Beatrice Lang
In electrical terms, a 'spur' is an extension of an existing power circuit, which is used to add an extra socket or lighting fixture without needing a complete circuit overhaul. Spurs are generally connected to a ring circuit, which is a common wiring arrangement in many homes. Fused spurs, in particular, are wired connections between an electrical cable and an appliance, bypassing the conventional plug and socket. They are used for higher-power, higher-voltage devices such as ovens, washing machines, and refrigerators. Fused spurs can be switched or unswitched, and they play an important role in safely expanding a home's electrical system while adhering to country-specific standards and regulations.
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What You'll Learn
Fused spurs are a type of switch
Fused spurs are available in both switched and unswitched variants. Switched fused spurs include a button to switch off the current to the unit, either within the live line only (single pole spurs) or in both the live and neutral lines (double pole spurs). Double pole fused spurs offer a good level of protection from accidental exposure to electrical current. Unswitched fused spurs, on the other hand, only contain the fuse cage without a switch. Fused spurs with neon lights indicate whether the switch is on or off through the illumination of the lights.
The term gang refers to the length of the electrical box housing spurs and sockets. A '1 gang' model is large enough for a single socket or fused spur, while a '2 gang' model incorporates a pair. Fused spurs can take a 13-amp load and are pre-loaded with a 13-amp fuse, although lower ampage fuses can be used if appropriate. 3 and 5-amp fused spurs are commonly used for light switches.
It is important to note that fused spurs are not the same as residual current device (RCD) sockets, which automatically switch off the live current to protect against electrocution in the event of a fault or short circuit. Fused spurs should only be installed or removed by a qualified electrician as they do not use a conventional plug and socket.
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Spur sockets vs. residual current device (RCD) sockets
A spur socket, or fused connection unit, is a switch that isolates electrical equipment from the mains supply. It is a directly wired connection between an electrical cable and an appliance, bypassing the conventional plug and socket. Spur sockets are typically used for appliances that require higher power and voltage, such as ovens, dishwashers, washing machines, and boilers. They are also used for safety reasons, providing an additional level of protection by allowing the device to operate on a separate cable outside the main electrical circuit. Spur sockets are particularly useful when access to the appliance is difficult, such as with under-counter appliances or devices in enclosed spaces.
The number of socket-outlets supplied by a fused spur is unlimited. However, it is important to assess the current demand of the equipment to ensure it does not exceed the rating of the fuse in the connection unit. Fused spurs can be switched or unswitched, with single or double poles, and are typically rated at 3 or 5 amps.
On the other hand, a residual current device (RCD) socket is a safety device designed to prevent fatal electric shocks and provide protection against electrical fires. RCDs constantly monitor the electric current flowing through circuits and automatically shut off the electricity supply in the event of a fault or short circuit. They offer a higher level of personal protection compared to ordinary fuses and circuit breakers. RCD sockets are available as fixed RCDs, socket-outlet RCDs, and portable RCDs. Fixed RCDs are installed inside the consumer unit (fusebox) and protect individual or groups of circuits, providing the highest level of protection. Socket-outlet RCDs, also known as RCD-protected spur sockets, replace standard socket-outlets and provide protection to individuals in contact with the equipment plugged into them. Portable RCDs, meanwhile, plug into standard socket-outlets, and an appliance is then plugged into the RCD.
While spur sockets provide a means of isolating circuits and enhancing safety by operating outside the main electrical circuit, RCD sockets focus on protecting individuals from electric shocks and fires. RCDs are sensitive safety devices that automatically shut off electricity when necessary. Both spur sockets and RCD sockets have their advantages and serve different purposes in electrical systems.
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Spur circuits
A spur circuit is a branch of the main electrical circuit ('ring circuit') that runs between a fused spur and the main electrical supply to a building. Fused spurs are directly wired connections between an electrical cable and an appliance, and they are used to isolate electrical equipment from the mains supply. They are particularly useful when access to the appliance is difficult, such as with appliances under a worktop or in enclosed spaces.
Fused spurs are used with higher-power, higher-voltage electrical devices that cannot use conventional plug sockets. In a domestic setting, fused spurs are commonly used with ovens, dishwashers, washing machines, tumble dryers, boilers, thermostats, refrigerators, and heaters. Fused spurs allow these devices to operate on a separate cable outside the main electrical circuit, providing an additional level of safety.
There are two main types of fused spurs: switched and unswitched. Switched fused spurs include a button to turn off the current to the unit, either within the live line (single pole spurs) or in both the live and neutral lines (double pole spurs). Double pole fused spurs offer a higher level of protection from accidental exposure to electrical current. Unswitched fused spurs, on the other hand, do not have a switch and are used when manual control over the connection is not necessary or desired.
When adding a spur to a ring final circuit, there are three common methods. The first is to connect it as a spur, which can be done in two ways: by adding a single cable from the new socket to an existing socket on the ring, or by connecting the spur at the consumer unit. The second method is to extend the ring by adding a socket to the end of the ring. The third option is to provide a dedicated radial circuit for a specific load, such as a high-power electric heater. It is important to note that the number of spurs on the ring should not exceed the number of other socket outlets, and if a large number of spurs are required, it is advisable to replace the entire circuit.
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Single pole vs. double pole fused spurs
A fused spur is a switch that isolates electrical equipment from the mains supply. Fused spurs are directly wired connections between an electrical cable and an appliance. They are used instead of conventional plug sockets with higher-power, higher-voltage electrical devices. In a domestic setting, typical uses include ovens, dishwashers, washing machines, boilers, thermostats, and refrigerators.
Single pole fused spurs have a lower safety rating than double pole models. They feature a simpler isolation mechanism that only affects the current through the live wire, leaving the neutral line unchanged. Single pole fused spurs are typically used when full isolation from the live current is not a priority.
On the other hand, double pole fused spurs isolate both the live and neutral wires within the device when the button is pressed and the socket is switched off. This provides an additional level of safety and is favoured when full isolation from the live current is a priority, such as with higher-voltage devices like boilers. Double pole fused spurs also provide good protection from accidental exposure to electrical current.
The type of fused spur to buy depends on the intended use. For example, a switched fuse spur attached to a refrigerator would allow the user to defrost the appliance. Switched fused spurs are also used when the ability to deactivate a live connection is beneficial.
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Safety considerations when using spurs
When it comes to electrical systems, a spur refers to an additional or secondary branch that is connected to the main circuit. In simpler terms, it is like a small offshoot or extension of the main wiring. Spurs are commonly used to supply power to additional outlets or lighting fixtures that are located away from the main circuit.
When installing or working with electrical spurs, there are several important safety considerations to keep in mind:
- Overloading: One of the primary concerns with spurs is the potential for overloading the circuit. Since a spur draws power from the main circuit, it is crucial to ensure that the total load on the circuit, including the spur, does not exceed the safe capacity. Overloading can lead to tripped breakers, blown fuses, and even fire hazards. To prevent this, calculate the total amperage draw of all devices connected to the circuit, including those on the spur, and ensure it remains within the circuit's safe operating capacity.
- Correct Wiring and Connections: Proper wiring and connections are critical for the safe operation of spurs. Ensure that the correct wire size and type are used for the spur, following local electrical codes and regulations. Inadequate wiring can lead to voltage drop and overheating. Secure all connections tightly and use appropriate connectors or junction boxes to prevent loose contacts and potential arcing.
- Protection Devices: Install appropriate protection devices, such as circuit breakers or fuses, specifically for the spur circuit. This ensures that in the event of a fault or overload on the spur, the power can be quickly and safely disconnected. It also isolates the issue to the spur, minimizing the impact on the rest of the electrical system.
- Earth and Bonding: Ensure that the spur is properly earthed and bonded to the main electrical system. This is crucial for safety as it provides a path for fault currents and helps prevent electric shock. Follow local regulations and standards for earthing and bonding requirements.
- Access and Enclosures: Provide easy access to the spur and its connections for maintenance and inspection. Use appropriate enclosures or conduit to protect the wiring from damage and to prevent accidental contact. This is especially important in areas where the spur may be exposed to physical impact or moisture.
- Marking and Identification: Clearly mark and identify the spur circuit and its components. This helps with future maintenance and troubleshooting. Label the spur at the distribution board or consumer unit, as well as at the point of connection to the main circuit. This ensures that anyone working on the electrical system can easily identify the purpose and function of the spur.
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Frequently asked questions
A spur is an extension from an existing power circuit, used to add an additional socket or lighting fixture without a complete circuit overhaul.
A fused spur is a switch used to isolate electrical equipment from the mains supply. Fused spurs are wired connections between an electrical cable and an appliance, and they are used instead of conventional plug sockets for higher-power devices.
A switched fused spur has a button to turn the unit on or off, while an unswitched fused spur does not have a switch. Switched fused spurs are used for appliances that may need to be shut off in the event of problems, while unswitched fused spurs are used for equipment that should not be accidentally turned off, such as alarm systems.
A single pole fused spur switches the current within the live line only, while a double pole fused spur switches the current in both the live and neutral lines.
You can identify spur sockets by turning off the power supply to the area you intend to inspect and then examining the electrical circuits. Spur sockets are typically added to ring circuits, which form a loop that begins and ends at the consumer unit, but they can also be added to radial circuits.
