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HVACR114 – Electrical for Gas

HVACR114 – Electrical for Gas

SymbolsSymbols

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Relay w/ Normally open and Normally closed contactsRelay w/ Normally open and Normally closed contacts

Normally Open Contact

Normally Closed Contact

Relay Coil

•Common symbol that is seen in many HVAC schematics.

•Parts of this symbol can be broken up into different parts of a wiring schematic.

•Example: Relay coil can be wired to 24 volts to control (2) 120 volt loads.

•Basic operation:•When the “relay coil” get energized, the “Normally open Contact” will CLOSE, turning on a load and the “Normally closed contact” will open, turning off a load.

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Three phase compressorThree phase compressor

• Basic symbol for a three phase compressor.

•Three phase compressors are commonly used in commercial and industrial applications.

•Three phase is an electrical composition of three single phase power supplies that are 120 degrees out of phase with each other.

•The color codes for 3 phase power is:

•L1= Black•L2- Red•L3= Blue•Neutral= White

L1

L2

L3

Neutral

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Red Signal LightRed Signal Light

• Commonly found on wiring diagrams with a circuit board.

•Used as a diagnostic tool on circuit boards.•The light will flash to give an indication of a problem with the system.

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FuseFuse

• Simplest form of circuit protection.

•Fuse will blow in the event of a over current situation.

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Pressure SwitchPressure Switch

•This is a symbol for a “ pressure switch”.

•This switch will close on rise in pressure.

Pressure Rise

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Crankcase heaterCrankcase heater

•Used to heat the crankcase of a compressor. •This can be multiple voltages depending on the situation.

•Most residential crankcase heaters are 115 volts.•Commercial applications can be much higher.

•Example 480 volts

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ThermostatsThermostats

• Thermostat will open on temperature rise.

•As the temperature falls in the space, the connection will be made, turning on the system.

•Thermostat will close on temperature rise.

•As the temperature rises in the space, the connection will be made, turning on the system.

Heating Thermostat

Cooling Thermostat

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3 pole contactor and coil3 pole contactor and coil

Contact 1

Contact 2

Contact 3

Coil

• Used on 3 phase systems.

•Can be wired to 208/203 volts•460 volts•480 volts

•Contactor coil can be powered by either 24,120, or 460 volts.

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Evaporator Fan MotorEvaporator Fan Motor

• Basic symbol for an evaporator fan motor.

•Used to circulate air across the evaporator in an air conditioning system.

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Single phase compressor with internal overloadSingle phase compressor with internal overload

•Commonly found on residential and light commercial systems. •Mostly wired to 115 volts.

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Single pole switch ( service switch)Single pole switch ( service switch)

•Common symbol for you everyday light switch.

•Can also be used to symbolize a breaker.

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Pressure SwitchPressure Switch

This is a close on “pressure drop” pressure switch.

Pressure drop

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Pilot duty thermal overloadPilot duty thermal overload

This can be found internally on compressors or motors.

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Double Pole Single Throw SwitchDouble Pole Single Throw Switch

This can symbolize a two pole breaker.

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TransformerTransformer

This is a basic symbol of a step down transformer (120volts to 24 volts)

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Single Pole Double Throw SwitchSingle Pole Double Throw Switch

May used to switch a appliance between two separate modes manually

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Normally closed push buttonNormally closed push button

May be found on circuit boards

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Red signal lightRed signal light

May be found on circuit boards and used a diagnostic tool

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Dual Pressure SwitchDual Pressure Switch

Commonly seen on Refrigeration and Air Conditioning systems to keep the system operating pressure within certain pressures

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Door SwitchDoor Switch

Used as a safety device to prevent fingers from getting sucked into the blower wheel of HVAC appliances.