Refrigeration, Air Conditioning Troubleshooting Flowchart Guide

REFRIGERATION TROUBLESHOOTING FLOWCHART

There are 7 Steps of a Systematic Refrigeration Troubleshooting Flowchart.

          1. Determine Problem

          2. Look for Signs/Symptoms

          3. Determine Causes of Problem

          4. Perform Logical Elimination Process

          5. Find the Most Probable Cause

          6. Correct the Defect

          7. Recheck System Operation

          

MOST COMMON REFRIGERATION PROBLEMS

1. Undercharge/Leak

2. Frozen/Iced Evaporator

3. Overcharge

4. Restriction

5. High Discharge Temperature/High Head Pressure

6. Compressor Problems

7. Fan/Motor Problems

8. Electrical Components Problems  

  

Example I:  REFRIGERATION TROUBLESHOOTING FLOWCHART

1. Determine Problem:  POOR COOLING

2. Signs/Symptoms:

·        presence of oil leaks

·        rapid compressor cycling (orifice tube systems)

·        bubbles/foam on sight glass

·        low side/suction pressure Low

·        high side/discharge/head pressure Low

3. Possible Causes of Problem:

·        undercharged – insufficient refrigerant charge (foam/bubbles in sight glass)

·        leak

·        plugged suction filter

·        ice build up on evaporator

·        dirty evaporator

·        restriction in evaporator

·        faulty/defective fan

·        metering device (expansion valve) underfeeding

4. Perform Logical Elimination Process

     - narrow down the causes of the problem in logical systematic fashion

5. Find Most Probable Cause

     - using tools to conduct functional tests and performance tests to find out

       the most likely root cause of the problem

     - example: most probable cause is undercharge due to a leak

6. Correct the Defect

     - repair the leak and add appropriate amount of refrigerant

7. Recheck System Operation

    - conduct another performance test and check temperatures and pressures

      to ensure system is back to correct normal operation

Example 2:  NO COOLING – UNDERCHARGED/LOW REFRIGERANT/LEAK

Actual Repairman/Serviceman procedure: R22 system

1. Customer complaint report – NO COOLING

2. Look at the Thermostat, ensure it is in COOL mode and set at 70 F

3. Feel the supply duct whether it is blowing hot air

4. Check the return air filter

5. Determine which loads are running: Indoor Fan, Outdoor Fan, Compressor

6. Measure amperage of compressor using Multi-tester clamp-on meter (for Residential AC: normal compressor amps = 11 A)

7. By the process of elimination, since all 3 loads are running, therefore the problem is mechanical

8. Check for debris around condensing unit (leaves, grass, etc.)

9. Calculate Superheat:

     a.  Measure indoor wet bulb temperature – place psychrometer in return air duct (psychrometer reading:  70 F)

     b. Measure outdoor dry bulb temperature – place psychrometer near condensing unit (measurement reading: 95 F)

     c. Measure suction line pressure using manifold gage (reading: 50 psig)

     d. Use PT CHART to determine evaporation temperature corresponding to 50 psig --- 26 F

    

  

     e. Determine actual temperature of suction line using Multimeter Probe:  75 F

     f. Calculate Superheat = Actual suction line temp – evaporation temp at 50 psig

         Superheat = 75 – 26 = 49 F

     g. Using SUPERHEAT CHART corresponding to 95 F dry bulb and 70 F wet bulb temperatures, the superheat is 18 F

 

10. Using Mechanical Air Conditioning Fault Table, determine what the problem is: Leak/Undercharged

11. Check for leaks on the indoor & outdoor units using soap and bubble or electronic leak detector

12. Add refrigerant

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Determine Problem:  INADEQUATE COOLING

Signs/Symptoms:

- suction pressure is high

- head pressure is high

- continuous compressor operation (orifice tube systems)

- ice or frost on condenser

- ice on evaporator coil

Possible Causes:

- overcharged – too much refrigerant charge

- evaporator freeze up/iced up

- thermostat temperature setting too high

- dirty condenser coil

- restriction in condenser coil

- fan not running

- fan blade reversed

- poor air circulation

- excessive load/warm products

- door open/door seal broken

- thermostatic expansion valve (TXV/TEV) overfeeding

- insufficient clearance around cabinet

- high ambient temperature

Determine Problem:  RESTRICTION

Signs/Symptoms:

- no cooling/poor cooling

- gauge pressures lower than normal

- compressor cycles frequently

- frost on high pressure lines

- suction pressure is from low to vacuum

- head pressure is low

Possible Causes:

- defective compressor

- contaminants such as dirt or corrosion

- defective TXV/TEV

- plugged orifice

- plugged/defective filter-drier

------------  OTHER  REFRIGERATION  PROBLEMS  ------------

Compressor Not Running, Correct Voltage & Phase:
1. Check voltage within 10%
2. Check Overload Protector
3. Check Start Capacitor
4. Check Start Relay
5. Check Amp Draw of compressor.  If very low compared to RLA/FLA, check:
       _ broken discharge valves
       _ broken suction valves
       _ broken crank
       _ broken push rod


Compressor Not Running, Incorrect Voltage & Phase:
1. Test circuit for voltage loss & phase loss
2. Test contactor
3. Check control relay
4. Check safety devices such as High Pressure Switch, Low Pressure Switch, Oil Pressure Safety Switch.
5. Before pressing Reset on the safety devices, find out reason why it tripped and fix it.


High Head Pressure on Water-cooled Condenser:
1. Check High Pressure Control. If tripped, adjust setting on water regulating valve to achieve manufacturer's recommended pressure.
2. Check water flow. If insufficient:
           - check water supply and plumbing
           - check water inlet temperature
           - check water outlet temperature, if high, adjust water regulating valve to recommended pressure
            - check condition of valve, if defective, worn or scaled with calcium/mineral deposit, replace valve
3. If water flow is sufficient:
            - reset high pressure control if tripped
            - determine temperature differential (TD) between condenser water outlet & inlet
            - if TD is too low, condenser is dirty or has calcium/mineral build-up
            - acid solution can be circulated into condenser to remove mineral deposits and improve heat transfer according to manufacturer's instructions/procedure


High Head Pressure on Air-cooled Condenser:
1. Check if condenser is dirty, clean coil using wash down or high pressure system
2. Check condenser fan motor correct rotation
3. Check for worn, loose or broken belt
4. Check fan blade condition, size, and correct direction (not installed backwards)
5. Check motor bearing, if there is side to side play, replace motor
6. If condenser is facing south, move north or install shade
7. If ambient temperature is high or condenser is located near heat-producing equipment, relocate and find solution to prevent overheating 

                                         --------------------------------------------------------------------------------------

NORMAL CONDITIONS FOR R134A SYSTEM:

Ambient temp:  80 F --- 27 C

Humidity:  50% RH

Air outlet temp of supply:  12 C --- 53 F

Lo-Side:  40 psig

Hi-Side:  320 psig

Sight glass:  clear --- adequate refrigerant

                      (foamy --- insufficient refrigerant

                        frosty --- almost nothing

                        no foam --- too much)

Air Conditioning Diagnostic Charging Table:

 

Compressor and Electric Components Troubleshooting:

Refrigeration Troubleshooting: Causes and Remedy

AC/Furnace Troubleshooting:

Heat Pump Troubleshooting Guide:

Sample Refrigeration Troubleshooting Flowchart:

                                                                                

Table 1.  HOW TO TROUBLESHOOT COMMON REFRIGERATION PROBLEMS:

PROBLEM	POSSIBLE CAUSES	SOLUTION/REMEDY
System Not Running	Power cord not plugged in	Plug in power cord
	Fuse blown	Replace fuse; find out reason blown
	Circuit breaker tripped	Reset circuit breaker; find out reason for the trip
	Main power switch is off	Turn on main power switch
	Incorrect voltage supply	Check voltage; ensure correct voltage is supplied
	Thermostat setting is too high	Lower down thermostat setting
	Thermostat defective/faulty	Replace thermostat
	System is in defrost cycle (freezer)	Wait and time defrost cycle (typical freezer defrost cycle is 30–45 minutes, 2-4 times per day)
	Compressor mechanical and or electrical problems	Check and repair mechanical and electrical compressor problems
Power is ON but no display on control board	Phase loss	Check wiring for breaks
	Fuse blown	Replace fuse
	Power phase open or transformer shorted	Check transformer output voltage (12 V AC/24 V AC)
	Control board failure	Replace control board
Control board displays but Compressor does not run	Compressor relay tripped	Find cause & perform corrective action
	Internal thermal overload tripped	Wait until compressor cools down for reset  ( 5 minutes )
	HI-LO pressure safety switch tripped	Determine reason and correct it before resetting safety switch
	Defective contactor or coil	Repair/replace
	Cold Room temperature is lower than setpoint	Reset temperature setpoint
	Compressor malfunction	Check compressor motor windings
Compressor Does Not Start, No Hum	Fuse blown	Replace fuse and determine the reasons why the fuse was blown (shorted/grounded/open/burnt windings, overloading, etc.)
	Tripped circuit breaker	Reset circuit breaker and find out the causes why it tripped
	Motor protector open/Thermal Overload tripped	Check motor/overload protector  (overload automatically resets)
	Improperly wired; Loose wiring	Repair/correct the wiring
	Burnt motor windings/open circuit	Check/replace motor winding
	Defective contactor/coil	Repair/replace
	Temperature control malfunction	Reset/Repair/replace temp. control
	Pressure control/switch broken	Reset/Repair/replace press. control
	Manual reset button	Press manual reset but find out why button went to reset lockout
	High pressure control lockout	Clean dirty condenser coil, check and repair fan not running, check/repair overcharged refrigerant, then press Reset
	Lube oil control tripped	Check lube oil sight glass, refrigerant migration, too low/too high oil level, oil leakage, P-trap piping (oil not returning to compressor), worn oil pump, oil contamination, crankcase pressurization due to piston blow-by (leakage into the crankcase)
Compressor Does Not Start, with Humming Sound	Supply voltage too low/too high	Check and correct supply voltage
	Faulty run or start capacitor	Replace run/start capacitor
	Defective start relay	Replace start relay
	Compressor improperly wired	Correct the wiring
	Shorted/grounded motor windings	Repair/replace motor windings
	Un-equalized system pressures on a PSC motor	Off cycle will eventually equalize system pressures, use hard start kit or bigger start capacitor
	Tight bearings, shaft seized, broken pistons or rods (mechanical issues)	Diagnose and repair/replace
Compressor Does Not Start, Hums & Trips on Overload	Dirty condenser coil	Clean the condenser coil
	Supply voltage too low/too high	Check and correct supply voltage
	Surrounding area too hot	Relocate cabinet or equipment
Compressor Starts but Short Cycles	Dirty condenser coil	Clean the condenser coil
	Recirculation of discharge air from condenser	Relocate condenser, vent out discharge air
	Recirculation of discharge air from evaporator	Check for blockage/obstruction
	Discharge pressure high	See Discharge Pressure High
	Suction pressure high	See Suction Pressure High
	High superheat, Low in refrigerant	Adjust the superheat (rule of thumb superheat for medium-temperature walk-in cooler is 8° to 10°F; low-temperature applications is 4° to 6°F)
	Overcharged, undercharged	Correct the amount of refrigerant
	High/Low voltage, voltage imbalance, voltage out of phase	Check and correct the supply voltage
	High amperage on 3-phase supply voltage	Check mechanical problems (crankshaft, piston, etc); partially shorted windings
	Low airflow in evaporator	Check fan/motor, obstruction
	Low outside air temperature	Check low ambient control
	Low humidity, Low load, No capacity control	Check, repair, adjust, install
	Low differential setting on pressure/temperature control	Adjust differential (typical is 15 psig differential on pump down system)
	Low ambient conditions making un-insulated receiver cold	Check/repair/replace insulation
	Liquid line solenoid valve leaking during off cycle	Repair/replace solenoid valve
	Compressor valve leaking	Replace compressor valve
Compressor Starts but Cycles Off on Overload Protector	Suction pressure high	See Suction Pressure High
	Head/discharge pressure high	See Discharge Pressure High
	Improper wiring	Correct the wiring
	Shorted/grounded motor windings	Repair/replace
	Supply voltage low	Check and correct the voltage
	Faulty overload protector	Replace
	Defective start relay	Replace
	Failed start or run capacitor	Replace
	Mechanical failure (tight bearings, seized shaft, broken rods, valves, etc)	Repair/replace damaged part/s
Compressor Pull High Amps	Excessive product load	Reduce load
	Wiring too small	Ensure correct gauge sizes of wiring
	Improperly wired	Check and correct the wiring
	Voltage High/Low/Imbalance	Check and correct supply voltage
	Burned relay, contactor contacts	Replace
	Start relay sticks	Replace
	Start/Run capacitor malfunctions	Replace
	Mechanical failure (tight bearings, seized shaft, broken rods, valves, etc)	Repair/replace damaged part/s
	Refrigerant wrong (incorrect)	Recover and put correct refrigerant
	Suction pressure high	See Suction Pressure High
	Head/discharge pressure high	See Discharge Pressure High
Discharge Pressure High	Dirty condenser coil	Clean
(normal head pressure for	Overcharged	Recover and charge proper amount
R404A walk-in cooler: 200-225 psi	Fan not running/poor air flow circulation	Repair/replace/re-arrange products
R134A: 150-300 psig)	Evaporator coil frozen, freeze up, blocked with ice	Check/allow defrost; check thermostat setting not too cold; check gasket seals
Estimate Hi-Side pressure = Ambient temp (F)  x  2.2	Thermostat set too high	Set thermostat to lower temperature
	Cabinet door is open/not sealing	Close door/check or replace door seals
	Excessive product/load inside cabinet	Decrease load/allow time to cool down
	Exterior thermometer out of calibration	Calibrate/replace thermometer
(Air-cooled system)	Condenser outlet air recirculation	Check condenser air outlet location
	Insufficient clearance around cabinet	Ensure adequate air space/flow
	Condenser air flow restriction	Ensure unobstructed air flow
	Ambient temperature too warm	Relocate away from heat generating equipment (oven, stove, dryer, etc.)
	Discharge line restriction	Fix restriction
	Incorrect fan motor or fan blade	Fix/replace with correct parts
	Air and/or non-condensable gases in the system	Remove air and non-condensable gases in the system; check for leaks
(Water-cooled system)	Restricted/Incorrect water flow	Check/repair water flow
	Cooling water too warm	Check water temperature
	Condenser tubes restricted	Clean condenser tubes
	Defective water regulating valve	Replace water regulating valve
Discharge Pressure Low	Low/insufficient refrigerant	Check for leaks, repair, add charge
	Low suction pressure	See Suction Pressure Low
	Ambient air too cold	Check/Install low ambient control
	Damaged compressor valves/rods	Repair/replace
	Uninsulated receiver acting as condenser	Insulate
	Water too cold/defective water regulating valve (water-cooled)	Repair/replace
Suction Pressure Low	Low/lack of refrigerant	Check for leaks, repair, add charge
	Dirty Evaporator	Clean evaporator
	Iced/frozen evaporator	Repair, defrost
	Fan motor/fan blade (air flow) defective	Repair/replace
	Expansion valve underfeeding	Adjust/regulate Superheat setting
	Plugged suction filter	Replace suction filter
Suction Pressure High	Excessive load	Reduce load
(normal suction pressure for R404A walkin cooler is 55-60 psig;	Metering device overfeeding	Adjust TXV Superheat setting
R134A: 30-40 psig)	Metering device Superheat set too low	Adjust TXV Superheat setting
	Compressor discharge valve leak	Repair leak
	Hot gas bypass valve leak	Repair leak
	Hot gas defrost solenoid leak	Repair leak
	Defective or incorrect metering device installed	Replace metering device
	Oversized metering device	Replace metering device
	Metering device held open by foreign material causing liquid flood back	Repair/replace
	Metering device frozen in open position due to moisture in the system	Repair, evacuate, recharge
	External equalizer on metering device is plugged or capped	Clean/repair/replace
	Ruptured suction line to the liquid line heat exchanger	Repair the rupture
	Unit has just completed Defrost Mode and has just started Cooling Mode	This is normal, wait and monitor
High-Temperature Alarm	Product Overload	Reduce product load
	Excessive door opening	Reduce door opening
	Poor refrigeration efficiency/performance	See Suction Pressure High See Discharge Pressure High
	Frost build-up on Evaporator	See Frost on Evaporator fins
Frost on Evaporator fins	Incomplete defrost cycle	Defrost manually, adjust defrost setting
[normal setting:  4 times a day,  30 minutes defrost (off) cycle]	Defrost time intervals too long	Adjust defrost time and interval setting ( 4 x 30 )
Coil frosted during defrost	Heater malfunction	Check/repair/replace
	Insufficient defrost cycles per day	Adjust defrost control settings
Ice build up on Drain Pan	Defective heater	Check/repair/replace
	Drain line plugged	Clean
Large Temperature Difference between actual cold storage box & control panel setpoint	Incorrect room temperature	Re-position sensing point of temperature sensor
	Sensor placement, wire too long	Check placement, enlarge wire section
	Sensor contactor open	Reconnect sensor
Walk-in Cooler, Refrigerator, or Freezer runs too long/continuously	Too much warm product is loaded on Cabinet/Cold Room Storage	Allow adequate time for product to cool down
	Door is open	Close door
	Excessive door opening	Avoid prolonged door openings
	Door gasket not sealing properly	Adjust door/Replace gasket
	No product inside the cabinet	Load cabinet with products
	Dirty condenser coil	Clean
	Airflow problems around condensing unit	Provide good air space; Relocate away from heat, hot equipment, sunlight
	Frozen/iced evaporator	Defrost coil, ensure door gasket is sealed and thermostat not set too cold
Cabinet is Noisy	Loose parts	Tighten
	Vibration of tubing	Ensure no contact of tubing with other components
Refrigerator is freezing products	Cabinet is overloaded with products	Decrease load and re-arrange products
	Thermostat set too low	Set thermostat to higher setting
Condensation on Cabinet face	Face heaters are turned OFF	Turn ON
Digital Thermometer blank, flashing, incorrect temperature, odd characters	System not running/temperature too high	See System Not Running, Discharge Pressure High, High Temperature Alarm
	Thermometer probe wire disconnected	Reconnect probe wire
	Incorrect power to thermometer	Check Transformer, Battery
	Display module out of calibration	Calibrate using procedure on Manual
Run Capacitor burned out	Supply voltage excessively high	Check/Repair/Replace
	Incorrect capacitor	Replace with correct specification
	Capacitor voltage rating too low	Replace with higher voltage rating
Start Capacitor burned out	Compressor is short cycling	Repair
	Relay contacts sticking	Replace
	Incorrect capacitor	Replace with correct one
	Start winding staying in circuit too long	Repair/replace
Start Relay contacts stick	Compressor runs in short time duration	Repair/Adjust
	No bleed resistor on the start capacitor	Replace with Start Capacitor having a bleed resistor
Start Relay burned out	Compressor short cycling	Repair/Check
	Supply voltage high or low	Adjust/Repair
	Relay improperly mounted	Ensure arrow is UP on the side of relay
	Start or Run Capacitor is incorrect	Replace with correct capacitors
	Starting Relay is incorrect	Replace with correct relay specifications with the compressor manufacturer

Credits/References:

- youtube

- delmar cengage

- trutechtools.com/testo

- lg ac mechanical troubleshooting guide

- http://www.hvacrinfo.com/trouble.htm