Several devices provide overall protection to an installation. The electrician needs to decide which type is best suited to individual installations as they arise.
A residual current device (RCD) is the generic term for a device that simultaneously performs the functions of detection of the residual current, comparison of this value with the rated residual operating value, and opening the protected circuit when the residual current exceeds this value. These devices can take several different forms such as Residual Current Circuit Breaker (RCCB) or Residual Current Circuit Breaker with integral Overload protection (RCBO)
Residual current operated circuit breakers with overcurrent protection (RCBOs) include residual current detection and overcurrent protection in one device and thus enable a combination of electric-shock protection, fire protection, and line protection in one device.
RCBOs are installed in all circuits of modern electrical installations, combining maximum operating safety with electric shock and line protection.
We will look into all features in more detail outlining the pros and cons.
Advantages of RCBO
RCBO has lots of strengths. The following list of benefits can help you make a wise technical decision.
All in one device
In the past, there were two types of protection devices typically installed in an electrical switchboard: a residual current device (RCD) and a miniature circuit breaker (MCB). The RCD is designed to protect the user from being exposed to dangerous currents, while the MCB protects the building wiring from being overloaded. Switchboards have a limited amount of space, and so the need to install two separate devices for electrical protection sometimes proved problematic.
The more recent development of RCBOs, which can perform the dual functions of protecting both users and the building wiring, freed up space in the switchboard because RCBOs can replace two separate devices. Overall installation time is also reduced by using RCBOs. Thus, RCBOs are now the preferred device used by electricians, instead of installing both an RCD and MCB.
RCBO is a compact protection device that provides MCB overcurrent protection and RCCB earth fault protection in a single unit. The device switches both the line and neutral conductors. The units feature indicators that show whether a trip is due to an overcurrent or earth fault.
RCBO is an ideal choice for installations where pole space is a problem. Small width allows a greater number of RCBOs to be installed in one enclosure.
Short installation time
RCBO is an effective way of providing reliable, discriminating residual current protection. Also, the elimination of separate fuses or circuit breakers substantially reduces installation time and space requirements.
High switching capacity
The rated switching capacity of RCBOs is considerably higher than that for residual current operated circuit breakers as the MCB component, which is specially provided for short-circuit protection, performs short-circuit clearing.
Better isolation and troubleshooting
In the event of a fault, all poles are disconnected from the power supply. All live parts are thus reliably disconnected from the supply and troubleshooting is simplified.
RCBOs are also increasing in popularity. The sales volume and market share of the device are increasing day by day.
RCBOs have a long lifespan. The mechanical life of an RCBO is around 20,000 operations.
Using an RCBO simplifies product selection and reduces inventory while enabling coverage of every conceivable application.
RCBOs are further divided into types depending on their operating function:
Type AC: For which tripping is ensured for residual sinusoidal alternating currents, whether suddenly applied or slowly rising.
Type A: For which tripping is ensured for residual sinusoidal alternating currents and residual pulsating direct currents, whether suddenly applied or slowly rising.
Type S: For selectivity, with time delay.
Disadvantages of RCBO
You should be aware of the drawbacks of RCBO. This will help you understand the weaknesses of the device.
As the price of these devices is dropping year by year, the RCBO is still expensive compared to RCD + MCCB solution.
When several RCBOs are installed side by side and operate simultaneously, the heat dissipation of one pole is limited. This results in an increased operating temperature for RCBOs which may cause false tripping.
RCBOs are mainly used in commercial/industrial installations. You cannot be able to use RCBOs in automation or harsh industrial applications.
Limited currents and sensitivities
RCBOs do not have a wide current and sensitivity range compared to MCBs and RCDs. The current range of an RCBO cannot be adjustable. Besides, it does not have a communication option.
Less accessory options
RCBOs have limited electrical and mechanical accessory options.