Thermo Products OPB (24, 36)- 80, 30 service manual Definition of Subcooling

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

The suction pressure and condenser subcooling are the most significant readings. If a unit is suspected of having a low refrigerant charge, the unit should be recharged using the suction pressure then topped off using subcooling. Any additional refrigerant may cause damage or unintended problems.

The pressure/temperature chart on the wiring diagram is to serve only as a guide. Pressures shown are realistic averages which will vary somewhat with changes in air temperatures, air flowrate across the evaporator and condenser coils and humidity – both inside and outside.

If a charge must be added to the system, connect to the suction service port of the service valve and add a vapor charge only while the system is operating. Addition of liquid refrigerant at the suction port may damage the compressor.

2.Definition of Subcooling:

Subcooling is extra heat removed from refrigerant below the saturation pressure/temperature of the refrigerant. A certain amount of refrigerant subcooling is usually beneficial and needed to help assure the best operation of the cooling system. Subcooling takes place in the condenser. It is a function of the amount of airflow into the condenser, the outside ambient air temperature, the refrigerant pressure into the condenser, and pressure drop through the condenser.

Refrigerant with low subcooling may partially change back into vapor, or “flash to gas”, while flowing to the evaporator. The resulting gas bubbles can block or interrupt flow through refrigerant controls causing the evaporator to “starve” for liquid refrigerant. The consequences are poor evaporator efficiency, high superheat, and generally poor cooling of the conditioned space. Unless very well- insulated, long liquid lines from the condenser to the evaporator, specifically liquid lines exposed to high ambient temperatures, are prone to reduce refrigerant subcooling. To insure sub-cooled liquid refrigerant reaches the evaporator under all conditions, it is usually advisable to take subcooling measurements during the warmest part of the day. Test measurements taken during this time would provide results typical of the most adverse conditions under which the cooling system would operate. Installing a liquid line sight glass at the inlet to the evaporator is a simple, but effective, way to prove liquid is feeding the evaporator. If the sight glass shows all liquid flow without bubbles this is a good indication that the amount of subcooling is adequate.

NOTICE: Do not attempt a superheat measurement when the ambient temperature is less than 60° F. Low loading on the cooling system will result in low or erroneous superheat measurements.

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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 INSTRUCTIONSA. Codes and Clearances a.Combustible materialb.Non-combustiblematerial 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 Operating Instructions For Your Safety Read Before Operatingi.STOP! Read the safety information above 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 D. Supply/Return Air Blower 1.Filter maintenance procedure2.Filter replacement 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 Diagnostic Features VIII. TROUBLESHOOTINGPower must be disconnected before servicing A.Heating SystemCad Cell Resistance in ohms CAD CELL CHECKOUT PROCEDURENumber of flashes 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 valve is not energized Start A. SEQUENCE OF OPERATIONS FOR THE HEATING SYSTEMStandby At any time the oil Start trial for ignitionControl System Action valve is not energized Start A. SEQUENCE OF OPERATIONS FOR THE HEATING SYSTEMStandby At any time the oil Start trial for ignitionPage Page PROPER COMBUSTION ACHIEVED? IS THE PROBLEM DELAYED IGNITION?ARE VENT TERMINAL AND HEAT EXCHANGER CLEAN? 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 Dimensions & Weight Heating Performance using # 2 fuel oilNominal Electrical Power Requirements Model NoXVI. APPENDIX G REPLACEMENT PARTS LIST Page
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