Amps - Current (I)
Watts - Power (W)
Volts - Voltage (V)
Ohms - Resistance (Ω)
P=V×I to calculate power (in watts)
OHMS Law triangle
V - Voltage
I - Current
R - Resistance
in (incoming supply)
supp (suppliers fuse)
me (meter)
con (consumer)
app (appliances)
Documents Manufacturer’s instructions - guidelines for safety
Electrical regulation - Electricity at Work Regulations (1989) for
Building regulation - Part P (Electrical safety in domestic buildings)
IET wiring regulations - BS 7671 (Design installation and testing)
Supplies AC - Changes directions periodically (Household mains)
DC - Flows in one direction (Batteries)
Voltages 240 Volts - household + heaters
230 Volts - Sockets
24 Volts - Tools
12 Volts - small tools / pumps
Lighting Circuits: 6A
Radial Circuit: 16A
Socket Ring Circuit: 32A
Cooker/Oven: 32A+
Electric Shower: 32A–45A
Immersion Heater: 16A
Towel Rail/Small Heater: 6A or 10A
RCD Trip Sensitivity: 30mA (personal), 100mA+ (equipment)
MCB Ratings: 6A, 16A, 20A, 32A, 40A
Extractor Fan: 3A
Central Heating Circuit: 3A
Uk socket (3pin) can handle 3kw / 230v / 13 amps
Wiring Colours (UK)
Live : Brown or Black (Old was red)
Neutral : Blue
Earth : Green and Yellow
Types of wire protection
electrical supplies and connections Lighting circuit - 1.5mm 6 amp ring mains - 2.5 32
amps spurs fused outlets - consumer units - s-plan - Uses two 2-port valves (one for
heating, one for hot water). y-plan - Uses a single 3-port valve in a "Y" configuration
Single phase - 230v (domestic) Three phase power - 400v (commercial)
Types TT System - Earth Rod or electrolyte TN System - Neutral + earth seperate TNS
System - Armoured cable TNCS system - Neutral + earth combined
Protection Methods (MCB) Miniature circuit breakers - in consumer unit and protects
one appliance or circuit
MCB with Lock off device
(RCD) Residual current devices - modern consumer units (plug in rcds used with 230v
tools) (CONTAINS A TEST BUTTON)
RCBO - Consumer unit contains MCB + RCD can be used in older circs
cartridge fuses - older circ protection + rewireable used in plugtops too
Rewireable fuse - consists of a thin metal wire stretched between two terminals
equipomential Bonding


Earthing: Provides a path to ground to prevent electric shock.
Bonding: Links different metal parts (pipes, frames) to reduce the risk of electric
shock.


Main bonding refers to the connection of the main earth conductor (from the
electrical supply) to all accessible metalwork in the building, including plumbing
pipes, gas pipes, and structural parts of the building. (10mm)
supplementary bonding is the connection of various exposed metal parts within
a building (such as water pipes, radiator pipes, and any other metal parts) to a
local eart (4mm)
Bonding conductors must be made from materials with low resistance to electrical
current, such as copper or galvanized steel.
Proper bonding helps protect people from electrical shocks, especially in wet areas like
bathrooms, kitchens, or areas where metal pipes are installed.
supplementary bonding ensures no dangerous potential difference between metal
parts. Proper bonding helps protect people from electrical hazards in plumbing systems.
incoming domestic main
cable sizes and their uses
1. Electrical Systems in Plumbing Design and Safety
1. Documents Required (1.1): Know the key documents like British Standard BS
7671, Building Regulations Part P, manufacturer’s instructions, and any local
electrical regulations.
2. Types of Supplies (1.2): Identify single-phase, three-phase, and battery/backup
power for domestic plumbing.
3. Common Voltages (1.3): Recognize 230V (standard domestic) and lower
voltages for specialized systems.
4. Electrical Layouts (1.4): Learn the differences between radial and ring circuits.
5. Earthing Systems (1.5): Understand TN-S, TN-C-S, TT, and IT configurations.
6. Protective Equipotential Bonding (1.6): Know bonding methods to reduce
shock risks.
7. Supplementary Earthing Bonding (1.7): Additional bonding in areas like
bathrooms.
8. ~~Protection Methods (1.8): Circuit breakers, fuses, and RCDs for user
protection.~~
9. Fuse Size & Current (1.9): How fuse size correlates with current rating for
safety.
2. Electrical Components and Wiring
1. Incoming Systems (2.1): Identify main boards, consumer units, etc.
2. Wiring Types (2.2): Twin and earth, armored cables, and where they're used.
3. Wire Protection (2.3): Use of conduits, trunking, etc., for wire safety.
4. Wire Size & Voltage Relationship (2.4): Thicker wires are needed for higher
currents.
5. Electrical Components (2.5): Switches, sockets, breakers, RCDs, transformers.
3. Safe Isolation Practices
1. Test Equipment (3.1): Voltage indicators, proving units, and lockout devices.
2. Voltage Indicators (3.2): Test indicators on a known source before isolation.
3. Safe Isolation Locations (3.3): Locate points like consumer units.
4. Preventing Re-Energization (3.4): Lockout devices, warning signs.
5. Confirming Isolation (3.5): Use a voltage tester to verify the supply is off.
4. Isolation Practice
1. Selecting Equipment (4.1): Choose suitable testing and lockout tools.
2. Testing on Known Sources (4.2): Ensure voltage indicators work properly.
3. Safe Locations (4.3): Proper isolation points.
4. Isolation Procedure (4.4): Practice safe isolation steps.
5. Fault Management
1. Consequences of Unrectified Faults (5.1): Risks include fire, injury, or
equipment damage.
2. Safety Critical Faults (5.2): Short circuits, poor insulation, etc.
3. Responsible Persons (5.3): Know who to inform—owners, managers,
electricians.
4. Action on Faults (5.4): Isolate, inform, document, and recommend repairs.
6. Practical Electrical Knowledge
1. Temporary Continuity Bonds (6.1): Explain why they are essential for safety.
2. Applying Continuity Bonds (6.2): Learn bonding procedures.
3. Wiring 3-Pin Plugs (6.3): Understand wiring correctly.
4. Cable Tools (6.4): Tools for cutting and joining cables.
5. Attaching to Junction Box (6.5): Steps to securely attach cables.
6. Basic Safety Checks (6.6): Fundamental checks for safe installation and use.