American Dryer Corp. ML-78III User manual

ML-78III
(Gas/DSI/Phase 7 with F.S.S.)
Installation Manual
For replacement parts, contact the reseller from which the dryer
was purchased or
AmericanDryerCorporation
88Currant Road
FallRiverMA02720-4781
Telephone:[phone] / Fax:[phone]
e-mail:[e-mail]
www.amdry.com
WARNING: Foryoursafetytheinformation in
thismanual mustbe followedto minimizethe
riskof fireor explosionor toprevent property
damage,personalinjuryor death.
— Donot storeoruse gasolineorother flammable
vapors and liquids in the vicinity of this or any
otherappliance.
— WHAT TO DO IFYOU SMELLGAS:
• Donottrytolight any appliance.
• Donottouch any electricalswitch;donot
useanyphoneinyourbuilding.
• Cleartheroom,building orareaofall
occupants.
• Immediatelycallyourgassupplierfroma
neighbor’sphone. Followthegas supplier’s
instructions.
• Ifyoucannotreach your gassupplier,call
thefiredepartment.
— Installationand servicemustbe performedbya
qualified installer, service agency or the gas
supplier.
AVERTISSEMENT: Assurez-vous de bien
suivrelesinstructionsdonnéesdanscettenotice
pourréduire auminimumle risqued’incendie
ou d’explosion ou pour éviter tout dommage
matériel,touteblessureoula mort.
— Ne pas entreposer ni utiliser d’essence ni
d’autres vapeurs ou liquides inflammables à
proximité de cet appareil ou de tout autre
appareil.
— QUEFAIRESIVOUSSENTEZUNEODEUR
DEGAZ:
• Nepastenter d’allumerd’appareils.
• Netouchez àaucun interrupteur. Ne pas
vousservirdes téléphonessetrouvantdans
lebâtiment.
• Évacuezlapièce,lebâtiment oulazone.
• Appelezimmédiatementvotrefournisseur
degazdepuisunvoisin. Suivezles
instructionsdufournisseur.
• Sivousnepouvezrejoindrelefournisseur
degaz,appelez leservicedesincendies.
— L’installationetl’entretiendoiventêtreassuréspar
uninstallateurouun serviced’entretienqualifié
ouparle fournisseur degaz.
102301JEV/mcronan ADC PartNo.113346

Retain This Manual In ASafe Place For Future Reference
American Dryer Corporation products embody advanced concepts in engineering, design, and safety. If this product is
properly maintained, it will provide many years of safe, efficient, and trouble free operation.
ONLY qualified technicians should service this equipment.
OBSERVE ALL SAFETY PRECAUTIONS displayed on the equipment or specified in the installation manual included with
the dryer.
The following “FOR YOUR SAFETY” caution must be posted near the dryer in a prominent location.
“IMPORTANTNOTETOPURCHASER”
Informationmustbeobtainedfromyourlocalgassupplierontheinstructions
tobefollowed iftheusersmells gas. These instructionsmustbepostedin a
prominentlocationnearthedryer.
FORYOUR SAFETY
Donot storeor usegasoline or
otherflammablevaporsand
liquidsinthevicinityofthisor
anyotherappliance.
POURVOTRESÉCURITÉ
Nepasentreposer niutiliserd’essence
nid’autresvapeursouliquides
inflammablesàproximitédecet
appareilou de toutautre appareil.
We have tried to make this manual as complete as possible and hope you will find it useful. ADC reserves the right to make
changes from time to time, without notice or obligation, in prices, specifications, colors, and material, and to change or
discontinue models. The illustrations included in this manual may not depict your particular dryer exactly.
Important
For your convenience, log the following information:
DATE OFPURCHASE________________________________ MODELNO. __________________________________________
RESELLER’SNAME ________________________________________________________________________________________
Serial Number(s) ________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
Replacement parts can be obtained from your reseller or the ADC factory. When ordering replacement parts from the factory,
you can FAX your order to ADC at [phone] or telephone your order directly to the ADC Parts Department at (508)
678-9000. Please specifythe dryer model numberand serialnumberin additionto thedescriptionand partnumber,so that
your order is processed accurately and promptly.
ML-78 Phase 7 (DSI)

IMPORTANT
YOUMUSTDISCONNECTANDLOCKOUTTHEELECTRICSUPPLYANDTHEGAS
SUPPLY BEFORE ANY COVERS OR GUARDS ARE REMOVED FROM THE
MACHINETOALLOWACCESSFORCLEANING,ADJUSTING,INSTALLATION,OR
TESTING OF ANY EQUIPMENT PER OSHA (Occupational Safety and Health
Administration)STANDARDS.
CHILDRENSHOULDNOTBEALLOWEDTOPLAYONORNEARTHEDRYER(S).
WARNING
CHILDRENSHOULDBESUPERVISEDIFNEARDRYERSINOPERATION.
DRYERSSHOULDNEVERBELEFTUNATTENDEDWHILEINOPERATION.
CAUTION
FORYOURSAFETY
DONOTDRYMOPHEADSINTHEDRYER.
DONOTUSEDRYERINTHEPRESENCE OFDRYCLEANINGFUMES.
WARNING
UNDER NO CIRCUMSTANCES should the dryer door switches, lint door switch, or
heat safety circuit ever be disabled.
“Caution: Label all wires prior to
disconnection when servicing controls. Wiring
errors can cause improper operation.”
«Attention: Au moment de l’entretien des
commandes,étiqueteztous les filsavantde
les débrancher. Des erreurs de câblage
peuvent entraîner un fonctionnement
inadéquatetdangereux.»

WARNING
The dryer must never be operated with any of the back guards, outer tops, or service
panelsremoved. PERSONALINJURYORFIRECOULDRESULT.
IMPORTANT
PLEASEOBSERVEALLSAFETYPRECAUTIONSdisplayedontheequipmentand/or
specified in the installation manual included with the dryer.
WARNING
DRYER MUST NEVERBEOPERATEDWITHOUTTHELINTFILTER/SCREENIN
PLACE,EVENIFANEXTERNALLINTCOLLECTIONSYSTEMISUSED.
Dryer mustnotbe installed or stored in an area where it will beexposed to water or weather.
The wiring diagram for the dryer is located in the front electrical control box area.
IMPORTANT
Dryer must be installed in a location/environment, which the ambient temperature
remains between 40° F (4.44° C) and 130° F (54.44° C).

SECTION I
IMPORTANT INFORMATION ............................................................................... 3
A. ReceivingandHandling ............................................................................................................... 3
B. SafetyPrecautions ...................................................................................................................... 4
SECTION II
SPECIFICATIONS/COMPONENT IDENTIFICATION.....................................6
A. Specifications ............................................................................................................................. 6
B. ComponentIdentification ............................................................................................................ 8
SECTION III
INSTALLATION PROCEDURES .........................................................................10
A. LocationRequirements ............................................................................................................. 10
B. Unpacking/SettingUp ............................................................................................................... 11
C. DryerEnclosureRequirements .................................................................................................. 12
D. FreshAirSupplyRequirements ................................................................................................. 13
E. ExhaustRequirements ............................................................................................................... 14
F. ElectricalInformation ................................................................................................................ 18
G. GasInformation ........................................................................................................................ 22
H. Preparationfor Operation/Start-Up........................................................................................... 26
I. PreoperationalTests ................................................................................................................. 27
J. PreoperationalInstructions ........................................................................................................ 29
K. ShutdownInstructions............................................................................................................... 29
SECTION IV
SERVICE/PARTS INFORMATION......................................................................30
A. Service ..................................................................................................................................... 30
B. Parts ........................................................................................................................................ 30
SECTION V
WARRANTY INFORMATION...............................................................................31
A. ReturningWarrantyCards......................................................................................................... 31
B. Warranty .................................................................................................................................. 31
C. ReturningWarrantyParts .......................................................................................................... 31
SECTION VI
ROUTINE MAINTENANCE..................................................................................33
A. Cleaning ................................................................................................................................... 33
B. Adjustments ............................................................................................................................. 34
C. Lubrication ............................................................................................................................... 34
Table of Contents

SECTION VII
REVERSING TIMER SPIN/DWELL ADJUSTMENTS.....................................35
SECTION VIII
DATA LABEL INFORMATION .............................................................................36
SECTION IX
PROCEDURE FOR FUNCTIONAL CHECK OF REPLACEMENT
COMPONENTS........................................................................................................38
SECTION X
MANUAL RESET HI-LIMIT INSTRUCTIONS..................................................40
A. Phase 7 .................................................................................................................................... 40
B. DualTimer................................................................................................................................40
SECTION XI
FIRE SUPPRESSION SYSTEM (F.S.S.) ..............................................................41

3
SECTIONI
IMPORTANTINFORMATION
A. RECEIVINGAND HANDLING
The dryer is shipped in a protective stretch wrap cover with protective cardboard corners and top cover (or
optional box) as a means of preventing damage in transit. Upon delivery, the dryer and/or packaging, and
wooden skid should be visually inspected for shipping damage. If any damage whatsoever is noticed, inspect
further before delivering carrier leaves.
Dryers damaged in shipment:
1. ALL dryers should be inspected upon receipt and before they are signed for.
2. If there is suspected damage or actual damage, the trucker’s receipt should be so noted.
3. If the dryer is damaged beyond repair, it should be refused. Those dryers, which were not damaged in a
damaged shipment should be accepted, but the number received and the number refused must be noted
on the receipt.
4. If you determine that the dryer was damaged after the trucker has left your location, you should call the
delivering carrier’s freight terminal immediately and file a claim. The freight company considers this
concealed damage. This type of freight claim is very difficult to have reimbursed and becomes extremely
difficult when more than a day or two passes after the freight was delivered. It is your responsibility to file
freight claims. Dryer/parts damaged in transit cannot be claimed under warranty.
5. Freight claims are the responsibility of the consignee, and ALL claims must be filed at the receiving end.
ADC assumes no responsibility for freight claims or damages.
6. If you need assistance in handling the situation, please contact the ADC Traffic Manager at (508)
678-9000.
IMPORTANT: The dryer mustbetransported and handledinan upright positionatALLtimes.

4
B. SAFETY PRECAUTIONS
WARNING: Foryoursafety,theinformationinthismanualmustbefollowedtominimizetheriskof
fireorexplosion ortopreventproperty damage, personalinjury,or lossoflife.
WARNING: The dryer mustnever be operatedwithany of theback guards, outertops,or
servicepanelsremoved. PERSONALINJURYOR FIRE COULDRESULT.
1. DO NOT store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other
appliance.
2. Purchaser/user should consult the local gas supplier for proper instructions to be followed in the event the
user smells gas. The instructions should be posted in a prominent location.
3. WHAT TO DO IF YOU SMELL GAS...
a. DO NOT try to light any appliance.
b. DO NOT touch any electrical switch.
c. DO NOT use any phone in your building.
d. Clear the room, building, or area of ALLoccupants.
e. Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
f. If you cannot reach your gas supplier, call the fire department.
4. Installation and service must be performed by a qualified installer, service agency, or gas supplier.
5. Dryers must be exhausted to the outdoors.
6. Although ADC produces a very versatile dryer, there are some articles that, due to fabric composition or
cleaning method, should not be dried in it.
WARNING: Dry onlywater washed fabrics. DONOTdry articlesspotted orwashed in drycleaning
solvents,acombustibledetergent,or“allpurpose”cleaner.
EXPLOSIONCOULDRESULT.
WARNING: DONOTdry ragsor articlescoatedor contaminatedwith gasoline, kerosene,oil, paint,
orwax.
EXPLOSIONCOULDRESULT.
WARNING: DONOTdrymopheads. Contamination bywaxor flammable solventswillcreate a
firehazard.
WARNING: DONOTuse heatfor drying articlesthat containplastic,foam, spongerubber,or
similarlytexturedrubbermaterials. Dryinginaheatedbasket(tumbler)maydamage
plasticsor rubberandmay bea firehazard.

5
7. A program shouldbe established for the inspection and cleaning of lint in the burner area, exhaust ductwork,
and area around the back of the dryer. The frequency of inspection and cleaning can best be determined
from experience at each location.
WARNING: Thecollection oflintintheburner area andexhaustductworkcan create apotentialfire
hazard.
8. For personal safety, the dryer must be electrically grounded in accordance with local codes and/or the
National Electrical Code ANSI/NFPA NO. 70-LATEST EDITION, or in Canada, the Canadian Electrical
Codes Parts 1 & 2 CSA C22.1-1990 or LATEST EDITION.
NOTE: Failureto do sowillVOID THEWARRANTY.
9. UNDER NO CIRCUMSTANCES should the dryer door switches, lint door switch, or heat safety circuit
ever be disabled.
WARNING: PERSONALINJURYORFIRE COULDRESULT.
10. This dryer is not to be used in the presence of dry cleaning solvents or fumes.
11. Remove articles from the dryer as soon as the drying cycle has been completed.
WARNING: Articlesleft in thedryerafterthedryingandcooling cycles havebeencompletedcan
createa fire hazard.
12. READ AND FOLLOW ALL CAUTION AND DIRECTION LABELS ATTACHED TO THE
DRYER.
13. For safety, proper operation, and optimum performance, the dryer must not be operated with a load less
than sixty-six percent (66%), 50 lbs (22.7 kg) of its rated capacity.
WARNING: YOUMUSTDISCONNECTAND LOCKOUTTHEELECTRICSUPPLYAND
THEGAS SUPPLYBEFOREANYCOVERSORGUARDSAREREMOVED
FROMTHEMACHINETOALLOWACCESSFORCLEANING,
ADJUSTING,INSTALLATION, ORTESTINGOFANYEQUIPMENTPER
OSHA(Occupational SafetyandHealthAdministration)STANDARDS.
IMPORTANT: Dryermustbe installedinalocation/environment,whichthe ambient
temperatureremains between40°F (4.44°C) and 130°F (54.44°C).

6
Gas
SECTIONII
SPECIFICATIONS/COMPONENTIDENTIFICATION
A. SPECIFICATIONS
Shaded areas are stated in metric equivalents 9/23/03
* For non-reversing models only.
** A minimum of 3/4” pipe must be supplied to the gas inlet for each dryer.
NOTE: ADCreservestheright tomakechangesinspecificationsatany time withoutnoticeor
obligation.
MAXIMUM CAPACITY (DRY WEIGHT) 75 lbs 34 kg
BASKET (TUMBLER) DIAMETER 44-1/2” 113.03 cm
BASKET (TUMBLER) DEPTH 24-7/8” 63.18 cm
BASKET (TUMBLER) VOLUME 22.4 cuft 0.634 cu m
BASKET (TUMBLER) MOTOR 1 hp* 0.746 kW
DOOR OPENING (DIAMETER) 31-3/8” 79.7 cm
F.S.S
. WATER CONNECTION 3/4-11.5 NH
DRYERS PER 20’/40’ CONTAINER 8/18
DRYERS PER 48’/53’ TRUCK 24/26
VOLTAGE AVAILABLE 120-480v 1, 3Ø 50/60 Hz
APPROX. NET WEIGHT 888 lbs 402.8 kg
APPROX. SHIPPING WEIGHT 938 lbs 425.5 kg
HEAT INPUT 204,000 Btu/hr 51,408 kcal/hr
AIRFLOW 1,200 cfm 33.98 cmm
INLET PIPE CONNECTION 3/4” F.N.P.T.**

7
Specifications
NOTE: ADCreservestheright tomakechangesinspecificationsatany time withoutnoticeor
obligation.

8
B. COMPONENT IDENTIFICATION
1. Dryer Front View
Illus. No. Description
1 Controls
2 Control (top access) Door Assembly
3 Main DoorAssembly
4 Lint CompartmentArea (lint screen located behind door)
5 Data Label and Installation Label

9
2. Dryer Rear View
Illus. No. Description
1 Heating Unit
2 Outer Top Area
3* Electric Service Relay Box
4 Basket (tumbler) Bearing MountAssembly
5 Idler Bearing MountAssembly
6 Basket (tumbler) (drive) MotorAssembly (for reversing models only)
7 Blower MotorAssembly
8 Dryer Exhaust
* Electrical service connections are made in this box.

10
SECTIONIII
INSTALLATIONPROCEDURES
Installation should be performed by competent technicians in accordance with local and state codes. In the
absence of these codes, the installation mustconform to applicableAmerican National Standards:ANSI Z223.1-
LATEST EDITION (National Fuel Gas Code) orANSI/NFPANO. 70-LATEST EDITION (National Electrical
Code) or in Canada, the installation must conform to applicable Canadian Standards: CAN/CGA-B149.1-M91
(Natural Gas) or CAN/CGA-B149.2-M91 (Liquid Propane [L.P.] Gas) or LATEST EDITION (for General
Installation and Gas Plumbing) or Canadian Electrical Codes Parts 1 & 2 CSAC22.1-1990 or LATEST EDITION
(for Electrical Connections).
A. LOCATION REQUIREMENTS
Before installing the dryer, be sure the location conforms to local codes and ordinances. In the absence of such
codes or ordinances the location must conform with the National Fuel Gas Code ANSI.Z223.1 LATEST
EDITION, or in Canada, the installation must conform to applicable Canadian Standards: CAN/CGA-B149.1-
M91 (Natural Gas) or CAN/CGA-B149.2-M91 (L.P. Gas) or LATEST EDITION (for General Installation and
Gas Plumbing).
1. The dryer must be installed on a sound level floor capable of supporting its weight. Carpeting must be
removed from the floor area that the dryer is to rest on.
IMPORTANT: “The dryer mustbeinstalledon noncombustiblefloors only.”
2. The dryer must not be installed or stored in an area where it will be exposed to water and/or weather.
3. Provisions for adequate air supply must be provided as noted in this manual (refer to Fresh Air Supply
Requirements in Section D).
4. Clearance provisions mustbemade from combustible construction as noted in this manual (refer to Dryer
Enclosure Requirements in Section C).
5. Provisions must be made for adequate clearances for servicing and for operation as noted in this manual
(refer to Dryer Enclosure Requirements in Section C).
6. Dryer must be exhausted to the outdoors as noted in this manual (refer to Exhaust Requirements in
Section E).
7. Dryer must be located in an area where correct exhaust venting can be achieved as noted in this manual
(refer to Exhaust Requirements in Section E).
IMPORTANT: Dryer shouldbelocated where aminimum amount of exhaustduct will be necessary.
8. The dryer must be installed with a proper exhaust duct connection to the outside.
9. The dryer must be installed with provisions for adequate combustion and make-up air supply.

11
CAUTION: This dryer producescombustible lint and mustbeexhausted totheoutdoors. Every 6
months,inspecttheexhaustductingand remove anylintbuildup.
IMPORTANT: Dryer mustbeinstalledinalocation/environment,whichtheambient
temperatureremains between40°F (4.44°C) and 130°F (54.44°C).
B. UNPACKING/SETTING UP
Remove protective shipping material (i.e., plastic wrap, and/or optional shipping box) from dryer.
IMPORTANT: Dryermustbetransportedand handled inanuprightposition at ALLtimes.
The dryer can be moved to its final location while still attached to the skid or with the skid removed. To unskid
the dryer, locate and remove the four (4) bolts securing the base of the dryer to the wooden skid. Two (2) are
at the rear base (remove the back panel for access) and two (2) are located in the bottom of the lint chamber. To
remove the two (2) bolts located in the lint chamber area, remove the lint door.
To increase bearing life and improve efficiency, the dryer should be tilted slightly to the rear.
The lint coop is supported during shipping by a bracket. REMOVE THIS BRACKET BEFORE STARTING
THE DRYER.
If more headroom is needed when moving dryer into position, the top console (module) may be removed.
1. To Remove Top Console (Module)
a. Disconnect the ground wire (A) at the rear upper left hand corner of dryer.
b. Remove the four (4) sets of nuts and
washers (B) holding the console
(module) to base.
c. Open the control door/control panel
and disconnect the white 9-pin plug
connector (C) located in the base of
the control box.
d. Disconnect motor harness(es) (D)
located in rear electrical box.
e. Disconnect 2-pin connector (E)
located in rear electrical box. (On
some dryers, this is optional.)
f. Liftthe console (module) offthedryer
base.

12
C. DRYER ENCLOSURE REQUIREMENTS
Bulkheads and partitions must be made of noncombustible materials and must be located a minimum of
12-inches (30.48 cm), 18-inches (45.72 cm) or more is recommended for ease of installation, maintenance, and
service above the dryer outer top, except along the front of the dryer which may be partially closed in if desired.
The clearance between the bulkhead header and the dryer must be a minimum of 4-inches (10.16 cm) and must
not extend more than 4-inches (10.16 cm) to the rear of the front. The bulkhead facing must not be closed in
ALL the way to the top of the dryer. A 1-inch (2.54 cm) clearance is required.
NOTE: Allowancesmustbe madefor openingthecontrol door.
Dryers may be positioned sidewall to sidewall. However, a 1/16” (1.587 mm) minimum allowance must be
made for the opening and closing of the control door and the lint door. It is suggested that the dryer be positioned
about 2 feet (0.61 meters) away from the nearest obstruction for ease of installation, maintenance, and service
(to be measured from the back guard). Refer to the illustration above for details.
NOTE: Airconsiderationsareimportant for properandefficientoperation.
IMPORTANT: Even though aminimumofonly12-inches(30.48cm)isrequiredbehindthedryer,
18-inches(45.72cm)or more issuggested(especiallywhenverticalventing is used).
Theadditionalclearanceisadvantageousforeaseof installation andservice.
IMPORTANT: When firesprinklersystemsarelocatedabove the dryers,aminimumof18-inches
(45.72cm) abovethedryer console(module)is required. Dryersmaybe positioned
sidewalltosidewall,however,a1/16”(1.587mm)minimumallowanceisrequired
betweendryers(orwall) for easeofinstallationandmaintenance. Allowances must
bemade forthe opening andclosingof thecontroldoor andthelint door.

13
D. FRESH AIR SUPPLYREQUIREMENTS
When the dryer is operating, it draws in room air, heats it, passes this air through the basket (tumbler), and
exhausts it out of the building. Therefore, the room air must be continually replenished from the outdoors. If the
make-up air is inadequate, drying time and drying efficiency will be adversely affected. Ignition problems and
sail switch “fluttering” problems may result, as well as premature motor failure from overheating.
Air supply (make-up air) must be given careful consideration to ensure proper performance of each dryer. An
unrestricted source of air is necessary for each dryer. An airflow of 1,200 cfm (cubic feet per minute) (33.98
cmm [cubic meters per minute]) must be supplied to each gas dryer. As a general rule, an unrestricted air
entrance from the outdoors (atmosphere) of a minimum of 1-1/2 square feet (0.41 square meters) is required for
each dryer. The dryer must be installed with provisions for adequate combustion and make-up air supply.
To compensate for the use of registers or louvers used over the openings, this make-up air must be increased by
approximately thirty-three percent (33%). Make-up air openings should not be located in an area directly near
where exhaust vents exit the building.
It is not necessary to have separate make-up air openings for each dryer. Common make-up air openings are
acceptable. However, they must be set up in such a manner that the make-up air is distributed equally to ALL
the dryers.
EXAMPLE: For a bank of four (4) dryers, two (2) unrestricted openings measuring 2 feet by 1-1/2 feet (0.60
meters by 0.45 meters) (6 square feet [0.56 square meters]) are acceptable.
Allowances must be made for remote or constricting passageways or where dryers are located at excessive
altitudes or predominantly low pressure areas.
IMPORTANT: Make-up airmustbe providedfrom a sourcefreeof drycleaningsolvent fumes.
Make-upairthatiscontaminatedbydrycleaningsolventfumeswillresultin
irreparabledamage to themotors and otherdryercomponents.
NOTE: ComponentfailureduetodrycleaningsolventfumeswillVOIDTHEWARRANTY.

14
E. EXHAUST REQUIREMENTS
1. General Exhaust Ductwork Information
Exhaust ductwork shouldbe designed and installed by a qualified professional. Improperly sized ductwork
will create excessive back pressure which results in slow drying, increased use of energy, overheating of
the dryer, and shutdown of the burner by the airflow (sail) switches, burner hi-limits, or basket (tumbler)
hi-limit thermostats. The dryer must be installed with a proper exhaust duct connection to the outside.
CAUTION: Thisdryer produces combustiblelint and mustbeexhaustedtothe outdoors.
CAUTION: DRYER MUST BE EXHAUSTEDTO THE OUTDOORS.
CAUTION: IMPROPERLY SIZEDOR INSTALLEDEXHAUSTDUCTWORKCAN
CREATEAPOTENTIALFIRE HAZARD.
The ductwork should be laid out in such a way that the ductwork travels as directly as possible to the
outdoors with as few turns as possible. Single or independent dryer venting is recommended.
HorizontalVenting:
When single dryer venting is used, the length of the ductwork from the dryer to the outside exhaust outlet
must not exceed 15 feet (4.6 meters). The minimum diameter of this ductwork must be at least
10-inches (25.4 cm). In the case of multiple (common) dryer venting, the distance from the last dryer to the
outside exhaust outlet must not exceed 15 feet (4.6 meters). The shape of the ductwork is not critical as
long as the minimum cross-sectional area is provided. It is suggested that the use of 90° turns be avoided;
use 30° and/or 45° angles instead. The radius of the elbows should preferably be 1-1/2 times the
diameter of the duct. Including basket (tumbler)/dryer elbow connections or elbows used for outside
protection from the weather, no more than two (2) elbows should be used in the exhaust duct run. If more
than two (2) elbows are used, the cross-sectional area of the ductwork must be increased. ALL ductwork
should be smooth inside with no projections from sheet metal screws or other obstructions, which will
collect lint. When adding ducts, the duct to be added should overlap the duct to which it is to be connected.
ALLductwork joints must betaped to prevent moisture and lint from escaping into the building. Inspection
doors shouldbeinstalled at strategic points in the exhaust ductwork for periodic inspection and cleaning of
lint from the ductwork.
Vertical Venting:
When single dryer venting is used, the length of the ductwork from the dryer to the outside exhaust outlet
must not exceed 20 feet (6.1 meters). The minimum diameter of this ductwork must be at least
12-inches (30.48 cm). In the case of multiple (common) dryer venting, the distance from the last dryer to
the outside exhaust outlet must not exceed 20 feet (6.1 meters). The shape of the ductwork is not critical
as long as the minimum cross-sectional area is provided. It is suggested that the use of 90º turns be
avoided; use 30º and/or 45º bends instead. The radius of the elbows should preferably be 1-1/2 times the
diameter of the duct. ALL ductwork should be smooth inside with no projections from sheet metal
screws or other obstructions, which will collect lint. When adding ducts, the duct to be added should
overlap the duct to which it is to be connected. ALL ductwork joints must be taped to prevent moisture
and lint from escaping into the building. Inspection doors should be installed at strategic points in the
exhaust ductwork for periodic inspection and cleaning of lint from the ductwork.
IMPORTANT: It isrecommendedthatexhaust or boosterfans notbe used inthe exhaustductwork
system.

15
NOTE: Asper theNationalFuel GasCode, “Exhaust ductsforType 2 clothesdryers shallbe
constructedofsheetmetalor other noncombustiblematerial. Suchductsshallbeequivalent
instrengthandcorrosion resistancetoductsmadeof galvanizedsheetsteelnotless than
0.0195-inches(26gauge [0.05mm])thick.”
IMPORTANT: Exhaust backpressure measured bya manometerinthe exhaustductmustbe no less
than 0 and mustnotexceed 0.3 inches (0.74 mb) of water column (W.C.).
IMPORTANT: Minimumductworkdiameterforhorizontalventingis 10-inches (25.4 cm) and for
verticalventingtheminimumis12-inches(30.48cm).
NOTE: Whentheexhaustductwork passes throughawall,ceiling,or roof madeofcombustible
materials,the openingmustbe 2-inches(5.08 cm) largerthanthe duct(allthe way around).
Theductmustbecentered withinthisopening.
a. Outside Ductwork Protection
1) To protect the outside end of the horizontal ductwork from the weather, a 90° elbow bent downward
should be installed where the exhaust exits the building. If the ductwork travels vertically up
through the roof, it should be protected from the weather by using a 180° turn to point the opening
downward. In either case, allow at least twice the diameter of the duct between the duct opening
and the nearest obstruction.
IMPORTANT: DO NOTusescreens, louvers,or capson theoutside openingof theexhaust
ductwork.
2. Single DryerVenting
When possible, it is suggested to provide a separate exhaust duct for each dryer. The exhaust duct should
be laid out in such a way that the ductwork travels as directly as possible to the outdoors with as few turns
as possible. It is suggested that the use of 90° turns in the ducting be avoided; use 30° and/or 45° angles
instead. The shape of the exhaust ductwork is not critical as long as the minimum cross-sectional area is
provided.

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IMPORTANT: Minimum ductsizeforadryerthatis vented horizontallyis10-inches(25.4cm)for a
roundduct or anequivalent of80square inches(516.3square centimeters). THE
DUCTSIZEMUST NOT BEREDUCEDANYWHERE DOWNSTREAMOF
THEDRYER.
IMPORTANT: Exhaust backpressure measuredbya manometerin the exhaustductmustbeno less
than 0 and mustnotexceed 0.3 inches (0.74 mb)of watercolumn.
IMPORTANT: Minimum ductsizeforadryer that isventedverticallyis12-inches (30.48 cm)fora
roundduct or anequivalent of120square inches(774.2square centimeters). THE
DUCTSIZE MUSTNOT BE REDUCEDANYWHERE DOWNSTREAMOF
THEDRYER.
IMPORTANT: For extendedductwork runs,the crosssection areaof the ductwork can onlybe
increasedtoanextent. When the ductworkapproachesthemaximumlimitsnoted in
thismanual,aprofessionalheating,ventilating,andair-conditioning(HVAC)firm
shouldbeconsultedforproper venting information.
ALLductwork should be smooth inside with no projections from sheet metal screws or other obstructions,
which will collect lint. When adding ducts, the duct to be added should overlap the duct to which it is to be
connected. ALL ductwork joints must be taped to prevent moisture and lint from escaping into the
building. Inspection doors should be installed at strategic points in the exhaust ductwork for periodic
inspection and cleaning of lint from the ductwork.