Attic Exhaust Fan System:
- Manual Operation:
- Fan motor mounted on the attic side.
- Manual switch installed in the power line allows turning the fan on/off.
- Simple operation by closing the switch to provide power to the fan.
- Temperature Control:
- Addition of a temperature control switch (thermostat) in series with the manual switch.
- Thermostat senses attic temperature, bimetal expands with rising temperature, closing contacts and turning the fan on.
- Real-world example: Both manual switch and thermostat wired in series to the fan motor.
Schematic Diagrams (Ladder Diagrams):
- Purpose:
- Best for troubleshooting, commonly used by service technicians.
- Show the normal sequence of operations, but not the component location.
- Structure:
- Represented with graphic symbols instead of actual pictures.
- Ladder sides (L1 and L2) signify power lines.
- Parallel circuits are represented by rungs of the ladder.
- Loads and switches are wired in series to control circuits.
Window Air Conditioner Diagram:
- Basic Components:
- Two loads: compressor and fan motor (operates both condenser fan and evaporator fan).
- Selector switch: Turns unit off, fan on, or cooling mode.
- Thermostat: Controls cooling mode, closes contacts as temperature rises.
- Operation:
- Fan can run for ventilation or switch to cooling mode.
- Compressor operates only when the thermostat closes its contacts.
Advanced Window Air Conditioner Diagram with Relays:
- Addition of Relays:
- Controls relay coils rather than directly controlling the compressor or fan.
- Relay coil controls the position of the switches (e.g., contactor for the compressor, fan relay for the fan).
- Fan Switch Operation:
- Fan On Position:
- Power available to evaporator fan relay continuously.
- Coil closes switch contacts, powering the evaporator fan.
- Fan Auto Position:
- Evaporator fan runs only when there is a call for cooling.
- Thermostat calls for cooling, closing contacts between R and Y.
- Power reaches contactor and evaporator fan relay, turning on compressor, condenser fan, and evaporator fan.
- Fan On Position:
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