E1 Electrical Fundamentals - Homestead

E1 – Electrical Fundamentals

# 4 - Symbols and Wiring Diagrams

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../Electrical Subjects.ppt#4. E1 – Electrical Fundamentals Subject 4 – Symbols and Wiring Diagrams


© 2005 Refrigeration Training Services - E1#4 Symbols and Wiring Diagrams v1.1 2

Electrical Loads

• Loads

– Consume electricity

– Do work

• Examples:

– Motors

– Solenoids

– Heaters

– Lights


../Refrigeration%20Subjects.ppt#4. R1 – Fundamentals of Refrigeration Topic 4 – Basic Math and Measurement








Motors

Common symbols:

(Letters tell what motor is represented)

COMP EFM IFM

CFM OFMCOMP

COMP

COMP

COMPressor

EFM

Evaporator Fan Motor

CFM

Condenser Fan Motor

IFM

Indoor Fan Motor

OFM

Outdoor Fan Motor





../../ELEC%20Main%20Table%20of%20Contents.ppt



Solenoid

• This will cause an action in a relay or valve

• When current flows through a coil of wire it

creates a magnetic field

• Electrical symbol for a solenoid coil:










Solenoid Valve

Magnetic coil

energized Plunger

pulled up

Fluid flowsFluid stops

Power off

Plunger drops

Plunger

Seat








Heaters

• Convert electrical energy to heat

• Symbol for resistance heaters:

• Examples of heaters:

– Auxiliary strip heaters

– Crankcase heaters










Signal Lights

Used to show when something is operating,

or when there is a problem.

Symbol for signal lights:

Letter in the center denotes bulb color:

R RedB Blue

G Green, etc.

RBG








Contactor

• It is a mechanical switch, operated by a

magnetic coil

• Energizing the coil closes the contacts

• Power flows through the contacts to the load

• For more on contactors:

– See Topic E2 Subject 3 “Contactors and Motor

Starters”










LOAD

CONTROL

CIRCUIT

LINE

1 Power In

4 Power Out

Contactor Cutaway

3 Contacts2 Coil








Symbols for Contactors

Symbols are shown “de-energized” (no power)

with contacts “normally open”

Coil

Single

pole

Contact

Double

pole

Triple

pole

115v 208-230v, 1 208-230v, 3








Visualizing symbols with power on

• The following slide illustrates what

happens when the power is turned on










Contactor coil “energized”

Contacts close

Single

pole

Double

pole

Triple

pole

115v 208-230v, 1 208-230v, 3

Coil Contact








Relays

• Similar to contactors

• Usually under 20 amp capacity

• Contacts may be:

– Normally open (NO)

– Normally closed (NC)

– Or a combination of NO and NC










Symbols for RELAYS

Coil “de-energized” (no power)

Single

pole

Normally Closed

“NC”

#1 NO

#2 NC

#1 NC

#2 NO

#3 NC

Normally Open

“NO”

Double

pole

Triple

pole

1 2 1 2 3








Visualizing symbols with power on

• The following slide illustrates what

happens when the power is turned on










Symbols for RELAYSCoil “energized” (powered up)

Single

pole

Normally Closed

“NC”

#1 NO

#2 NC

#1 NC

#2 NO

#3 NC

Normally Open

“NO”

Double

pole

Triple

pole

1 2 1 2 3








Introduction to switches

• Switches open and close contacts to

control a load

– Contact:

• the conducting part of a switch

– Poles:

• the number of contacts in a switch

– Throw:

• the number of closed contact positions per pole










Single Throw Switch Symbols

Single Pole – Single Throw

(SPST)

Double Pole – Single Throw

(DPST)

Switch openSwitch closed

L2

Switch openSwitch closed

L1








Double Throw Switches

• Each switch position closes a circuit










Single Pole - Double Throw (DPDT)

Contacts 1-3 open Contacts 1-3 closed

1

2

3

Contacts 1-2 closedContacts 1-2 open








Double Pole – Double Throw (DPDT)

1

2

3

4

5

6

Contacts 1-2 closed

Contacts 4-5 closed

Contacts 1-3 closed

Contacts 4-6 closed








Thermostats

B

O

W

Y

G

R

• Symbol depicts a bimetal

spring which closes and

opens the contacts

• Tstats are usually shown in

their “normal” position, which

is open










Symbols for Thermostats

Cooling thermostat

In actual operationAs the temperature goes up

the rise in temperature causes the bimetal to expand

the expanded bimetal raises the arm

the raised arm closes the contacts








Symbols for Thermostats

Heating thermostat

In actual operationAs the room temperature falls

the fall in temperature causes the bimetal to contract

the contracted bimetal pulls down on the arm

the arm closes the contacts








Pressure Controls

• Symbol depicts a bellows which

operates the contacts

• Pressure safety controls are usually

shown in their “normal” position, which

is closed










Low Pressure Control










Symbols for Pressure Controls

Low pressure control

In actual operationAs the system pressure falls

the fall in pressure causes the bellows to deflate

the deflated bellows pulls down on the arm

the arm opens the contacts








Symbols for Pressure Controls

In actual operationAs the system pressure rises

the rise in pressure causes the bellows to inflate

the inflated bellows raises the arm

the raised arm opens the contacts

High pressure control








Fuses and Overloads

• Symbols for safety devices, such as

fuses and overloads, are usually shown

closed










Safety Device Symbols

Bimetal overload:

Thermal overload relay:Excessive amperage heats the thermal

element, which opens the switch.

Magnetic overload relay:

Excessive amperage creates a magnetic

field, which opens the switch.

High heat and high amperage open this

overload switch.








Introduction to Wiring Diagrams

• The following slide is a diagram of an

attic exhaust fan

– The fan is controlled by a standard switch










N

Switch controls fan

FM

Attic Exhaust Fan

L1








Adding controls to the diagram

• A thermostat replaces the standard switch

• This allows the fan to operate automatically,

based on attic temperatures










L1 N

Add a Thermostat

FM

Simple Circuit for Attic Exhaust Fan








Schematic Diagrams

• The wiring diagram on the following slide is

a very basic air conditioning unit:

– The diagram animations show how energizing a

relay coil will close a set of contacts










L1 L2

COMP: Compressor

C

BR

LEGEND

BR: Blower relay

BM: Blower motor

C: Contactor coil

BR

TS: ThermostatTS

COMP

BM

C Contactor switch

Blower relay switch

Heat closes Tstat

Compressor

runs

Blower

runs

A/C Unit with Line Voltage Controls








Schematic Diagrams

• The diagram on the following slide is a little

more complex

– A transformer is used to supply power to a low

voltage control circuit










C

IFR

L1 L2LEGEND

G

Air Conditioner Schematic Diagram(Low voltage controls)

IFM

COMP: Compressor

CFM: Condenser fan motor

IFM: Indoor fan motor

C: Contactor

IFR: Indoor fan relay

CR: Control relay

HPS: High pressure switch

LPS: Low pressure switch

CIT: Comp. Internal tstat

Trans: Transformer

CT: Cooling Thermostat

Y: Yellow tstat terminal

R: Red tstat terminal

G: Green tstat terminal

C

IFR

CR

C

TRANS

Auto

On

CFM

COMP

RCR

Y

HPS LPS CIT

CT








Schematic Diagrams

The next slide shows how the

low voltage side relates to the

high voltage side of the system










IFR

CFM

COMP

C

L1 L2

CR

LEGEND

Y

G

R

Air Conditioner Schematic Diagram(Low voltage controls)

COMP: Compressor

CFM: Condenser fan motor

IFM: Indoor fan motor

C: Contactor

IFR: Indoor fan relay

CR: Control relay

HPS: High pressure switch

LPS: Low pressure switch

CIT: Comp. Internal tstat

Trans: Transformer

CT: Cooling Thermostat

Y: Yellow tstat terminal

R: Red tstat terminal

G: Green tstat terminal

C

CR

C

TRANS

Check out fan circuitAuto

On

Turn Fan “ON”

IFM

HPS LPS CIT

CT

IFR








How switch contacts are shown on wiring diagrams:

• Operating controls are shown in the open position

– Example: Thermostats and fan switches

• Safety controls are shown in the “normal” position

– Example: High pressure control (closed)

– Example: High limit switch (closed)

• Relay contacts are shown with coil de-energized

– Example: Indoor Fan Relay NO contacts (open)

– Example: Indoor Fan relay NC contacts (closed)

HVACR Industry Standards for

Electrical Diagrams









L1 L2

Auto

On

TRANS

R

CFM

Comp

IFR

High

Low

FS

LS

C C

CR

GV

IFM

GIFR

Off CT

Y

HT

W

Cool

Heat


Operating controls shown

in the “open” position

• Fan switch (FS)

• Cooling Tstat (CT)

• Heating Tstat (HT)

Safety controls shown in the

“normal” position

• Limit Switch (LS)

Relay switches shown with

coil de-energized.

• Indoor Fan Relay (IFR) coil

• Normally open contacts

• Normally closed contacts

Schematic Diagram of A/C Unit with Gas Heating








“Detailed Schematic”

• Numbers on the left are line or circuit numbers

• Numbers on the right indicate switching

information:

– Which sets of contacts the relay controls (line number)

– Contact configuration (NO or NC)

HVACR Industry Standards for

Electrical Diagrams









L1 L2

Auto

On

TRANS

R

CFM

Comp

IFR

High

Low

FS

LS

C C

CR

GV

IFM

GIFR

Off CT

Y

HT

W

Cool

Heat


1

2

3

4

5

6

7

9

8

10

(3, 4)

(1)

Each line is numbered

Each line has a load

Location of relay’s switch

contacts

Underlined numbers are

normally closed (NC)

contacts

4

“Detailed” Schematic Diagram








Reading wiring diagrams

• Try to visualize what happens when the

controls close and power energizes loads

• The following slide illustrates continuous

fan operation










Off

Continuous Fan OperationL1 L2

CT

Auto

On

Y

TRANS

R

CFM

HT

W

Comp

IFR

High

Low

FS

LS

Cool

Heat

C C

CR

GV

1

2

3

4

5

6

7

9

8

10

IFM

GIFR 1 - Switch fan to On

2 - Fan relay coil energized

3 - Fan relay contacts

change position

4 - Fan motor will now run

continuously on high speed

in Off, Heat, or A/C settings

(3,4)

(1)









• Which controls, switches, and loads are

affected when the A/C is turned on?










Off

Cooling Mode – Auto FanL1 L2

Auto

On

Y

TRANS

R

HT

W

IFR

High

Low

FS

LS

Cool

Heat

C C

GV

1

2

3

4

5

6

7

9

8

10

(3,4)

(1)

IFM

GIFR

2 - Room temperature rises

1 - Switch t-stat to “cool”

4 - Fan Relay contacts

change position

CT

CR

7 - Contactor closes(Compressor and Condenser Fan start)

3 - Fan relay coil energized

5 - Fan motor starts(higher fan speeds are used in A/C)

6 - A/C contactor coil energized

CFM

Comp









• Which controls, switches, and loads are

affected when the Heat is turned on?










Off

Heating Mode – Auto FanL1 L2

CT

Auto

On

Y

TRANS

R

CFM

Comp

IFR

High

Low

FS

LS

Cool

Heat

C C

CR

1

2

3

4

5

6

7

9

8

10

IFM

GIFR

1 - Switch t-stat to heat

2 - Room temperature falls

4 - Furnace heat rises,

fan switch closes

(3,4)

(1)

3 - Gas valve opens

W

HT

GV

5 - Fan motor starts on low speed

Note: Few controls are

needed for heating








Four Schematics Show Operation

• The diagrams on the following slides show

these conditions:

1. Evaporator motor operation

2. Condenser motor operation

3. Compressor operation

4. Crankcase heater operation










23 4 3

21 4 1

1

2

2

13

11

C

C C2

C2

1

A

L1 2

2

3

1

431CFR

1

C2

1

CLO

LOGIC

CC2C3HPSLPS

2

CHR

C1

FAN

TB1

OFF

COOL

SW

T

C

C

CHR

CLO

OFR

CHR

IFC

TRAN

CLO

IFC

COMP

IFM

TRAN

4 5

C2 C2

IFC

FIELD

POWER

SUPPLY

Neutral

L2

L1

L3

Equip end

CLB

CLA

SCHEMATIC

CHR CCH

5

CLO

Indoor fan

motor STARTS

IFC

23

2111

13

Switch fan on

IFM contactor energized

1

240v

24v

2

SEPARATEPOWER SOURCE

OUTDOOR

FAN MOTOR

REMOTECFM

1 3

CFRL4

L5

Start Indoor Fan Motor (IFM)

C11

3








4 3

21 4 1

1

2

2

13

11

CA

1L1 2

2

3

1

431

3

1

CLO

LOGIC

C2C3HPSLPS

2

CHR

C1

FAN

TB1

OFF

COOL

SW

CT

C

C

CHR

CLO

OFR

CHR

IFC

TRAN

CLO

IFC

COMP

IFM

TRAN

5

C2C1

IFC

FIELD

POWER

SUPPLY

Neutral

L2

L1

L3

Equip end

CLB

CLA

SCHEMATIC

CHR CCH

CLO

IFC

23

21

13

Switch to COOL

CFM relay energized

2

Tstat Closes

CFM Starts

240v

24v

OUTDOOR

FAN MOTOR


REMOTECFM

1 3

CFRL4

L5

CFRCFR

REMOTECFM

REMOTECFM

Start Condenser Fan Motor (CFM)

5

C2

1

C

C2

1

C2

C2

23

C

4

11








1

2

2

C

C C2

C2

1

A

1L1 2

2

3

1

431

3

CFR

1

C2

1

CLO

LOGIC

CC2C

HPSLPS

CHR

FAN

TB1

OFF

COOL

SW

T

C

C

CHR

CLO

OFR

CHR

IFC

TRAN

CLO

IFC

COMP

IFM

TRAN

4 5

C2C1 C2

IFC

FIELD

POWER

SUPPLY

Neutral

L2

L1

L3

Equip end

CLB

CLA

SCHEMATIC

CHR CCH

CLO

IFC

23

2111

13

COMP contactor energized

3

13

11Compressor

Starts

240v

24v


OUTDOOR

FAN MOTOR

REMOTECFM

1 3

CFRL4

L5

REMOTECFM

CFR

3

2

Start Compressor (Comp)

C1

5

4

4

23

21

3

1








4 3

4 1

1

2

2

C

C C2

C2

1

A

1L1 2

2

3

1

431

3

CFR

1

C2

1

CLO

LOGIC

CC2C3HPSLPS

2

CHR

C1

FAN

TB1

OFF

COOL

SW

T

C

C

CHR

CLO

OFR

CHR

IFC

TRAN

CLO

IFC

COMP

IFM

TRAN

C2C1 C2

IFC

FIELD

POWER

SUPPLY

Neutral

L2

L1

L3

Equip end

CLB

CLA

SCHEMATIC

CHR CCH

5

CLO

IFC

23

2111

13

CHR relay energized

423

21

13

11

CCH Off

4 5

240v

24v

REMOTECFM

1 3

CFRL4

L5

REMOTECFM

Shut off Crankcase Heater (CHR)








Large Air Conditioning System Diagram

• Part winding compressors require two contactors

• 1st contactor pulls in, then

• 2nd contactor pulls in 1 - 3 seconds later

• Compressor starts easier, less wear

• Outdoor thermostats control 2nd and 3rd

condenser fans










Commercial A/C remote condensing unit

COMP

OFM1 OFM2 OFM3

C1

TDR

C2

OFC1

OFC2

CR

CR

CR

LPS HPS DLT

OPS OL1 OL2

CR

CB3

CB2

CB1

C1

FU

OFC1 OFC2 OFC3

L1 L2 L3

C2

OFC3

TS1

TS2

From building

control system

CH

C1

COMPCOMP

TDR

C2

OFC1

OFC2

OFC3

OFM1 OFM2 OFM3

CR

TDR

C: ContactorCB: Circuit breakerCH: Crankcase heaterCR: Control RelayDLT: Discharge line tstatFU: FuseHPS: High pressure switch

LPS: Low pressure switchOFC: Outdoor fan contactorOFM: Outdoor fan motorOL: OverloadOPS: Oil pressure switchOTS: Outdoor temperature switchTDR: Time delay relay

Call for cooling

Crankcase heater off

Compressor contactor #1 on

Compressor contactor #2 on

Time delay relay starts

Time delay contacts close

2nd Winding energized,

Compressor starts

One Outdoor fan starts

1st Winding energized

Other Outdoor fans start
















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E1 Electrical Fundamentals - Homestead