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HVACR114 – Electrical for Gas Heat. FAN CENTERS. Fan centers . When adding air conditioning to an existing heating system, the furnace my not have a fan relay to start the fan.
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HVACR114 – Electrical for Gas Heat FAN CENTERS
Fan centers • When adding air conditioning to an existing heating system, the furnace my not have a fan relay to start the fan. • Most fossil fuel furnaces ( oil or gas) will start the fan with a thermal type of fan switch in the heating mode. ( Fan limit switch)
When there is none, a separate fan relay must be added when the air conditioning is installed. • This relay is sometimes furnished in a package with the control transformer called a “transformer relay package”, or “fan center”.
This fan relay is controlled by the ‘G’ terminal on the thermostat. • Caution!!! The fan center is part of the low voltage and high voltage circuits. Use proper caution whenever you work with them.
This is a fan center • Consists of a relay, a transformer, and a low voltage terminal board. Relay Terminal board Transformer
How to wire a fan center • 120 volts is applied to the primary side of the transformer. • The thermostat wires are wired directly to the terminal board on the transformer. • The terminal ‘C’ and ‘G’ power up the coil on the relay. • Your wires from your fan connect to the terminals on the relay, whether they are normally open or normally closed