Maytag MDG-75 User Manual
MDG-75
(Direct Spark Ignition)
Installation Manual
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.
For replacement parts, contact the distributor from which the dryer
was purchased or
MAYTAG
403 West Fourth Street North
Newton, Iowa 50208
(515) 792-7000
122299MS/tcosta Part No. 113123
Retain This Manual In A Safe Place For Future Reference
Our 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.
FOR YOUR SAFETY
Do not store or use gasoline or
other flammable vapors or liquids
in the vicinity of this or any other
appliance.
We have tried to make this manual as complete as possible and hope you will find it useful. Manufacturer 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.
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.
Important
For your convenience, log the following information:
DATE OF PURCHASE MODEL NO.
DISTRIBUTORS NAME
Serial Number(s)
MDG-75
For replacement parts, contact the distributor from which the dryer was purchased or contact:
MAYTAG
403 West Fourth Street North
Newton, Iowa 50208
(515) 792-7000
“IMPORTANT NOTE TO PURCHASER”
Information must be obtained 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.
IMPORTANT
YOU MUST DISCONNECT and LOCKOUT THE ELECTRIC SUPPLY 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.
«Attention: Lor des opérations d’entretien
“Caution: Label all wires prior to
disconnection when servicing controls. Wiring
errors can cause improper operation.”
des commandes étiqueter tous fils avant
de les déconnecter. Toute erreur de
câblage peut étre une source de danger et
de panne.»
CAUTION
DRYER(S) SHOULD NEVER BE LEFT UNATTENDED WHILE IN OPERATION.
WARNING
CHILDREN SHOULD NOT BE ALLOWED TO PLAY ON OR NEAR THE DRYER(S).
CHILDREN SHOULD BE SUPERVISED IF NEAR DRYER(S) IN OPERATION.
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 switch or the heat safety circuit
devices ever be disabled.
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.
WARNING
DRYER MUST NEVER BE OPERATED WITHOUT THE LINT FILTER/SCREEN IN
PLACE, EVEN IF AN EXTERNAL LINT COLLECTION SYSTEM IS USED.
IMPORTANT
PLEASE OBSERVE ALL SAFETY PRECAUTIONS displayed on the equipment and/or
specified in the installation manual included with the dryer.
Dryers must not be installed or stored in an area where it will be exposed to water or weather.
The wiring diagram for the dryer is located in the front electrical control box area.
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 ................................................................................................................ 19
G. Gas Information........................................................................................................................ 25
H. Preparation For Operation/Start-up .......................................................................................... 29
I. Preoperational Tests ................................................................................................................. 30
J. Preoperational Instructions ........................................................................................................ 32
K. Shut Down Instructions ............................................................................................................. 33
SECTION IV
SERVICE/PARTS INFORMATION ................................................................. 34
A. Service ..................................................................................................................................... 34
B. Parts ........................................................................................................................................ 34
SECTION V
WARRANTY INFORMATION ......................................................................... 35
A. Returning Warranty Cards......................................................................................................... 35
SECTION VI
ROUTINE MAINTENANCE ............................................................................36
A. Cleaning ................................................................................................................................... 36
B. Adjustments ............................................................................................................................. 37
C. Lubrication ............................................................................................................................... 37
SECTION VII
PROCEDURE FOR FUNCTIONAL CHECK OF REPLACEMENT
COMPONENTS ................................................................................................38
SECTION VIII
REVERSING TIMER SPIN/DWELL ADJUSTMENTS..................................41
SECTION IX
DATA LABEL INFORMATION........................................................................42
A. Data Label ............................................................................................................................... 42
SECTION X
TROUBLESHOOTING.....................................................................................44
Microprocessor Controller (Computer) Models .............................................................................. 44
Timer Models ................................................................................................................................. 52
SECTION XI
BURNER and BASKET (TUMBLER)/LINT CHAMBER
MANUAL RESET HI-LIMIT INSTRUCTIONS .............................................. 58
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.
Manufacturer assumes no responsibility for freight claims or damages.
6. If you need assistance in handling the situation, please contact the manufacturer Traffic Manager at (508)
678-9000.
IMPORTANT: The tumbler section of the dryer must be transported and handled in an upright
position at ALL times.
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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 ALL occupants.
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. Dryer(s) must be exhausted to the outdoors.
6. Although the manufacturer 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.
7. A program should be established for the inspection and cleaning of lint in the heating unit area, exhaust
ductwork, and inside 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 switch or heat safety circuit ever be disabled.
WARNING: PERSONAL INJURY 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%), 49 lbs (22 kg) of its rated capacity.
WARNING: YOU MUST DISCONNECT and LOCKOUT THE ELECTRIC SUPPLY 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.
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SECTION II
SPECIFICATIONS/COMPONENT IDENTIFICATION
A. SPECIFICATIONS
MAXIMUM CAPACITY (DRY WEIGHT) 75 lbs. 34 kg
BASKET (TUMBLER) DIAMETER 37" 94 cm
BASKET (TUMBLER) DEPTH 36" 91.5 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.
DRYERS PER 20'/40' CONTAINER 10/20
DRYERS PER 45'/48' TRUCK 24/24
VOLTAGE AVAILABLE 120-460v 1ø-3ø 50/60 Hz
APPROX. WEIGHT (UNCRATED) 721 lbs. 327 kg
APPROX. WEIGHT (CRATED) 771 lbs. 349.7 kg
HEAT INPUT 200,000 btu/hr 50,400 kcal/hr
GAS
AIRFLOW 1,200 cfm 33.98 cmm
INLET PIPE SIZE** 3/4"
Shaded areas are stated in metric equivalents
* For non-reversing models.
** A minimum of 3/4” pipe must be supplied to the gas inlet for each dryer.
NOTE: Manufacturer reserves the right to make changes in specifications at any time without notice or
obligation.
Specifications
MDG-75
(Direct Spark Ignition)
*
* Duct size varies with installation conditions.
NOTE: Manufacturer reserves the right to make changes in specifications at any time without notice or
obligation.
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B. COMPONENT IDENTIFICATION
1. Dryer Front View
Illus. No. Description
1 Controls
2 Control (top access) Door Assembly
3 Main Door Assembly
4 Lint Compartment Area (lint screen located behind door)
5 Data Label and Installation Label (located back side of the top front control/service door)
2. Dryer Rear View
Illus. No. Description
1 Heating Unit
2* Electric Service Relay Box
3 Tumbler Bearing Mount Assembly
4 Idler Bearing Mount Assembly
5 Blower Motor Assembly
6 Leveling Leg (rear)
7 Basket (Drive) Motor Assembly (Reversing Models Only)
8 Dryer Exhaust
* Electric service connections for Gas Models are made in this box.
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SECTION III
INST ALLATION 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 to applicable American National Standards: ANSI Z223.1LATEST 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
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 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.
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 or optional shipping box) from dryer.
IMPORTANT: Dryer must be transported and handled in an upright position at ALL times.
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.
With the skid removed, to make it easier to slide the dryer into its final position, slightly lower ALL four (4)
leveling legs, so that the dryer will slide on the legs instead of the base frame.
To increase bearing life and improve efficiency, the dryer should be tilted slightly to the rear.
The lint coops of ALL MDG-75 dryers are supported during shipping by a bracket. REMOVE THIS BRACKET
BEFORE STARTING THE DRYER.
1. Leveling Dryer
The dryer is equipped with four (4) leveling legs, one (1) at each corner of the base. Two (2) are located at
the rear of the dryer base, and two (2) are located in the lint chamber (coop). To increase bearing life and
improve efficiency, the dryer should be tilted slightly to the rear.
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C. DRYER ENCLOSURE REQUIREMENTS
Bulkheads and partitions should be made of noncombustible materials and must be located a minimum of 12inches (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: Allowances must be made for opening the control door.
Dryers may be positioned sidewall to sidewall. However, a 1/16” (1.58 mm) minimum allowance must be made
for opening and closing of the control door and the lint door. It is suggested that the dryer be positioned about 30inches (76.2 cm) 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: For overhead clearance, even though a minimum of only 12-inches (30.48 cm) is
required, 18-inches (45.72 cm) or more is suggested. 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-inch (1.58 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.
D. FRESH AIR SUPPLY REQUIREMENTS
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. The dryer must
be installed with provisions for adequate combustion and make-up air supply.
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 (33.98 cmm) must be supplied to
each dryer. As a general rule, an unrestricted air entrance from the outdoors (atmosphere) of a minimum of
1-1/2 square feet (0.14 square meters) is required for each dryer.
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 a separate make-up air opening 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 0.46 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 motors and other dryer components.
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NOTE: Component failure due to dry cleaning solvent fumes will VOID THE WARRANTY.
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-heat
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 EXHAUST DUCTWORK CAN
CREATE A POTENTIAL FIRE 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.
Horizontal Venting:
When single dryer venting is used, the length of ductwork, from the dryer to the outside exhaust outlet,
should not exceed 15 feet (1.52 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 should 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° 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. 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
should not exceed 20-feet (6.1 meters). The minimum diameter of this ductwork must be at least
12-inches (30.48 cm) (even though the dryer exhaust duct is only 10-inches [25.4 cm]). In the case of
multiple (common) dryer venting, the distance from the last dryer to the outside exhaust outlet should not
exceed 20-feet (6.1 meters). The shape of the ductwork is not so critical so long as the minimum crosssectional 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: 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 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° or 45° angles instead.
The shape of the exhaust ductwork is not critical so long as the minimum cross section 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 square centimeters). THE
DUCT SIZE MUST NOT BE REDUCED ANYWHERE DOWN STREAM
OF THE DRYER.
IMPORTANT: Exhaust back pressure measured by a manometer at each basket (tumbler) exhaust
duct area must be no less than 0 and must not exceed 0.3 inches (0.74 mb) of water
column.
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