Cejas Cooling & Construction

I. Common HVAC Repairs

1. Capacitor Replacement
   • Start, run, or dual capacitor
   • Causes: age, heat exposure, electrical surges
   • Corrective Action: test microfarads (within +/-6%), replace if out of spec
2. Contactors / Relays
   • Causes: pitted contacts, stuck contacts, coil not energizing
   • Corrective Action: test coil voltage, replace faulty contactor
3. Compressor Repairs / Replacements
   • Conditions & Symptoms:
     • Open winding (infinite ohms)
     • Shorted winding (0 ohms or continuity to ground)
     • Locked rotor (high amp draw, trips breaker)
     • Burnt terminals (signs of heat damage)
     • Liquid slugging (damaged internals)
     • No start: check for relay, capacitor, overload failure
   • Possible Causes:
     • Open circuits (relays, fuses, overload)
     • Low voltage
     • Unequalized pressures (start issues)
     • Thermostat stuck closed
     • Evaporator coil iced over
     • Excessive refrigerant charge
     • Trapped refrigerant vapor
     • Internal damage (broken rods, valves, etc.)
   • Corrective Action:
     • Test start components (capacitor, relay, overload)
     • Test ohms and megohms for windings
     • Verify refrigerant charge
     • Replace compressor if confirmed failed
4. Refrigerant System Diagnostics & Charging
   • Common issues:
     • Low charge: high superheat, low subcooling
     • Overcharge: low superheat, high subcooling
     • Restriction (TXV, drier, strainer): high subcooling, low suction
     • Liquid line frosting or sweating (TXV stuck, clogged filter drier)
     • Evaporator coil icing
   • Corrective Actions:
     • Recover & weigh in charge
     • Check for restriction pressure drop
     • Replace driers, clean coil, confirm airflow
5. TXV/Expansion Valve Issues
   • Symptoms:
     • Flooding evaporator (low superheat)
     • Starving evaporator (high superheat)
     • Liquid flashing in sight glass
   • Corrective Action: inspect sensing bulb, equalizer line, replace valve if defective
6. High Head Pressure
   • Causes:
     • Dirty condenser coil
     • Non-condensables
     • Overcharge
     • Restricted airflow (condenser)
     • TXV stuck open
   • Corrective Actions:
     • Clean condenser
     • Verify airflow and fan operation
     • Recover and recharge
7. Low Head Pressure
   • Causes:
     • Low refrigerant charge
     • TXV stuck closed
     • Leaking orifice
     • Defrost valve stuck
   • Corrective Action: leak search, repair, recharge, replace defective components
8. High Suction Pressure
   • Causes:
     • Overcharge
     • TXV stuck open
     • Return air temp too high
     • Leaky compressor valves
   • Corrective Actions: verify superheat, inspect TXV, test compressor performance
9. Low Suction Pressure
   • Causes:
     • Low charge
     • TXV restricted
     • Evaporator iced
     • Blocked return airflow
     • Undersized ducting
   • Corrective Actions: inspect airflow, check for restrictions, weigh refrigerant
10. Airflow / Airside Issues
    • Restricted airflow (dirty filter, blocked coil, collapsed duct)
    • Evaporator freezing due to poor airflow
    • Blower motor or capacitor failure
    • Incorrect duct sizing
11. Electrical Controls
    • Blown fuses
    • Faulty defrost control boards
    • Burned or stuck start relays
    • Shorted wires, failed transformers
    • Contactor coils not energizing
12. Defrost Controls / Heat Pump Components
    • Defrost timer or board
    • Reversing valve solenoid coil failure
    • Defrost sensor out of range

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II. HVAC System Calculations & Measurements

1. Superheat & Subcooling
   • Superheat = Suction line temp – Evaporator saturation temp
   • Subcooling = Liquid line temp – Condenser saturation temp
   • Determines charge accuracy, TXV function
2. Airflow Calculation
   • CFM = (BTUh) / (1.08 x Delta T)
   • Static pressure measurement across coil and filter
3. Delta T (Temperature Split)
   • Supply air temp – Return air temp (should be ~16–22°F)
4. Compressor Amp Draw
   • Compare to RLA (Rated Load Amps)
   • Excessive draw = mechanical issue or refrigerant imbalance
5. Voltage Drop
   • Voltage loss across contactors, relays, wiring
   • Check during start-up and run loads
6. Duct Sizing & Static Pressure
   • Measure total external static pressure (TESP)
   • Confirm proper blower selection
7. Refrigerant Leak Search
   • Electronic leak detection
   • Nitrogen pressure test
   • Soap bubble test
8. Combustion Testing (Gas Furnaces)
   • CO levels, draft pressure, combustion efficiency
   • Check heat exchanger condition

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III. Preventive and Predictive Maintenance Needs

• Coil cleaning (evaporator & condenser)
• Filter replacements
• Blower wheel cleaning
• Checking amp draws and capacitor µF
• Drain line flush
• Lubrication of motors (if applicable)
• Checking insulation on suction lines
• Thermostat calibration and programming
• Confirm refrigerant levels
• Inspect ductwork for leaks
• Test defrost cycles