1. EKAS 2.19.36 Fault find- General Appliances
UEE31307 Certificate III in
Refrigeration and Air Conditioning
Stage 2A
Units: UEENEEPOO2B
Chris Hungerford
Friday, March 31, 2017

2. The two golden rules
Test before you touch, this protects you physically, so you can have a good day!
Test your work is electrically safe when completed, tests include insulation resistance, earth continuity, polarity, and visual inspection, this protects you financially. A

3. Procedure to isolate a Supply
Safe Isolation of a Supply
Test before you touch, this protects you physically, so you can have a good day!
Procedure to isolate a Supply
Notify all persons likely to be affected by the isolation.
Determine the method to isolating the supply.
Test the supply availability.
Isolate the supply.
Danger tag the isolation device.
Test that the supply is isolated.
Test the testing device. A

4. Electrical Safety Regulation 2002
WARNING
Are you working LIVE? Using a voltmeter to measure low voltage is working live!
Electrical Safety Regulation 2002
11 Requirements for electrical work
(1) An employer or self-employed person must ensure that, unless the circumstances required under this division for the performance of live work apply, live work is not performed.
Maximum penalty—40 penalty units.
As per Regulation 12 “Requirement for performance of live work”, to perform live work you must satisfy the following seven (7) questions:
Have you prepared a risk assessment?
Is your test equipment appropriate to perform live work? Minimum Cat 500v ac.
Has your test equipment been maintained and confirmed that it is operating correctly? Regulation 18.2(b) “the instrument is tested at least every 6 mths to ensure it is in proper working order”, and Regulation 12.1(f) “the instrument is tested immediately prior to work to confirm that the instrument is operating correctly”
Have you the correct PPE, (Safety boots, long pants, long sleeved shirt, insulated gloves, safety glasses)? As per AS/NZS 4836 Safe working on low voltage electrical installations.
Is the isolation point clearly identified?
Is the isolation point able to be reached without any obstructions?
Is the area where the electrical live work is performed clear of any obstructions?
Note: if you are not working within the requirements of the above laws then your inaction to comply threatens the following;
Your right to claim workcover in the event of an accident
Your right to claim any insurance benefits in the event of an accident
You will be fined the prescribed penalty units for those laws that you have breached. A

5. What’s the bottom line?
If you work on power circuits, you need a CAT III-600 V or CAT IV-600 V/ CAT III 1000 V meter.
Look for the CAT rating and voltage rating marked near the input jacks.
CAT or voltage rating alone can be misleading
Look for independent certification.
Some manufacturers mark their meters as CAT III-750 V. The IEC standard does not allow spacing in between 600 V and 1000 V; i.e., a meter can only “meet” CAT III-750 V by meeting CAT III-1000 V, in which case any manufacturer would presumably mark it CAT III-1000 V. Some manufacturer’s meters have 1000 V marked on the front, with no reference to CAT I, II or III. Only on the back and in the manual does it become clear that the meter is CAT I V (it is dual rated as CAT III-300 V). It is fair to say that there appears to be some “confusion” among manufacturers with regard to these relatively new standards., which is why it is important for you to educate yourself with regard to the new safety standards.
CAT IV-600 V CAT III-1000 V A

6. Heaters & heating devices
All heating devices are resistive, therefore:
Current can be calculated using the power rule.
Resistance can be calculated using Ohm’s Law.
Determine the current & resistance of this
12kW 240V Duct heater.
I = P/V = 12000/240 = 50A
R= V2/P = (240 x240) / = 4.8W B

7. 24 60 Volts 240v 4A 5A 100v 48 Current Power 250W 3.6kW 1.2kW
Determine the unknown values of the heating elements
Volts
Current
Power
Resistance
240v
24 4A
60 5A
250W
100v
3.6kW
48
1.2kW B

8. 24 Answers 60 10 Volts 240v 10A 240v 4A 50v 5A 100v 36A 240v 5A 48
Current
Power
Resistance
240v
10A
24
2.4kW
240v 4A
60
960W
50v
10 5A
250W
100v
36A
2.7
3.6kW
240v 5A
48
1.2kW B

9. Temperature control. AS/NZS 3000:2007 4.11 ELECTRIC DUCT HEATERS
The electrical portion of any electric duct heater installation shall comply with the requirements of this Standard.
NOTE: Attention is drawn to the fact that—
(a) such installations are within the scope of AS/NZS ; and
(b) safety requirements are contained in AS/NZS 3102; and
(c) compliance therewith may be required by the relevant regulatory authorities. B

10. AS/NZS 3102:2002 2.19.36.B 7 PROTECTION AGAINST HEAT AND FIRE
7.1 Fixing of heating units
An electric heating unit incorporated in a duct heater shall be assembled and firmly supported so that it will not introduce a risk of fire through displacement resulting from loosening of fixings or other defects likely to be brought about by vibration or other conditions of service.
7.2 Interlocking of supply to heater unit and blower motor
The electrical supply to the heating unit(s) shall be interlocked with the supply to the associated blower motor such that interruption of supply to the blower motor will automatically interrupt supply to the heating units.
7.3 Devices to prevent overheating
The duct heater shall be provided with both the following devices as a safeguard against overheating under abnormal operating conditions:
a) A device to interrupt electric supply to the heating unit if airflow through the duct heater ceases. This device may be a thermal cutout or an air supply failure switch. The device shall comply with the test requirements of Clause
b) A non-self-resetting thermal cutout, located within the duct heater casing or air duct adjacent to the heating units, so that the air temperature in the immediate vicinity of the heating units does not exceed 120°C under abnormal operation. The thermal cutout shall comply with the test requirements of Clauses and
NOTE “immediate vicinity” is considered to be a distance of 25 mm. The devices mentioned in a) and b) may interrupt the heating unit current directly or they may form part of a system in which they interrupt the heating unit current indirectly via a component such as a contactor. The device or system providing protection during abnormal operation shall not operate during normal operation.
The devices or systems are not required if the air temperature in the immediate vicinity of the heating units does not exceed 120°C under the abnormal operation conditions described with the devices short-circuited. B

11. Thermostat
Fluid operated bellows. These are not that common in small appliances but often found in refrigerators, air conditioners, domestic ovens, and so forth. An expanding fluid (alcohol is common) operates a bellows which is coupled to a set of movable contacts. B

12. Thermostat
Expanding Tube thermostat B

13. Thermostats are closedN
Oven
Element
Thermostats are closed
Loop control
Liquid Filled
Bellows
Electrical
Contacts B

14. Liquid Filled ThermostatB

15. Thermostat
Electronic thermostats. These typically use a temperature controlled resistance (thermistor) driving some kind of amplifier or logic circuit which then controls a thyristor or contactor. B

16. Thermostat NTC Thermistors: Are non-linear
Change resistance dramatically with temperature (they have a very high sensitivity)
Are not interchangeable
Are not suited to wide spans
Suffer from drift and decalibration at high temperatures
If the resistance of a thermistor is 5,000Ω at room temp, it may drop to about 20Ω at 300C and rise to about 200,000Ω at -50C.
TEMPERATURE °C
RESISTANCE (Ohms)
200K
100K
20k
200
100
300
-100
40k B

17. Other temperature measuring devices
Thermocouples
Resistance Temperature Detectors(RTD’s)
Diodes and semiconductor IC’s
Gas expansion system
Mercury expansion system
Coiled bimetal strip
Radiation Pyrometers B

18. Thermostat settings Differential Set Point Differential Temperature
It is the difference between the turn-on
temperature and the turn-off temperature
of the thermostat.
Temperature
20°C
Time B

19. Simmerstat control
The simmerstat consists of a parallel connected heater that causes a bi-metallic switch to bend and open circuit.
Problems; No control, open circuit heater or welded switch contact. No output, damaged switch contacts.
Load
Line
Load N B

20. Energy cut-outs They are not adjustable.
Designed to cut off the supply before the appliance damages itself due to a failure of the thermostat. B

21. Fault finding heating circuitsB
Fault finding heating circuits
Fuse
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
A 240V A N A N
Switchboard
Voltmeter
= 240v
Field (on heater)
Voltmeter = 240v
Client: Hello…..Heater does not operate!
Step 1. Test supply is available at heater terminals and element.
Caution: Working live….. All work as per regulation 12.

22. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N
isolate
Ohmmeter = 20MW
R= V2/P = (240 x240) / = 2.4W
Ask yourself, “I have supply at the element, this heater should operate”?
Step 2. Isolate the supply and test to confirm isolation, tag, ……..supply isolated.
Step 3. Measure the resistance of the element, compare the value to your determined value using ohm’s law. B

23. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N
These two values should be approximately equal
Ohmmeter = 20MW
R= V2/P = (240 x240) / = 2.4W
Remember; Very high values of resistance = open circuit.
Very low values of resistance = short circuit.
Therefore the fault with this circuit is an open circuit element. B

24. Fault finding heating circuitsB
Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V A N A N
Voltmeter = 0v
Client: Hello…..Heater does not operate!
Step 1. Test supply is available at heater terminals and element.
Caution: Working live….. All work as per regulation 12.

25. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N E
Ohmmeter
= 20MW
Voltmeter = 240v
High resistance = open circuited fuse
This fuse has blow for a reason, do not replace it until the reason for blowing has been determined.
No supply available at heater!
Step 1. Check supply at switchboard.
Step 2. Check condition of fuse or circuit breaker. B

26. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N
120A
Reasons for a Fuse to blow
An overload.
A Short circuit.
A partial short circuit.
Ohmmeter = 1.5W
I = V/R = 240/1.5 =160A.
The calculated value should be less than the fuse rating.
An overload.
Step 1. measure the resistance of the circuit.
Step 2. determine the current from the measured values.
Step 3. compare determined current to the size of the fuse. B

27. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N
120A
Ohmmeter = 0.005W
2. A Short circuit.
Step 1. Measure the resistance of the circuit.
Step 2. Break the circuit at the element and measure it’s resistance.
the ohmmeter scale should be set to the x1 scale. B

28. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N
120A
R= V2/P = (240 x240) / = 2.4W
Ohmmeter = 0.005W
The correct value of element resistance = 2.4W.
The measured value is very low therefore the fault is a short circuit, look for loose or damaged wiring, or replace the element.
Step 2. Break the circuit at the element and measure it’s resistance. B

29. Fault finding heating circuitsB
Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N E
120A
Here the megohmmeter indicates a leakage to earth,
But which component of the circuit is faulty?
Step 3. Break the circuit in ½ and test each side.
Megohmmeter = 500W
3. A Partial Short circuit
This type of fault is commonly a leakage to earth fault.
The fuse may or may not be blown, Safety switches will trip.
The client may report shock tingles from the equipment.
Step 1. Isolate the supply and test to confirm isolation, tag, ……..supply isolated.
Step 2. Perform an insulation resistance test on the whole circuit between all active conductor to earth. AS/NZS 3000 minimum value > 1MW
The meghommeter scale should be set to 500vDC

30. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N E E
120A
Megohmmeter = 500W
Step 3. Break the circuit in ½ and test each side.
Megohmmeter = 120MW
The insulation resistance of the heating element is> 1MW, therefore is good. The reading on the thermostat side of the circuit is < 1MW, therefore faulty.
Step 4. Break the faulty circuit in ½ and test each side. B

31. Fault finding heating circuits
Thermostat
Blower
interlock
thermal
cutout
24kw
heater
Fuse
A 240V N A N E E
120A
Megohmmeter
= 120MW
Megohmmeter = 500W
The blower interlock circuit is less than 1MW, Therefore the fault is within that area of the circuit.
Step 4. Break the faulty circuit in ½ and test each side. B

32. Electric Motors
The electric motor is an inductive device, ie, it has coils of wire and principle operation is due to the magnetic effect. B

33. The Stator
Iron core
Copper winding
Mounting frame B

34. The rotor The rotor earns the name being the moving part of the motor.
Rotor bars
Cooling fan
The rotor bars induce a current that sets up a magnetic field that opposes the original magnetic field, thus, set up a magnetic repulsion-attraction action. B

35. Testing motor windings
Check the resistance of the motor windings to determine if a fault has occurred.
On single phase motors measure: start to common winding, run to common winding, and start to run winding.
Check phase to ground.
Ohms reading between S-R should be the total of both R & S winding.
High insulation resistance between any winding conductor to ground
Determine the condition of motor windings:
Some motor failures are due to shorts, grounds or opens in the windings. While a motor circuit tester may be necessary for a complete checkout, these failures are easily detected with a higher-end digital multimeter. For example, the Fluke 179 digital multimeter works well for checking motor windings and relays for shorts, grounds, and opens (as shown above). To take an ohm measurement across the windings, first disconnect the system wiring from the compressor; this includes the relay, capacitors, and overload protection. Then check the resistance of the motor windings to determine if a fault has occurred. Maintenance records or measurement of other known good components can be used for comparison during troubleshooting. On single phase motors, check the following: Start to common winding, run to common winding, start to run winding. The ohms reading between the 3 windings will provide three different readings as follows: the highest resistance is found between the start and run windings, the least resistance between the common and run windings, and the middle amount of resistance is between the common and run windings (refer to above diagram). On three motors, check phase to phase and then phase to ground. The phase to phase ohm readings should be equal between phases, with no continuity from any phase to ground.
Typical resistance test on a 1 motor B

36. Testing motors on the bench
Continuity of winding
Resistance of windings
Insulation resistance
At least 1MΩ
Mechanical check
Can it turn
Visual check
Vents, end shields, balance weights in place, key not dangerous
Bench tests B

37. Supply indicates 240V, therefore the fault maybe with the appliance.
Small domestic refrigerator
Door switch
240v 25W
Lamp
A 240V N A N E
240v 100W
Evaporator fan
Compressor
Thermostat
Current
Relay
Run
Thermal
overload
Issue: Refrigerator does not operate!
Refrigerator does not make any sounds!
Start
Step 1. Remove plug top from socket outlet.
Step2. Using your voltmeter test socket outlet for a supply
Supply indicates 240V, therefore the fault maybe with the appliance. B

38. Small domestic refrigerator
Door switch
240v 25W
Lamp
A 240V N A N E
Ohmmeter = 15MW
240v 100W
Evaporator fan
Thermostat
Current
Relay
Run
Thermal
overload
Issue: Refrigerator does not operate!
Refrigerator does not make any sounds!
Start
Step 3. Place an ohmmeter across the A & N pins on the plug top.
Step 4. Think..! At this point of time what should be operating within this refrigerator?
The evaporator fan and the compressor.
Now determine what value of resistance should the ohmmeter be indicating.
Compressor approx 20W, evap fan approx 80W = total resistance approx 16W
The ohmmeter indicates a high value of resistance therefore = open circuit, but where? B

39. Small domestic refrigerator
Door switch
240v 25W
Lamp
A 240V N A N E
Ohmmeter = 0.5W
Good reading
240v 100W
Evaporator fan
Thermostat
Current
Relay
Run
Thermal
overload
Start
Compressor
Step 5. Remove compressor terminal cover and connect an ohmmeter between the neutral pin of plugtop and circuit wiring.
Ohmmeter = 20W
Good reading B

40. Fault identified as an open circuit of the Active conductor
Small domestic refrigerator
Door switch
240v 25W
Lamp
A 240V N A N E
240v 100W
Evaporator fan
Thermostat
Current
Relay
Run
Thermal
overload
Ohmmeter = 15MW
Bad reading!
Start
Compressor
Step 6. Remove thermostat cover.
Attach an ohmmeter between A pin of plugtop and circuit
Fault identified as an open circuit of the Active conductor B

41. Final Tests 1 Visual inspection, is the work as per AS/NZS-3760?
2 Earth continuity test, is the earthing circuit continuous? AS/NZS-3760: < 1W, .
Insulation resistance test, is the conductors insulation able to contain the operating voltage?
AS/NZS > 1MW
4 Polarity, are the outlets correctly connected, are the circuit actives switched? C

42. Small domestic refrigerator
Door switch
240v 25W
Lamp
A 240V N A N E
240v 100W
Evaporator fan
Thermostat
Current
Relay
Run
Thermal
overload
Start
Compressor
AS/NZS3760
< 1W
Don’t forget to perform your safety tests on the appliance!
1. Visual inspection.
2. Earth continuity.
One connection on the earth pin
The other on the metal frame. C

43. > 1MW Small domestic refrigerator Compressor
Door switch
240v 25W
Lamp
A 240V N A N E
240v 100W
Evaporator fan
Thermostat
Current
Relay
Run
Thermal
overload
AS/NZS 3760
> 1MW
Start
Compressor
Don’t forget to perform your safety tests on the appliance!
1. Visual inspection.
2. Earth continuity.
3. Insulation resistance test C

44. Work Record required by Regulations
Electrical Safety Regulation 2002
Part 2 Electrical work
14 Testing of electrical equipment after electrical work
(1) This section applies if electrical work is performed on electrical equipment.
(2) A person who performs part or all of the electrical work, and is responsible for bringing the electrical equipment to a state of readiness for connection to a source of electricity for use for its intended purpose, must ensure the electrical equipment is tested, as required under subsections (5) and (6).
Maximum penalty—40 penalty units. .
Date of inspection
Appliance
Visual inspection
Earth continuity W
Insulation resistance MW
Polaritya = Correct
RCD test current
30 MA trip time
Milliseconds
0h h Test butt
2/7/09
Refrigerator ( LG model R Serial )
O.K
0.3
75M
N/A
Safetypac (Clipsal mod 56B, serial )
o.K.
0.8
187M a 22 18 C

45. Work Record required by Regulations
Electrical Safety Regulation 2002 Part 2 Electrical work
15 Certificate of testing and safety
This section applies if a licensed electrical contractor performs electrical work that must be tested under this division.
(2) The contractor must, as soon as practicable after the testing, ensure that the person for whom the electrical work was performed is given a certificate complying with this section.
(5) A licensed electrical contractor must keep a copy of a certificate given under this section for at least 5 years after the certificate is given.
Maximum penalty for subsection (5)—20 penalty units
Certificate of Testing and Safety
As per Electricity Safety Regulation 2002,Part 8”Electricity Supply”, Division 2 “Testing”, Regulation 15,”Certificate of Testing & Work”
Electrical worker who tested the electrical work.
Phone
Licence No:
Contractors Licence
Details of work
Details of Electrical Contractor
Inspection Certificate No:
Acts, Regulations,
Codes of Practices & Standards.
Electricity Act 1994 & Electricity Regulation 2006
Electrical Safety Act 2002 & Electrical Safety Regulation 2002
AS/NZS 3000:2000. Incorporating Amendment No. 1 (September 2001), Amendment No. 2 (April 2002), & Amendment No. 3 (July 2003). The Wiring Rules.
AS/NZS :1998, Electrical installations— Selection of cables Part 1.1: Cables for alternating voltages up to and including 0.6/1 kV—Typical Australian installation conditions
I certify that the electrical installation work listed above has been tested in accordance with the prescribed procedures and that such work is electrically safe and complies in every respect with the requirement of the Electricity Safety Regulation 2002, regulation 159.
Signature of Electrical worker:
Date of Certification: C

46. Manufacturer Specifications of disconnected & replacement equipment.
When replacing any load you should be sure that the new item is suitable with regards to: Speed, Rotation, Power rating, Voltage, Current, Physical size, Environmental conditions & design of replacement, Dust & waterproof, temperature, UV rating, touch proof, life span. C

47. Energising supply
Only after the visual inspections and safety testing as per AS/NZS 3000:2007 has proven that the circuit is fit for purpose are you to energise the circuit.
Remove only your Danger tag. If another worker has their danger tag on the isolated point then you can not energise.
If clear: Energise the circuit.
Test for the correct and safe operation of the circuit, i.e. rotation, system performance, current draw, voltage, etc.
Prepare all your safety and performance documentation. C

48. Further reading: Textbook
Questions: Workbook, Topic 5, Q1 – Q10