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

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

Piping from the natural gas meter to the furnace shall be in accordance with requirements of the local utility. Piping from the propane tank to the furnace must follow the recommendations of the gas supplier.

A readily accessible, design certified manual shut off valve with a non- displaceable rotor member shall be installed within six feet of the gas equipment it serves. A union or flanged connection shall be provided downstream from the manual valve to permit removal of controls. A 1/8" N.P.T. plugged tapping is provided at the inlet of the gas control for connection of a test gage to check gas supply pressure to the furnace. Unions must be of a ground joint type or flanged- jointed using a gasket resistant to LP gas. Pipe dope or sealant certified to be resistant to the action of liquefied petroleum gases shall be used on all threaded joints.

Left and Right Gas Supply Piping - This furnace is set up to accept either left or right side gas piping using a street elbow and a straight pipe.

A sediment trap (drip leg) must be used on both propane and natural gas installations, to trap oil, condensate and other impurities, which might otherwise lodge in the gas, valve or plug the burner orifice. The sediment trap shall be installed as close to the furnace inlet as possible. When there is excessive condensation between the gas meter and the furnace, a sediment trap shall be provided at the outlet of the gas meter. Failure to install a sediment trap may void the limited warranty on the furnace, refer to Fig. 6.

If local codes permit the use of a flexible gas appliance connector, always use a new listed connector. Do not use a connector, which has previously served another gas appliance.

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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 Replacement Filter Maintenance ProcedureReturn 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