Transcript Disconnect / Reconnect - HVAC Education Australia

EKAS 2.19.29
Disconnect & Reconnect
UEE31307 Certificate III in
Refrigeration and Air Conditioning
Stage 2A
Units: UEENEEPOO1B
Chris Hungerford
Tuesday, April 12, 2016
Voltage measurement
Voltage measuring devices have high values of internal
resistance, however a series test lamp has a low
resistance whereas voltmeter has a very high
internal resistance.
A voltage measuring device is connected in parallel
across the terminals you are measuring.
The highest range on the voltmeter should be chosen
when beginning your measurements.
2.19.29.A
Resistance measurement
•An ohmmeter has a it’s own internal power supply
and should not be placed across a live supply.
2.19.29.A
Handheld test tool safety
How not to save time...
Last known earthly
residence of automotive
fuse used to replace
original fuse
2.19.29.A
Handheld test tool safety
The wrong meter to use on a power circuit.
250V fuse
didn’t open
in time
Probe tips
burned off
Fingerprints burned
into probes
2.19.29.A
Testing Practices
• Ensure that the correct testing device and scale are chosen
• Ensure that your hand and test probes are dry and clear of
conductive materials.
• Test the testing device on a known source.
• Ensure that you do not contact the supply with yourself.
• Allow plenty of working space.
• If possible the first probe to contact should be a neutral or earth
potential.
• Do not leave live exposed terminals when finished.
2.19.29.A
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.
UL 3111
CAT IV-600 V
CAT III-1000 V
2.19.29.A
Electricity Safety Regulation 2002
18 Employer or self-employed person to ensure suitability of testing instruments
(1) This section applies to the following—
(a) an employer of a person required to perform tests on electrical work or safety
equipment;
(b) a self-employed person required to perform tests on electrical work or safety
equipment.
(2) The employer or self-employed person must ensure—
(a) the test instruments used for the testing are designed for, and capable of
correctly performing, the required tests; and
(b) if a testing instrument can not be visually confirmed as being correctly
functioning and safe—that the instrument is tested at least every 6 months to
ensure it is in proper working order; and
(c) records of tests performed are kept for at least 5 years.
Maximum penalty for subsection (2)—40 penalty units.
2.19.29.A
M.E.N. system
MEN point
2.19.29.B
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.
2.19.29.B
ELECTRICAL SAFETY
REGULATION 2002
63 Work involving direct contact with electrical part
(1) Work may be performed involving a person coming
into direct contact with an electrical part if the electrical
part is—
(a) isolated from all sources of electricity; and
(b) tested to ensure it is, or otherwise confirmed to be,
isolated from all sources of electricity; and
(c) if the electrical part is a high voltage electrical part—
earthed.
2.19.29.B
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.
2.19.29.C
ELECTRICAL SAFETY REGULATION 2002
20 Signs on switches and disconnection points
(1) This section applies if—
(a) a licensed electrical worker is performing electrical work; and
(b) to perform the work, the worker has de-energised, or otherwise isolated from
electricity, an item of electrical equipment that is the subject of the electrical work
or that is near where the electrical work is being performed; and
(c) to de-energise, or otherwise isolate, the item of electrical equipment, the
licensed electrical worker has operated a device; and
(d) while the worker is performing the work, the worker does not have the device
under the worker’s sole effective control.
(2) The licensed electrical worker must ensure that there is attached to the device,
in a prominent position, a warning sign that is suitable in the circumstances,
having regard to AS 1319 (Safety signs for the occupational environment).
Maximum penalty—40 penalty units.
2.19.29.C
Lockout Tags
• “Out of Service” tags are
equipment protection only.
• “Danger” tags are personal
protection.
• Can only be removed by the
person who placed the tag or
the principle with written
permission.
Danger
Name
Dept
Reason
Do Not Energize
2.19.29.C
Isolating Supplies
Fuse
• Remove the fuse wedge
• Remove the fusible link.
• Replace the wedge to
cover the otherwise
exposed terminals.
• Fit the danger tag.
• Remove the fusible link
from the switchboard
area (place it in your
pocket).
2.19.29.B
Circuit Breaker
• Turn off circuit breaker
• Fit the danger tag.
Working with the plug in
• Remove the plug from the socket before working on
an appliance.
• Only when testing an appliance’s operation should
the plug remain connected to a power point.
• The switch mechanism on a power point only
isolates one active conductor. If the polarity is
reversed then the mechanism isolates the neutral
conductor, leaving an active at the appliance.
• Always test before you touch.
2.19.29.B
Storage Devices
Storage devices such as capacitors must be discharged
before any work is to be commenced.
Devices such as microwave ovens, variable speed
drives, switch mode power supplies are considered
very dangerous if the capacitor is not discharged.
2.19.29.C
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.
Disconnection of Cables
• Check the supply is isolated.
• Make a sketch of the connection showing the terminal
positions and cable colours\numbering etc..
• Number or label each cable as it is disconnected.
• Insulate the cable ends , damaged cable lugs or ends should be
cut off to be refitted latter.
• Enclose the cable ends in an appropriate enclosure such as a
PVC junction box.
• Ensure a danger tag is fitted at the point of isolation. Fit a
danger tag to the cable end and identify the isolation point.
2.19.29.C
Manufacturer Specifications of disconnected & replacement equipment.
• The rated supply voltage for a replacement appliance
must be the same as the unit it replaces.
• Determine the circuit current of the appliance being
connected. Most appliance plates have voltage and
power ratings.
• The current carrying capacity of the connecting cables
needs to be assessed using AS/NZS-3008.1.1
• Also check the rating of the Fuse or circuit breaker.
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.
2.19.29.D
Electric Shock
•
To receive an electric shock two conditions
must be reached
1. Access to electricity
•
•
•
Direct contact.
Indirect contact ( insulation resistance failure)
Insulation Resistance Test.
2. elevated potential of the electricity.
•
•
2.19.29.D
Earthing circuit is at zero volts due to the low resistance of the MEN
point, therefore if the earthing circuit is kept to very low resistance
values the voltage will also stay low.
Earth Continuity Test
Final Tests
1 Visual inspection, is the work as per AS/NZS 3000:2007?
2 Earth continuity test, is the earthing circuit continuous?
AS/NZS 3000:2007 < 0.5W, .
3 Insulation resistance test, is the conductors insulation able to
contain the operating voltage? AS/NZS 3000:2007 > 1MW
4 Polarity, are the outlets correctly connected, are the circuit
actives switched?
2.19.29.D
Analogue insulation-continuity Tester
2.19.29.D
Scale Plate
Megohm scale
Megohm Selector switch
2.19.29.D
Scale Plate
Low reading ohm scale
Low reading ohm Selector switch
2.19.29.D
Scale Plate
500 ohm scale
500 ohm Selector switch
2.19.29.D
Always check your
batteries before using
the meter
Battery check scale
Battery check Selector switch
2.19.29.D
Test Button
2.19.29.D
When measuring continuity it is important to adjust
your meter to zero ohms before you commence.
Ohms zero adjust
2.19.29.D
Measuring insulation resistance at 250vDC
Megohm Selector switch is set to 250V
i.e needle reading = 5
IR = 5 x ½ = 2.5 MW
2.19.29.D
2.19.29.D
Megohm scale x ½
Measuring insulation resistance at 500vDC
Megohm Selector switch is set to 500V
i.e needle reading = 2.5
IR = 2.5 x 1 = 2.5 MW
2.19.29.D
2.19.29.D
Megohm scale x 1
Measuring insulation resistance at 1000vDC
Megohm Selector switch is set to 1000V
i.e needle reading = 1.25
IR = 1.25 x 2 = 2.5 MW
2.19.29.D
Megohm scale x 2
Other lead connected to the metal frame
One lead connected to the earth pin
Instrument set to low reading ohms
2.19.29.E
Class 2 equipment
2.19.29.E
Instrument set to 500vdc MW scale
One lead connected to the earth pin
Other lead connected across active &
neutral pin
2.19.29.E
No earth wire from plugtop
X, Wrong
Class 2 equipment
2.19.29.E
Lead connected to frame of appliance
Correct
Class 2 equipment
2.19.29.E
AS/NZS 3760 Clause 2.3.3.2 (b).
MOV
Instrument set to 250vdc
2.19.29.E
Circuit integrity
•
•
•
•
Switch off the supply to the circuit.
Determine the current draw for the circuit, (name plate).
Measure the Resistance of the circuit.
Using Ohm’s Law, determined if the current is greater
than the rating of the fuse element then investigate the
cause.
• If the circuit is OK, re-energise.
2.19.29.E
Reconnection of Cables
• Never assume the cables are dead,
– TEST BEFORE YOU TOUCH
•
•
•
•
•
Measure the insulation resistance of the cables.
Measure the insulation resistance of the replacement article.
Reconnect cables as per your disconnection diagram.
Test your connections for firmness and visual correctness.
Measure the Earth continuity of the earthing circuit.
2.19.29.F
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.
2.19.29.G
Further readings
Questions Topic 6 Q1-Q48