1 / 27

EKAS 2.19.28 Fault find- General Principles

EKAS 2.19.28 Fault find- General Principles. UEE31307 Certificate III in Refrigeration and Air Conditioning Stage 2A Units: UEENEEPOO1B Chris Hungerford Monday, August 25, 2014. The two golden rules. Test before you touch , this protects you physically, so you can have a good day!

zayit
Télécharger la présentation

EKAS 2.19.28 Fault find- General Principles

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EKAS 2.19.28Fault find- General Principles UEE31307 Certificate III in Refrigeration and Air Conditioning Stage 2A Units: UEENEEPOO1B Chris Hungerford Monday, August 25, 2014

  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. 2.19.28.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 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. 2.19.28.A

  4. 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 III @ 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. 2.19.28.A

  5. What is a Fault? • Any condition in an electrical system that is dangerous or unsafe is a fault. • Any condition that will prevent the electrical system from operating correctly is a fault. 2.19.28.B

  6. Overload An overload is a condition where the load on the circuit is too much, causing the current to exceed the current rating of the cables and supply. If the excessive current was allowed to continue, the cables would heat above their rating and may lead to a short circuit. 6A fuse 6A fuse Load 48 48 48 240v 240v I = V = 240 = 5A R 48 I = V = 240 = 10A R 24 2.19.28.B

  7. Short circuit, A very severe condition and will cause fire, burns, and equipment damage if not protected against. The only resistance to the current is that of the supply cables and the size of the electrical source. short circuit 0.5 cables = 0.5 cables = 0.5 Load 47.5 Load 48 240v, 500A supply 240v, 500A supply I = V = 240 = 5A R (47.5+.5) I = V = 240 = 240A R (.5+.5) 8A fuse short circuit 0.5 240v, 500A supply The fuse will open circuit when the current exceeds it’s rating. 2.19.28.B

  8. Partial open circuit, (hot joint) caused by loose or dirty connections that causes an increased circuit resistance. This increased resistance causes a heating effect at the joint and reduces the current at the load. Will cause fire and equipment damage. A fuse or circuit breaker will not protect against this type of fault. The only combat is by visual inspections or thermal imageries. 12 2 2 P=I R = 4 *12 = 192W P=V*I =240 *5 = 1200W 48 48 240v 240v 2 2 P=I *R =4 *48=768W I = V = 240 = 5A R 48 I = V = 240 = 4A R (12+48) 2.19.28.B

  9. Partial short circuit Like a short circuit with a higher resistance. Normally earth faults. Fuses and circuit breakers may not open circuit if the fault current does not exceed their rating. Earth leakages are good examples. 6A fuse 6A fuse 5A 2A Load 48 120 240v 48 240v I = V = 240 = 7A R 34.2 I = V = 240 = 5A R 48 2.19.28.B

  10. Procedures for fault finding Voltage Present Not present Measure current Measure resistance No current High current Low current Low resistance Very low resistance Measure resistance Open circuit Short circuit Partial short circuit or overload Partial short circuit or overload Partial open circuit 2.19.28.B

  11. Flowchart For Problem Resolution Is It Working? NO YES Don’t Stuff With It! Did You Stuff With It? YES YOU IDIOT! NO Anyone Else Know? Will it Blow Up In Your Hands? You’re SCREWED! YES YES Can You Blame Someone Else? NO NO NO Hide It Look The Other Way Yes NO PROBLEM!

  12. Overvoltage category Common sense ways to think of categories • The higher the short circuit fault current available, the higher the category • High energy transients are much more dangerous, because they can trigger an arc blast • The greater the source impedance, the lower the category 2.19.28.B

  13. 2.19.28.B

  14. 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. CAT IV-600 V CAT III-1000 V 2.19.28.B

  15. Fault finding: Continuity technique • Warning: Disconnect the supply. • All healthy component’s circuit have a value of resistance. • Placing an ohmmeter across the component should indicate the components condition. • Values of 0W are considered as short circuited. • Values of infinite ohms are considered as open circuited. 2.19.28.B

  16. Fault finding: Supply available technique • Low voltage is present therefore Regulation 12 ESR2002 must be satisfied before working live. • Voltmeter set to highest scale • Place voltmeter across the circuit with supply available: • the voltmeter should indicate the supply if healthy. • If the voltmeter does not indicate the supply then search across the circuit devices for the voltage. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter should indicate 240v if healthy 2.19.28.B

  17. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 0v • NO supply indicated by the voltmeter, be careful, • just because the voltmeter does not indicate any voltage does not mean there is no voltage present, the voltage difference across the across the HP/LP is zero. It could be 240v each side of the HP/LP therefore the difference is zero. 2.19.28.B

  18. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 0v Voltmeter=0v, the fault has not shown itself. 2.19.28.B

  19. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 240v Voltmeter=240v, the fault has shown itself. A healthy circuit the voltage should be 0v across a closed switch. This voltmeter indicates a difference therefore the T/O is defective. 2.19.28.B

  20. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 180v 2.19.28.B

  21. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 180v Voltmeter = 180v, therefore the circuit between HP/LP to A1 is OK. 2.19.28.B

  22. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 240v Voltmeter = 240v, and 180v as before, therefore, the problem must be across the HP/LP. 2.19.28.B

  23. contactor T=25deg C T/O HP/LP A 240V N A1 A2 Voltmeter = 60v Voltmeter = 180v The Voltmeter across the HP/LP should be equal to 0v as the resistance of a closed switch should be as close to zero ohms. The voltmeter indicates an elevated voltage (60v) therefore there must be an elevated resistance, i.e. high resistance. 2.19.28.B

  24. 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. . 2.19.28.B

  25. 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 2.19.28.B

  26. 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. 2.19.28.C

  27. 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. 2.19.28.C

More Related