loose wire.   Glad that was all that the problem was!

Happy New Year!

dhx227,

You bring very interesting point of sending DC power (3V substitute of two AAA Battery) via AC wire. I love to experiment things if you can help me out.

 

How about using external 3V DC power adapter, stripping end pin out and using two wired and connecting to thermostat ? If you can help me with which wire I should connect where I can test it out with my 3 V DC power adapter (I have several different power adapter sitting at home). I am assuming if I strip off DC adapter I will have two wire. Which wire I should connect to where in thermostat ?. Once we can make it work with direct connection to thermostat, we can test it out how we can connect the same in combination of zone valve.

 

If you have any YouTube video pertain to same explaining, I will love to explore as well.

 

 

dhx227
Silver Product Expert
Silver Product Expert

So, normally in order to do this, you need a device on either end: one to inject the DC current, and then one on the other end to pull the DC current off and clean the AC back to normal (non-biased).

In the case of the Nest couple with the Google Power Connector, these two devices would be working together to accomplish that.

Also, whether or not that is what is happening is purely a guess (I do not have a Power Connector and have not tested what it is doing myself).  It would be a reasonable engineering solution.  However, there are also other engineering solutions like switching to a pure DC solution with low-level signaling between the Nest and the Power Connector whereby the Nest gets power and then signals to the Power Connector to operate the 24VAC relay connected to the furnace.   The Nest would then look at the R/W pair and see what kind of voltage/signal is present and then operate in the appropriate mode.  If it senses there is 24VAC present, then it operates in regular thermostat mode, if instead is senses something like 3VDC, then it might send a low-level coded signal to the other end to check if it's connected to a Power Connector.

If you are up to experimenting, what you could do is with a basic voltmeter and the Power Connector wired in, check the AC voltage between Power Connector's R wire going to the Nest and the transformer (C)ommon.   If it does read 24VAC, then it's likely there is a DC bias...   You can then switch the voltmeter into DC mode and see if it shows a DC voltage between the R and W wires from the Power Connector to the Nest (and depending on which wires you randomly tested +/- with the voltmeter, it may read a + or - voltage).

If instead, you read no AC voltage (or very minimal < 1V), but you do read a DC voltage, then it's more likely the Power Connector is sending DC power and communicating with a low-level signaling protocol.

I would be very curious to know what you find on this.

Hi, I have a similar setup. So your diagram is good finally? Did you have to remove the jumper on the Nest Power Connector? For this kind of setup, this is what the (advanced) manual says but not sure this applies to this situation with a zone valve...

I am not aware of any jumper in google power connector. Can you please elaborate more on this ?

By the way, I wired the way you did and it seems to work. I have 3rd gen learning + E models and I believe there is no way of knowing for sure except by checking the voltage on the device. Nest Thermostats (2020) seem to report the presence of the Power Connector.

Thank you for sharing document. I did not have this document and I never noticed there was jumper. I went back and checked my power connector and indeed there is jumper. In fact I did not remove Jumper but this document calls for removing jumper if No C wire exist in HVAC system per PAGE# ############. Strange it worked without removing Jumper.

dhx227
Silver Product Expert
Silver Product Expert

Are you talking about pages TEN and ELEVEN where it refers to how to connect when there is no C wire available in your HVAC?   That is the only jumper one can change in the power connector.  Removing this jumper isolates the R&W wires going to the HVAC from the thermostat and then allows you to wire in an additional, independent transformer that supplies power only to the thermostat.   In this scenario, the external transformer is supplying power for everything, both the thermostat and the zone valve, so you do not need to remove the jumper that would then isolate the thermostat from the HVAC.   Though, the way it is wired, it would also not break anything.   Again, you only need to remove that jumper if there would be two different transformers (possibly of different voltages) - one powering the HVAC and then the added external one powering the thermostat.

pdespres
Community Member

Yes page ten and eleven (don't know why this is scambled as ####). OK I guess this is clearer. Since I have only one 24 VAC transfo on the thermostat+valve circuit, I leave the jumper in. Red cables on the valve activate the relay for the pump and turn the HVAC on in my setup.

dhx227
Silver Product Expert
Silver Product Expert

The cool thing about this (I was also not aware of this jumper option on the power connector), is that people with millivolt gas systems could use the power connector and remove the jumper too isolate the gas millivolt side.   So, thanks for posting that doc!!

That make sense. In my case I am using external transformer which is powering thermostat and Zone valves only. It does not power HVAC system at all. So in my case, I should remove them based on diagram.

Strange thing is that it seems to work with the jumper in (although no clear way to verify this as 3rd gen learning and E model are not reporting the presence of the Power Connector). Let us know the results of your experiments!

I did not tested with my real HVAC system. I just tested with outside setup with 24V Transformer, C Power Connector,  Honey Well Zone valve and Nest Thermostat combination to check if Nest is reporting power or not and I did test without removing the jumper and it did show correct power at thermostat.

If I were to install Power Connector in my real HVAC system, I should remove jumper since control board of Boiler itself will feed 24V to boiler and it may conflict without removing jumper. 

This was my test only since, I really did not install Nest in my case, I ended up replacing with my extra Nest "E" and it did not need C- Power at all. To be honest I do not like fact that Nest needs C-Wire when E and Learning both are working great without any C-Wire. I am probably going to sell my Nest on EBay and forget about complexity of C-Wire.

dhx227
Silver Product Expert
Silver Product Expert

You're fine with leaving it in since the zone valves are running on the same transformer.   You only need to remove it if the controlled circuit is on a different transformer than the one supplying power to the thermostat.  That is the case that will not work.   Note, that with the way you have it wired, it will still run fine with it removed - you just don't have to remove it.

pdespres
Community Member

Well, overnight testing was a failure. The thermostat battery drained to the point where wifi connection was deactivated (voltage gos below 3.7 V) . The Power Connector did not seem to do its job. Too bad the device (Nest T-stat E) is not reporting the presence of the Power Connector just like the newer Nest Thermostat does...

 

Please provide us full wiring diagram how you wired your thermostat, and hvac system. 

Same diagram as the one at the top of this thread. I am starting to think that the state of my battery is bad. Other users have reported battery problems after 2-3 years, which is my case. This thermostat is in a zone frequently going to 11 C in the winter. Just like my iPhone battery, which is allergic to cold weather, the Nest battery might have difficulty to operate properly in non-Californian climates... Too bad this battery is not user replaceable (as oppose to the newer generation operating on AAA). I guess Google decided to go for replaceable battery after many complaints...

 

Are you saying your current wiring setup working for 2-3 years and now you are having low battery error ? You should able to replace any aaa rechargeable battery in this case. If your power connector is providing  required power then it should still work since aaa is ony backup power in your case. What is the error message. It should not be N260 error which is no power from power connector. Still you should able to connect to wifi etc and everything else should work as expected. Regardless of everything I am not too impressed with this thermostat. I like learning and E lot better since no error ever whatsoever without needing any external power

I added the Power Connector to an E model, with built-in, non-replaceable Li-ion battery. I thought the two-wire circuit could not deliver enough power although it work fine for 2-3 years.  Still, with the Power Connector on, the wifi was deactivated this night. Battery is often in the 3.6-3.7 V range. I have another E and a 3rd learning on similar two-wire circuits and they constantly report 3.8+ V. That is why I think the battery is kind of weared out.

dhx227
Silver Product Expert
Silver Product Expert

Did you make sure the Nest has the latest firmware?   There was a firmware update about a year ago to update the E and Learning thermostats to recognize the Power Connector.   I'm not sure exactly which firmware version you need, but I thought I saw that somewhere.

pdespres
Community Member

Yes I am on 6.2-22, October 2021.

dhx227
Silver Product Expert
Silver Product Expert

Hmmm.   Also you mentioned it gets pretty cold.   is it possible you are hitting the safety temp?   there's a known bug where the thermostat will get stuck in safety mode and won't call for heat.  check out this post: https://www.googlenestcommunity.com/t5/Nest-Thermostats/Nest-not-calling-for-heat/m-p/76653

I have the same firmware. I have had issues with nest E where itvstarted showing offline and wifi disconnected. I had to reset annually directly from thermostat and remove from nest and redo configuration and it worked fine since then. You may want to try that. Does it show any error message in thermostat at all ? Or you are seeing offline in Nest app ?

Its going offline because of low battery voltage. I will try a full reset.  This thread seems to point towards a display draining too much power after the october 2021 firmware update: https://www.googlenestcommunity.com/t5/Nest-Thermostats/Nest-3rd-gen-Thermostat-low-battery-issue-af...

 

lordofthering
Community Member

I will try that out.

dhx227
Silver Product Expert
Silver Product Expert

Be sure to follow my most recent edit.  After re-reading it, I realized there were some tests I had slightly wrong.

erezyanco
Community Member

Joining the discussion, I have a similar system of gas boiler for hydrant heating, only with two Honeywell zone valves. I’m looking to install a nest 2020 thermostat for each zone at my house, would I need two power connectors? Can anyone share what would the wiring look like?