1. 1 HVAC 214 Electricity For Oil Heat Fan Center Relays

2. 2 Fan Center Relay

3. 3 Fan Center Relays Designed to provide low voltage control of blower motors and auxiliary circuits. Designed to provide a good junction point for other circuits. Used on heating systems with air conditioning. Designed to provide low voltage control of blower motors and auxiliary circuits. Designed to provide a good junction point for other circuits. Used on heating systems with air conditioning.

4. 4 Fan Center Relays Contain the following components: –A low voltage transformer (step down from 120 to 24 volts) –A pre-wired multifunction switching relay –A Low voltage terminal board. Contain the following components: –A low voltage transformer (step down from 120 to 24 volts) –A pre-wired multifunction switching relay –A Low voltage terminal board.

5. 5 Fan Centers Sometimes used when there are two transformers, one on the heating equipment and one on the cooling equipment. These transformers must be isolated from each other based on whether the thermostat is calling for cooling or heating. Sometimes used when there are two transformers, one on the heating equipment and one on the cooling equipment. These transformers must be isolated from each other based on whether the thermostat is calling for cooling or heating.

6. 6 Fan Center Wiring Connections Connections: –R is output power from the internal transformer –W is the junction point for W from tstat and W from equipment –G is the connection from G from the thermostat –Y is a junction point from for Y from the t-stat –C is common from internal transformer Connections: –R is output power from the internal transformer –W is the junction point for W from tstat and W from equipment –G is the connection from G from the thermostat –Y is a junction point from for Y from the t-stat –C is common from internal transformer

7. 7 Thermostat calls for heat During a call for heat, the normally closed relay contact for the low speed blower stays closed and the blower is controlled by a Fan/Limit switch mounted in the furnace plenum.

8. 8 Call for heat Low speed blower wire goes through N/C contact onto the Fan/Limit

9. 9 The thermostat call for cooling During a call for cooling, the thermostat closes R to G which energizes the relay coil. When the coil is energized, the N/O contact closes and allows the blower to operate on high speed.

10. 10 Call for cooling The high speed blower wire goes through the N/O contact which closes when the coil is energized. Thermostat closes R to G & R to Y

11. 11 Fan Center The W, Y, and any additional terminals are just junction points.