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

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

b.Turn on the fuel gas and cause the appliance to activate the heating section by answering a “call for heat”.

c.Allow the heating section to operate for 15 minutes.

d.Note the manifold gas pressure.

e.To adjust the pressure, remove the brass screw from the regulator on the outlet side of the gas control valve. Using a common screwdriver, increase the manifold pressure by turning the screw inward (clockwise), or decrease it by turning the screw outward (counterclockwise). Adjustments to the listed pressure must not exceed 0.3 in. W.G. A 0.3 in. W.G. adjustment will change the input approximately 4.0%.

f.Measure the heat input rate by counting the number of seconds required for the appliance to consume a specified quantity of gas. Refer to the preceding procedure to calculate the heat-input rate.

g.If required, repeat the manifold pressure adjustment again. Repeat the input rate measurement.

h.When the input rate adjustment has been completed, shut off the fuel gas to the appliance. Remove the pressure gage. Reinstall the manifold pipe plug using a thread compound resistant to the action of LP gases. Replace the regulator screw (cap) in the gas valve.

If an input rate within the allowable range cannot be obtained with the present orifice over the range of manifold pressures given, make sure the gas supply pressure is within the specified range. If the supply pressure is less than required, the upstream supply pressure regulator may have to be adjusted to increase the pressure. If increasing the gas supply pressure fails to provide adequate gas pressure at the unit, the supply piping may have to be modified to reduce pressure drop.

C. Burner Adjustment

There are no manual adjustments to the main burners. With the burner compartment door removed, the flames can be observed. Natural gas flames should be relatively short in length, have well defined shapes, and are bright light to deep blue in color, refer to Figure 10.

NOTICE: For appliance operation with propane gas, it is not unusual to observe mostly blue flames having yellow or yellow-orange tips.

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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