Tuesday, December 19, 2017

Walk-in cooler wiring diagram, walk in freezer, domestic refrigerator wiring

                                           Walk-in cooler mechanical diagram:

                               Walk-in freezer electrical wiring diagram with heater

                             Walk in freezer with defrost - electrical wiring diagram

                         Walk-in cooler with pump down - electrical wiring diagram

                          Walk in freezer with electric defrost - electrical wiring diagram

                              Domestic refrigerator - simple electrical wiring diagram

Watch Youtube video:

Tuesday, December 12, 2017



Purpose/Why: Provide knowledge & safety awareness of R134a Refrigerant

Where can you use this knowledge: Workplace, in the field, Home, Office

Definition, use, characteristics

What is a refrigerant?

Refrigerant = a substance that is used to transfer heat energy.

What is R134a?

R134a is a refrigerant that is primarily used in domestic refrigeration and automobile air conditioners.

My fridge at home uses R134a refrigerant
My car's A/C uses R134a refrigerant as well

Chemical name: Tetrafluoroethane

Characteristics: Non-flammable, Non-explosive, Non-toxic, Colorless, Odorless  gas


1.       Frost bite – may result when it contacts your skin
2.      Eye damage – may result when it contacts your eyes
3.      Inhalation of too much vapour can cause headaches, unconsciousness, or suffocation.

­First Aid

1. Skin contact:
·         Take off all contaminated clothing immediately.
·         Flush skin with lukewarm water.
·         Call a physician.

2. Eye contact:
·         Flush eyes with plenty of water for at least 15 minutes.
·         Get medical attention.

·         Move away from exposure to an area of fresh air.
·         Keep the patient warm and at rest.
·         Consult a physician.

Safety Precautions

1.       Always wear PPE.      ---  (Safety glasses, gloves)
2.      Avoid breathing vapours or mist.
3.      Avoid contact with skin and clothing.
4.      Ventilate work area. Provide sufficient air exchange and/or exhaust.

Storage of Refrigerant Cylinders:
5.      Keep cylinder upright and valves tightly closed.
6.      Store cylinders in cool, dry well ventilated place.   (Temperature:  45 C/113 F)


R134 is a useful refrigerant in domestic refrigeration and automobile air conditioners, however there are also hazards that we need to be aware of. To minimize injuries, all safety precautions must be followed.

R134a other info:       

Zero Ozone Depletion Potential (ODP): 0
Global Warming Potential (GWP): 1.2

Other uses:

  • Domestic air-conditioners
  • Commercial refrigeration
  • Aerosol propellant in pharmaceutical, pesticide, cosmetics and cleaning industry
  • Flame retardant
  • Blowing agent


102.03 g/mol

Colorless gas

0.00425 g/cm3, gas

−103.3°C (−153.9°F; 169.8 K)
−26.3 °C (−15.3°F; 246.8 K)

  0.15 wt%

Main hazards

Flash Point

250°C (482°F; 523 K)

Wednesday, September 13, 2017

Refrigeration, Air Conditioning Troubleshooting Flowchart Guide

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


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  


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


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


Determine Problem:  INADEQUATE COOLING
- 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
- 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 


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:

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

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

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

Supply voltage low
Check and correct the voltage

Faulty overload protector

Defective start relay

Failed start or run capacitor

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

Start relay sticks

Start/Run capacitor malfunctions

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
(normal head pressure for
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

Uninsulated receiver acting as condenser

Water too cold/defective water regulating valve (water-cooled)

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

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

Metering device frozen in open position due to moisture in the system
Repair, evacuate, recharge

External equalizer on metering device is plugged or capped

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

Insufficient defrost cycles per day
Adjust defrost control settings

Ice build up on Drain Pan
Defective heater

Drain line plugged

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

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

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

Incorrect capacitor
Replace with correct specification

Capacitor voltage rating too low
Replace with higher voltage rating

Start Capacitor burned out
Compressor is short cycling

Relay contacts sticking

Incorrect capacitor
Replace with correct one

Start winding staying in circuit too long

Start Relay contacts stick
Compressor runs in short time duration

No bleed resistor on the start capacitor
Replace with Start Capacitor having a bleed resistor

Start Relay burned out
Compressor short cycling

Supply voltage high or low

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

- youtube
- delmar cengage
- trutechtools.com/testo
- lg ac mechanical troubleshooting guide
- http://www.hvacrinfo.com/trouble.htm