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I have observed that at the input (supply side) of some electrical units, only MCB is used for overcurrent protection; whereas in other units, a fuse is used as well as MCB at the input side.

Why and when are -

  1. Both fuse and MCB required/preferred (as both function to protect against overcurrents)?
  2. Only MCB required/preferred (to protect against overcurrents)?
  3. Only fuse required/preferred (to protect against overcurrents)?

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  • \$\begingroup\$ Breakers for protection wires, fire safety. Fuse protect device. \$\endgroup\$
    – user263983
    Commented Feb 4, 2021 at 12:25
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    \$\begingroup\$ I would be wary of using "in tandem" in an electrical context, just in case someone thinks it means in parallel with rather than in series with. \$\endgroup\$
    – Andrew Morton
    Commented Feb 6, 2021 at 17:35

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It actually does not make a difference if you use an MCB or an fuse as long as you choose the right size and type.

It is usually a question of money and convenience as MCBs are usually more expensive but provide the convenience of not needing a replacement if tripped.

If a fuse and MCB are used in the same circuit then the fuse usually will protect more than one circuit and is a lot bigger than the MCB so it doesn't usually trip and because it rarely trips you don't really need the more expensive MCB.

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