Taco SR503 Common Wire


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Old 04-08-22, 01:29 PM
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Taco SR503 Common Wire

I have a taco SR503 and need to connect a common wire for a nest. Do I connect it to one of the connections I circled in my picture?
 
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Old 04-08-22, 04:44 PM
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Hi, take a voltmeter and measure from each of those terminals to R , the one that gives you 24VAC will be your C terminal.
Geo🇺🇸
 
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Old 04-08-22, 05:16 PM
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Ok great! Thanks so much!
 
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Old 04-08-22, 05:23 PM
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That terminal strip is labeled. We can't see it in the picture.
I believe the left is com and the right is 24vac.
If that is correct...... you must change your red and white wires to match this diagram........
 
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Old 04-09-22, 07:21 AM
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Thanks PJ. My thermostat red/white is connected to the top bar first spot in my photo. Now, Im pretty sure its the correct wire because at my thermostat I have a red, white, and green and this wire at the Taco is the only one that has those colors.
I tested from the red connector to the green block on com and 24v. I got a 0 reading.
so I have this other taco and I tested from my red wire in the 503 to the green connector I circled and got around a reading of 14. That green wire circled is the green wire from my thermostat.


 
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Old 04-11-22, 07:31 PM
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Working!

Thanks so much everyone for the help! I hooked my common wire working by hooking it up to the com connector. I tested the com connector with my tester on the wrong setting at first and realized it after the fact. Thanks again!
 
 

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