The 0-10 volt modulation terminals on a SmartCom3 control panel are terminal 64 - ground / 0 - terminal 66 - 10volt +. Please see the SmartCom3 Control Panel Installation and User Manual (https://www.reznor.co.uk/wp-content/uploads/2023/12/2a.-704020-SC3ML-Installation-and-Operating-Manual-v3a-Ben-EN-0416-A4F-GBSCOM1200416-1.pdf) for more information.
What terminals are the 0-10 volt modulation on a Smartcom 3 control panel?
Information on Reznor's range of control panels