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

 

 

11 

Table 2: Minimum Filter Area Required (Sq. in.) 

Furnace Model 

Filter Type 

Maximum 

Rate of 

Velocity 

(FPM) 

MHA1-50 
MDA1-50 

MHA1-75 
MDA1-75 

MHA1-100 
MDA1-100 

MHA1-125 
MDA1-125 

*THERMO 
PRODUCTS 
 SUPPLIED  
 PERMANENT 
FILTER

 

600 

 

172

 

254

 

328

 

402

 

STANDARD  
PERMANENT 
FILTER

 

500  

208

 

304

 

394

 

484

 

DISPOSABLE 
TYPE 
FILTER

 

300 

 

344

 

506

 

656

 

804

 

* The Thermo Products supplied filter can be cut to size to fit other filter retention 
systems as long as the minimum size requirement is met.   

 

NOTICE:

 The filter areas in Table 2 are the 

minimum

 areas required based on 

the flowrate generated by the furnace for standard heating speeds only. The 
following formula can be used to determine the minimum filter area required for 
cooling, if the unit is equipped with cooling. This value should then be compared 
to the value shown in table 2 and the larger of the two should then be used for 
determining the minimum filter area required for that installation. 

 

FORMULA: 

 (tons of cooling)(400 CFM per ton)(144 sq. in. per foot) = filter area sq. inches 
(max. air velocity of filter from table 5 for the filter type)          
 

EXAMPLE:

 If you had an MHA1/MDA1-100 furnace and 4 tons of cooling and a 

standard reusable filter. 

 

4 tons x 400 CFM x 144 = 460 square inches for cooling 

 

             

500 

 

For heating an MHA/MDA-100 needs 328 square inches of standard reusable 
filter. The filter system must be designed for the larger flow requirement 
determined for cooling of 460 square inches. A filter would have to be sized so 
that the area (length x width) was at least 460 sq. in.

 

 
 
 
 

Summary of Contents for MDA1-100N

Page 1: ...lain paper Printed text black Binder staple upper left corner Individual page specifications Cover page printed single side up Table of contents page printed single side up Warranty page printed singl...

Page 2: ...O NOT USE ANY PHONE IN YOUR BUILDING LEAVE THE BUILDING IMMEDIATELY IMMEDIATELY CALL YOUR GAS SUPPLIER FROM A NEIGHBOR S PHONE FOLLOW THE GAS SUPPLIER S INSTRUCTIONS IF YOU CANNOT REACH YOUR GAS SUPPL...

Page 3: ...t Flue Vent Connector 16 K Sidewall Venting 19 1 Horizontal Size and Lengths for Horizontal Vents 20 L Gas Gas Piping 21 1 Installation of Natural Gas Piping 23 2 Installation of Propane Gas Piping 24...

Page 4: ...INSTALLER S INSTRUCTIONS TO USER 41 APPENDIX A SOURCES FOR REFERENCED STANDARDS 42 APPENDIX B SEQUENCE OF OPERATION 43 APPENDIX C TROUBLESHOOTING FLOWCHART 45 APPENDIX D PARTS PACKAGE COMPONENTS 49 A...

Page 5: ...propane gas in this manual any other label or markings on the furnace is to be construed to be propane HD 5 a commercial grade of liquefied petroleum gases composed of a minimum of 90 percent liquid...

Page 6: ...ation dates for replacement of any warranted part s I Safety The following guidelines and warnings should be read and understood before continuing with the installation of this furnace Failure to foll...

Page 7: ...relocation associated with horizontal installation of the MDA1 10 Inform and demonstrate to the user the correct operation and maintenance of the appliance as explained in the Users Information Manual...

Page 8: ...ing a concrete base bricks patio blocks etc When installing this furnace provisions must be made to insure the supply of adequate combustion and ventilation air in accordance with the air for combusti...

Page 9: ...urn whether flameproof or not or whether plastered or not plastered Non combustible Material Material which will not ignite and burn such materials consisting entirely of steel iron brick concrete sla...

Page 10: ...salt Tile adhesives Avoid installing the furnace in areas where it is evident these chemicals are being stored or used within close proximity to the furnace In addition avoid storing or using any che...

Page 11: ...ished with properly screened metal sleeves If an exhaust fan or additional fuel burning appliances are present in the furnace room there should be increased concern about providing adequate airflow to...

Page 12: ...ides and service access to the front of the furnace refer to Table 1 If the furnace is suspended it must be supported at both ends and in the middle with clearance allowed for removal of both access d...

Page 13: ...oil must be installed on the air outlet side of the furnace to avoid water vapor condensation in the furnace heat exchanger NOTICE Return air grilles and supply registers in the air distribution syste...

Page 14: ...hermo Pride Filter Rack I Use of Non Thermo Pride Filter Retention Means Failure to comply with minimum filter installation requirements may affect the performance and or void the warranty on this fur...

Page 15: ...y The following formula can be used to determine the minimum filter area required for cooling if the unit is equipped with cooling This value should then be compared to the value shown in table 2 and...

Page 16: ...zontal series furnace must be vented in accordance with these instructions into a factory built chimney or vent complying with a recognized standard Type B1 or double wall vent as well as masonry chim...

Page 17: ...sealed The inside of the vent should be free of all obstructions 2 Replacing An Existing Furnace From a Common Vent CARBON MONOXIDE POISONING HAZARD Failure to follow the steps outlined below for each...

Page 18: ...tion Use the flame of a match or use a draft gauge 8 If the improper venting is observed on any of the appliances during the above testing the common vent system must be corrected Follow the steps out...

Page 19: ...it rises and the bottom will be heated first This heating of the walls will cause the flue gas temperature to drop which in turn may reduce the wall temperature below the dew point causing condensati...

Page 20: ...of two or more appliances These requirements as well as all the installation requirements outlined in this manual for an MHA1 MDA1 series furnace must be followed when an MHA1 MDA1 furnace is common...

Page 21: ...6 temperature rating 480 F minimum should be used to secure both the flue pipe MHA1 MDA1 50 and the Thermo Products supplied 4 in adapter MHA1 MDA1 75 MHA1 MDA1 100 MHA1 MDA1 125 to the outlet of the...

Page 22: ...ould 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 in...

Page 23: ...vent K Sidewall Venting The MHA1 MDA1 Series furnaces SHALL NOT BE COMMON VENTED IF SIDEWALL VENTING IS EMPLOYED Before sidewall venting the MHA1 MDA1 furnace read and understand this section as well...

Page 24: ...consequential damages The above limitations or exclusions may not apply to you IMPORTANT It is the installer s responsibility to inform and demonstrate to the user the correct operation and maintenan...

Page 25: ...ng and should include the furnace piping and gas valve Never use an open flame to check for a gas leak Care must be taken not to wet electronic components during leak test Wetting the electronic compo...

Page 26: ...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...

Page 27: ...ll gas appliances installed on any main or trunk line must be totaled to determine its required carrying capacity EXAMPLE A line must supply a furnace of 100 000 BTU hr input a hot water heater of 40...

Page 28: ...ure for natural gas is 14 0 in W C and minimum supply for purpose of input adjustment is 4 5 in W C 2 INSTALLATION OF PROPANE GAS PIPING Copper and brass tubing and fittings except tin lined shall not...

Page 29: ...stem Table 5 COPPER TUBING SIZE FOR PROPANE GASES All black pipe sizes shown are nominal iron pipe sizes Seamless copper tubing may only be used with gases that are not corrosive to it See note below...

Page 30: ...f bushing is provided for support of the supply wire harness Make the 115 volt supply connection in this junction box A green screw is provided in order to connect the power supply ground wire A disco...

Page 31: ...currents from supply or return air registers or such that natural circulation of air is blocked such as behind doors in shelves or in corners It should always be located on an interior wall In additi...

Page 32: ...airflow The wires for the unused speeds should then be reconnected to the module in the park positions Figure 8 Blower and Control Panel The option switches on the W R integrated control are used to...

Page 33: ...ments section of this manual regarding the installation and leak testing of gas piping For initial start up of the appliance after installation it may be necessary to purge the air out of the gas line...

Page 34: ...Do not attempt to light the burner by hand BEFORE OPERATING smell all around the appliance area for gas Be sure to smell next to the ground because some gas is heavier than air and will settle on the...

Page 35: ...nd If you smell gas STOP Follow section h in the safety information above If you don t smell gas go to the next step Rotate the gas control valve knob or switch lever to the ON position Replace the bu...

Page 36: ...elevation of 5 000 feet If the furnace is installed at an elevation of 2 000 feet or less no reduction in input rate is required For high altitude installations your local gas supplier may assist in d...

Page 37: ...gauge or manometer at the 1 8 in NPT plugged tap on the inlet side of the appliance gas control valve shown in the General Gas Piping Requirements section of this manual An Allen wrench is normally r...

Page 38: ...nt 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...

Page 39: ...ed may vary depending on a number of factors A few of these factors are changes in the actual resistance of the duct system to airflow at any time de rating of the appliance due to elevation fouling o...

Page 40: ...g power b Block return air opening or disconnect blower motor leads c Restore power to appliance d In the heating mode set the thermostat above room temperature producing a call for heat e When high a...

Page 41: ...rning off power or removing the necessary to restart the furnace and have the failure occur again DIAGNOSTIC FEATURES The 50A65 control used on this furnace continuously monitors its operation and the...

Page 42: ...procedures which must be performed by the homeowner user can be found in the Users Information Manual The following maintenance procedures should be performed at the beginning of each heating season...

Page 43: ...et must be replaced if they show any sign of having been damaged 5 Clean all furnace markings as necessary and verify that all are still legible Any illegible or missing markings must be replaced Repl...

Page 44: ...A1 series units Slide dirty filter out of the filter rack Clean the filter by vacuuming rinsing with tap water hosing or dipping in an ordinary detergent solution After cleaning replace the completely...

Page 45: ...users information manual 5 That failure to maintain and operate this furnace in accordance with these instructions could result in hazardous conditions bodily injury and property damage and may void...

Page 46: ...nd 21279 0230 301 617 7819 3 American National Standards Institute Inc Attn Customer Service 11 West 42 nd Street New York New York 10036 212 642 4900 4 American Society for Testing and Materials 100...

Page 47: ...t or roll out switch opens system energizes inducer fan and circulator blower at high speed until situation correction occurs Thermostat calls for heat contacts close Pressure switch senses adequate p...

Page 48: ...ition control module goes into system lockout If flame is detected then lost the ignition control module will repeat the initial ignition sequence for a total of four recycles After four unsuccessful...

Page 49: ...to the thermostat Yes No Replace thermostat Yes Are the thermostat wires connected properly Replace control transformer Correct wire connections No Is there 24 VAC across TH TR terminals of the igniti...

Page 50: ...continuously replace ignition control module No Check wiring to draft inducer If okay replace inducer assembly Is there 120 VAC across draft inducer power terminals IND IND N at the ignition control m...

Page 51: ...me on when energized Does blower wheel spin freely Yes Is blower motor capacitor working properly Yes Replace Motor No No Replace blower motor capacitor No Check for blower wheel rubbing against housi...

Page 52: ...n diagram Reset if necessary No Check for short in wire to thermostat Replace thermostat if necessary No Yes No Yes Does system run until thermostat is satisfied If LED Light Flashes 1 Flash then paus...

Page 53: ...X4 J BOX 350024 1 2X4 J BOX COVER 350020 1 GROUNDING INSTRUCTIONS MG 966 1 HEYCO SR 34 2 350016 1 HEYCO UB 875 350750 1 INSTALLATION PARTS PACKAGE MHA1 MDA1 75 S00S4427 MDA1 MHA1 100 S00S4428 MDA1 MHA...

Page 54: ...All installations and services must be performed by qualified service personnel 50 APPENDIX E REPLACEMENT PARTS LIST MHA1 120v 24v 3 4 2 1 O N...

Page 55: ...All installations and services must be performed by qualified service personnel 51...

Page 56: ...All installations and services must be performed by qualified service personnel 52 REPLACEMENT PARTS LIST MDA1...

Page 57: ...All installations and services must be performed by qualified service personnel 53...

Page 58: ...All installations and services must be performed by qualified service personnel 54 APPENDIX F WIRING DIAGRAM...

Page 59: ...All installations and services must be performed by qualified service personnel 55...

Page 60: ...nent split capacitor air over 48 Y Blower motor nominal HP 1 5 1 3 1 2 3 4 Blower motor full load amps 3 25 6 0 8 0 11 0 Motor shaft diameter Direction of rotation shaft end Clockwise No of speeds 3 4...

Page 61: ...ir over 48 Y Blower motor nominal HP 1 5 1 3 1 2 3 4 Blower motor full load amps 3 25 6 0 8 0 11 0 Motor shaft diameter Direction of rotation shaft end Clockwise No of speeds 3 4 4 4 Run capacitor 10...

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