This document is a service manual for the Maytag Commercial Laundry MDG-35 dryer. It provides comprehensive information on the dryer's function, technical specifications, usage, and maintenance procedures.
Function Description
The MDG-35 is a commercial laundry dryer designed for efficient and safe drying of various fabrics. It operates using either natural gas or L.P. gas as a fuel source for heating. The dryer incorporates a control panel (microprocessor) for managing operations, a gas burner assembly for heat generation, a drive motor for tumbling, a motorized impellor (blower motor) for airflow, and a tumbler for holding clothes. Safety features include a sail switch to ensure proper airflow before the burner ignites, and a hi-limit thermostat to prevent overheating. The dryer is designed for continuous operation in commercial settings, with robust components and safety interlocks to ensure reliable performance.
Important Technical Specifications
- Model: MDG-35
- Fuel Type: Natural Gas or L.P. Gas
- Heat Input: 10,000 to 2,000 Ft.3 (Gas/Natural)
- Orifice Size: Varies based on gas type and elevation. For natural gas, typical orifice sizes are 3.5 inches (8.7 mb) water column. For L.P. gas, typical orifice sizes are 10.5 inches (26.1 mb) water column.
- Electrical Service: 115 to 230 volts, 50/60 Hz.
- Drive Motor: 1/4 HP motor.
- Blower Motor: Motorized impellor, backward curved fan.
- Pressure Tap: Located on the gas valve for measuring gas pressure.
- Lint Collection: Features a lint drawer for easy removal of accumulated lint.
- Safety Devices: Sail switch, hi-limit thermostat, automatic reset thermostat, and various electrical safety interlocks.
- Drying Temperature: Monitored by exhaust temperature transducers. Normal operating temperature range is more than 3-seconds.
- Steam Pressure: For steam dryers, pressure should not exceed 125 PSI (8.61 bars).
Usage Features
The MDG-35 dryer is designed for straightforward operation in a commercial laundry environment.
- Control Panel: The microprocessor-based control panel allows users to select various drying cycles and monitor the dryer's status. Inputs are provided via a keypad, and outputs are displayed on the computer screen.
- Gas Burner Assembly: The gas burner assembly, including a burner tube, gas valve, and Glo-Bar infrared sensor, ensures efficient heat generation. The inlet piping enters through the rear of the dryer on the right-hand side.
- Tumbler: The tumbler consists of three ribs, a front, and a back, which are forced together as an assembly to ensure proper tumbling of clothes.
- Main Door Switch: Located in the main control panel, the main door switch prevents the dryer from operating when the door is open, ensuring user safety.
- Sail Switch: This switch is located on the rear of the machine and ensures proper airflow before the burner ignites. It creates a negative pressure inside the burner box, pulling air through the tumbler and activating the sail switch.
- Hi-Limit Thermostat: An automatic reset disc-type thermostat set at 205°F (96.11°C) located at the top of the heat duct. It automatically shuts off the burner if the flame in the burner duct gets too hot.
- Automatic Reset Thermostat: A 190°C automatic thermostat located inside the dryer in the lint compartment above the lint drawer. It shuts off the burner if the air temperature gets too hot.
- Lint Drawer: A pullout type lint drawer located at the bottom of the dryer in the lint compartment. It must be kept clean for proper dryer operation and efficiency.
- Reversing Relay: Located behind the control panel, this relay manages the reversing action of the dryer.
Maintenance Features
Regular maintenance is crucial for the MDG-35 dryer's longevity and safe operation. The manual outlines several key maintenance procedures:
- Lint Cleaning: Lint must be cleaned from the drawer and screen every third or fourth load. The lint chamber, thermostat, and microprocessor temperature sensor (sensor bracket) area should also be cleaned weekly. Accumulation of lint can restrict airflow and create a fire hazard.
- Exhaust Ductwork Cleaning: The exhaust ductwork should be inspected and cleaned periodically (every 6 months) to prevent lint accumulation, which can lead to reduced airflow and potential fire hazards. A back draft damper that is sticking partially closed can result in slow drying and shutdown of heat circuit safety switches or thermostats.
- Adjustments: Inspect bolts, nuts, screws, grounding connections, and nonpermanent gas connections (unions, shutoff valves, and orifices) every 6 months. Motor and drive belts should be examined. Cracked or seriously frayed belts should be replaced. Complete operational check of controls and valves should be performed.
- Electrical and Gas Requirements: All electrical and gas installations must comply with applicable national and local codes. The dryer must be connected to the type of gas (natural or L.P.) indicated on the dryer data label.
- Operational Service Check Procedure: This includes turning on electric power, starting the dryer, checking the display, pressing "E" on the keypad of the microprocessor controller, checking the dryer's start and display, making a complete operational check of all operating controls, and checking all safety-related circuits.
- Manometer Test: Periodically test the gas water column pressure using a manometer to ensure it meets specifications for natural gas (3.5 inches water column) or L.P. gas (10.5 inches water column).
- Component Replacement: Detailed instructions are provided for replacing various components, including the computer, keypad assembly, microprocessor temperature sensor probe, Glo-Bar, gas valve, burner orifices, burner hi-limit thermostat, lint compartment hi-heat protector, sail switch, main door, front panel, tumbler, drive motor, and blower housing.
- Diagnostic Mode: The dryer features a diagnostic mode that allows users to troubleshoot problems by displaying event IDs and failure descriptions. This mode helps identify issues such as radiant sensor fault, burner ignitor fault, exhaust high limit, coin errors, pocket forward/reverse rotation sensor faults, and S.A.F.E. (Water not connected) status.
- Help Menu: A help menu provides additional information on feature symbols, feature text, and help codes, aiding in troubleshooting and understanding dryer status.
- Important Safety Precautions: The manual emphasizes critical safety warnings, including the risk of fire or explosion if gasoline or other flammable vapors are stored near the dryer, the danger of personal injury or fire if the dryer is operated without back guards, outer tops, or service panels removed, and the necessity of proper ventilation and lint cleaning to prevent fire hazards. It also warns against operating steam dryers with more than 125 PSI steam pressure.
- Preventive Maintenance: A program or schedule should be established for periodic inspection, cleaning, and removal of lint from various areas of the dryer, as well as throughout the ductwork system. The frequency of cleaning can be best determined from experience at each location.
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