EMS Si - wiring / connection description

Thermostat to HVAC Equipment

18 AWG          20 AWG          22 AWG

128 ft/380 m                  80 ft/240 m                     50 ft/150 m


Terminal Description and Electrical Ratings

Terminal             Description                                     Voltage                   Current Max

N/C                     Unused                                          N/A                            N/A

Y                         1st stage compressor                    24VAC                      2A

W (O/B)              1st stage heating                           24VAC                      2A
                           or reversing valve

G                        Fan                                                 24VAC                      2A

RC                     Cool transformer *                          24VAC                      2A

RH                     Heat transformer *                          24VAC                      2A

C                       Common                                         24VAC                      2A

Y2                     2nd stage compressor                    24VAC                      2A

W2 (AUX)         2nd stage heating or                       24VAC                      2A
                         1st stage auxiliary heat

R1+                   Input 1+                                         Temperature/dry contact only

R1-                    Input 1-                                          Temperature/dry contact only

R2+                   Input 2+                                         Temperature/dry contact only

R2-                    Input 2-                                         Temperature/dry contact only

* Factory jumper installed between RC and RH. Remove jumper for 2-transformer applications. See wiring diagrams for additional information.


Was this article helpful?

Have more questions? Submit a request