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UEE31307 Certificate III in Refrigeration and Air Conditioning Stage 2A Units: UEENEEPOO2B Chris Hungerford Saturday, May 31, 2014 EKAS 2.19.36 Fault find-

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Presentation on theme: "UEE31307 Certificate III in Refrigeration and Air Conditioning Stage 2A Units: UEENEEPOO2B Chris Hungerford Saturday, May 31, 2014 EKAS 2.19.36 Fault find-"— Presentation transcript:

1 UEE31307 Certificate III in Refrigeration and Air Conditioning Stage 2A Units: UEENEEPOO2B Chris Hungerford Saturday, May 31, 2014 EKAS Fault find- General Appliances

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 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 1.Notify all persons likely to be affected by the isolation. 2.Determine the method to isolating the supply. 3.Test the supply availability. 4.Isolate the supply. 5.Danger tag the isolation device. 6.Test that the supply is isolated. 7.Test the testing device A

4 Are you working LIVE? Using a voltmeter to measure low voltage is working live! Electrical Safety Regulation 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 penalty40 penalty units. WARNING As per Regulation 12 Requirement for performance of live work, to perform live work you must satisfy the following seven (7) questions: 1.Have you prepared a risk assessment? 2.Is your test equipment appropriate to perform live work? Minimum Cat 500v ac. 3.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 4.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. 5.Is the isolation point clearly identified? 6.Is the isolation point able to be reached without any obstructions? 7.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; 1.Your right to claim workcover in the event of an accident 2.Your right to claim any insurance benefits in the event of an accident 3.You will be fined the prescribed penalty units for those laws that you have breached A

5 CAT IV-600 V CAT III-1000 V Whats 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 A

6 Heaters & heating devices All heating devices are resistive, therefore: –Current can be calculated using the power rule. –Resistance can be calculated using Ohms Law. Determine the current & resistance of this 12kW 240V Duct heater. I = P/V = 12000/240 = 50A R= V 2 /P = (240 x240) / = B

7 Volts Current 240v A 100v kW 1.2kW Resistance Power 250W 5A5A Determine the unknown values of the heating elements B

8 Volts Current 240v A 100v kW 1.2kW Resistance Power 250W 5A5A 10A 36A 5A 240v 50v kW 960W Answers B

9 Temperature control. AS/NZS 3000: 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: 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 Expanding Tube thermostat Thermostat B

13 Oven Element Thermostat A N Thermostats are closed Loop control Liquid Filled Bellows Electrical Contacts B

14 Liquid Filled Thermostat B

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 k B

17 Other temperature measuring devices Thermocouples Resistance Temperature Detectors(RTDs) Diodes and semiconductor ICs Gas expansion system Mercury expansion system Coiled bimetal strip Radiation Pyrometers B

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

19 Simmerstat control The simmerstat consists of a parallel connected heater that causes a bi- metallic switch to bend and open circuit. Load N Line Load Problems; No control, open circuit heater or welded switch contact. No output, damaged switch contacts 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 circuits AN N A 240V thermal cutout Blower interlock Thermostat 24kw heater Voltmeter = 240v Fuse 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. A Voltmeter = 240v Switchboard Field (on heater) B

22 Fault finding heating circuits AN N A 240V thermal cutout Blower interlock Thermostat 24kw heater Fuse 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 ohms law. isolate R= V 2 /P = (240 x240) / = 2.4 Ohmmeter = 20M B

23 Fault finding heating circuits AN N A 240V thermal cutout Blower interlock Thermostat 24kw heater Fuse Ohmmeter = 20M R= V 2 /P = (240 x240) / = 2.4 These two values should be approximately equal 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 circuits AN N A 240V thermal cutout Blower interlock Thermostat 24kw heater Fuse 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. Voltmeter = 0v A B

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

26 Fault finding heating circuits AN N A 240V thermal cutout Blower interlock Thermostat 24kw heater Fuse Reasons for a Fuse to blow 1.An overload. 2.A Short circuit. 3.A partial short circuit. 1.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. Ohmmeter = 1.5 I = V/R = 240/1.5 =160A. 120A The calculated value should be less than the fuse rating B

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

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

29 Fault finding heating circuits AN N A 240V thermal cutout Blower interlock Thermostat 24kw heater Fuse 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. E 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 > 1M The meghommeter scale should be set to 500vDC Megohmmeter = 500 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. 120A B

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

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

37 AN N A 240V 240v 25W Lamp 240v 100W Evaporator fan Door switch E Thermostat Run Start Thermal overload Current Relay Compressor Small domestic refrigerator Issue: Refrigerator does not operate! Refrigerator does not make any sounds! 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 AN N A 240V 240v 25W Lamp 240v 100W Evaporator fan Door switch E Thermostat Run Start Thermal overload Current Relay Small domestic refrigerator Issue: Refrigerator does not operate! Refrigerator does not make any sounds! 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 20, evap fan approx 80 = total resistance approx 16 Ohmmeter = 15M The ohmmeter indicates a high value of resistance therefore = open circuit, but where? B

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

40 AN N A 240V 240v 25W Lamp 240v 100W Evaporator fan Door switch E Thermostat Run Start Thermal overload Current Relay Compressor Small domestic refrigerator Step 6. Remove thermostat cover. Attach an ohmmeter between A pin of plugtop and circuit Ohmmeter = 15M Bad reading! 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: < 1. 3Insulation resistance test, is the conductors insulation able to contain the operating voltage? AS/NZS > 1M 4 Polarity, are the outlets correctly connected, are the circuit actives switched? C

42 AN N A 240V 240v 25W Lamp 240v 100W Evaporator fan Door switch E Thermostat Run Start Thermal overload Current Relay Compressor Small domestic refrigerator Dont 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. AS/NZS3760 < C

43 AN N A 240V 240v 25W Lamp 240v 100W Evaporator fan Door switch E Thermostat Run Start Thermal overload Current Relay Compressor Small domestic refrigerator Dont forget to perform your safety tests on the appliance! 1. Visual inspection. 2. Earth continuity. 3. Insulation resistance test AS/NZS 3760 > 1M 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 penalty40 penalty units C Date of inspection Appliance Visual inspection Earth continuity Insulation resistance M Polarity = Correct RCD test current 30 MA trip time Milliseconds Test butt 2/7/09 Refrigerator ( LG model R Serial ) O.K0.375MN/A 2/7/09 Safetypac (Clipsal mod 56B, serial ) o.K M 2218

45 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 Work Record required by Regulations Certificate of Testing and Safety As per Electricity Safety Regulation 2002,Part 8Electricity 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 kVTypical 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


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