2391 Exam Questions !

[Zenn]

Dear Friends

I have booked my 2391 exam on October 18th for third time and this is my last chance to pass it.

I have about five past exam papers and I want to post them here, My main problem is on Section B which is the hardest part.

I would really appreciate if you guys help me out to answer these questions and be ready for the exam. It will indeed be helpful for those who need to do this exam.

I will only posting Section (B) of each paper, If anyone need the Section (A) just ask me and I'm happy to take a photo and post them for you.

I have posted my answers in green, but for most of the question I don't know how to write down the answers, specially the ones with explanations.


DECEMBER 2011:

Section (B)

The owners of a small retail outlet have been advised to install security lighting to the rear of their property. The installation has been completed and is ready for inspection and testing. At the same time the owners require an inspection and test of the existing installation for their insurance company.

The installation forms part of 400/230 V, three-phase, TN-C-S system with a Ze of 0.1 (Ω) and a PFC of 8 (kA). The new circuit comprises single-core,copper conductors with thermoplastic insulation installed in a PVC conduit containment system. The luminaires contain sodium vapour discharge lamps and are controlled by a photo-cell mounted at the apex of the roof.

The existing installation comprises single-core, copper conductors with thermoplastic insulation contained within pvc conduit and trunking. The three phase and neutral distribution board is located at the origin of the installation at the front of the shop.
Circuit protection is by BS EN 60898 circuit breakers and BS EN 61009 RCBOs.

The circuit protective conductors are the same CSA as the live conductors for all the final circuits.


State :

1.

a) The documents that must be completed and passed to the client on completion of the electrical work.
Electrical Installation Certificate, Periodic inspection report, 2x Schedule of inspection, 2x Schedule of test report.

b) What must be agreed with the client before the inspection of the existing installation is carried out.
Extent and limitations of the inspection, such as access to the cables under the floors or disconnecting the system from supply.

c) Who is involved in the agreement process in (b) above.
inspector and client

d) Where the agreement in (b) above is recorded.
in the extent and limitations of the inspection section on PIR.

e) Two items of information related to DNO protective device which should be made available to the inspector.
Type of Protective device and Rated current.
____________________________________________________________________________________________

2.

a) Permission has been given and the installation isolated to allow the inspection at the origin to be undertaken. The cover has been removed from the distribution board.

Identify,

i) Three items within the DB which are to be inspected using the sense of touch stating what is being checked for in each case.
to checking that the circuit breakers functioning correctly, connection of all conductors to circuit breakers are sound and the earthing conductors are connected correctly.

ii) Two items within the DB which are to be inspected using the sense of sight stating what is being checked for in each case.
to checking that : there are no any crack or visible damaged to the DB or any part inside.
correct labelling and sequencing of all conductors.

b) State two items that would be checked during the inspection of the new lighting installation containment system stating what is being checked for in each case.
choosing the correct switches and conductor size.

c) State one other sense which may be used during the inspection of the existing installation.
sense of smell.
_________________________________________________________________________________________

3. A test of continuity of protective conductors is to be carried out on the new lighting circuit to determine the (R1 + R2) value before the circuit is connected to the DB.

Describe, in detail, How this test is to be carried out.
___________________________________________________________________________________________

4. Describe, in detail, How the external earth fault loop impedance for the installation is carried out by direct measurement.

___________________________________________________________________________________________________

5. The client has complained that the single phase motor for the hoist at the rear of the premises has been slow and getting hot. Due to the length of run it is suspected that
there may be a voltage drop problem.

a) Determine the voltage drop for the circuit if the combined measured resistance of the line and neutral conductors is 0.38 (Ω) and the load current of the motor is 30 (A).

b) Determine whether the voltage drop calculated in (a) above meets the requirements of BS 7671.

c) Explain one course of action that could be taken if the voltage drop is exceeded on this circuit, giving reasons for your choice.
______________________________________________________________________________________________________

6. Describe, with the aid of a fully labelled diagram, the earth fault loop impedance path for the new lighting circuit.

_______________________________________________________________________________________________

END



I will add more questions on here tomorrow.

 

[telectrix]

what i think you should do is add your ideas for answers, perhaps in red type, then we could see how well you are coping and advise if and when you're going wrong.

 

[Zenn]

your are right, I will post my answers and the new questions tomorrow.

 

[timbobelfast]

Zenn, you need to brush up on your terminology. A PIR is no more, it is known as an EICR!

 

[Deleted member 26818]

Read question 2(b) again, the answers do not relate to the question asked.

 

[telectrix]

as spin says. containment is the key word.

 

[Paul.M]

"The new circuit comprises single-core,copper conductors with thermoplastic insulation installed in a PVC conduit containment system."


b) State two items that would be checked during the inspection of the new lighting installation containment system stating what is being checked for in each case.


Nothing to do with switches or cable size mate.

 

[telectrix]

a tip with 2391 questions is to make sure you read the question exactly. some of them are worded to trip you up, see if you are alert.

 

[telectrix]

a pointer in this one..... secure fixings to the building structure. suitably sized for the amount of cables contained within . if metallic, is it earthed and does it have continuity, and no sharp edges to damage cables.

 

[Paul.M]

Most of the questions are about safety. As Tel says above look at cable grouping and solid fixing to the building. You could also say making sure the bushes and glands are secure so not to compromise the IP4x rating for the top of the cu. Also spacing of the saddles, 600mm horizontally and 1000mm vertically. All saddle screws in place. No damage to the conduit. Routing of the pvc conduit away from hot pipes, steam vents etc.

Pick the two that mean the most regarding safety.

 

[Zenn]

what EICR stands for ?
Electrical inspection certificate report ?

 

[Deleted member 26818]

Electrical Installation Condition Report.
It's the report produced when conducting a Periodic Inspection.

 

[Zenn]

hehe I found it : Electrical Installation Condition Report

 

[Zenn]

honestly I don't have much experience in electrical field, I have worked in food related industry such as takeaways and coffee shops but I want to change my career to an electrician. I have done the 2330 in 2008 and got my 17th edition just 6 month ago, but I still cannot find myself any electrical job..
I thought if I do the inspection and testing course I will definitely find myself a job. I'm still making coffees at Starbucks hehe.

 

[scotsparky]

ii) Two items within the DB which are to be inspected using the sense of sight stating what is being checked for in each case.
to checking that : there are no any crack or visible damaged to the DB or any part inside.
correct labelling and sequencing of all conductors.


You cannot prove correct labelling of circuits by looking at them to fully verify you isolate and test.

I would suggest visual damage,IP rating of D.B,Overated breakers for conductor size, Amount of copper shown at termination, Any sighn of heat damage.

 

[Zenn]

JUNE 2010:

Section B:

The owner of a small industrial unit requires an additional exterior lighting circuit to be installed for security purposes. At the same time the existing electrical installation is to be inspected and tested in order to obtain insurance cover for the premises.

The electrical installation forms part of a 400/230 V TN-C-S system with a Ze of 0.1Ω and a PFC of 4.6 kA. The existing installation comprises 70 °C
thermoplastic insulated single core copper cables contained within a steel trunking and conduit containment system.
A separated cpc is installed for each circuit and is contained within the trunking and conduit.

The three-phase DB is located at the origin of the installation and contains a mixture of BS EN 60898 circuit breakers and BS EN 61009 RCBOs.

Figure 1 Below shows information on the resistance of conductors in mΩ/m
______________________________________
Conductor csa (mm2) | mΩ/m at 20°C
_________________________________
1.5 .......................12.10
2.5 .......................7.41
4.0 .......................4.61
6.0 .......................3.08
10.0 .....................1.83
_________________________________

1.
a) List the documents that must be completed and issued to the client on the completion of the electrical work.

b) List the parties who would be involved in determining the extent and limitation of the inspection and testing of the existing installation.

c) state where the decision reached in (b) above is to be recorded.

d) state the
i) title given in law to the inspector.
ii) legal status of the inspector.

e) List three items of information which must be available to the inspector regarding the distribution network operator's equipment.
_____________________________________________________________________________

2.
a) One part of the building has an area where chemical etching and washing down takes place.

i) List three factors which must be considered when inspecting the containment system in this particular area.

ii) Identify, for each of the factors given in (ai) above, the human senses that would best determine compliance.

b) The owner has agreed that the whole installation may be isolated in order for testing to be carried out. There has been period of one hour
allocated for this work.
List the tests that must be carried out during this period (individual circuits may be isolated after this period)
___________________________________________________________________________________

3. A test of continuity is to be carried out on the main protective bonding conductor to the gas service located 30 (m) from the origin of the
installation.
Describe how this test is to be carried out after safe isolation has been completed. your answer should include

a) initial safety precautions
b) instrument used
c) test procedure
d) final safety procedures.
_________________________________________________________________________________

4. A continuity of ring circuit conductors test is to be carried out on the circuit supplying the office.
The circuit is wired in 2.5 mm2 cable with a 1.5 mm2 CPC. The loop length of the cable is 65 m. All socket outlets are connected directly on the
ring.
Explain in detail, using the information given in figure 1, the three steps required to confirm the continuity of this circuit.
your explanation should include the
. Test instrument
. Test connections and the expected reading at each stage.
Show all calculations.
________________________________________________________________________________

5. Draw a fully labelled diagram showing the complete earth fault loop path for the newly installed lighting circuit. the diagram should identify the
a) Correct system
b) Complete fault path
c) All the component parts of the earth fault loop.
_________________________________________________________________________________

6. During the course of the inspection one of the single phase radial circuits supplying an item of fixed equipment is to be checked for voltage
drop compliance. The circuit has the following characteristics.
. Load current = 45 A
. Circuit length = 80 m
. Live conductors = 10 mm2

a) Using the information in figure 1 determine whether the circuit meets the requirements for voltage drop. show all calculations.

b) State
i) A suitable observation to be recorded on the periodic report if the voltage drop fails to comply.

ii) One action which could be taken to rectify the situation in (b,i) above.

 

[Paul.M]

Zenn you have approached this forum in the correct manner. Well done sir.

When you post up these questions please have a go at answering them and let us correct you when your wrong. We are happy to help but we are not here to do your homework.

Zenn you've got our attention so don't waist it.

 

[scotsparky]

b) State two items that would be checked during the inspection of the new lighting installation containment system stating what is being checked for in each case.
choosing the correct switches and conductor size.

What has conductor size and switch got to do with th containment system? try BS standard of containment system?


BS number on conduit does is comply wit Appendix 1 of BS7671?
What is the length of run and number of bends? does it meet the requierments?
How many cables are in the containment? Does that comply with spacing factor?



Read more: http://www.electriciansforums.net/i.../64856-2391-exam-questions.html#ixzz28C4Bw3iw

 

[scotsparky]

a) Determine the voltage drop for the circuit if the combined measured resistance of the line and neutral conductors is 0.38 (Ω) and the load current of the motor is 30 (A).

b) Determine whether the voltage drop calculated in (a) above meets the requirements of BS 7671.


Easy marks this one! work out voltage drop Vd= IxLxOhms/1000 (remember resistance is in milli ohms)

Check this as a percentage of the supply voltage power 5% lights 3 % if under that no problem .

Read more: http://www.electriciansforums.net/i.../64856-2391-exam-questions.html#ixzz28C8O33Mp

 

[scotsparky]

2.
a) One part of the building has an area where chemical etching and washing down takes place.

i) List three factors which must be considered when inspecting the containment system in this particular area.

ii) Identify, for each of the factors given in (ai) above, the human senses that would best determine compliance.

b) The owner has agreed that the whole installation may be isolated in order for testing to be carried out. There has been period of one hour
allocated for this work.
List the tests that must be carried out during this period (individual circuits may be isolated after this period)


Another one for easy marks!

Its says chemical etching and washdown so

Suitabuity of containment so IP rating if there is water jets?
Suitability against corrosion? PVC conduit as metal rusts anc corrodes very fast
RCD protection as it will be a special location with water jets (think showers)


all the above is a visual inspection


Inspection and testing.

A true Ze,PFC,PSCC can only be done with main bonds disconnected so full shutdown.
Main bond resistance?
Full insulation resistance can be done if you follow section 2 of GN3 and disconnect imcomming Neutral. Connect line conductors together and test to the main earth point. Be wary of paralell resistances as it will drastically affect readings. It means you do not have to disconnect all lights and equipment suseptable to Insulation testing but has to be noted on limitations.







Read more: http://www.electriciansforums.net/i...4856-2391-exam-questions-2.html#ixzz28CA8R4bV