A practical series on the four inspection questions and 15 tests in SANS 10142-1
Part 3: Disconnecting devices and correct switching
The third inspection question reads:
“Disconnecting devices are correctly located and all switchgear switches the phase conductors.”
Clause 8.5.2 requires this statement to be confirmed with a “Yes”. A “No” answer prevents the issuing of the test report.
This question is about safe isolation. A person must be able to find the correct disconnecting device, operate it safely and be confident that the conductors that could make the equipment live have actually been disconnected.
Why is this important?
A disconnecting device in the wrong place, or one that does not disconnect the correct conductors, can leave equipment live when someone believes it is safe. This creates a serious shock and maintenance risk.
The standard therefore deals with both where disconnecting devices are located and which conductors they must disconnect.
What must be confirmed?
The registered person must establish that:
- The installation has the required main switch-disconnector.
- Separate parts of the installation can be disconnected where required.
- Disconnecting devices for fixed equipment are correctly positioned and accessible.
- Motors, including gate and garage-door motors, have a suitable manually operated means of disconnection.
- Switchgear switches the phase conductors and is not incorrectly connected in the neutral only.
- In a single-phase circuit, the disconnecting device disconnects the live conductor and neutral.
- In a multiphase circuit, the disconnecting device disconnects all phase conductors. Where the neutral is directly earthed, it need not normally be disconnected.
- Where there is no direct connection between earth and any live conductor, the disconnecting device disconnects all live conductors. For example, in a safety supply, none of the conductors are connected to earth, so both conductors must be disconnected.
- Installations with more than one supply have the required disconnecting devices and notices.
How is the inspection carried out?
Start at the main distribution board and identify the main switch-disconnector. Confirm that it can disconnect the installation and that it is easily accessible. Where rapid isolation may be necessary, it must also be easy to identify and operate.
Where there is more than one supply, each supply must have its own disconnecting device and a notice must indicate that the installation has more than one main switch-disconnector.
Then work through sub-distribution boards and fixed equipment. Clause 6.9.3.1 requires equipment that is not supplied from a socket-outlet to have an easily accessible switch-disconnector. Unless another specific requirement applies, it must be within arm’s reach of the appliance terminals or be in a distribution board where it can be locked in the open position.
Fixed appliances have a more specific requirement. Clause 6.16.1.4 requires the disconnecting device to be within 1,5 m of the appliance, or in a distribution board where it can be locked in the open position. Even where a disconnecting device is provided on the appliance, a separate disconnecting device is required in the fixed installation to allow the appliance to be completely removed.
Motors have their own specific provisions. For motors such as gate motors and garage-door motors, confirm that a suitable manually operated means of disconnection is provided. Depending on the arrangement, it may be positioned next to or visible from the motor, be capable of being locked in the open position, be housed in a lockable enclosure other than a distribution board, or be achieved by removing a plug from a socket-outlet where applicable. The important point is that a person working on the motor must be able to isolate it safely and prevent unexpected reconnection.
Check which conductors are being switched. A neutral conductor must not have a single-pole disconnecting device. In a single-phase circuit, the disconnecting device must disconnect live and neutral. In a multiphase circuit, all phase conductors must be disconnected, although the neutral need not be disconnected where it is directly earthed.
Where the supply has no direct connection between earth and a live conductor, confirm that all live conductors are disconnected.
This inspection question looks mainly at the location and arrangement of the switching. Test 15 on the standard test report later confirms that switching devices actually make and break the circuits correctly.
Common mistakes
Common mistakes include:
- Installing a disconnecting device where it cannot be reached or operated safely.
- Assuming every motor isolator must be within arm’s reach without considering the motor-specific provisions.
- Relying only on a switch built into a fixed appliance instead of providing the required separate means of disconnection in the fixed installation.
- Using a normal switch where a switch-disconnector is required.
- Switching only the neutral with a single-pole device.
- Failing to disconnect all phase conductors of a multiphase circuit.
- Failing to disconnect all live conductors on a safety supply or another supply system where no live conductor is directly connected to earth.
- Having a main switch that is hidden, obstructed or difficult to operate.
- Failing to provide the correct disconnection arrangements or notices where more than one supply is present.
What if the result is unacceptable?
The disconnecting device may need to be relocated, replaced, rewired or correctly identified. Where suitable isolation is not provided, or the wrong conductors are being switched, the installation must be corrected before this inspection item can be marked “Yes”.
Regulation 9(3) of the Electrical Installation Regulations requires the registered person to refuse to issue the Certificate of Compliance until the fault or defect has been rectified.
Practical tip
Do not ask only:
“Is there an isolator?”
Ask:
“Can I find it easily, operate it safely, and be sure that it has disconnected the conductors that could make the equipment live?”
Key takeaway
Correct disconnection means more than simply fitting a switch. The device must be in the right place, be suitable for isolation, and disconnect the correct conductors so that the installation or equipment can be made safe.
