SERVICE TECHNICIAN
TRAINING
I
TS TIME FOR SOME HOUSEKEEP
ING 4HIS CHAPTER GATHERS TOGETHER
THE SYMBOLS AND TERMINOLOGY ROUTINELY USED IN CONVEYING ELECTRICAL
INFORMATION
Electrical Properties
of Components
%LECTRICAL COMPONENTS CAN HAVE ONLY
THESE THREE PROPERTIES IN ANY COMBINA
TION RESISTANCE INDUCTANCE AND CAPACITANCE
Table 1 TABULATES THE WAYS THESE PROPERTIES
ARE WRITTEN DRAWN AND MEASURED
Properties of Electricity Itself
%LECTRICITY ITSELF HAS A NUMBER
OF PROPERTIES 4HOSE
by Gary
Weidner
MOST COMMONLY
ENCOUNTERED ARE LISTED IN Table 2
Prefixes
#ERTAIN STANDARD PREFIXES ARE USED WHEN
WRITING THE VALUES OF QUANTITIES LISTED IN
4ABLES AND 4HE PREFIXES REPRESENT MULTIPLIERS THEIR PURPOSE IS TO MAKE LARGE AND
SMALL NUMBERS EASILY READABLE 4HE FOUR
PREFIXES MOST LIKELY TO BE ENCOUNTERED IN
PRESSURE WASHER WORK ARE AS FOLLOWS
— -)#2/ 4HIS 'REEK LETTER IS USED TO
REPRESENT THE WORD PREFIX hMICROv -ICRO
Key Concepts
UÊ 9œÕʘii`Ê̜ʎ˜œÜÊ̅iÊÃޓLœÃÊ>˜`Ê
units of measure for the basic electrical components R, L, and C, and for
electricity itself.
UÊ Ê«ÀivˆÝʈ˜ÊvÀœ˜ÌʜvÊ>ʘՓLiÀʓ>ŽiÃÊ
it larger or smaller; four prefixes are
commonly encountered in pressure
washer work.
UÊ Ì½Ãʈ“«œÀÌ>˜ÌÊ̜Ê՘`iÀÃÌ>˜`Ê̅iÊ
symbols used on electrical schematics
or wiring diagrams, because they can
be a big help in troubleshooting.
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MEANS ONEMILLIONTH &OR EXAMPLE ONE
MICROFARAD IS ONEMILLIONTH OF A FARAD
OR FARAD
M -),,) ! LOWER CASE hMv IS
USED TO REPRESENT THE WORD PREFIX
hMILLIv -ILLI MEANS ONETHOUSANDTH
&OR EXAMPLE ONE MILLIVOLT IS ONE
THOUSANDTH OF A VOLT OR VOLT
K +),/ ! LOWER CASE hKv IS USED
TO REPRESENT THE WORD PREFIX hKILOv
+ILO MEANS ONE THOUSAND &OR EXAMPLE
ONE KILOWATT IS ONE THOUSAND WATTS
OR WATTS
- -%' OR -%'! !N UPPER CASE
h-v IS USED TO REPRESENT THE WORD
PREFIX hMEGv OR hMEGAv -EGMEGA
MEANS ONE MILLION &OR EXAMPLE ONE
MEGOHM IS ONE MILLION OHMS OR
OHMS /NE MEGAWATT IS ONE
MILLION WATTS OR WATTS .OTE
5NFORTUNATELY IN BUSINESS AND COMMERCE THE UPPER CASE h-v IS OFTEN
USED TO REPRESENT A QUANTITY OF A THOUSAND "E CAREFUL NOT TO CONFUSE THAT
USAGE WITH TECHNICAL USAGE WHERE
h-v MEANS ONE MILLION
Diagram Symbols
-ANKIND HAS COME UP WITH AN
ALMOST UNCOUNTABLE NUMBER OF DEVICES
THAT USE ELECTRICITY TO OPERATE A LIGHT
BULB IS AN EXAMPLE OR THAT OPERATE
IN SUCH A WAY AS TO CONTROL THE FLOW OF
ELECTRICITY A SWITCH IS AN EXAMPLE
Table 3 PRESENTS A FEW OF THE DEVICES
THAT MAY BE ENCOUNTERED IN PRESSURE
WASHER ELECTRICAL SYSTEMS 5NDER
STANDING THESE DEVICES AND RECOGNIZING
THEIR SYMBOLS ON ELECTRICAL DIAGRAMS
IS A GREAT HELP IN TROUBLESHOOTING
LIKE BEING ABLE TO READ A MAP TO GET
WHERE YOU WANT TO GO 4HE TEXT BELOW
FOLLOWS THE ORDER OF THE SYMBOLS
SHOWN IN Table 3
Ground Connection
4HE FIRST SYMBOL IN Table 3 IS THE
GROUND CONNECTION POINT )N MANY
PRESSURE WASHERS THAT USE ELECTRICITY FOR
ANY PART OF THEIR OPERATION SOME PART
OF THE ELECTRICAL SYSTEM IS GROUNDED
CONNECTED TO THE FRAME OF THE
MACHINE 7HEN YOU SEE THIS SYMBOL
ON A WIRING DIAGRAM IT IS TELLING YOU
WHAT WIRE IS CONNECTED TO THE FRAME
%XAMPLES /N MACHINES POWERED BY
6!# AN INCOMING GREEN WIRE IS
GROUNDED TO THE FRAME /N ENGINE
DRIVEN EQUIPMENT WITH BATTERY START
ONE TERMINAL OF THE BATTERY IS USUALLY
GROUNDED TO THE FRAME
Wires
7HEN FOLLOWING WIRES AROUND A
DIAGRAM YOU WILL NOTICE THAT THE LINES
REPRESENTING THE WIRES OFTEN CROSS
4HERE IS NO CONNECTION BETWEEN THESE
CROSSING WIRES UNLESS THE POINT WHERE
THEY JOIN IS MARKED WITH A DOT
Battery
4HE SYMBOL SHOWN IS THE SYMBOL
FOR ANY BATTERY BE IT A WATCH BATTERY
OR A CAR BATTERY 4HE END OF THE SYMBOL
WITH THE SHORT LINE IS ALWAYS THE BATTERY
Cleaner Times | IWA s .OV s NEGATIVE TERMINAL 4HE END OF THE SYMBOL WITH THE LONG LINE
IS ALWAYS THE BATTERY POSITIVE TERMINAL 2EMEMBER THAT
BATTERIES PRODUCE DIRECT CURRENT ONLY
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Rectifier
! DEVICE THAT CHANGES ALTERNATING CURRENT TO DIRECT CURRENT
)T WORKS JUST LIKE A CHECK VALVE IN THAT IT ALLOWS CURRENT FLOW
IN ONE DIRECTION ONLY 2ECTIFIERS ARE ONLY OCCASIONALLY SEEN
ON PRESSURE WASHERS !N EXAMPLE IS THE EXTERNALLY MOUNTED
RECTIFIER USED WITH SOME GASOLINE ENGINES TO CONVERT THE
ENGINE ALTERNATOR OUTPUT FROM AC TO DC FOR BATTERY CHARGING
Lamp
)NDICATOR LAMPS ARE DEPICTED IN SEVERAL WAYS THE SYMBOL
SHOWN IS PROBABLY THAT MOST COMMONLY USED 4HE LETTER INSIDE
THE CIRCLE TELLS THE COLOR OF THE BULB OR LENS !LTHOUGH REFERRED
TO AS LAMPS SMALL INDICATOR LIGHTS CAN ACTUALLY BE NEON OR LIGHT
EMITTING DIODE ,%$ TYPES AS WELL AS INCANDESCENT BULBS
Fuse
7HO AMONG US HAS NEVER BLOWN A FUSE 4ROUBLE IS FUSES
ON EQUIPMENT COME IN QUITE A NUMBER OF SHAPES SIZES AND
MOUNTING ARRANGEMENTS 3OMETIMES THEYRE DIFFICULT TO FIND
IN A HEAVILY WIRED CONTROL PANEL #HECKING FOR THE SYMBOL
ON A WIRING DIAGRAM CAN HELP IN LOCATING A FUSE
Switch
.OW HERES A CAN OF WORMS 4HERE ARE MANY DIFFERENT
KINDS OF SWITCHES EVEN JUST AMONG THOSE USED ON PRESSURE
WASHERS (OWEVER LIKE SO MANY THINGS IN LIFE MOST OF THEM
ARE ELABORATIONS ON A BASIC FUNCTION
! SWITCH OPERATED BY A LEVER TYPE HANDLE IS CALLED A 4/'',%
SWITCH -ANY SWITCHES ARE MANUFACTURED SO THAT THE CIRCUIT
DESIGNER CAN CHOOSE A MOMENTARY OPERATOR ACTION IF DESIRED 4HIS MEANS THAT
WHEN THE BUTTON OR HANDLE OF SUCH A
SWITCH IS RELEASED IT WILL SPRING BACK TO
ITS ORIGINAL POSITION
SPST
4HESE LETTERS STAND FOR 3INGLE 0OLE
3INGLE 4HROW 4HIS IS THE SIMPLEST
KIND OF SWITCH AND BY FAR THE MOST
COMMONLY USED )T HAS TWO TERMINALS
WHICH ARE ELECTRICALLY JOINED TOGETHER
WHEN THE SWITCH HANDLE IS MOVED TO
THE hONv POSITION )N OTHER WORDS
WHEN A SWITCH IS hONv ALSO REFERRED
TO AS hCLOSEDv IT PROVIDES A CONTINUOUS ELECTRICAL PATH ! CLOSED SWITCH IS
LIKE A PIECE OF WIRE
4HE MAJORITY OF SWITCHES ARE hNORMALLY OPENv ./ AND CLOSE WHEN
OPERATED "UT ITS NOT UNUSUAL FOR A
CIRCUIT TO REQUIRE A hNORMALLY CLOSEDv
.# SWITCH 4HE NORMALLY CLOSED
SWITCH IS ALWAYS CLOSED IN ITS BASIC
REST POSITION EVEN IF THE CONTROL PANEL
SAYS hOFFv 7HEN A NORMALLY CLOSED
SWITCH IS OPERATED IT OPENS EVEN IF
THE CONTROL PANEL SAYS hONv
DPST
! $OUBLE 0OLE 3INGLE 4HROW SWITCH
IS NOTHING MORE THAN TWO 3034
SWITCHES CONSTRUCTED SO THAT THEY ARE
BOTH OPERATED SIMULTANEOUSLY BY
THE SAME ACTUATOR HANDLE BUTTON
OR WHATEVER %LECTRICALLY THE TWO
SWITCHES HAVE NOTHING WHATSOEVER TO
DO WITH EACH OTHER 4HEY JUST SHARE
THE SAME HANDLE !NY NUMBER OF
SWITCHES CAN BE GANGED TOGETHER IN
THIS FASHION &OR EXAMPLE 034 DESIGNATES A THREE POLE SINGLE THROW SWITCH
SPDT
4HE 3INGLE 0OLE $OUBLE 4HROW SWITCH
ADDS A THIRD TERMINAL TO THE BASIC 3034
SWITCH 4HE hDOUBLE THROWv DESIGNATION
MEANS THAT ONE OF THE SWITCH TERMINALS
MAKES ALTERNATE CONTACT WITH THE OTHER
TWO ONE AT EACH OF THE TWO SWITCH POSITIONS 4HE COMMON hTHREE WAYv WALL
SWITCH USED WHEN TWO SWITCHES MUST
OPERATE THE SAME LIGHT FIXTURE IS 30$4
)N A VARIATION FOUND ON CONTROL SWITCHES
AN hOFFv POSITION MAY BE PROVIDED MIDWAY BETWEEN THE TWO hONv POSITIONS
DPDT
!S WITH THE $034 THIS IS SIMPLY
TWO 30$4 SWITCHES OPERATED BY THE
SAME HANDLE !NY NUMBER OF DOUBLE
POLE SWITCHES CAN BE GANGED TOGETHER
! 0$4 SWITCH IS THREE 30$4 SWITCHES
WITH A COMMON ACTUATOR
Cleaner Times | IWA s .OV s (N)P(N)T
!LTHOUGH NOT LISTED IN THE TABLE IT
SHOULD BE NOTED THAT ANY NUMBER OF
POLES AND POSITIONS CAN BE COMBINED
Pushbutton Switch
3INGLE./AND.#VERSIONSARESHOWN
.OTE HOW THE SYMBOL IS DRAWN TO RESEMBLE THE REAL THING !NY NUMBER OF ./ AND
.# POLES CAN BE OPERATED BY ONE BUTTON
Temperature Switch
4HIS IS SIMPLY A TEMPERATURE SENSITIVE OPERATING DEVICE LINKED TO A
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SWITCH !LTHOUGH 3034./ IS SHOWN
VARIATIONS SUCH AS 30$4 ARE COMMON
Flow Switch
! FLOW SENSING DEVICE LINKED TO A
SWITCH 6ARIOUS SWITCH COMBINATIONS
ARE AVAILABLE WITH 3034./ AND
30$4 MOST COMMON 4HE FLOW SENSING
DEVICE USUALLY CAN OPERATE WITH ONLY
ONE DIRECTION OF FLOW
Pressure Switch
! PRESSURE SENSING DEVICE LINKED TO
A SWITCH 3034./ AND 30$4 SWITCHES
ARE THE MOST COMMON (OWEVER VACUUM SENSING SWITCHES A FORM OF PRESSURE SWITCH USED ON PRESSURE WASHERS
USUALLY HAVE $034./ CONTACTS
Relay, DPDT
-OST RELAYS ARE ELECTROMECHANICAL
DEVICES USED TO CONTROL THE FLOW OF ELECTRICITY 7HEN VOLTAGE IS APPLIED TO A RELAYS
MAGNETIC COIL THE RESULTING MAGNETIC FIELD
CAUSES A SET OF SWITCH CONTACTS TO MOVE
TO A DIFFERENT POSITION 2ELAYS ARE BUILT
WITH VARIOUS NUMBERS OF SWITCH POLES
AVAILABLE BUT THE NUMBER OF POSITIONS IS
USUALLY LIMITED TO TWO CORRESPONDING TO
THE COIL BEING ENERGIZED OR DEENERGIZED
4HE $0$4 CONFIGURATION IS USED FOR
ILLUSTRATION IN Table 3 BECAUSE IT IS SEEN
ON SOME PRESSURE WASHERS .OTICE THAT
THIS IS JUST A $0$4 SWITCH OPERATED
BY A MAGNETIC COIL INSTEAD OF A HANDLE
2ELAYS ARE USED BECAUSE THEY ALLOW
ONE ELECTRICAL SIGNAL OFTEN A RELATIVELY
hWEAKv ONE TO CONTROL ONE OR MORE
OTHER ELECTRICAL SIGNALS
! FORM OF RELAY USED ON MANY PRESSURE WASHERS IS THE CONTACTOR ALSO
REFERRED TO AS A MAGNETIC MOTOR STARTER
4HIS IS JUST A HEAVYDUTY TYPE OF RELAY
THAT USES A SMALL CONTROL SIGNAL TO
SWITCH LARGE AMOUNTS OF POWER SUCH
AS THE FEED TO A PUMP MOTOR OR TO THE
HIGH POWER HEATERS IN AN ELECTRICALLY
HEATED MACHINE !NOTHER WRINKLE IS
THE TIME DELAY RELAY (ERE THE RELAY
OPERATES AS USUAL EXCEPT THAT WHEN AN
ENERGIZING VOLTAGE IS SENT TO THE TIME
DELAY RELAY IT WAITS FOR A SPECIFIED OR
ADJUSTABLE AMOUNT OF TIME BEFORE IT
OPERATES ITS CONTACTS 2ELAYS IN GENERAL CAN EMPLOY OTHER MEANS OF SWITCHING BESIDES THE MAGNETIC COIL BIMETAL
AND SOLID STATE ARE EXAMPLES BUT THE
MAGNETIC COIL TYPE IS MOST COMMON
Other Relay Symbols
)N ADDITION TO THE PRECEDING OTHER
SYMBOLS ARE IN COMMON USE TO REPRESENT THE RELAY IN ELECTRICAL DIAGRAMS
4HE PRECEDING WAY OF DEPICTING A RELAY
DRAWS IT MUCH LIKE IT IS ACTUALLY CONSTRUCTED !LTERNATIVELY THE COMPONENTS OF THE RELAY COIL AND CONTACTS
CAN BE SEPARATED AND SPREAD AROUND
THE DIAGRAM 4HAT MAY SOUND LIKE A
COMPLICATION BUT IN FACT IT OFTEN MAKES
DIAGRAMS EASIER TO UNDERSTAND
)N ORDER TO KEEP STRAIGHT WHAT BELONGS
TO WHAT LETTERS NUMBERS AND SYMBOLS
ARE USED TO IDENTIFY COILS AND CONTACTS
4HE DESIGNATION USED FOR RELAYS IN DIAGRAMS IS EITHER h+v OR h#2v .UMBERS
IDENTIFY EACH RELAY + + + OR #2
#2 #2 ETC 7E CANT USE h2v FOR
RELAY BECAUSE THATS ALREADY USED TO
DESIGNATE A RESISTOR 4HE DESIGNATION
FOR A GIVEN RELAY SUCH AS #2 IS PLACED
NEXT TO ITS COIL AND ALL OF ITS CONTACTS
WHEREVER THEY APPEAR ON A DIAGRAM
Relay, SPDT (In Ladder Diagram)
!S AN ILLUSTRATIVE EXAMPLE THE 30$4
RELAY #2 IS SHOWN IN A DIAGRAM HAVING
A hLADDERv FORMAT 4HE OPERATION IS AS
FOLLOWS 7HEN SWITCH 3 IS OPEN THE
RED LAMP IS LIT 7HEN 3WITCH 3 IS
CLOSED THE GREEN LAMP IS LIT
Overload Relay, Magnetic
4HIS RELAY FUNCTIONS MUCH LIKE A CIRCUIT
BREAKER BUT WITH hREMOTE CONTROLv CAPABILITY BECAUSE ITS A RELAY )TS COIL IS
DESIGNED SO THAT A SPECIFIED AMOUNT OF
CURRENT THE hTRIPv CURRENT MUST FLOW
THROUGH IT FOR A SPECIFIED TIME BEFORE THE
CONTACTS OPERATE 4HE COIL IS WIRED IN
SERIES WITH THE LOAD TO BE PROTECTED 4HE
.# CONTACT IS USUALLY WIRED IN SERIES WITH
THE COIL OF A CONTACTOR FEEDING A LOAD
/PERATION OF THE OVERLOAD RELAY CAUSES
THE CONTACTOR TO BE DEENERGIZED DIS
CONNECTING POWER FROM THE LOAD
Overload Relay, Thermal
4HE THERMAL OVERLOAD RELAY PERFORMS
THE SAME FUNCTIONS AS THE MAGNETIC
OVERLOAD RELAY 4HE ONLY DIFFERENCE IS
THAT INSTEAD OF A MAGNETIC COIL THE
THERMAL OVERLOAD FEEDS THE CURRENT TO
BE SENSED THROUGH A HEATER WHICH IN
TURN OPERATES A BIMETAL SWITCH IF THE
CURRENT IS EXCESSIVE
Conclusion
! LOT OF THE QUANTITIES AND DEVICES
INCLUDED IN THIS CHAPTER WERE DISCUSSED IN EARLIER CHAPTERS BUT SOME
ARE NEW 4HE PURPOSE HERE IS TO GATHER
THEM ALL TOGETHER IN ONE PLACE FOR REFERENCE 9OU WILL BECOME MORE COMFORTABLE WITH THESE THINGS WHEN YOU
ENCOUNTER THEM REGULARLY IN ELECTRICAL
DIAGRAMS $O NOT BE DISMAYED IF YOU
RUN INTO VARIATIONS OF THESE REPRESENTATIONS JUST AS WITH A LANGUAGE THERE
CAN BE DIALECTS OR EVEN SLANG CT
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