Google Nest Power Adapter Install


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Old 04-02-22, 03:28 PM
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Google Nest Power Adapter Install

Hola -

I'm installing a Nest Power Adapter on a heating-only hydronic system that consists of a 25 year old Burnham boiler with a Honeywell Triple Aquastat. The house has 4 zones with Taco valves. I successfully installed a Nest Learning thermostat on the 2-wire system... but it's pricey. I bought another Nest Smart thermostat that needs a C wire or a Power Adapter to keep the WiFi on (though it does function as a simple thermostat as it has 2 AA batteries in it).

The Power Adapter wiring diagram calls for putting the Power Adapter in between the T thermostat terminals and the thermostat wires and attaching the C wire to the C terminal on the board....



Power Adapter Heat Only Diagram

The issue is, I have no explicit C terminal on the board.



I tried connecting it to CZ but that didn't work....


The top 2 are the thermostat wires...

The electrician who wired my house used telephone wire twisted together to handle the current... It's not pretty.



This is how the Nest Learning thermostat is connected ... (successfully)

This is the (working) Nest Learning connections

The Nest Smart thermostat:



Any help appreciated!!
 
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Old 04-02-22, 06:32 PM
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If you have zone valves then you don't touch the Aquastat as it is normally power isolated from the thermostats. You need to trace the thermostat wires to the zone valve (or zone controller). The typical 3 terminal Taco zone valve has #1 as W and #2 as C.
 
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Old 04-03-22, 11:46 AM
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Thanks for your help -

I ran a wire from the 2 terminal on the Taco zone valve to the C connection on the Nest Power Adapter but I'm still getting error N260 on the thermostat -

Did I damage it by connecting it to ZC (which is 120VAC)?
 
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Old 04-03-22, 11:54 AM
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The electrician who wired my house used telephone wire twisted together to handle the current... It's not pretty.
That's not an electrician in my book.

You do not connect to the aquastat.
Where did the wires on the aquastat go ?

You need to get the C or the connections for the power adapter AT the associated zone valve.
Post a picture of the zone valve and wiring.
 
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Old 04-03-22, 12:20 PM
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I connected the Nest Power Connector R and W wires where the T wires connect on the Aquastat. I ran a wire from one of the 4 zone valves I have to the C wire on the Nest Power Connector. Since all the power wires appear to be jumpered to each other on the rat's next of telephone wire on the 4 valves, I didn't think it would really matter where I applied the power to R.

Maybe I should have attached the Power Connector to the specific valve I'm controlling with the Nest Thermostat....

Peter
 
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Old 04-03-22, 12:37 PM
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There is no usable power at that aquastat. It requires a contact closure to start the pump/burner.
 
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Old 04-03-22, 12:43 PM
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The wiring mess in general......


The zone valve in question....

Should I just intall the Nest Power Connector to the valve? Put R on 1, C on 2, and W on 3?

Good grief.
 

Last edited by PJmax; 04-03-22 at 01:28 PM. Reason: labeled 2nd pic
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Old 04-03-22, 01:26 PM
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Disconnect the thermostat wiring and connect to the two dark gray wires. No polarity with these two.
Connect light gray W wire to terminal 1
Connect light gray C wire to terminal 2.
Connect light gray R wire to where the orange from the stat WAS connected.
 
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Old 04-03-22, 02:23 PM
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Hi Pete -


......and I just saw your great marked up diagram. Disregard below lol.

When you say 'disconnect the thermostat wiring' I'm assuming you mean the wires from 1 and 3 on the Taco.

I did that half an hour ago.

When I connected W to 1, C to 2, and R to 3 it appeared that the power connector worked since the Nest Tstat stopped complaining about needing a C wire.....

HOWEVER - when I turned the tstat above ambient (to heat the room) my boiler immediately kicked on. No waiting for the boiler temperature to drop to the set point. I turned the tstat below ambient, and the boiler immediately shut off.

Figuring that the R and W were inverted (maybe) I swapped them. When I flipped the boiler emergency switch from OFF to ON, the Aquastat board just hummed and buzzed. I immediately turned it off so I don't know if upstairs the Nest was complaining about the lack of a C wire or not...



TIA
 

Last edited by peterbrown77; 04-03-22 at 02:55 PM.
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Old 04-03-22, 03:16 PM
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Hi, unless I am missing something, it looks like you have enough conductors between the stat and the valves to do away with that add on device. Split one of those twisted conductors and make a common, they shouldnít be paralleled in the first place.
Geo🇺🇸
 
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Old 04-03-22, 11:15 PM
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You've missed something and not followed my diagram. The thermostat connects to one side of the transformer known as system R. The other thermostat wire connects to terminal 1 on ZV which is the W terminal.

Terminal 2 is system C and one half of TT to the the aquastat.
Terminal 3 is the other half of the TT to the aquastat.

I believe the cable I labeled is the thermostat cable. If that is correct.... follow the orange wire to the R connection.

This is the basic Taco wiring......


Yes... Geo.... you could convert the wiring to four wire and not use the nest power adapter but that is 22-24 gauge network cabling..... not #18 thermostat wiring.
 
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Old 04-04-22, 05:57 PM
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Thanks!

It's correct now..

As an aside, I ordered a backup Power Connector from Amazon for $24.99 in case connecting C to the 120V terminal on the board had damaged it.

I received today a box of them in an obvious mistake. Who needs a dozen Power Connectors lol?

Thanks again
 
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Old 04-04-22, 07:03 PM
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Good job. Thanks for letting us know how you made out.
 
 

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