Reference no: EM133840277

Electrical systems design

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 thermoliteTM 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 vinylfinish.
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 suspended ceilings 2.4 m above ffl forming an enclosed roof space above.
Inner walls are plasterboard partitions having aluminium frames.
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 0.21 Ω and 2.2 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.

The client is considering an electric vehicle charging unit in the car park, to be 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.

In the space below, 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.

Draw a diagram, illustrating the arrangement of the isolating transformer incorporated in the shaver points in the hotel extension bathrooms using the Protective Measure: Electrical Separation.

Explain how this arrangement provides protection against electric shock.

List, using the box below, four typical extraneous conductive parts and five typical exposed conductive parts that may be found within this entire complex.

The installation requires protective earthing and protective bonding in accordance with Chapter 41 of BS 7671. Complete the box below relating to the earthing and bonding conductors.

The installation requires switching for a variety of purposes. Research the definition of each of the switching functions and compete the box below.

The new hotel extension is to be wired and each room will need provision for various items of equipment provided in the rooms:
See the attached drawing number 2365 - AS2 which includes full details of all the task requirements.

This is a stand-alone task and is not linked in any away with question 7 - 10, below.

For this question you should refer to drawings 2365 - AS3, AS4 and AS5
Select, providing manufacturers' data, including images, and giving reasons for your choice, suitable luminaires for all parts of the pool/café block with the exception of the sauna and external lighting. Your selection should consider
energy efficiency
environment/external influences
aesthetics
Your selection should take into consideration suitable levels of illumination (E) for the café area, the kitchen and the pool. (Search for ‘Lux Levels') By using the lumens method with a combined utilisation/maintenance factor of, say 0.8, and a suitable illuminance level selected (E) you can work out an approximate number of luminaires needed.

Show, on drawings, the types of luminaire selected for each location, giving each a suitable form of identification on a key. It should be clear to anybody examining the drawing which circuit is which, so they can then consult your circuit data to identify the design information.

Show, on the drawings, how each lighting circuit in the new pool/café block is to be arranged including the switching arrangement.
Give each circuit a unique form of identification - this should be a short code which makes it easy to cross-refer between the drawings and the circuit design details on the schedules.

Complete the legend on the drawings using recognised symbols and descriptions for each symbol used on the drawings. This includes all lights, switches, socket-outlets, etc.

Notes:
For each of the main areas - café, kitchen and pool - you should provide an image of the luminaires chosen, with reasons for those choices and a calculation of the approximate number of luminaires needed. Each area will need a different type of lighting, because the circumstances are different.

For the other areas - changing rooms, pool equipment room, intake room, etc, a suitable type of luminaire should be selected and manufacturers data provided, but there is no requirement to do a ‘lumens method' calculation.

These lights, however, should also be arranged into logical circuits and included in the data submitted for question 8.

This question may be answered using the schedule supplied, or a word-processed or spreadsheet version, but all work must be printed out for assessment.
You may use pencil if completing the table by hand, to allow for recalculation of figures, but you must submit the finished table in ink for final marking.
Select a suitable range of circuit protective devices for each circuit, giving consideration to the type of loads and any requirements for additional protection and special locations.
Draw each circuit route on the project drawings - you will need to do this to estimate circuit lengths, which should be rounded up to whole metres and include a generous allowance for rises and drops.

Determine, for every final circuit, in the café/pool block, each of the following.

Design current (Ib)
Nominal rating and type of protective device (In)
Method of installation reference
Rating factors that apply
Minimum cross-sectional area of live conductors for current capacity and voltage drop
Actual voltage drop.
Maximum permissible disconnection time for each circuit as given in BS 7671.
Earth fault loop impedance
Maximum earth fault loop impedance as stated in BS 7671.

You need not provide detailed calculations for every circuit, but you must show examples of the complete calculation for:
a specified load, e.g. dishwasher, food holding unit, or pool supply
a socket circuit - use standard circuits as detailed in Appendix H of the On-Site guide
at least 1 lighting circuit.

The calculations should show each stage in the process from load calculation, cable selection, voltage drop, and (R1 + R2) through to ZS.

Notes:

There is no need to draw in any extra DBs - all circuits should be supplied from the DB shown
The pool equipment isolator is supplied from the main DB in the intake room.
A minimum of around 15 circuits will be required to supply all the equipment, but you should not normally need to exceed around 20 circuits.
Keep your circuits simple and logical

Determine the maximum demand for the pool/café block electrical installation before and after the application of diversity. Can you do my assignment for me? We sure can!
Your assessment should include all final circuits in the location, as given in the specification as well as your new lighting circuits. (The circuits as detailed in your answer to question 8)

Give brief reasons for your choice of diversity factors. You should consider the following factors
Intermittent/infrequent use
Equipment with temperature controls
Actual loads, as compared with circuit rating

The New Pool/Café block is supplied by a steel wire armoured cable.

Using the site drawing (AS1) mark on a suitable route between the Main DB in the existing hotel block and the new distribution board in the proposed Pool/Café block and establish the length of this circuit. (Remember the scale is 1cm = 5m and the absolute minimum length would be around 35m)
Length = m

Using your maximum demand figure from question 9, select a suitable armoured cable from the information in the table below and specify a suitable size of BS 88-2 fuse.

Verify that this cable meets the requirements for disconnection under the protective method Automatic Disconnection of Supply (ADS) under earth fault conditions, using the armour as the circuit protective conductor. (Show all calculations below)

Verify the armour meets the adiabatic requirements of Regulation 543. 1.3 in BS 7671