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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2011
Module Title: Electrical Installation Practice
Module Code: ELEC 6001
School: Electrical and Electronic Engineering
Programme Title: Bachelor of Engineering in Electrical Engineering – Year 1
Programme Code: EELEC_7_Y
External Examiner(s): Mr G. Beecher, Dr M. Duffy Internal Examiner(s): Mr. D. Neally
Instructions: Answer SIX questions. All questions carry equal marks. Do not spend more than 20 minutes per question. Students are permitted the use of ETC Rules, ET101:
Duration: 2 Hours
Sitting: Autumn 2011
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination. If in doubt please contact an Invigilator.
(a) With the aid of neat labelled sketches describe the construction of any THREE of the following multi-core copper cables: i. PVC/SWA/PVC ii. PVC/PVC iii. NYM-J iv. N.Y.C.Y. (9 marks)
(b) Describe the construction of: i. Three compartment metal trunking ii. Perforated metal cable tray (4 marks)
(c) Give one example of where each of the wiring systems in part (b) may be used.
(4 marks)
Q2.
(a) Define the term “Space Factor”.
(4 marks)
(b) What is the space factor for cables in metal trunking? (4 marks)
(c) Using the „unit system‟ what size metal conduit is required to carry the following combination of PVC insulated cables: i. 8 x 1.5mm^2 ii. 3 x 2.5mm^2 iii. 3 x 4.0mm^2 The length of run of the conduit is 3.2m and it incorporates two bends.
(9 marks)
Q3.
A PVC/SWA/PVC cable is to be used to supply a single phase 230V distribution. The total connected load is 12kW with a diversity of 80% and an average power factor of 0. lagging. The length of run is 35m and the cable passes through an area where the ambient temperature may read 35ºC. The cable is to be attached to a perforated steel tray with two other similar type cables. Calculate the minimum size cable required.
(17 marks)
(a) State ONE advantage and ONE disadvantage of EACH of the following wiring systems: i. PVC sheathed cable (2 marks) ii. Steel Conduit (2 marks) iii. Steel Trunking (2 marks) iv. Mineral Insulated Cable (2 marks)
(b) State the colour code for PVC covered MICC cable, when used for the following types of installation: i. Fire Alarms (3 marks) ii. Emergency Lighting (3 marks) iii. General Services (3 marks)
Q8.
(a) The voltage drop between the supply terminals of a wiring installation and a socket outlet is not to exceed 4% of the 230V supply. Calculate the maximum current the selected 25m supply cable may carry if the quoted voltage drop for that cable is 18mV/A/m. (9 marks)
(b) Define in your own words the terms “Band 1” and “Band 2” relative to values of A.C. voltage.
(8 marks)
