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STUDY COURSEfor Home Appliances

UNDERSTANDING DRYER:

HEATER ELEMENT/GAS BURNER

COMPONENTS and

CHECKING PROCEDURES

Module 2LIT 787849 Rev. C

DRYER

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All rights reserved. No port ion of this book ma y be reprodu ced in a ny form

w ithou t w ritten p erm ission from WHIRLPOOL CORPORATION.

1989, 1993, 1996, 2001 WHIRLPOOL CORP ORATION

WHIRLP OOL CORPORATION does n ot as su me a ny re spo nsi bilityor any l iabil i ty in conn ection w ith the use of this manual .

The tradem arks WHIRLPOOL , , , an d FSP are registe red

trademarks of Whirlpool Corporation.

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INTRODUCTION

The ma terial present ed in this module is int ended to provide you with a n u nderst an ding of the

fundam enta ls of gas a nd electric dryer ser vicing.

Major a ppliances have become more sophisticated, tak ing th em out of the screwdriver an d pliers

category. Their electrical circuits include several different types of automatic controls, switches,

hea ter s, valves, etc.. Semicond uctors, solid-stat e contr ols, and other component s usu ally associat ed

with r adio and t elevision electr onic circuits ar e being engineered into aut omatic washers, dr yers,

dishwashers and refrigerators.

The appliance technician is emerging into a professional status of his own. He must prepare

himself now to be able to perform his dut ies today as well as to reta in his pr ofessiona lism in th e

future.

No longer is on-the-job tr ain ing sufficient to prepa re t echnicians for t he complicated pr ocedur es

required for t odays sophisticated applian ces. This tr aining can best be obtained th rough organized

classroom study and application. However, much of the knowledge necessary to service todays

appliances can be obtained thr ough study cour ses. Completion of th is an d other cour ses will provide

you with sufficient understanding of appliances and their operation to enable you to do minor

service. It will also serve as a valu able stepping stone t o more a dvanced stu dy and on-th e-job tra ining

to impr ove your s ervicing sk ills.

Informa tion cont ained in th is module is used on WHIRLP OOL appliances.

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2

TABLE of CONTENTS

PAGE

CHAP TER 1 - E LECTR ICAL COMP ONE NTS ................................................................... 3

Th erm ost at s ....................................................................................................................... 4

Adju st ab le ....................................................................................................................... 4

Fi xed ................................................................................................................................. 5

Operating Thermostats ................................................................................................... 6

Hi gh -Lim it (Safe ty ) Th e rm os ta ts .................................................................................. 7

Th erm al F use ..................................................................................................................... 8Buzz e r ................................................................................................................................. 9

P u sh -To-Sta rt Sw itch (Re la y) ....................................................................................... 10

Do or S w it ch ...................................................................................................................... 12

Tw o-Term in al ................................................................................................................ 12

Th re e -Term in al ............................................................................................................. 12

Fi ve -Term in al ................................................................................................................ 13

Te m pera tu re Sw it ch ....................................................................................................... 14

Dr iv e Moto rs ..................................................................................................................... 16

Ce n tr ifugal Sw it ch .......................................................................................................... 19

Tim e rs ............................................................................................................................... 20

On e an d Tw o Cyc le ..................................................................................................... 20Th re e an d Four Cycle .................................................................................................. 21

Tim e r Mot or ..................................................................................................................... 23

P u ls er Tim e r .................................................................................................................... 24

Bias Heater ...................................................................................................................... 26

Th erm al Cut -Off .............................................................................................................. 27

TEST .............................................................................................. See Test Book LIT787852

*NOTE: We recomm end tak ing the TEST for MODULE 2 , r ight a f ter stud ying it .

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CHAPTER 1

HEATER ELEMEN TIn the electric dryer an electric heating element

substitutes for t he heat of the sun.

When hea t is applied to the su rroun ding air, it driesthe a ir and m akes it rea ct like a sponge. The hot air

hea t s the c lo th ing , and causes mois ture in the

clothing t o vaporize and at the same t ime the dr yness

of the heated air allows it to absorb the moisture

released by the cloth ing and discha rge it out of th e

exhaust vent. The more heat that is applied, the

faster the evaporat ion and the faster the drying

action. However, too much heat can damage the

clothing, so the h eat mu st be controlled.

Lets look a t t he h eat source of th e electr ic dryer.

The wattage output determines the a mount of heatbeing genera ted. One wat t equa ls 3.41 Btu (British

ther ma l units), an d so a 4400-watt element will put

out about 15,004 Btu of heat . (4400 watt s x 3.41 Btu

= 15,004 Btu.)

The hea t element and heat er box is shown below. The

e lement s l ides up in to the hea te r box wi th an

int erferen ce fit for qu iet operat ion. It is h eld in place

by one screw. When r eplacing th e element, be su re

the h eat sh ield an d inlet man ifold are in place.

Dryer h eating element s ar e ma de of coiled nichrome

r es i s t ance wi r e m oun t ed i n a f r am e . Ce r am i c

insulators separate the f rame from the current-

car ry ing res i s tance wi re . Checking across the

t e r m i n a l s o f t h e s e e l e m e n t s s h o u l d p r o d u c e

resistan ce readings of less tha n 50 ohms. Any time

an element does not indicate resistance, it is open

and should be considered defective.

In th e mid 1970s, th e expanded meta l element (Flex-

A-Therm) was used for a short time. This element

consists of expanded metal wound around ceramic

insulators as shown below. The element mounts to

the current heater box with three mounting screws.

Because of less rad ian t h eat given off by the element ,

the h eater box high-limit therm ostat was chan ged to

a 225F thermostat . Previous product ion used a

290F thermostat.

The Flex-A-Therm element is very efficient. For

example: A 5200-watt Flex-A-Therm element gives

the same heat ing effect as a 5600-watt coil element .

Checking across the termina ls of this element should

also produce a r eading of less tha n 50 ohms.

HEAT SELECTIONSIN GLE LEVEL

Most electr ic dryers are designed to permit the

selection of heat levels according t o the type of fabr ic

an d th e size of th e load bein g dried. The sin gle-level

element u sed in conjunction with t wo or t hr ee fixed

t e m p e r a t u r e t h e r m o s t a t s o f d i f f e r e n t c u t - o u t

temper atu res, will allow th e user to have a choice of

several tempera tu re selections. With t his system, all

of the electrical circuitry to the fixed temperature

ther mostats is contr olled thr ough t he timer conta cts.

3

INLET MANIFOLD

HEATER BOX

HIGH-LIMITTHERMOSTAT

TERMINALBLOCK

HEATSHIELD

HEATINGCOILS

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Another temperature control system use with the

s i n g l e - l e v e l h e a t e l e m e n t u s e s a n a d j u s t a b l e

thermostat and a t emperatur e selector switch. The

temperature selector switch controls the electrical

path to the operating therm ostat s. The timer contr ols

th e electrical pat h to the temp erat ur e selector switch,

th e motor, an d other electrical components.

The single-level heat elements are rated at 4400

watts, 5200 watts or 5600 watts, determined by the

dryer model specifications and features. Always use

th e correct element par t nu mber as called out in t he

par ts list for ea ch dr yer model.

The temperature control of dryers having a single-

level heat element controlled by the action of the

timer a nd th e operat ing therm ostats, will be reviewed

first becau se th e electr ical circuitr y is simple and easy

to describe.

Firs t , you should know that centr i fugal switch

cont acts 1M to 2M are in t he hea ter circuit as sh ownbelow. Therefore, th e motor m ust be ru nn ing before

th e heat er can be energized, because the centrifugal

switch cont acts ar e in th e motor centr ifugal switch.

Notice also, that the operating thermostat an d th ehigh-limit thermostat are in the electrical circuit

which controls the hea ting element.

If you refer to the timer schedule below, which

accompanies th is wiring diagram, you will see th at

several drying options are available. The user has

the choice of timed, perma nent press, regular, or air

cycles.

1. TIMED CYCLE is a 75-minu te cycle which ha s all

three of the timer switches closed for the first 70

minutes, at which time the contacts Y to R which

control the heater circuit open, while contacts Y to

BG an d BG to TM rema in closed for a n a dditiona l 5

minutes, allowing the motor and timer to run for a

cool-down peroid. During t he t ime when th e hea ter

i s on , the e lec t r i ca l c i rcu i t passes through the

operating therm ostat and the high-limit t hermostat.

The operating t herm ostat will control the on an d off

cycles of th e heat ing element a nd t he tem perat ur e of

the a ir circulating thr ough the dryer, as it senses th e

air temperatu re near th e dryer exhaust outlet .

Please note tha t th e user of the dr yer does not have

to use the full 75-minute cycle. The dial may be set

to a shorter increment of t ime, for example 30

minut es. The last 5 minu tes of th is timed schedule is

alwa ys an air-only cycle.

2. PERMANEN T PRE SS CYCLE is a 30-minut e cycle

during which the heater contacts Y to R are closed

for t he first 20 min ut es. Conta ct Y to BG is closed for

the en tire 30 minu tes an d cont act BG to TM is closed

for slightly longer th an 10 minut es at the en d of the

cycle, so th at ther e will be a circuit to the timer when

th e Y to R cont act opens.

3. REGULAR CYCLE is a cycle very similar to the

permm an ent p ress cycle, except t ha t it p rovides only

a 5-minute cool-down peroid after contact Y to R

opens.

4. AIR CYCLE is a 19-minut e cycle in wh ich only Y

to BG an d BG t o TM conta cts ar e closed. The air cycleprovides an air only option so that th e user can fluff

pillows, etc.

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The diagram below is showing the use of a simple

timer with two contacts. The h eat selection is ma de

wi t h a t em pe r a t u r e - s e l ec t o r s wi t ch . The us e r

man ua lly sets th e switch for t he cont rol of the hea ter

element t hrough the high tempera tur e thermostat ,

the low temperature thermostat, or for air only.

The timer motor and the dr ive motor ar e cont rolled

thr ough timer conta cts Y to BG. Timer cont acts Y to

R route t he electrical cur rent to th e selector switch.

Depending on th e setting you selected (in th is case

the LOW temp erat ure wa s selected). Cont acts AH t o

AH2 close the switch, then current can tr avel to th e

operat ing th erm ostat LT1 to LT3. The air position

directs t he curr ent t o a dead term inal which is not

conn ected t o any electr ical component an d t he dr ive

motor and timer operat e thr ough termina ls Y to BG.

TWO-LEVEL HEATING ELEMENTS

There a re two bas ic des igns of two- leve l hea t

elements. Ea rlier models ha d two element s wired in

parallel; later models have two elements wired in

series. A selector s witch cont rols one of th e elemen ts

and allows the user to select between two drying

temperatures.

Paral lel Method

When t he selector switch is open, only one heat ing

element is en ergized. This occurs wh en gent le speed

is selected. This produces 4600 watts of heat. With

the switch closed on super speed, both heating

elements are energized and produce 5600 watts of

heat as sh own below.

Series Method

The series meth od produces 4600 wat ts of heat when

the two elements are energized in series, and 5600

watts of heat when the selector switch is closed,

allowing one element to be energized while the other

element is bypassed as shown below.

Selecting a high-temperature heat selection closes

the switch contacts, bridging the second element so

that only one element is energized. The current

passes through the lower resistance of only one

element and produces 5600 watts for high heat. In

effect, the selector switch establishes a line of least

resistan ce, bypassing the second element .

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THREE -COIL ELEMEN TS

Some dryers have a heating element composed of

th ree heat er coils. This permits th e dryer to operat e

on a m odulating type of heat , where one heat element

does not cycle off during any heat cycle, the other

two heat element s ar e ther mostatically controlled and

do cycle off.

A three-position air-heat switch on the console

permits three settings NORMAL, DELICATE, and

AIR. The illust ra tion sh ows th e switch a nd element

circuits.

When t he selector switch is set on AIR, the AH7 to

AH8 switch is open. No heat is produced. The dru m

rotat es and th e blower circulates room temper atu re

air.

Choosing the NORMAL air-heat position closes air-

heat switches AH7 to AH8, and AH3 to AH9. This

provides a circuit t hr ough the 1500-watt, 1000-watt ,

an d 3100-watt sections of the heat ing element . Heat

input to the dryer will be 5600 watts. When the

exhaust stat is satisfied, switch contacts EX to EX

open , r em ov i ng t he 1000- wa t t and 3100- wa t telements from the circuit. The circuit to the 1500-

watt element section is always completed dur ing the

entire heat-on phase of the drying cycle. It is not

thermostatically controlled.

Choosing the DELICATE position closes switch

cont acts AH7 to AH8 an d opens s witch contact AH3

to AH9. Th is action removes the 1000-watt element

section from the circuit, an d th e dryer t hen fun ctions

on the 1500-wat t a nd 3100-watt sections for a total

heat input of 4600 watts. When th e exhau st sta t is

satisfied, it will cycle the 3100-watt section of the

elemen t. The 1500-wat t elemen t does not cycle off.

NOTE: You will not see many two- or three-coil

heater elements , s ince they were phased out of

produ ction in t he ea rly 1970s.

CHECKING PROCEDUR E

Obtain an ohmmeter from your local store. We will

be doing RESISTANCE checks. This is the safest wa y

becau se th e dryer is unp lugged from th e power source

and avoids the poss ib i l i ty of you rece iv ing an

electr ical shock.

NOTE: If the heat element ha s shorted out (blown

f u s e s ) , i t i s i m p o r t a n t t h a t t h e t i m e r a n d a l l

thermostats be checked for proper operation. Also

check th e drive motor sta rt s witch, 1M and 2M sh ould

be open. These components may h ave been dama ged

when the h eat element shorted.

S t e p 1 Remove one wire at a time, carefully label-

ing each wire according to the term inal ma rking on

the h eat element. This procedure should assure th at

the right wire is reconnected to the right terminal

after checking or r eplacement .

S t e p 2 Set th e ohm meter scale to the lowest ohmssetting and ZERO the meter.

S t e p 3 Touch a nd hold one ohmm eter probe to one

of th e termina ls.

S t e p 4 Touch t he other ohmm eter pr obe to the other

terminals.

S t e p 5 The ohmmeter should show a reading

between 5-50 ohms on the ohms scale. If you do not

get t his reading, the heat element is bad an d needsreplacing.

6

HEATERBOX

HIGH LIMITTHERMOSTAT

HEATELEMENT

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S t e p 6 Touch a nd h old one ohmmeter probe to the

middle termin al (H2).

S t e p 7 Touch t he other ohm meter probe to the out-

side term inal ha ving two wires (H1).



get t his reading, the h eat element is bad and n eeds

replacing.

S t e p 9 Touch and hold one ohmmeter probe to one

of the outside term inals (H1).

Step 10 Touch the other ohmmeter probe to the

other outside ter mina l (H3).

Ste p 11 The ohmmeter should show a reading


get t his reading, the h eat element is bad and n eedreplacing.

NOTE: This heat element should not be shorted to

ground. Make sur e the h eat element is retained by

the insu lators an d does not contact an ything else.

Step 12 Touch a nd h old one of th e ohmmet er pr obes

to any one of th e thr ee termina ls.

Step 13 Touch the other ohmmeter probe to any

bare m etal (heater box) on the dr yer.

Step 14 The ohmmet er sh ould show an open circuit.

If not, the hea t element is bad an d needs replacing.

Step 15 Check the other terminals as in steps 12,

13 & 14.

Step 16 Reconnect the heat element wires to the

proper termina ls as previously ma rked.

7

HEATERBOX

HEATELEMENT

HEATERBOX

HIGH LIMITTHERMOSTAT

HEATELEMENT

HEAT ELEMENT

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CHAP TER 2

GAS BU RNER

SEQUENCE OF BURNE R OPE RATION

The instant voltage is applied to the gas burner, amomentary circuit is established from 1V through

th e No. 1 coil, the latching switch, the r adian t sen sor

switch a nd ba ck to 3V as s hown below.

Magn etism developed by th e No. 1 coil will ra ise th e

valve plunger and cause the latching switch to

transfer to the other side. No gas will flow at this

instant .

Another circuit is established th rough th e ignitor, th e

sensor switch an d back t o termina l 3V.

The No. 2 coil is not energized because circuitry is

shu nted th rough the sensor switch, which is the pathof least resistan ce.

The latching switch is now shown transferred. The

switch is a make-before-break design. Circuitry is

now thr ough th e No. 1 coil, the lat ching switch, a nd

back to 3V. The lat ching switch will mainta in th is

latched position as long as the gas burner remains

ener gized as shown below.

Volta ge contin ues t o be ap plied to the ignitor u nt il it

heat s to 2200F. The r adian t sen sor switch cont acts

wil l sense this radiant heat , causing the sensorcont acts t o open a s sh own below.

With t he sensor switch n ow open, th e only path for

t he cu r r en t t o t ake i s t h r ough t he No . 2 co i l .

Energizing the No. 2 coil opens the No. 2 valve,

allowing gas to flow through the burner, which is

ignited by t he int ense 2200F heat of th e ignitor. The

gas flame will continue to hold the radiant sensor

open.

When th e gas burn er circuitry is briefly interr upt ed

by unplugging the ma chine, tur ning the timer OF F,

or open ing th e loadin g door, th e No. 1 an d No. 2 valves

will both dr op out , shu tt ing off the flow of gas th rough

the valve assembly. If circuitry is quickly restored,

only th e No. 2 valve will be energized an d th e rad ian t

sensor cont act will remain open. Because t he ignitor

is now in ser ies with t he N o. 2 coil, it will not opera te

as shown below.

Circuitr y does not exist at t his time t o energize the

No. 1 coil, un til the radian t sen sor switch cont act cools

sufficient ly for it t o close. This a ction will per mit th e

burn er to recycle and again ignite main burn er gas.

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THE SPLIT-COIL SILICON

CARBIDE BU RNER

Many silicon carbide gas burners utilize a split coil

design. Valve No. 1 has two coils to actuate i ts

plunger, thus giving the split-coil burner its name.

Neith er t he h old coil nor t he a ssist coil alone is str ong

enough to open the valve. The combined magneticaction of both coils is needed . Once th e valve is open,

however, the h old coil can hold it open by itself. The

circuits of both coils will serve as a quick shut-off

function.

When voltage is applied to 1V and 3V, a circuit is

completed from 1V to the ignitor, and through the

sens or to 3V as sh own below.

Simultaneously, the hold coil is energized, and theassist coil is energized through the radiant sensor.

This action mea ns th at t he ignitor is heating an d No.

1 valve is open. No gas flows, however, until No. 2

valve also opens. Note th e resistor in series with t he

assist coil. This is a ba lancing resistor which is u sed

only on one st yle of valve. It will not be pres ent on all

split-coil valves.

The ignitor has reached a temperature sufficient to

open t he ra diant sensor cont acts as s hown below. This

action causes valve No. 2 to be energized through

th e ignitor. Gas flows th rough t he valve an d is ignited

instan tly by th e still hot ignitor. Curr ent t hrough th eassist coil on valve No. 1 is very low at this point.

Magnetism created by the hold coil is sufficient to

hold th e No. 1 valve open.

If voltage to the burn er is momenta rily interr upt ed

an d th en rest ored, circuitr y as illust rat ed below will

exist.

Valve No. 2 is open bu t magn etism pr oduced by th e

hold coil is not su fficient to open t he N o. 1 valve. When

the sensor cools a nd the sensor conta cts reclose, re-

ignition will occur.

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GLOW-SIL IGNITORS

The glow-sil (also kn own a s t he posi-lite) ignition

burner uses a glowing silicon ignitor to ignite the

m a i n bu r ne r ga s . The i gn i t o r i s f o r m ed f r om

recrysta llized silicon car bide and is very brit tle. Care

mu st be used when servicing this burner to prevent

dam age to th e ignitor a s shown below.

Although you mu st be careful, th e glow-sil ihn itor is

easily rem oved a nd repla ced. Looking below, you can

see tha t t he ignitor is held in place by th e clamping

action of th e moun ting clips. You mu st be very carefulwhenever you ar e insta lling these clips. Other wise,

you will damage the ignitor.

In t his illust ra tion, you can also identify the ceramic

insulator, the mica insulator an d th e mounting screw.

Another glow-sil ignitor being used on gas dryers

is shown below.

This ignitor has the terminal ends molded into a

ceramic base and a terminal block for connection to

the burner wi r ing harness . The revi sed igni tor

mounts to the gas burner as shown be low. I t s

performa nce char acteristics ar e no different tha n t he

other glow-sil ignitor.

These glow-si l igni tors must be handled very

carefully. If you drop the ignitor or give it a severe

jolt, t he fra gile silicon carbide crysta ls will probably

fracture.

CHECKING PROCEDUR E

Obtain an ohmmeter from your local store. We will

be doing RESISTANCE checks. This is the safest wa y

becau se th e dryer is unp lugged from th e power source


electr ical shock.

S t e p 1 Refer to the instr uctions th at came with your

ohmmeter to find the proper scale to measure 50-

400 ohms . Set th e ohms scale an d ZERO the m eter.


of the sides, just un der t he fin.

10

LOCATING FIN

GLOW-SIL IGNITOR

ELECTRICALCONNECTOR

CERAMICBASE

CERAMICINSULATOR MICA INSULATOR

VENTURI

GLOW-SILIGNITOR

MOUNTINGCLIPS

MOUNTINGSCREW

MOUNTINGSCREW

ELECTRICALCONNECTOR

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side, just un der th e fin.


between 50-400 ohms on the ohms scale. If you do

not get this reading, the ignitor is bad an d needs re-

placing.

OR

S t e p 5 Disconnect the har ness plug from the bur ner

to th e plug on th e ignitor.

S t e p 6 Touch and hold one ohmmeter probe to one

of the bullet-like termina ls in th e ignitor plug.


bullet-like termina l in th e ignitor plug.


between 50-400 ohms on the ohms scale. If you do

not get this reading, the ignitor is bad an d needs re-

placing.

S t e p 9 Reconn ect the ha rn ess plug tha t comes from

the ignitor to the plug on th e burn er.

11

IGNITORS

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RADIANT SEN SOR

The radiant heat sensor is mounted on the side of

th e burn er funn el assembly. A cut -out in th e funnel

allows radiant heat from the ignitor and the gas flame

to reach t he sen sor as shown below.

The ignitor will normally reach a temperature of

2200F in about 15 to 30 seconds after line volta ge is

applied. The ra diant sensor opens th e circuit to th e

ignitor when this temperature is reached. The gas

valve is energized simultaneously, and when gas

cont acts t he h ot ignitor, ignition ta kes place.

CHECKING PROCEDUR E

Obtain an ohmmeter from your local store. We willbe doing RESI STANCE checks. This is th e safest way

becau se the dr yer is unplugged from th e power source


electr ical shock.

S t e p 1 Remove one wire at a time, carefully label-

ing each wire according to the term inal ma rking on

the sensor. This procedure should assure that the

right wire is reconn ected to the r ight term inal after

checking or r eplacement .

S t e p 2 Set th e ohmm eter scale to th e lowest ohms

setting and ZERO the meter.


of the term inals on the sen sor.


term inal on the sensor.

S t e p 5 The ohmmeter should show ZERO resis-

tan ce (continu ity). If not, th e sensor is bad an d needs

replacing.

S t e p 6 If this check sh owed ZERO resista nce, then

reconnect the wires to the proper terminals on the

sensor.

S t e p 7 Remove th e toe panel.

S t e p 8 Set the timer control and sta rt the dryer.

S t e p 9 Wat ch th e ignitor for a couple of min ut es. If

this sta ys red hot and t he gas does not come out an d

ignite, th e sensor is bad an d needs replacing.

12

RADIANT SENSOR

RADIANTSENSOR

BURNERFUNNEL

MOUNTINGBRACKET

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These two (2) par ts h ave holes thr ough them to vent

the area above the diaphragm to the atmosphere.

This is done so that when t he gas pressu re below the

diaphragm increases or decreases, i t a l lows the

diaphragm to move up or down, closing or opening

th e va lve below.

The Spring is nextit applies pressure to the top

of th e diaphra gm.

The Diaphragm Assemblyis made of a flexible

material and h as a valve atta ched to it .

As gas en ters t hr ough the va lve opening, it applies

pressure to the underside of the diaphragm, which

in turn pulls the valve up, reducing the size of the

valve opening. The higher th e inlet pressur e, the more

th e valve opening size is redu ced. This will effectively

control th e pressure of gas tha t ent ers th e burner. In

those rare occasions where regulator adjustment is

necessary, remove th e leak limiter cap screw and t ur n

the adjustment screw to change the gas pressureregulated by t he r egulator as shown below.

GAS FLOW

The Dryer Gas Pressu re Regulator

The sole function of a gas pressure regulator is to

maintain, wi thin close l imits , a constant out let

(burner, or manifold) pressure, regardless of inlet

pressur e cha nges. The regulat or must consequen tlysense al l changes in inlet pressure and be able

au tomatically to adjust t he gas flow as r equired. The

s e n s i n g d e v i c e i s a d i a p h r a g m a n d s p r i n g

arrangement attached to a valve ball which is used

to restrict gas flow th rough th e ball seat.

All Whirlpool-built gas dryers are shipped with gas

burn er assemblies that h ave a gas pressure regulator

built into the main valve body. The sole function of

the r egulator is to reduce and m ainta in within close

limits a consta nt gas pr essure in the bur ner a ssembly

of three (3) inches of water column. In order for the

regulator t o fun ction properly, gas su pply pressur eto the dr yer mu st be a bove 3 inches of water colum n.

The regulator can not increase gas pressur e. The part s

involved in cont rolling the gas pressur e are, sta rt ing

at t he top:

The Leak Limiter Screw in case the diaphra gm

develops a leak.

The Adjustment Screw for adjusting the spring

pressur e as shown below.

13

VALVE

DIAPHRAGM

SPRING

ADJUSTMENT SCREW

VENT CAPLEAK LIMITER

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Gas Flow Through the Valves

After passing through the regulator, the next thing

the gas encounters is the two (2) electrical solenoid

con t r o l va l ve s . The m os t i m por t an t t h i ngs t o

remember about the valves are:

1. Each burn er assembly always has two (2) valves.

2. Both of th e valves are spring loaded closed and

the solenoids mu st be en ergized to open t hem.

3. Both valves must be open for th e burner t o work

as shown below.

These gas flow diagram s can h elp you visua lize what

is happen ing when the various circuits a re energized.

After passing through the valves, the gas comes to

the orifice. The main function of the orifice is tocontrol the gas output from the valve body at a set

level into the burner and shutter assembly. Since

burners are designed to perform best a t t heir rat ed

input s, th e orifice is very importa nt as shown below.

The orifice is a precision-made pa rt a nd sh ould never

be redr illed in t he field t o alter ga s flow. Ha nd drilling

could leave a burr which would change the flow

pattern of the gas a nd create tu rbulence inside the

burner tube. This problem usually causes slower

movement t hrough th e tube, reducing the am ount of

primar y air being sucked in.

As the gas leaves the orifice, it draws primary air

thr ough the pr imar y air opening. Recent production

burner s do not require any air adjustm ent when u sed

with natural or LP gas, and therefore do not need

the a ir shu tt er assem bly pictured below.

In operation, the str eam of gas issuing from t he ma in

burn er orifice is aimed into the t hr oat of th e burn er.

The speed of the gas s t ream se t s up a vacuum

(suction), drawing a ir into t his lower-pressure a rea

through the primary air port. As the air and gas

mixture passes th rough the ventu ri, or m ixing barrel,

the mixing of th e air a nd ga s is completed. This airan d gas m ixture t hen flows out by th e flame scoop. It

is at th is point wher e secondary air is mixed in a nd

combu stion ta kes pla ce. The flame scoop is designed

to spread the f l ame and cont ro l the amount of

secondary air being mixed with the gas as shown

below.

14

SOLENOIDS

SPRING

ORIFICE

SHUTTER

CLAMPSCREW

PRIMARY AIR

SECONDARY AIR

VENTURI THROAT

FLAME SCOOPGAS JET

PRIMARY AIR

GAS

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A bent bur ner-mounting bracket can cause the burn er

to be out of line in its relationship with the valve

body an d orifice. Should th e ventu ri be m isaligned,

as sh own below, th e flow of gas will str ike th e bar rel

o f t he ven t u r i t h r oa t , r educ i ng i t s s peed and

consequently reducing the amount of primary air

sucked th rough t he port.

Therefore, precise alignment of the orifice to the

ventur i is of the ut most importan ce.

The t ell tale sign of too little pr ima ry air is a yellowf l am e . Th i s t ype o f f l am e i s m uch l ower i n

tempera ture than a normal f l ame and one tha t

usually gives off carbon or soot. The yellowness is

due t o the incomplete bur ning of car bon conta ined in

t h e g a s . I t s h o u l d b e n o t e d t h a t d u s t i n t h e

atm osphere will cau se the bur ner flame to take on a

reddish cast or to show momenta ry red flecks as dust

o r l i n t i s d r awn t h r ough t he a i r s hu t t e r . Th i s

condition can be disregarded since it is a normal

occurrence.

You p robably wont experien ce a cond ition of too mu ch

primary air, since it is not likely to occur except on

manu factured gas.

Too mu ch primar y air will result in wh at is called a

ha rd or blowing flame. On e sign of this t ype of flam e

is an increase in t he n oise level of th e bur ner. Another

clue to excessive primary air is flashback, where

ignition sta rt s to migrate back into th e burner t ube.

A third clue is a fairly loud popping n oise when th e

main burn er shu ts off. In a ll cases you need only to

reduce the p rimar y air to corr ect t he pr oblem. Since

recent production bur ners a re produced with out a ir

shut ters , you wil l need to instal l an ai r shut ter

conversion kit. The conversion kit includes an air

shu tter as pictured below.

Make sure t o refer to the par ts list for this air shu tter

assembly when order ing the manufac tured gas

conversion kit or other parts of the revised burner

assembly.

Wi thout the convers ion k i t , the burner wi l l be

extremely noisy when operating on manufactured

(type 3) gas.

All gas dryers are shipped from the factory orificed,

and with th e regulator adjusted to burn n atur al gas.

Or i f i c e o r r egu l a t o r p r e s s u r e changes m ay be

necessary for operation on mixed or manufactured

gases. Consu lt th e local utility about t his.

Convert ing to LP Gas

Liquefied petroleum gas or L.P. is mainly propane

(2500 B.T.U. per cubic foot) or butane (3200 B.T.U.),

or a mixture of both . It is widely distr ibuted in ru ra l

areas which may be far beyond city gas lines. L.P.gas un der moderat e pressur e is converted to a liquid

an d consequently is easily ha ndled and t ran sported

in pressurized bottles or tanks. When released to

normal atmospheric pressure and temperatu re, the

pressur ized l iquid au tomat ica l ly re turns to i t s

gaseous form. L.P. gas is heavier than air and will

lay in the lowest spot it can find if released into a

room. As a result, technicians working th e L.P. gas

should ha ve special tr aining t o recognize the s afety

procedures which need to be taken. Conversions to

L.P. gas and s torage tank regulator adjustments

should be performed by trained (usually licensed)

LPG technician s.

The LPG fuels ar e always regulated at the bottle as

shown below, or a t a larger su pply tank , elimina ting

the n eed for regulation a t t he burn er un it .

As a r esult , the gas pressure regulator on th e burner

control is immobilized (held open) by installing a

special regulator plug. The conversion kit number

for converting the bur ner can be foun d on the bur ner

base or in th e part s list.

15

AIRSHUTTER

REDUCEDPRIMARY AIR

MISALIGNEDVENTURI

PRESSUREREGULATOR

TANK

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Remove th e leak limiting cap screw an d gasket from

the pr essure regulator a nd install the r egulator plug

and gasket furnished with the kit. The plug, shown

below, is designed with out a vent h ole and ha s a long

stem that protrudes down through the hole in the

adjustment screw and pushes against the diaphragm,

holding the valve in the open position. The plug cap

wil l a lways be color coded with a blue top foridentificat ion. The rea son the vent hole is not presen t

on the LP regulator plug is becau se the r egulator is

held in its full open position, a nd t her e is no need for

the regulator diaphragm to move up and down as

was described previously. Also by eliminating the

hole, a potentia l gas leak is elimina ted in t he event

tha t the regulator diaphragm ruptu res.

The other parts included in the conversion kit are

easily installed by following the directions included

in th e kit. Remove th e complete bur ner assembly from

the machine. Remove the orifice with a 3/8" box

wrench, an d reinst all the new orifice received in th e

kit .

On burners that have a pilot light, the pilot orifice

mu st also be changed.

Reinsta ll th e burn er an d apply the two (2) convers ion

decals furnished with the kit. One must be placed

over the burner data label on t he burner baseplate

and t he other is applied next to the data rating plate

in th e door well. These decals mu st be a pplied to meet

A . G . A . r e q u i r e m e n t s a n d t o w a r n a n y f u t u r e

technicians who might be servicing the product.Gener ally, hooku p mu st be m ade by a L.P. gas dea ler.

Convert ing From LPG to Other Gases

If a conversion is to be made from LPG back to

natural, mixed or manufactured gases, observe the

following procedures.

If the pr essure regulator was demobilized, reactivate

the pr essure regulat or by removing the LP r egulator

plug and by adding the parts shown below. Also,

inst all th e specified bur ner orifice an d pilot orifice if

a pilot is used.

Pr oviding local codes perm it, reconversion from LP G

to natu ra l, mixed, or manu factu red gas ma y be done

by non-licensed personnel.

16

REGULATOR

PLUG

GASKET

CAP

REMOVE FROMREGULATOR

ADD TOREGULATOR

GASKET

ADD TO REGULATOR

ADJUSTINGSCREW

SPRING

GASKET

LEAK LIMITINGDEVICE

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5. Reconverting back to natura l gas burners in the

field does not invalidate AGA approval, if done

according to instructions.

6. A decal, supplied with each conversion kit, mu st

be affixed next to the ra ting plate on th e dryer

door well. When the pressur e r egulator is im-

mobilized for an LPG conversion, place the ad-

ditiona l decal on t he bur ner ba seplate.

BTU Ratings

As we continue with our study of gas drying heat,

you will see the ter m BTU used m an y times.

The term BTU stan ds for British Thermal Unit an d

represent s a measu remen t of heat volume. One Btu

i s t h a t a m o u n t o f h e a t r e q u i r e d t o r a i s e t h e

tempera ture of one pound of water one degree

Fahrenheit . For example, the heat generated by a

burn ing wood match is a pproximat ely one BTU. TheBTU value of gas fuels is customarily given as BTU

per cubic foot of gas. Thus the BTU rating is the

amount of hea t (not the t empera ture) a burner

creat es while opera ting for one hour. Most gas dr yers

are designed for 20,000 to 37,000 Btu per h our inpu t.

The design and the size of a number of operating

components in the dryer are determined according

to the BTU r at ing of the dryer.

This is a n ecessary measure to ensure th at the volume

of air movement in th e dryer is coordinated with the

BTU input. Otherwise, overheat ing or un derhea tingwould certainly resu lt.

Overrating a burner beyond rating plate input, or

s e v e r e u n d e r r a t i n g , c a n r e s u l t i n s h o r t e n e d

componen t life, fault y ignition, poor combu stion a nd

lack of air adjust ment ran ge.

NOTE: For a rea s over 2000 feet elevat ion a bove sea

level, de-ra te from na meplat e ra ting 4% per 1000 feet

elevat ion. To make th e job easier, most ga s compa nies

ha ve cha rt s th at will give you t he orifice size required

at different elevat ions.

The Orifice

The orifice per form s t wo fun ctions:

1. It contr ols the amount of gas to be burn ed.

2. It directs the flow of gas being injected into

the burn er.

The amount of gas being supplied to the burner is

controlled by the size of the opening in the orifice.

The size of the orifice opening is determined by the

Btu r ating of the dr yer an d by the type of gas available

for fu el.

1. All gas dryers are manufactur ed with natur al gas

orifices.

2. All gas bur ners can be converted for use with dif-

ferent gases t hr ough orifice chan ge.

NOTE: Do not ream or enlarge any burner orifice.

These orifices ar e precision mad e in resp ect t o length ,

hole size, and modulator-needle position. Use only

the replacement orifice specified for conversion to

an other type of gas. Ea ch orifice ha s its ident ificat ion

nu mber st amp ed on it. You may h ave to remove the

orifice to rea d th e nu mber. The locat ion of the orifice

is shown below.

3. Special kits or orifices for converting bur ner s from

one gas to another a re ava ilable. To determine th e

corr ect kit for a specific dryer, refer t o the cur ren t

repair part s l ist a t your parts source.

4. Corr ect orifices should be determ ined and insta lled

before delivering new dryers.

17

ORIFICE

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Gas Fuels

There are four different types of gas fuels available

for use in domes t ic gas dryers . These four a re

sometimes designa ted by nu mber.

No. 1Natu ral gas.

No. 2Mixed gas.

No. 3Manufactur ed gas.

No. 4Liquefied petroleum gas.

No. 1Nat ura l gas is found underground, sometimes

with oil (petroleum). In its n at ur al sta te it is called

wet gas, sin ce it conta ins h eavy hydr ocar bons such

as propane, butane an d other su bstances.

Gas su ppliers will process th is wet gas, r emoving th e

heavier hydrocar bons an d leaving only metha ne an d

ethane. In some areas, natural gas wil l contain

significant a moun ts of hydr ogen su lfide and is called

sour gas. Sour gas has a corrosive action on brass

parts and consequently aluminum orifices must beused in these supply areas. Natu ral gas ma y conta in

between 900 an d 1200 BTU per cubic foot, but it will

usually contain between 1000 and 1100 BTU. This

would seem to indicate t hat th ere is a great var iation

in the BTU content of the gas at any one location,

but that is not true. Utilities are required by law to

hold the BTU content of the gas to very c lose

tolera nces. You will notice also in t he char t below,

th at th e specific gravity of nat ura l gas is .65 to .70.

The specific gravity of any gas is the comparison of

its weight to the weight of air which is a specific

gravity of 1. So you can see n ow th at na tu ra l gas islighter th an air.

No. 2When manufactured gas is combined with

nat ura l gas, it is called mixed gas. It ha s a Btu r ating

of between 700 and 900 per cubic foot. The specific

g r a v i t y i s u s u a l l y a b o u t . 5 0 . M i x e d g a s w a s

distributed extensively in t he Ea stern part of the U.S.

at one time, but it has been r eplaced by na tu ral gas

in m ost places.

No. 3Manufactured (artificial) gas is made from

coal and pet roleum with a heat value of 500 to 700

Btu per cubic foot. It s specific gra vity will be about

.38 to .40. Remember that a conversion kit which

includes orifices and a ir shut ter for th e burner mus t

be installed when using th is type of gas.

No. 4Liquified Petroleum Gas (LPG) is mainly

propan e (2500 Btu per cubic foot), buta ne (3200 Btu),

or a mixture of both . In north ern clima tes where t he

tempera tures regular ly drop be low 32 degrees

Fa hren heit, you can expect th at pr opane gas will be

used exclusively. Butane gas will not vaporize at

temper atu res below 32 degrees, an d th erefore it can

only be used in southern climates. The illustration

below shows th e great differen ce in t he boiling points

of the gases which we use in th e gas dryers.

As mentioned previously, all LPG containers havet h e i r o w n r e g u l a t o r s w h i c h s h o u l d b e s e t t o

app r ox i m a t e l y 11 i nches wa t e r co l um n ( WC)

pressure.

18

Gas Fuels

Natural

Mixed

Manufactured

Propane

Butane

BTU Value/Cu. Ft. Specific Gravity

.65 to .70

.50

.38 to .40

1.53

2.0

1075 (may vary from900 to 1200)

1075 (may vary from900 to 1200)

BUTANE

PROPANE

LP

NATURALMIXED

MANUFACTURED

FAHRENHEITDEGREES

ZERO

200

100

32

-44

-100

-200

-300

BOILING POINTS of GASES

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At the present time it is only necessary for you to

know that the regulator for LP gas installations is

located at th e ta nk, a s shown below.

Adjust ment s to the LP gas regulator should be made

by a qualified LP gas service technician.

LP gas is heavier tha n air. When a leak is present in

a system using LP gas, th is gas will lay low an d formpools or puddles and wil l not readi ly disperse,

resulting in a dangerous situation. The proper way

to check for leaks with LP gas, or a ny other ga s is to

use a bubble solution. The bubble solution can be a

mixture of liquid detergent m ixed with a litt le water,

or you can use the bubble solution which is sold for

childrens bubble-blowing pleasu re. Use a sm all brus h

to put the bubble solution around each joint on the

tubing or pipe in areas where it is normally under

pressur e. Bubbles will appear wh en th ere is a leak.

NOTE: Never ever use a flame t o test for a gas leak,

regardless of the type of gas.

19

PRESSUREREGULATOR

TANK

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NOTES

20

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