T-Levels Building Services Engineering for Construction Flashcards

24 sample cards from the Building Services Engineering for Construction deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. What is the formula for the quantity of heat energy required to change the temperature of a substance?

   $$Q = m c \Delta T$$ where $Q$ is heat energy (J), $m$ is mass (kg), $c$ is specific heat capacity (J/kg·K), and $\Delta T$ is the temperature change (K or °C).

2. Define U-value and state its units.

   The U-value (thermal transmittance) is the rate of heat transfer through a building element per unit area per degree of temperature difference. Units are $\text{W/m}^{2}\text{K}$. A lower U-value means better insulation.

3. How are U-value and R-value (thermal resistance) related?

   The U-value is the reciprocal of the total thermal resistance: $$U = \frac{1}{R_{total}}$$ where $R_{total}$ is the sum of the resistances of all the layers in the element (including surface resistances).

4. What is embodied carbon and how does it differ from operational carbon?

   Embodied carbon is the CO$_2$ emitted in producing, transporting, constructing and disposing of building materials. Operational carbon is the CO$_2$ emitted from energy used to run the building (heating, cooling, lighting) during its lifetime.

5. List measures that improve a building's energy efficiency.

   Improved insulation (lower U-values), airtightness, high-performance glazing, efficient HVAC and controls, LED lighting, heat recovery ventilation, renewable energy (solar PV, heat pumps), and passive design (orientation, solar shading).

6. What are the main categories of building services systems?

   Electrical (power, lighting, data), mechanical (heating, ventilation, air conditioning - HVAC), plumbing (hot and cold water, sanitation, drainage), gas supply, fire protection, lifts/transportation, and security/communications systems.

7. What is Building Information Modelling (BIM)?

   BIM is a collaborative process of creating and managing a shared 3D digital model containing geometric and data information about a building throughout its lifecycle. It enables coordination, clash detection, scheduling (4D), cost (5D), and facilities management.

8. What does a 'clash detection' in BIM identify?

   Clash detection identifies physical conflicts between building elements or services in the digital model (e.g. a duct passing through a beam, or pipework intersecting electrical trays) before construction, reducing rework and on-site errors.

9. What standards govern UK electrical installation design and what is BS 7671?

   BS 7671, the IET Wiring Regulations, is the national standard for electrical installation design, erection and verification. It sets requirements for safety, protection against shock, overcurrent, and correct selection of equipment.

10. What factors must be considered when designing an electrical installation?

    Maximum demand and diversity, cable sizing (current-carrying capacity and voltage drop), protective device selection, earthing and bonding arrangement, circuit segregation, supply type (TN-S, TN-C-S, TT), and compliance with BS 7671.

11. State the formula for voltage drop in a cable and the typical permitted limit.

    Voltage drop is calculated as $$V_{d} = \frac{mV/A/m \times I_{b} \times L}{1000}$$ where $I_b$ is design current (A) and $L$ is length (m). BS 7671 typically limits voltage drop to 3% for lighting and 5% for other circuits from a public low-voltage supply.

12. Compare radial and ring final circuits.

    A radial circuit runs from the consumer unit to outlets in a single line, terminating at the last point. A ring final circuit forms a loop returning to the consumer unit, allowing current to flow both ways, so smaller conductors can be used for a given load (commonly a 32 A ring with 2.5 mm² cable in UK socket circuits).

13. Name common wiring systems and containment methods used in installations.

    PVC twin-and-earth cable, SWA (steel wire armoured) cable, MICC (mineral insulated), and FP fire-rated cable; containment includes conduit (steel/PVC), trunking, cable tray, cable basket, and ducting.

14. What is the standard UK colour code for fixed wiring conductors (single-phase AC)?

    Line (live) is brown, Neutral is blue, and the protective earth (CPC) is green-and-yellow. (In older installations, line was red and neutral black.)

15. List the sequence of tests for initial verification of an electrical installation.

    Dead tests first: continuity of protective conductors, continuity of ring final conductors, insulation resistance, polarity. Then live tests: earth fault loop impedance ($Z_s$), prospective fault current, and RCD operation. Results are recorded on an Electrical Installation Certificate.

16. What is the minimum acceptable insulation resistance value for a 230/400 V installation under BS 7671?

    The minimum insulation resistance is $1\ \text{M}\Omega$, tested at $500\ \text{V DC}$ for circuits up to 500 V. Values well above this are expected on a healthy installation.

17. What does commissioning of a building services system involve?

    Commissioning is the process of setting up, testing, adjusting and verifying that a system operates correctly to its design specification before handover, including balancing flows, calibrating controls, functional testing, and producing records/O&M manuals.

18. Describe a logical fault-finding (diagnosis) procedure.

    (1) Gather information/symptoms, (2) Identify and verify the fault, (3) Isolate and make safe, (4) Determine the likely cause systematically (half-split method), (5) Rectify the fault, (6) Test and verify correct operation, (7) Record the work.

19. Compare a direct (gravity) and an indirect cold water system.

    A direct system supplies all cold outlets directly from the rising main at mains pressure. An indirect system feeds a cold water storage cistern (tank) which then supplies most outlets by gravity, with only the kitchen tap (drinking water) on the rising main. Indirect provides storage/reserve and reduces mains demand.

20. Compare an unvented and a vented (open) hot water cylinder system.

    A vented system has a cold feed and an open vent pipe to a feed/expansion cistern, operating at low pressure by gravity. An unvented (sealed, pressurised) system is fed directly from the mains, giving high-pressure hot water at all outlets but requires safety devices (expansion vessel, T&P relief valve) and must comply with G3 Building Regulations.

21. What are the main types of central heating system layout?

    One-pipe (single-pipe) circuits, two-pipe systems (separate flow and return giving even heat distribution), and microbore/small-bore radiator systems; modern systems are typically sealed two-pipe with a combi or system boiler. Underfloor heating uses a manifold-fed pipe loop.

22. What controls are used in a domestic heating system and what does each do?

    Room thermostat (controls air temperature), programmer/timer (sets on/off times), thermostatic radiator valves (TRVs - control individual radiator output), cylinder thermostat (controls stored hot water temperature), and motorised zone valves (direct flow to heating or hot water).

23. What is the purpose of ventilation, and how do natural and mechanical ventilation differ?

    Ventilation supplies fresh air, removes stale/moist air and pollutants, and controls condensation. Natural ventilation uses openings, wind and stack/buoyancy effect with no fans. Mechanical ventilation uses fans/ductwork (extract, supply, or balanced) to control airflow, e.g. MVHR which recovers heat from extracted air.

24. What is the formula for the volumetric air flow rate through a duct?

    $$Q = A \times v$$ where $Q$ is the volume flow rate (m$^3$/s), $A$ is the cross-sectional area of the duct (m$^2$), and $v$ is the air velocity (m/s).

What this deck covers

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