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No c wire and nest power connector not working

Grepes
Community Member

Hello,

I have r/w/c heat only system running to a new addition. I have a taco sr503 control board. The nest was not detecting the cwire (connected to com on the taco board) so I purchased a power connector. Neither are able to pick up power with the nest. Additionally I tried running the c wire and power connector to the 24v slot on the taco board and this did not work. This works for my Nest learning (through power connector/older thermostat wiring).

I have 3 zones. 

any ideas?

 

1 Recommended Answer

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@Grepes ,:When using a TACO relay pack, including the SR-503 you need to install a 1000 Ohm, 1/2 Watt resister between the 24VAC Common and the W terminal of the thermostat connection.  This is necessary for the Nest to be able to reach the 24 VAC common of the TACO SR-503. Your other choice is to use an available wire conductor attached to the Nest C terminal and the TACO SR-503 24VAC Common block in the upper left corner. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.

View Recommended Answer in original post

4 REPLIES 4

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@Grepes ,:When using a TACO relay pack, including the SR-503 you need to install a 1000 Ohm, 1/2 Watt resister between the 24VAC Common and the W terminal of the thermostat connection.  This is necessary for the Nest to be able to reach the 24 VAC common of the TACO SR-503. Your other choice is to use an available wire conductor attached to the Nest C terminal and the TACO SR-503 24VAC Common block in the upper left corner. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.

Thank you, attaching the wire connector didn’t seem to work. How would I get the resistor all the way across the panel?

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@Grepes , the resister does not have to go all the way across the panel. You can get a 1/2watt 1000 Ohm resister and insert one en in the Common terminal, then if the W is to far away, use a short wire and attach it to the W and the other end to the resister. 

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.

Grepes
Community Member

Thank you @CoolingWizard. There is a COM and a 24v which should the 1k Ohm Resister be connected too? Additionally is this with or without the Nest power connector?