Rear entry three phase board

[Gigsy]

If there is a fault on one of the final circuits you would want the MCB to trip faster than the MCCB. A practical example of this I recall was one of the final circuits we installed the chippy put a nail through the cable now as we had a low ELI it took out the RCBO as well as the existing 50A MCB protecting this D.B. bad discrimination ( sorry selectivity new word)

Trip faster? Does the MCCB not have to trip within 0.4s ?

 

[Gigsy]

I thought an MCCB was the same as a MCB (actrually CB not MCB as everyone calls them) only for higher Amps, over 63A

 

[Toneyz]

Trip faster? Does the MCCB not have to trip within 0.4s ?

Sorry, disconnect, 5 sec for distribution circuit.

 

[Gigsy]

If there is a fault on one of the final circuits you would want the MCB to trip faster than the MCCB. A practical example of this I recall was one of the final circuits we installed the chippy put a nail through the cable now as we had a low ELI it took out the RCBO as well as the existing 50A MCB protecting this D.B. bad discrimination ( sorry selectivity new word)

In that situation you would wanna substitute the 50A MCB for a type C or type D MCB?

 

[Toneyz]

I thought an MCCB was the same as a MCB (actrually CB not MCB as everyone calls them) only for higher Amps, over 63A

 

[Toneyz]

No start at 16A.

 

[Gigsy]

Sorry, disconnect, 5 sec for distribution circuit.

0.4 sec under 32A and 5 sec over 32A
In the situation you describe surly a 50A type c or type D MCB would be the solution?

 

[Gigsy]

SO what exactly is the difference between a 16A MCB and a 16A MCCB

 

[Deleted member 26818]

All distribution circuits and any final circuits greater than 32A have a maximum disconnection of 5s.
Or has that changed recently?

 

[ipf]

0.4 sec under 32A and 5 sec over 32A
In the situation you describe surly a 50A type c or type D MCB would be the solution?

There's a small matter of short circuit capacity rating involved, here, mate.

 

[Deleted member 26818]

There's a small matter of short circuit capacity involved, here, mate.

Do you mean withstand capability?

 

[Gigsy]

There's a small matter of short circuit capacity involved, here, mate.

The interrupting rating for an MCB is 18,000 amps, and up to 200,000 amps for an MCCB.

 

[Gigsy]

My question would be, say if you're PFC and PSSC are less then 18,000 Amps, why would you use a MCCB over an MCB on a main DB supplying a sub DB?

 

[Ian1981]

Your tripping characteristics are completely different from your standard circuit breakers hence manufacturers data should be sought as have you never noticed how no maximum zs values are published in bs7671 regarding mccb’s?
They can have both the magnetic and overload characteristics set , depending on the application they are being used for and what they intended to supply and protect.

 

[Leesparkykent]

I’ve had to delete loads of posts....It took me ages . I’ve had to delete posts that were just silly/off topic, other posts that quoted such posts and then posts which would no longer make sense due to previously deleted posts. Please play nice and keep the thread on track. Cheers guys and girls.

 

[westward10]

Okay Gigsy, from afar and not seeing the job first hand this is probably what I would do. Shorten the swa supply cable and make it off into a 63A isolator, from here take some 6181Y tails to the meter that way you have no unenclosed conductors. Those protective devices at the main board with the orange toggles are BS3871 Type 3, cant make out the other but it is not compatible with the enclosure and the cover has probably been cut away to fit it.

 

[Gigsy]

Okay Gigsy, from afar and not seeing the job first hand this is probably what I would do. Shorten the swa supply cable and make it off into a 63A isolator, from here take some 6181Y tails to the meter that way you have no unenclosed conductors. Those protective devices at the main board with the orange toggles are BS3871 Type 3, cant make out the other but it is not compatible with the enclosure and the cover has probably been cut away to fit it.

Thank you
I will not use rear entry again. From now on 4 inch metal trunking top and bottom into glands and make off the SWA into the board. And I would insist on the customer purchasing the meter designed to go in the board.