Circuit protection is a mandatory items that we MUST consider carefully for Electrical Installation project.I will take a fully attention during sizing and follow standard requirement for circuit breaker.
If the circuit protection not function properly, it’s can cause a serious damage to equipment and personnel.On my last post,I had discussed about Circuit Breaker Sizing.
This time I want to share some information about general requirement for circuit breaker that commonly apply for Electrical Installation project.I hope this post can help to have a basic guideline during handle any project of electrical installation.
Circuit Protection General Requirement
1) Over-current protection shall be sized to provide protection for devices as well as conductors.
2) Fuse sizes shall be indicated with a label directly over the respective fuse block and can be part the label that indicates the name of the device.
3) Use fuse blocks with indication instead of circuit breakers for three phase power distribution.
Note: Fuse Blocks for globally designed equipment are required because they can be installed on all types of grounding systems found globally and have better characteristics for flash hazard protection. EU Norms require that the fuses required be readily available locally. Since there are no global standards for fuses, it may be difficult to ensure that a given fuse type is available in all global locations, therefore sites can evaluate and replace the fuse blocks with circuit breakers once they have determined circuit breakers can be implemented safely on their grounding system.
4) Circuit breakers can be used for single phase and or 24 VDC protection.
5) Circuit breakers rated for supplementary protection (i.e. UL Recognized under UL 1077) shall not be used for branch protection. Only circuit breakers rated for branch circuit protection (i.e. UL Listed under UL 489 or multi-rated devices with UL and other EU 3rd party approval) shall be used for branch circuit protection.
6) All protective devices shall be listed for the application and will be rated for the desired application with regards to supply voltage, operating current and short circuit current or amps interrupting capacity (AIC).
7) Circuit breakers or fuses with indication are acceptable. Site grounding scheme should be considered when selecting either fuses or circuit breakers.
8) Fuses, when used, shall be current limiting fuses to minimize flash hazard ratings.
9) Circuit breakers rated for supplementary protection (i.e. UL Recognized under UL 1077) shall not be used for branch circuit protection.
10) Only circuit breakers rated for branch circuit protection (i.e. UL Listed under UL 489) shall be used for branch circuit protection.
11) All protective devices shall be listed for the application and shall have ratings exceeding the desired application requirements with regards to voltage, operating current and short circuit current or amps interrupting capacity (AIC).
12) Use circuit breakers that are IEC rated for the application (IEC 60947 – Switchgear and Controlgear, IEC 60934 – Equipment, IEC 61008 – Residual Current) and are approved by an EU recognized 3rd party approval. (ex. – TUV, VDE)