questions asked on assessment day ?

[james king]

Hi every one just a few question for every one as I have a assessment due very soon pretend I know nothing and try to answer them as well and detailed as you can would really help!!!!

1)y do a R1 test
2)y do a R2 test
3)y do a Rn
4)y do a R1+R2 test
5)y do a insulation resistance test
6)y do a Ze test
7)y do a Zs test
8)why do a pfc test

what reading would u expect to get for a tn c s and tt and tnc system for each test

r1+r2= tt ………… tns ………… tncs
Ze= same as above and so on for Zs and pfc and IR

And also the max result you should be getting ?

 

[Des 56]

Wow thats a tall order,so I'm avoiding a reply sorry


By being competent to ask these questions and being aware of the terminology you may be trying to be foolproof when you are assessed

You will not know everything and will not be expected to
The assessor will more than likely ease you through any tests that you flounder on or are unsure about

If the assessment is near,getting your paperwork set and organised may prove more helpful,and the teapot


The money that you have paid will be more the issue than looking to find something to fail you on
Good luck

 

[flukey]

Hi every one just a few question for every one as I have a assessment due very soon pretend I know nothing and try to answer them as well and detailed as you can would really help!!!!

1)y do a R1 test
2)y do a R2 test
3)y do a Rn
4)y do a R1+R2 test
5)y do a insulation resistance test
6)y do a Ze test
7)y do a Zs test
8)why do a pfc test

what reading would u expect to get for a tn c s and tt and tnc system for each test

r1+r2= tt ………… tns ………… tncs
Ze= same as above and so on for Zs and pfc and IR

And also the max result you should be getting ?

how about you tell us how you would answer the questions and we will help you with your answers

there are some very basic questions there that any competent person shouldnt really need help with so if you are struggling i would hit the books hard

 

[james king]

r test are to test continuaity end to end test l n e
r1 r2 cable crossed over to test cpc and live continuty and polarity

ze test incoming live and nutal with bonding disconnected should not be more than 0.35 i think on tncs
zs done at end of circut witch is a live test test the earthing potental

 

[Sintra]

ze test incoming live and nutal with bonding disconnected should not be more than 0.35 i think on tncs

Not quite right.

Ze test is Live to Earth with bonding disconnected at mains incommer.

 

[james king]

Not quite right.

Ze test is Live to Earth with bonding disconnected at mains incommer.

that wat i said lol bonding disconed test between to phases lol

pfc is meauring the fault current between live n earth? now u tell me how u would say it i just want to pass lol

 

[Sintra]

PFC = prospective fault current and is the highest of either the PSCC (prospective short circuit current measure betwwen L & N) or Pefc (prospective earth fault current measured L to E at supply with all bonding in place and main earth reconnected).

 

[james king]

how would u describe IR testing ?

do u think my genral knowlege is ok i no its not best but need to get it all sorted

 

[Sintra]

A low resistance between phase and neutral conductors, or from live conductors to earth, will result in a leakage current. This current could cause deterioration of the insulation, as well as involving a waste of energy which would increase the running costs of the installation. In addition to the leakage current due to insulation resistance, there is a further current leakage in the reactance of the insulation, because it acts as the dielectric of a capacitor. This current dissipates no energy and is not harmful, but we wish to measure the resistance of the insulation, so a direct voltage is used to prevent reactance from being included in the measurement. Insulation will sometimes have high resistance when low potential differences apply across it, but will break down and offer low resistance when a higher voltage is applied
Before commencing the test it is important that:
1. - electronic equipment which could be damaged by the application of the high test voltage should be disconnected. Included in this category are electronic fluorescent starter switches, touch switches, dimmer switches, power controllers, delay timers, switches associated with passive infrared detectors (PIRs), RCDs with electronic operation etc. An alternative to disconnection is to ensure that phase and neutral are connected together before an insulation test is made between them and earth.
2 capacitors and indicator or pilot lamps must be disconnected or an inaccurate test reading will result.
Where any equipment is disconnected for testing purposes, it must be subjected to its own insulation test, using a voltage which is not likely to result in damage. The result must conform with that specified in the British Standard concerned. The test to earth must be carried out on the complete installation with the main switch off, with phase and neutral connected together, with lamps and other equipment disconnected, but with fuses in, circuit breakers closed and all circuit switches closed. Where two-way switching is wired, only one of the two strapper wires will be tested. To test the other, both two-way switches should be operated and the system retested. If desired, the installation can be tested as a whole, when a value of at least 1.0 M Ohms should be achieved. In the case of a very large installation where there are many earth paths in parallel, the reading would be expected to be lower. If this happens, the installation should be subdivided and retested, when each part must meet the minimum requirement.
The tests to earth and between phases must be carried out as indicated, with a minimum acceptable value for each test of 1.0 M Ohms. However, where a reading of less than 2 M Ohms is recorded for an individual circuit, (the minimum value required by the Health and Safety Executive), there is the possibility of defective insulation, and remedial work may be necessary. A test result of 2 M Ohms may sometimes be unsatisfactory. If such a reading is the result of a re-test, it is necessary to consult the data from previous tests to identify deterioration. A visual inspection of cables to determine their condition is necessary during periodic tests; perished insulation may not always give low insulation readings
As indicated above, tests on SELV and PELV circuits are carried out at 250 V. However tests between these circuits and the live conductors of other circuits must be made at 500 V. Tests to earth for PELV circuits are at 250 V.

 

[james king]

bloody hell thank u

 

[Sintra]

The R1+R2 test sequence for ring final circuits

Step 1

Securely isolate the circuit and using a low ohms continuity test meter measure the resistance of the phase (r1), neutral (rn) and cpc (r2).

Step 2

i. cross connect the phase and neutral of the ring.
ii. measure the resistance between the pairs at the point where the cross-connection is made.
iii. the reading should be approx 1/2 that for either the p or n conductor in Step 1.

Step 3

With the p+n still cross connected measure between p+n at each point on the ring. The reading should be approx the same as in Step 2. Spurs will give a slightly higher reading.

Step 4

Repeat the procedure as in Steps 2+3, but using the phase and cpc conductors. These readings should differ slightly at each point. The highest value represents the R1+R2 value for the circuit. This test sequence also verifies polarity and cpc continuity to all points in the ring unless the testing has been carried out at the terminals on the reverse of the accessories then a visual inspection is required to confirm polarity


The R1+R2 test sequence for radial final circuits

Securely isolate the supply.

Disconnect any bonding connections that could affect the test readings.

Make a temporary connection at the ccu between the phase and cpc of the circuit to be tested.

Using a low ohms continuity test meter measure the resistance between phase and cpc at each point on the circuit also confirming polarity.

The R1+R2 is the reading taken at the furthest point on the circuit.

Re-connect any bonding conductors disconnected for the test.

Remove the temporary connection at the ccu.

 

[james king]

thank u very nice of u to help cheers

 

[Sintra]

Ze Test Sequence

Turn off the supply to the ccu.

Disconnect the main earthing conductor from the main earthing terminal.

Using an earth fault loop impedance tester connect the earth lead to the main earthing conductor, the phase lead to the phase conductor of the incoming supply and perform a test.

Reconnect the main earthing conductor.

Re-instate the supply.


Zs Test Procedure

The Zs value must be measured at the furthest point on each circuit.

Direct measurement of Zs can only be made on a live installation. The main earth and bonding conductors are not disconnected. At the furthest point on the circuit from the ccu perform an earth fault loop impedance test. The reading given by the loop impedance tester will usually be less than Ze+(R1+R2) because of parallel earth return paths provided by any bonded extraneous conductive parts.

 

[james king]

my megger mft 1553 says trip wen i just use live and earth for ze only works if u put nutral on to ne ideals?

 

[Sintra]

my megger mft 1553 says trip wen i just use live and earth for ze only works if u put nutral on to ne ideals?

You must be using the no trip setting which is not needed when testing Ze. Use the loop hi setting.