Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 32 replies
  • Subscribers 32 subscribers
  • Views 3496 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Unusual MCB

Sparkymania
Here's an interesting one.

Federal Electric 20A MCB. Had no type on it and was taking a long time to trip. Opened one up and discovered why it didn't have a type.

Others with it were ECC but virtually the same design. Only thermal. Both are plug in types called stab-lok and are bakerlite.


No instantaneous trip mechanism. Only a thermal one.



34200b5e07a12e120f5fc679b8b1b9aa-huge-mcb-with-no-instantanious-trip-mechanism-4.jpg
Parents
  • 0
    The RCD part will of course deal with L-E faults, but not a L-N short circuit.


    Let's put the short circuit near to the CU with a loop impedance of 0.2 Ω and so a PSSC of 1150 A - that might heat up the bimetallic strip pretty sharpish. However, at the end of a circuit where the impedance might be 1.0 Ω or more, and if the short circuit has a little more than a negligible impedance, it might cook for long enough to do some damage.


    What did the 15th Edn (or even 14th Edn) require? Surely they must have been compliant!
Reply
  • 0
    The RCD part will of course deal with L-E faults, but not a L-N short circuit.


    Let's put the short circuit near to the CU with a loop impedance of 0.2 Ω and so a PSSC of 1150 A - that might heat up the bimetallic strip pretty sharpish. However, at the end of a circuit where the impedance might be 1.0 Ω or more, and if the short circuit has a little more than a negligible impedance, it might cook for long enough to do some damage.


    What did the 15th Edn (or even 14th Edn) require? Surely they must have been compliant!
Children
No Data

Community Rules & Guidelines