Nest T-Stat questions


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Old 12-07-22, 09:45 AM
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Nest T-Stat questions

I would like to install 2 nest T-stats to my 2 zone heat only system.I have an oil boiler with a TacoSR503 3 zone switching relay.I ran all new 6 wire to both thermostats.Is there a terminal I can hook into inside the taco unit for c wire or should I just hook up new transformers with separate plugs of each t-stat?
 
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Old 12-07-22, 11:11 AM
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Takes all image files..... png and jpg are the most popular.
If it's a massive picture.... the board can't resize it.
If it's from your phone.... the default is large format pictures.

Yes.... you can use the COM side of the COM - 24V connector BUT that means the thermostat connections must be labeled R and W. If they are labeled T T ..... you need to identify the R and W.
 
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Old 12-07-22, 10:19 AM
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Welcome to the forums.

There are many variations in the Taco controllers.... even among similar models.
Post a picture of yours with the cover off ... How to insert pictures.
 
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Old 12-07-22, 11:02 AM
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when I try to download pics it tells me it is not an acceptable file type
 
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Old 12-07-22, 11:04 AM
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I can see a terminal with 2 connectors inside the taco unit that says 24 vac on top and com on the bottom of it'd you think I can plug the c wire into that?
 
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Old 12-07-22, 11:15 AM
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Old 12-07-22, 11:37 AM
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so just leave everything else hooked up the way it currently is and just add the c wire from both t-stats to each of the terminals where it says 24vac and com?
 
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Old 12-07-22, 11:43 AM
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You're in good shape. Make sure R and W match R and W at the stat. C to COM terminal.
 
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Old 12-07-22, 11:48 AM
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can both t-stat c wires be hooked up to that C terminal?
 
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Old 12-07-22, 11:52 AM
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Certainly. You can put two wires in that terminal.
 
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Old 12-07-22, 12:01 PM
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another question ,currently white wire inserted in W on t-stat,red wire inserted to Rc with a jumper to R.Nest t-stat only has R.Do I just install red wire to R now ?
 
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Old 12-07-22, 12:02 PM
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Old 12-07-22, 12:07 PM
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R stands for 24v in.
Rh is heating functions
Rc is cooling functions.

You could have two different units..... like a boiler and an air conditioner.
Then you would need the R's to remain separate.
The jumper is used when there is only one appliance.... furnace w/split A/C.

The nest can only operate with one system.
 
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Old 12-07-22, 12:11 PM
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I only have an oil furnace for baseboard cast iron heat, no AC
 
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Old 12-07-22, 12:40 PM
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upstairs is just white to W and red to R,not sure why downstairs is different
 
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Old 12-07-22, 01:31 PM
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You are just running heat..... so all you need to use is W and Rh.
The Rh - Rc jumper is not needed. Won't hurt to be connected.

When you connect a C wire.... it is referenced to Rc.
That means the jumper would need to be in place.

Y, G, C, O, B are all considered cooling functions and Rc is used. (doesn't matter if no A/C)
W is heat and uses Rh.
 
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Old 12-07-22, 01:44 PM
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so I should jump c and r on the downstairs t-stat?
 
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Old 12-07-22, 03:23 PM
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It's not C and R.... it's Rc and Rh.
C = common and R = 24vac.

I'm trying to be descriptive so that you know how the system works.
 

Last edited by PJmax; 12-07-22 at 04:17 PM.
 

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