American Dryer Corp. ML-78II User manual

For replacement parts, contact the reseller from which the dryer
was purchased or
American Dryer Corporation
88 Currant Road
Fall River MA 02720-4781
Telephone: [phone] / Fax: [phone]
e-mail: [email protected]
www.amdry.com
WARNING: For your safety the
information in this manual must be
followed to minimize the risk of fire or
explosion or to prevent property damage,
personal injury or death.
Do not store or use gasoline or other flammable
vapor and liquids in the vicinity of this or any
other appliance.
WHAT DO YOU DO IF YOU SMELL GAS
*Do not try to light any appliance.
*Do not touch any electrical switch; do not use
any phone in your building.
*Clear the room, building or area of all
occupants.
*Immediately call your gas supplier from a
neighbor's phone. Follow the gas supplier's
instructions.
*If you cannot reach your gas supplier, call the
fire department.
Installation and service must be performed by a
qualified installer, service agency or the gas
supplier.
AVERTISSEMENT: Assurez-vous de bien
suivre les instructions données dans cette
notice pour réduire au minimum le risque
d’incendie ou d’explosion ou pour éviter tout
dommage matériel, toute blessure ou la mort.
Ne pas entreposer ni utiliser d’essence ni
d’autres vapeurs ou liquides inflammables dans
le voisinage de cet appareil ou de tout autre
appareil.
QUE FAIRE SI VOUS SENTEZ UNE ODEUR
DE GAZ:
*Ne pas tenter d’allumer d’appareil.
*Ne touchez à aucun interrupteur. Ne pas
vous servir des téléphones se trouvant dans
le bâtiment où vous vous trouvez.
*Évacuez la pièce, le bâtiment ou la zone.
*Appelez immédiatement votre fournisseur de
gaz depuis un voisin. Suivez les instructions
du fournisseur.
*Si vous ne pouvez rejoindre le fournisseur
de gaz, appelez le service des incendies.
L’installation et l’entretien doivent être assurés
par un installateur ou un service d’entretien
qualifié ou par le fournisseur de gaz.
ML-78II
(Gas HSI)
Installation Manual
080699GS/cms ADC Part No. 113106

Retain This Manual In A Safe 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.
OBSERVEALLSAFETYPRECAUTIONS 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.
ML-78II
“IMPORTANT NOTE TO PURCHASER”
Information must beobtained from your local gas supplier on the instructions
to be followed if the user smells gas. These instructions must be posted in a
prominent location near the dryer.
FOR YOUR SAFETY
Do not store or use gasoline or
other flammable vapors or
liquids in the vicinity of this or
any other appliance.
POUR VOTRE SÉCURITÉ
Ne pas entreposer ni utiliser d’essence
ni d’autres vapeurs ou liquides
inflammables dans le voisinage de cet
appareil ou de yout autre 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 OF PURCHASE________________________________ MODELNO. __________________________________________
RESELLER’S NAME ________________________________________________________________________________________
Serial Number(s) ________________________________________________________________________________________
________________________________________________________________________________________
________________________________________________________________________________________
Replacement parts can be obtained from your reseller or theADCfactory. When orderingreplacement partsfromthefactory,
you can FAX your order to ADC at [phone] or telephone your order directly to the ADC Parts Department at (508)
678-9000. Please specify the dryer model number andserialnumberin addition to the description andpart number,sothat
your order is processed accurately and promptly.

IMPORTANT
YOUMUSTDISCONNECTANDLOCKOUTTHEELECTRICSUPPLY ANDTHEGAS
SUPPLY BEFORE ANY COVERS OR GUARDS ARE REMOVED FROM THE
MACHINE TO ALLOW ACCESS FOR CLEANING, ADJUSTING, INSTALLATION,
OR TESTING OF ANY EQUIPMENT PER OSHA (Occupational Safety and Health
Administration) STANDARDS.
CHILDREN SHOULD NOTBEALLOWED TO PLAY ON OR NEAR THE DRYER(S).
WARNING
CHILDREN SHOULD BESUPERVISED IF NEAR DRYERS IN OPERATION.
DRYERS SHOULD NEVER BE LEFT UNATTENDED WHILE IN OPERATION.
CAUTION
FOR YOUR SAFETY
DO NOT DRY MOP HEADS IN THE DRYER.
DO NOT USE DRYER IN THE PRESENCE OF DRY CLEANING FUMES.
WARNING
UNDER NO CIRCUMSTANCES should the dryer door switches, lint drawer 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: Lordesopérationsd’entretien
des commandes étiqueter tous fils avant
de les déconnecter. Toute erreur de
câblage peut étre une source de danger et
de panne.»

WARNING
The dryer must never be operated with any of the back guards, outer tops, or service
panels removed. PERSONAL INJURY OR FIRE COULD RESULT.
IMPORTANT
PLEASE OBSERVEALLSAFETY PRECAUTIONS displayed on the equipment and/or
specified in the installation manual included with the dryer.
Dryers must not beinstalled or stored in an area where itwillbe exposed to water or weather.
The wiring diagram for the dryer is located in the front electrical control box area.
DRYER MUST NEVER BE OPERATED WITHOUT THE LINT FILTER/SCREEN IN
PLACE, EVEN IF AN EXTERNAL LINT COLLECTION SYSTEM IS USED.
WARNING

Table of Contents
SECTION I
IMPORTANT INFORMATION..........................................................................3
A. Receiving and Handling ............................................................................................................... 3
B. Safety Precautions ...................................................................................................................... 4
SECTION II
SPECIFICATIONS/COMPONENT IDENTIFICATION..................................6
A. Specifications ............................................................................................................................. 6
B. Component Identification ............................................................................................................ 8
SECTION III
INSTALLATION PROCEDURES ....................................................................10
A. Location Requirements ............................................................................................................. 10
B. Unpacking/Setting Up ................................................................................................................11
C. Dryer Enclosure Requirements .................................................................................................. 12
D. Fresh Air Supply Requirements ................................................................................................. 13
E. Exhaust Requirements ............................................................................................................... 14
F. Electrical Information ................................................................................................................ 18
G. Gas Information........................................................................................................................ 24
H. Preparation For Operation/Start-Up ......................................................................................... 28
I. Preoperational Tests ................................................................................................................. 29
J. Preoperational Instructions ........................................................................................................ 31
K. Shut Down Instructions ............................................................................................................. 31
SECTION IV
SERVICE/PARTS INFORMATION .................................................................32
A. Service ..................................................................................................................................... 32
B. Parts ........................................................................................................................................ 32
SECTION V
WARRANTY INFORMATION .........................................................................33
A. Returning Warranty Card(s) ...................................................................................................... 33
B. Warranty .................................................................................................................................. 33
C. Returning Warranty Part(s)........................................................................................................ 33

SECTION VI
ROUTINE MAINTENANCE ............................................................................35
A. Cleaning ................................................................................................................................... 35
B. Adjustments ............................................................................................................................. 36
C. Lubrication ............................................................................................................................... 36
SECTION VII
REVERSING TIMER SPIN/DWELL ADJUSTMENTS..................................37
SECTION VIII
DATA LABEL INFORMATION........................................................................38
A. Data Label ............................................................................................................................... 38
SECTION IX
PROCEDURE FOR FUNCTIONAL CHECK OF REPLACEMENT
COMPONENTS ................................................................................................40
SECTION X
BURNER AND BASKET (TUMBLER)/LINT CHAMBER MANUAL RESET
HI-LIMIT INSTRUCTIONS .............................................................................41

3
SECTION I
IMPORTANT INFORMATION
A. RECEIVING AND 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 get paid 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 theADC Traffic Manager at [phone].
IMPORTANT: The dryer must be transported and handled in an upright position at ALLtimes.

4
B. SAFETY PRECAUTIONS
WARNING: For your safety, the information in this manual must be followed to minimize the risk of
fire or explosion or to prevent property damage, personal injury, or loss of life.
WARNING: The dryer must never be operated with any of the back guards, outer tops, or
service panels removed. PERSONAL INJURY OR FIRE COULD RESULT.
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 only water washed fabrics. DO NOT dry articles spotted or washed in dry cleaning
solvents, a combustible detergent, or “all purpose” cleaner.
EXPLOSION COULD RESULT.
WARNING: DO NOT dry rags or articles coated or contaminated with gasoline, kerosene, oil, paint,
or wax.
EXPLOSION COULD RESULT.
WARNING: DO NOT dry mop heads. Contamination by wax or flammable solvents will create a
fire hazard.
WARNING: DO NOT use heat for drying articles that contain plastic, foam, sponge rubber, or
similarly textured rubber materials. Drying in a heated basket (tumbler) may damage
plastics or rubber and may be a fire hazard.

5
7. A program should be 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: The collection of lint in the burner area and exhaust ductwork can create a potential fire
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: Failure to do so will VOID THE WARRANTY.
9. UNDER NO CIRCUMSTANCES should the dryer door switches, lint drawer switch, or heat safety
circuit ever be disabled.
WARNING: PERSONALINJURY OR FIRE COULD RESULT.
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: Articles left in the dryer after the drying and cooling cycles have been completed can
create a 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%), 29 lbs (13 kg) of its rated capacity.
WARNING: YOU MUST DISCONNECT ANDLOCKOUTTHEELECTRICSUPPLY AND
THE GAS SUPPLY BEFORE ANY COVERS OR GUARDS ARE REMOVED
FROM THE MACHINE TO ALLOW ACCESS FOR CLEANING,
ADJUSTING, INSTALLATION, OR TESTING OF ANY EQUIPMENT PER
OSHA (Occupational Safety and Health Administration) STANDARDS.

6
Gas
SECTION II
SPECIFICATIONS/COMPONENT IDENTIFICATION
A. SPECIFICATIONS
*For non-reversing models only.
** A minimum of 3/4” pipe must be supplied to the gas inlet for each dryer.
NOTE: ADCreserves the right to make changes in specifications at any time without notice or
obligation.
BASKET (TUMBLER) DIAMETER 44-1/2” 113 cm
BASKET (TUMBLER) DEPTH 24-7/8” 63.2 cm
BASKET (TUMBLER) MOTOR 1 HP* 0.746 kw
DOOR OPENING (DIAMETER) 31-3/8” 79.7 cm
BASKET (TUMBLER) VOLUME 22.4 cu. ft. 0.634 cu. m.
EXHAUST CONNECTION (DIAMETER) 10" 25.4 cm
DRYERS PER 20’/40’ CONTAINER 8/18
DRYERS PER 45’/48’ TRUCK 25/27
VOLTAGE AVAILABLE 120-460v 1ø-3ø 50/60 Hz
APPROX. WEIGHT (UNCRATED) 895 lbs 406 kg
APPROX. WEIGHT (CRATED) 938 lbs 425.5 kg
HEAT INPUT 204,000 btu/hr 51,408 kcal/hr
AIRFLOW 1,200 cfm 33.98 cmm
INLET PIPE SIZE** 3/4” F.P.T.
Shaded areas are stated in metric equivalents

7
Specifications
MLG-78II (Gas)
NOTE: ADCreserves the right to make changes in specifications at any time without notice or
obligation.

8
B. COMPONENT IDENTIFICATION
1. Dryer Front View
Illus. No. Description
1Controls
2Control (top access) Door Assembly
3Main Door Assembly
4Lint Compartment Area (lint screen located behind door)
5Wire Diagram
6Data Label and Installation Label (located in the left side panel/wall area behind the control
door)

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

10
SECTION III
INSTALLATION PROCEDURES
Installation should be performed by competent technicians in accordance with local and state codes. In the
absence of these codes, the installation must conform toapplicableAmerican NationalStandards: ANSI Z223.1-
LATEST EDITION (National Fuel Gas Code) or ANSI/NFPA NO. 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 CSA C22.1-1990 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
codesorordinances the locationmust conform withtheNationalFuelGasCodeANSI.Z223.1LATESTEDITION,
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 must be installed on noncombustible floors only.”
2. The dryer must not be installed or stored in an area where it will be exposed to water and/or weather.
3. The dryer is for use in noncombustible locations.
4. Provisions for adequate air supply must be provided as noted in this manual (refer to Fresh Air Supply
Requirements in Section D).
5. Clearance provisions must be made from combustible construction as noted in this manual (refer to Dryer
Enclosure Requirements in Section C).
6. 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).
7. Dryer must be exhausted to the outdoors as noted in this manual (refer to Exhaust Requirements in
Section E).
8. 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 should be located where a minimum amount of exhaust duct will be necessary.
9. The dryer must be installed with a proper exhaust duct connection to the outside.

11
10. The dryer must be installed with provisions for adequate combustion and make-up air supply.
CAUTION: This dryer produces combustible lint and must be exhausted to the outdoors. Every 6
months, inspect the exhaust ducting and remove any lint build up.
B. UNPACKING/SETTING UP
Remove protective shipping material (i.e., plastic wrap, and/or optional shipping box) from dryer.
IMPORTANT:Dryer must be transported and handled in an upright position 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 coops of ALL ML-78 dryers are 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) set 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. Lift the console (module) off the dryer
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 bea 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: Allowances must be made for opening the control 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: Air considerations are important for proper and efficient operation.
IMPORTANT: Even though a minimum of only 12-inches (30.48 cm) is required behind the dryer,
18-inches (45.72 cm) or more is suggested (especially when vertical venting is used).
The additional clearance is advantageous for ease of installation and service.
IMPORTANT: When fire sprinkler systems are located above the dryers, a minimum of 18-inches
(45.72 cm) above the dryer console (module) is required. Dryers may be positioned
sidewall to sidewall, however, a 1/16” (1.587 mm) minimum allowance is required
between dryers (or wall) for ease of installation and maintenance. Allowances must
be made for the opening and closing of the control door and the lint 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 airmust 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 assure 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 airmust beincreased 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 x 1-1/2 feet
(0.60 meters x 0.45 meters) (6 square feet [0.56 square meters]) is 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 air must be provided from a source free of dry cleaning solvent fumes.
Make-up air that is contaminated by dry cleaning solvent fumes will result in
irreparable damage to the motors and other dryer components.
NOTE: Component failure due to dry cleaning solvent fumes will VOID THE WARRANTY.

14
E. EXHAUST REQUIREMENTS
1. General Exhaust Ductwork Information
Exhaust ductwork should be 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: This dryer produces combustible lint and must be exhausted to the outdoors.
CAUTION: DRYER MUST BE EXHAUSTED TO THE OUTDOORS.
CAUTION: IMPROPERLY SIZED OR INSTALLED EXHAUSTDUCTWORKCAN
CREATE APOTENTIALFIREHAZARD.
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.
HORIZONTAL VENTING:
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 so
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 elbowsshould 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. 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.
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 exceed20 feet (6.1 meters). The shape of the ductwork is not critical
so long as the minimum cross-sectional area is provided. It is suggested that the use of 90º turnsbe 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 jointsmust 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.

15
IMPORTANT: Exhaust back pressure measured by a manometer in the exhaust duct must be no less
than 0 and must not exceed 0.3 inches (0.74 mb) of water column (W.C.).
IMPORTANT: Minimum ductwork diameter for horizontal venting is 10-inches (25.4 cm) and for
vertical venting the minimum is 12-inches (30.48 cm).
NOTE: When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches (5.08 cm) larger than the duct (all the way around).
The duct must be centered within this opening.
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 NOT use screens, louvers, or caps on the outside opening of the exhaust
ductwork.
2. Single Dryer Venting
Where possible, it is suggested to provide a separate exhaust duct for each dryer. The exhaust ductshould
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 so long as the minimum cross-sectional area is
provided.
IMPORTANT: Minimum duct size for a dryer that is vented horizontally is 10-inches (25.4 cm) for a
round duct or an equivalent of 80 square inches (516.3 square centimeters). THE
DUCT SIZE MUST NOT BE REDUCED ANYWHERE DOWNSTREAM
OF THE DRYER.
IMPORTANT: Exhaust back pressure measured by a manometer in the exhaust duct must be no less
than 0 and must not exceed 0.3 inches (0.74 mb) of water column.

16
IMPORTANT: Minimum duct size for a dryer that is vented vertically is 12-inches (30.48 cm) for a
round duct or an equivalent of 120 square inches (774.2 square centimeters). THE
DUCT SIZE MUST NOT BE REDUCED ANYWHERE DOWNSTREAM
OF THE DRYER.
IMPORTANT: For extended ductwork runs, the cross section area of the ductwork can only be
increased to an extent. When the ductwork approaches the maximum limits noted in
this manual, a professional heating, venting, and air conditioning (HVAC) firm should
be consulted for proper venting information.
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 jointsmust 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.
NOTE: When the exhaust ductwork passes through a wall, ceiling, or roof made of combustible
materials, the opening must be 2-inches (5.08 cm) larger than the duct (all the way around).
The duct must be centered within this opening.