HELP! Have Five Nest Thermostats & 5 Nest Power Connectors - How Do I Wire It?

[Dobermann]

I have drawn a schematic of my heat only (two wire) system.  My components are as follows and as pictured:

Existing:

2  Emerson S84A-410 Class 2 Transformers

1 Honeywell RA832A1066 Hydronic Switching Relay

5 Honeywell 40004850-001 zone controllers

5 Old two wire mercury Honeywell Thermostats 

Trying to install:

5 Nest Thermostats with 5 Nest Power Connectors

Can someone please explain how to properly wire these so they work?  Very disappointed with misleading sales material and limited installation instructions!  

 Thanks

[ThermalDave]

Connect your current W and R to the W and R on the left side of the Nest Power Connector( as seen on Nests wiring schematic). Then run the three wire(C W R) on the right side of the power connectors to your new nest Thermostats. You will do that for each power connector and thermostat. Best Regards.

[ThermalDave]

You could have also just have one 24volt transform and run its output to each of the nest thermostats as the C wire.

[Houptee]

Any chance you can run new thermostat cables to each Nest with 5 conductors?

That would be the simplest way and better way to solve the issue.

If you want to do the power connectors then something I noticed in your wiring diagram that will confuse you is you have red and white reversed.

I modified your drawing you would have to re label your transformer and and wire it like this.

[Dobermann]

I very much appreciate your help.  Unfortunately it's nearly impossible for me to re-wire with a 5 wire.  I wish could run 5 wire as I have same issue with separate AC thermostats (two wire) will tackle that one in spring.  My house is multi levels and would be very difficult to snake new wire in the walls/levels.  I'll try your suggestion and do one zone at a time to confirm it works.   Thanks again! 

[Houptee · Accepted solution]

You can't do just one nest. 

You have to do all of the nests on the same transformer at same time because you have the wiring backwards. You have all the whites together going to W on all the tstats. It should be all reds together then feeding the + R on each tstat.

White W is always the heat call from tstat output to the boiler, you have R red as outputs. 

If you notice the 2 wires to each nest go directly to the R W power adapter not to anything else.  Then the other wires go to the valve input YW and all the valve output wires YC tie together to the C common on the transformer. 

So you can't do just 1 because the power adapter has to have the common correct for all the valves. 

I would try my wiring diagram on the section with the 2 Nest on the separate transformer first to confirm its working. 

[Dobermann]

Thanks for that clarification will give that a go.

[Dobermann]

Houptee, Just finished and it's working great.  Was about to throw in the towel until you responded.  Really appreciate you sharing your expertise.  Could not have done it without your insight on my wiring.

Happy Holidays!

[Houptee]

Great news!  Looks good.

If you dont like twisting all those wire nuts you can buy wire connectors like the ones that come with the adapters on Amazon. They have the real ones made by Wago and there are also knockoff ones that work pretty good.

These work good https://www.amazon.com/dp/B09WYQ8F5Z

[Jhonleanmel]

Hey folks, 
 

Houptee, thanks for the help.
Dobermann, awesome — glad to hear that your issue is fixed. It looks like we can consider this one complete, so I will lock the thread shortly unless I can help out with anything else. 

Best, 
Mel

[Dobermann]

All done -thanks to all

[Jhonleanmel]

Hi Dobermann,

You're welcome. Feel free to create a new thread if you have other questions or concerns as I will be locking this thread now.

Cheers,

Mel