Thermo Products 30, OPB (24, 36)- 80 service manual H. Airflow Requirements and Sizing of Duct Work

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

H. Airflow Requirements and Sizing of Duct Work

The duct system must be sized and installed by a qualified installer or service person, following the design standards of the Air Conditioning Contractors of America (ACCA) or the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE). This furnace has been designed to operate against a maximum external static pressure of 0.4 in. W.G. This is equivalent to .2 in. W.G. supply and .2 in. W.G. return pressure drops.

1.Supply and return air ducts have to be furnished by the installer and run between the appliance, which must be installed outdoors, and the interior of the structure the appliance serves. These ducts must be sealed to the casing of the appliance.

2.To reduce the transmission of vibration and noise to the duct system and to reduce flexure of the duct system due to thermal expansion and contraction, it is recommended that flexible joints be installed at the supply and return duct connections to the unit.

3.The return air duct system must equal the supply air duct system in the flow capacity (CFM) for a given pressure drop. Use a supplier's catalog for proper sizing of outlet and return air registers and grills to ensure that they meet the flow requirements of the run to which they are connected.

4.The duct system shall be sized to provide the maximum air flowrate (CFM) required of the installation. Two common rules for determining minimum airflow in heating and cooling systems follow:

a.For heating, 14 CFM of airflow are required per 1000 BTU/hr of heat output, based on steady state operation and a 50° to 80° temperature rise.

b.For cooling, 400 CFM of airflow are required per ton of air conditioning. (For reference, a ton of A/C = 12,000 BTU/hr removed from the space.)

Refer to Example 1, in Appendix B: Calculations of this manual, for a sample calculation of how to determine the required minimum air flowrate.

5.Duct sizing is based upon both air velocity and pressure drop considerations. When possible, current practice favors designing ductwork for lower air velocities. (For residences, a maximum air velocity of 800 FPM is suggested.) This results in quieter duct systems, systems which require less fan power (reduced operating costs), and less carefully constructed ductwork (lower initial costs).

However, lower air velocities also result in larger duct sizes than necessary at higher velocities. In some cases, space restrictions may limit the ductwork to smaller than optimal sizes.

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Contents Page Contents SECTION I. SAFETY INFORMATION Page IF YOU DO NOT FOLLOW THESE INSTRUCTIONS EXACTLY, A FIRE OR EXPLOSION MAY RESULT CAUSING PROPERTY DAMAGE, PERSONAL INJURY, OR LOSS OF LIFE Waterproof type connectors must be used when connecting electrical power and control wiring to the unit to prevent moisture from being drawn into the unit during operation For initial start-upof the appliance after installation, it may be necessary to purge the air out of the oil line. A qualified heating contractor should do this 1.This appliance shall be used with only the type of fuel oil for which it is approved. Refer to the appliance-ratinglabel for the required type of fuel III.GENERAL INSTALLATION II. GENERAL INSTRUCTIONSb.Non-combustiblematerial A. Codes and Clearancesa.Combustible material B.Selection of Installation Location The unit is manufactured with runner supports that raise the unit, about 1.25 inches above the mounting base, allowing air circulation beneath the metal surfaces. This clearance helps to promote air circulation under the base that allows the unit to be mounted on combustible materials. This clearance also helps to reduce metal corrosion caused by a buildup of moisture under the appliance C.Venting of Combustion Products FIGURE 2 Vent Terminal Mounting Position D. Condensate DrainE. Oil Tank and Piping 5.A readily accessible, design-certified,manual oil shutoff valve, with a non- displaceable rotor member, shall be installed in the fuel oil supply piping within 6 feet of the appliance G. Burner Specifications And Performance F. Oil FilterOil Pump H. Airflow Requirements and Sizing of Duct Work 6.The following method can be used to size ductwork when air velocities are low to moderate h.The resistance of the take-offand the outlet register or return grill should then be summed together to determine the total pressure drop for each branch. This value should be close to the assumed value for the pressure drop of the system. If it is not close, then flowrates for each branch must be adjusted, or the design of the duct system must be altered, to give the proper pressure drops. Usually, the cross-sectionalarea of the ductwork should be changed in order to adjust the pressure drop to a suitable value 7.The supply and return air ducts, or flexible joints, should be carefully secured and sealed to the appliance housing to prevent air leakage from, or into, the duct system. For best performance, insulate the outside surfaces of the ducts to reduce heat loss from, or heat gain to, the ducts. The insulation system should be carefully selected and installed to minimize water and moisture absorption by the insulation I.Air Filters 1.Filter Installation J. Electrical Wiring Typically, control wiring between the outdoor appliance and the indoor thermostat, and if used, electronic air cleaner or humidifier, will be required. Field wiring of control circuits should consist of copper conductors rated for at least 240 VAC with an insulation temperature rating conforming to Type T wire, 35C temperature rise. Depending upon code requirements, rigid or flexible conduit is recommended, and may be required. Make connections between the thermostat, and electronic air cleaner or humidifier if used, and the fan control module, inside the burner compartment. Consult the wiring diagram for the appropriate connection points on the thermostat and the fan control module 3.All wiring sizes must comply with local codes or the National Electrical Code. To minimize voltage drop to the appliance, the next larger size wire should be used when long wiring runs, in excess of 100 ft., are employed. Refer to the wiring diagrams when wiring or servicing Figure 4 The Fan Control Module 2. Thermostat Anticipator Setting Figure 5 Heat Anticipator Adjustment ScalePreferred method of adjustment 3. Blower Motor Speed Selection IV. STARTUP PROCEDURES A.Heating System For Your Safety Read Before Operating i.STOP! Read the safety information aboveOperating Instructions To Turn Off Oil to Appliance2.Adjustment of Burner Combustion g.Turn the disconnecting switch to “ON” ii.CARBON DIOXIDE CO2 OR OXYGEN O2 Take a CO2 sample from flue passageway. It is possible to achieve readings of up to 14% CO2 or 2% O2 , but it is better to have a slightly lower CO2 or higher O2 reading with zero smoke measured. To achieve a lower CO2 reading, open the air band, or shutter, on the burner until zero smoke is measured 3.Adjustment Of Heat Input Rate 4.Setting Supply Air Temperature Rise 5.Checkout Procedure Page B.Cooling Section 1.Initial Startup 2.Definition of Subcooling 3.Condenser Subcooling 4.Definition of Superheat5.Evaporator Superheat V. INSTALLERS INSTRUCTIONS TO USER VI. DEALER MAINTENANCE B.Heat Exchanger Remove the clean-outcovers. Also, remove the burner compartment cover, the burner, and the burner mounting plate. When removing the clean-outcovers, special care must be taken not to damage the gaskets. Should any of the gaskets separate, show evidence of cracks or breaks, or otherwise be unable to provide the necessary seal, the gasket must be replaced before reattaching the clean-outcovers, refer to Figure Burner Operation section Figure 10 View of OPB Heat ExchangerC.Electrical System 1.Filter maintenance procedure 2.Filter replacementD. Supply/Return Air Blower E. Supply/Return Air FilterF. Extended Appliance Shutdown Figure 13 Location of Oil Pump Vent Plug 2.Remove the burner compartment cover Burner Motor The following maintenance points should be reviewed periodically to assure the heating and cooling systems continue to function properly ducts for any signs of collapse, holes, or excessive corrosion. Repair or replace components as required VIII. TROUBLESHOOTING Power must be disconnected before servicingDiagnostic Features A.Heating SystemCAD CELL CHECKOUT PROCEDURE Number of flashesCad Cell Resistance in ohms Model R7184B2.Is the sub-baseof the thermostat switched to the “COOL” position? IX. REFERENCES X. APPENDIX A SOURCES FOR REFERENCED STANDARDS XI. APPENDIX B CALCULATIONS Example Figure 15 Plan View of a Typical Residence Area for Example See page 75 for a copy of the ASHRAE chart So, the total equivalent straight duct length is or approximately the same as without the elbow Using the previous pressure drop equation, the pressure drop through segment “A” is 0.0321 in. W.G. Then, the pressure drop for the “D” and “E” branch is Likewise for the other branches PSIG Page Now, the degree of superheat can be calculated Page All installations and services must be performed by qualified service personnel A. SEQUENCE OF OPERATIONS FOR THE HEATING SYSTEM Standby At any time the oilvalve is not energized Start Start trial for ignitionControl System Action A. SEQUENCE OF OPERATIONS FOR THE HEATING SYSTEM Standby At any time the oilvalve is not energized Start Start trial for ignitionPage Page IS THE PROBLEM DELAYED IGNITION? ARE VENT TERMINAL AND HEAT EXCHANGER CLEAN?PROPER COMBUSTION ACHIEVED? CORRECT INSERTION OR AIR TUBE BURNOFF MAY OCCUREFFECTS OF PRESSURE ON NOZZLE FLOW RATE Page 1.201.6 Check capacitance of the run capacitor 1Loose wire connections 3.301.2 Check for a properly sized expansion valve Heating Performance using # 2 fuel oil Nominal Electrical Power RequirementsDimensions & Weight Model NoXVI. APPENDIX G REPLACEMENT PARTS LIST Page
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