2365 Level 3 Electrical Installations Candidate Pack 56 Assessment 615: Electrical Systems Design Task A – Design project

2365 Level 3 Electrical Installations Candidate Pack 56
Assessment 615: Electrical Systems Design
Task A – Design project
Candidate name:
Date:

Time allowed There are no time constraints to this assignment however, it is estimated that
the work involved should take approximately 20 hours.
Task instructions Candidates are required to successfully complete the following task consisting
of 10 questions to achieve this assignment:
Candidates are permitted any relevant reference material such as IET On‐site
Guide, BS 7671 and internet access.
Read all information relating to the task carefully before attempting any
questions. For this task you will require a copy of drawings 5357‐A1 to A5. For
the purpose of scaling, these should be provided in A3 format. You may, when
marking up drawings, use A4 format if desired.
All questions must be completed for this project. You may use the space
provided for your answers or you may produce them electronically on separate
named sheets. Read each question carefully before attempting.
Drawings 5357‐A1 to A5 show the proposed new hotel extension and new
pool/café block. Information relating to building design and construction are
detailed below. You may however make reasonable assumptions throughout
your design giving reasons.
Candidate pre‐assessment plan
I am aware of assessment requirements, criteria and time allocation
Candidate signature Date
The task has been successfully completed to the standards required
Person Print name Signature Date
Candidate
Assessor
Internal quality
assurance
(if required)

2365 Level 3 Electrical Installations Candidate Pack 57
Assessor/Tutor feedback to candidate on outcome of assessment (if applicable)
2365 Level 3 Electrical Installations Candidate Pack 47
Building Specification
Building Construction
Hotel Extension:

The building is constructed on a concrete raft with 50 mm screed to the ground floor and chipboard on
100 mm wooded joists for the first floor.
The walls are thermolite blocks with uPVC cladding, cavity and inner leaf blockwork with plaster finish.
Inner wall partitions are blockwork with plaster finish.
The roof is tiled on a wooden roof truss with waterproof membrane.
Internal ceilings are plasterboard on the underside of wood joists.

Pool/Café block:

The building is constructed on a re‐enforced concrete base forming the swimming pool and floor with
tiled finish throughout the basement areas.
The first floor is pre‐cast concrete on steel supports with 50 mm screed and non‐slip vinyl finish.
The basement walls are re‐enforced concrete with internal uPVC cladding.
The basement ceiling utilises the underside of the concrete floor above.
The café area walls are wood framed with uPVC outer cladding, thermal insulation and plasterboard
inner lining.
The tiled roof is supported on exposed decorative wooden trusses with internal plasterboard infills on
the underside forming an open ’A’ roof space with the exception of the building section above the
kitchen end of the building which has plasterboard ceilings 2.4 m above ffl forming an enclosed roof
space above.
Inner walls are plasterboard partitions having aluminium frame.



Electrical Installation:
The existing hotel building forms part of a 400 V three‐phase TN‐C‐S system. It has been assessed that
there is sufficient capacity for the new works and a new CCU will be installed to supply the new distribution
circuits. Ze and PFC have been measured and recorded as 0.09 Ω and 5 kA respectively.
It has been assessed that following installation of the new three‐phase distribution circuit to the pool/café
block, Zdb and PFC for the new distribution board within the block will be 0.11 Ω and 3.7 kA respectively.
Fire alarm system
This is to be installed by specialist contractors but a 13 A un‐switched fused connection unit will be required
in the pool/café block to supply a repeater panel.
Heating, ventilation and air‐conditioning
This is to be installed by specialist contractors and any supply details are contained in the design
specification. Any further considerations can be ignored.
2365 Level 3 Electrical Installations Candidate Pack 48
Design Specification Detail
Within the pool/café block, the following design criteria applies‐
Ambient temperatures All basement pool areas 40 °C
Café open area 25 °C
Café Kitchen/servery 35 °C
Wiring systems for
lighting and small
power (see additional
information below for
specific circuits)
All basement pool areas PVC surface conduit with 90 °C
thermosetting single‐core non‐
sheathed cables
Café open area PVC surface conduit with 70 °C
thermosetting single‐core non‐
sheathed cables
Café Kitchen/servery PVC surface conduit with 70 °C
thermosetting single‐core non‐
sheathed cables
Grouping of circuits for
lighting and small
power (see additional
information below for
specific circuits)
All basement pool areas Each circuit will be grouped with
no more than 2 other circuits
Café open area Each circuit will be grouped with
no more than 1 other circuit
Café Kitchen/servery Each circuit will be grouped with
no more than 3 other circuit
Thermal Insulation All areas No thermal insulation affects the
wiring systems
Circuit lengths All areas To be estimated from drawing
scales. For the purpose of this
project, no circuit should exceed
approximately 30 m.
Other circuit specific
detail
230 V 16 A dishwasher in kitchen Supplied by a three core 70 °C
thermoplastic SWA cable clipped
direct
Servery food holding equipment. This
unit requires a 16 A 400 V three‐phase
and neutral supply.
Supplied using five core 90 °C
thermosetting SWA cable clipped
direct
2365 Level 3 Electrical Installations Candidate Pack 49
All pool equipment and sauna
equipment. This equipment requires a
32 A 400 V three‐phase and neutral
supply. All equipment associated will be
installed by a specialist from a local
supply point in the equipment room
provided as part of the contract.
Supplied using five core 90 °C
thermosetting SWA cable clipped
direct
The four fridges within the kitchen area
should be supplied by two 16 A single‐
phase circuits to specifically labelled
socket‐outlets for each fridge.
Additional protection should be
omitted for these circuits.
Supplied by single‐core 70 °C
thermoplastic non‐sheathed
cable in surface PVC conduit
New summer house by existing pool. A
32 A distribution circuit from the
pool/café block will supply this new
structure which will have a four‐way
SP‐N distribution board fitted.
Supplied by a three core 70 °C
thermoplastic SWA cable clipped
direct
2365 Level 3 Electrical Installations Candidate Pack 50
Assessment 615: Electrical Systems Design
Task A – Design project
Candidate name:
Date:
Note: this question paper and associated drawings must be submitted for marking
1 As part of the electrical contract, the client is considering an electric vehicle charging unit in the car
park supplied from the existing TN‐C‐S supply in the main hotel building. The IET Code of Practice
for Electric Vehicle Charging Equipment Installations recommends a TT earthing arrangement for
the unit.
Draw a fully labelled circuit diagram illustrating the three‐phase 400 V supply system and earthing
arrangement from the sub‐station transformer through to the charging unit. The diagram should
show the total earth fault loop path for the charging unit.
Your diagram does not need to show the complete detail of distribution boards, metering or
consumer control equipment although the diagram should, as a minimum, indicate a connection
point for each item of equipment.
2365 Level 3 Electrical Installations Candidate Pack 51

2 a) Select, using manufacturers’ data, suitable luminaires for all parts of the pool/café block with
exception of the sauna. Your selection should be based on



energy efficiency
environment/external influences
aesthetics
Your selection does not need to take into consideration suitable levels of illumination
for the purpose of this project or any outdoor lighting.

b) Show, on either electronic or hard copies of the drawing, the types of luminaires selected for
each location giving each type a suitable form of identification on a separate key. You are
encouraged to research basic lighting design techniques and apply this to positioning of
luminaires however, you will not lose marks for insufficient lighting design.
c) Show, on either electronic or hard copies of the drawing, positions of socket‐outlets and
fused connection units for the new hotel block giving consideration to the following items of
equipment in each room





kettle
TV
provision for phone charging and/or laptop use
supply to a 700 W air handling unit for heating/cooling (installed by specialist)
electric towel rail.

d) Show, on either electronic or hard copies of the drawing, how each circuit in the new hotel
extension is to be arranged. The arrangement must take into account that a fault in any one
room must not effect another room.
e) Give each circuit a unique form of identification.
f) Show, on either electronic or hard copies of the drawing, any further distribution boards that
may be required in the hotel extension.
g) Show, on either electronic or hard copies of the drawing, how each lighting circuit in the new
pool/café block is to be arranged including switching.
h) Give each circuit a unique form of identification.
i) Complete the legend on the drawings using recognised symbols and descriptions for each
symbol used on the drawings.
3 Select, with the aid of manufacturers’ data, a suitable range of circuit protective devices for this
contract. Your selection should be based on the following

Prospective short circuit currents
Requirements for additional protection and special locations

2365 Level 3 Electrical Installations Candidate Pack 52
4 This question may be answered using the tables 1 or 2. It is strongly recommended that you use
pencil when completing the table to allow for recalculation of figures.
Determine, for every final circuit in the café/pool block, each of the following.
a) Design current (Ib)
b) Nominal rating and type of protective device (In)
c) Method of installation reference
d) Rating factors that apply
e) Minimum cross‐sectional area of live conductors for current capacity and voltage drop
f) Actual voltage drop.
g) Maximum permissible disconnection time for each circuit as given in BS 7671.
h) Earth fault loop impedance
i) Maximum earth fault loop impedance as stated in BS 7671.
5 Determine, for one of the circuits supplying the fridges, the minimum possible cross sectional area of
cpc which will satisfy the requirements disconnection as ADS under earth fault conditions and the
adiabatic equation as Regulation 543.1.3 in BS 7671.
2365 Level 3 Electrical Installations Candidate Pack 53
6 For this question, use the table below. More copies may be made as necessary.
a) Determine the maximum demand for the pool/café block electrical installation before the
application of diversity.
b) Determine the maximum demand for the pool/café block electrical installation following the
application of diversity.

Circuit Demand Diversity factor Demand following
diversity
Total Total

2365 Level 3 Electrical Installations Candidate Pack 54
7 Explain, with the aid of a diagram, how electric shock protection is provided by one of the shaver
points in the hotel extension bathrooms using the Protective Measure: Electrical Separation.
2365 Level 3 Electrical Installations Candidate Pack 55
8 List, using the box below, five typical extraneous conductive parts and five typical exposed
conductive parts that may be found within this entire complex.

Typical Extraneous Conductive Parts Typical Exposed Conductive Parts

9 Complete the box below relating to earthing and bonding.

Type of protective
(earthing/bonding)
conductor
Example of where this may be found within this
complex
Minimum
permissible csa as
BS 7671 (where
applicable)
Main Protective
Bonding
Where PME
conditions apply
For non‐PME
applications
Supplementary
equipotential
bonding
Without mechanical
protection
With mechanical
protection
Functional earth
Earthing
Conductor
For TT installations
For TN installations
cpc Without mechanical
protection
With mechanical
protection

2365 Level 3 Electrical Installations Candidate Pack 56
10
Complete the box below relating to isolation and switching.

Type of isolation
or switching
Example of where this may be found within
this complex
Further requirements
Isolation for
electrical
maintenance
purposes
Relating to securing safe
isolation
Switching for
mechanical
maintenance
Relating to devices which
are not under effective
control
Relating to switching
capability
Functional
Switching
Relating to rating where
used for discharge
lighting

2365 Level 3 Electrical Installations Candidate Pack 57
Assessment 615: Electrical Systems Design
Assignment feedback (if applicable)
Candidate’s name:
Assessor’s name:

Tasks 1st Submission
Outcome
Pass/Fail
Resubmission
Outcome
Pass/Fail
QC Signature (if
sampled)
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
Q10
Target date and action plan for resubmission (if applicable)

2365 Level 3 Electrical Installations Candidate Pack 58
Assessor/Tutor feedback to candidate on outcome of resubmission
2365 Level 3 Electrical Installations Candidate Pack 59
Table 1‐ Design Grid: Sample 1
Using voltage drop to select cable size then confirming Iz

11 Circuit number 1 2 3 4 5 6 7 8 9 10
Ze= Voltage =
Watts (where stated) 1
Ib design current 2
In device rating and type 3
Method of installation 4
Ambient temp in °C 5
Cable type/insulation 6
Ca Ambient factor 7
Cg Grouping factor 8
Length in metres 9
Max Volt Drop 10
mV/A/m max 11
Size selected mm2 12
It 13
Iz (must be larger than In) 14
Actual Voltage Drop 15
Max Disc. time 16
Actual ZS 17
Max Zs as BS 7671 18

2365 Level 3 Electrical Installations Candidate Pack 60
Table 2‐ Design Grid: Sample 2
Using current capacity to select cable size then confirming voltage drop

11 Circuit number 1 2 3 4 5 6 7 8 9 10
Ze= Voltage =
Watts (where stated) 1
Ib design current 2
In device rating and type 3
Method of installation 4
Ambient temp in 0C 5
Cable type/insulation 6
Length in meters 7
Ca Ambient factor 8
Cg Grouping factor see note A 10
Size selected mm2 12
It 13
mV/A/m 14
Actual voltage drop 15
Max Disc. time 16
Actual ZS 17
Max Zs as BS 7671 18
11

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