White Rogers 50A50-241 and Nest thermostat C wire

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Old 12-05-19, 06:50 AM
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White Rogers 50A50-241 and Nest thermostat C wire

Hey Everyone,

I'm Looking for some help in hooking up my Nest Gen3 to the White Rogers 50A50-241 Module.
My dual zone system is 1999 vintage I believe. I have since reattached my wires off the insulation.

My C wire doesn't have the 24 volts required to run the nest. However, the other wires work fine.

The red and blue wires are connected to the C terminal. How can I test if there's 24 volts?

Is there a way to connect the blue wire to a always live 24V terminal?
Any help will be greatly appreciated!

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Old 12-05-19, 08:46 PM
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Welcome to the forums.

I may see a problem...... look closely at the furnace board where the thermostat wiring connects. It looks like the screw terminals are on the insulation and not the copper wire.

I see five thermostat wires connected.
Furnace - color - nest
C --------> blue -------> C
G --------> green -----> G
R --------> red --------> Rh
W -------> white ------> W1
Y --------> yellow -----> Y1

With HVAC wiring..... everything is switched to R (24v).
Heat is W + R
A/C is Y + G + R
Blower is G + R
The thermostat doesn't require the C connection to control functions.
C is equivalent to common or ground and is only used for the thermostat electronics.
If you want to measure for 24vAC...... measure from C to R.
 
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Old 12-07-19, 10:56 AM
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Pete,

Good info....Yes, I fixed the wires and moved them away from the insulation.

I noticed I have a red and blue wire connected to the C terminal.
Is this correct? Or should the red wire be connected to the R terminal with the other red wire?

I do have 24v as follows:
R --->G
R --->W1
R --->Y1
However: R --->B 1-2v

Any other suggestions?

My system has been working like this for many years.

Thanks!

Mike
 
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Old 12-07-19, 07:42 PM
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If you noticed..... I labeled your picture. You have two cables meeting there.
The thermostat cable with blue, green, red, yellow and white.
The A/C condenser cable with two wires in use. Red and white.
You'll see the red from the condenser is picking up a C connection and the white is picking up a Y connection. This is correct.

What is R to B ?
Do you mean R to C ?
 
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Old 12-07-19, 10:04 PM
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What is R to B ? Red to Blue wire
Do you mean R to C ? Yes as in the red and blue wire are both connected to the C terminal.

I've attached another picture to show the control unit that runs the dual zones.
This is in between the furnace and wall thermostat.

At this point I'd need to hire a Pro to do the hook ups. Since it's not worth the cost etc, I'll keep my system old school and return the nest.

Many thanks for your help.
 
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Old 12-08-19, 06:03 PM
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You needed to post the zone controller up front. Your thermostat does not go to the furnace..... it goes to the zone controller. The zone controller feeds the furnace. Some zone controllers require special thermostats.
 
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