Thermo Products MDA1-75N, MDA1-50N, MHA1-75N, MHA1-100N, MHA1-50N, MHA1-125N Inducer Mounting

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All installations and services must be performed by qualified service personnel.

When venting the MDA1 series through the blower compartment a vent chute (AOPS4941) must be used. Refer to Figure 4. This option requires the removal of the two 4-inch diameter plastic plug from the blower pan and the top panel of the unit. After removing the plastic plugs, run the 3-inch diameter vent through the vent chute and the top and bottom openings.

The MDA1-75, MDA1-100 and MDA1-125 will require the use of the 3-inch to 4- inch adapter provided. This adapter is to be installed after the 3-inch vent exits the furnace.

The 3-inch diameter vent running through the vent chute must be a continuous section. No connections should be within the vent chute.

If this venting option is not utilized, the 4-inch diameter plastic plug in the blower pan and the 3 1/2 inch diameter plastic plug in the top panel of the unit should be left in place for proper furnace operation.

The flue may exit the unit through the top, left side, or right side of the unit, refer to Figure 5. The inducer can be rotated by removing the four (4) inducer mounting screws and rotating the inducer housing. Ensure that inducer gasket is in place before reinstalling inducer.

Figure 5: Inducer Mounting

All vent connectors connecting the furnace to the vent must be rigidly supported with hangers and straps in order to prevent sagging and movement after installation. The vent connector must be supported at a maximum of every four feet depending on the design and weight of the material used, to maintain clearances, and to prevent physical damage. The vent pipe must slope upward a minimum of 1/4" for each foot of horizontal run away from the furnace.

Vent connectors used in connecting the furnace to the vent cannot be channeled through floors, ceilings, and walls without the proper protective construction. This construction must be in accordance with the requirements of the National Fuel Gas Code, NFPA 54/ANSI Z223.1-2002 or the latest edition thereof.

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Contents Induced Draft Highboy COUNTERFLOW/HORIZONTAL GAS Furnace Section Safety II. Installation Guidelines Page Shipping Damage PackagingSafety Codes II. Installation GuidelinesCloset and Alcove Installation Installation LocationRefer to Figure Standard ClearancesNon-combustible Material Plenum Flue or Vent All Models Covered by This ManualAir for Combustion and Ventilation MDA1 Horizontal Installation MDA1 Installed Horizontal Duct Work and Air Conditioning Filters/ Filter InstallationOptional Thermo Pride Filter Rack Use of Non-Thermo Pride Filter Retention MeansFormula FPMVenting Carbon Monoxide Poisoning Hazard Replacing An Existing Furnace From a Common VentCondensing in the Chimney Page Page Vent Connection to Inducer Inducer Mounting Automated Literature FAX Sidewall VentingHorizontal Size and Length for Sidewall Venting Horizontal Size and Lengths for Horizontal VentsGeneral GAS Piping Fire or Explosion Hazard GAS PipingPage Typical Gas Piping Installation of Natural GAS PipingSteel Pipe Size for Natural Gas IPS Installation of Propane GAS PipingPage Electrical Field Wiring and Replacing WiringRoom Thermostat Electronic Air Cleaner and Humidifier ConnectionsBlower and Control Panel Initial Startup To delay fan Set SwitchWhat to do if YOU Smell GAS To Turn Off Gas To Appliance Adjustment Of Heat Input Rate Page Burner Adjustment Typical Observation of Main Burner Flames Setting Supply Air Temperature RiseImportant Remove flue blockage when done Checkout ProcedureLED will also flash once at power-up Diagnostic FeaturesGeneral Inspection Shut off gas and disconnect power before continuingHouse Air Blower Filter Maintenance Procedure Filter ReplacementReturn Air Filter VI. Installers Instructions to User Appendix a Sources for Reference Standards Sequence of Operations for Heating System Appendix B Sequence of OperationsMode of Operation Control System Action Heating System Appendix C Troubleshooting FlowchartsYes Is ignitor positioned Correctly? Does system run until thermostat is satisfied? Description Part Number QTY MDA1/MHA1-50S00S4426Appendix E Replacement Parts List MHA1 Page Replacement Parts List MDA1 Page Appendix F Wiring Diagram Page MID-EFFICIENCY Highboy GAS Furnace SPECIFICATIONS5 Appendix G MID-EFFICENCY Furnace SpecificationsNominal temp. rise Heating fan speed