10KA or 6KA breakers?

[yellowvanman]

I know the difference between the 2 sorts but I'm thinking do I need to fit 10KA breakers in this scenario, when I've got 6KA MCBs in the van!

3 phase DB, Isc 4.9KA (phase to earth), all circuits from this DB are single phase. Will never be 3 phase in future (HMO).

Worst case short circuit (phase to phase) would be 9.8KA, but that could only happen in the DB itself, which is protected by the 100A 1361 DNO fuse.

 

[yellowvanman]

Eh? If you are going to connect a large motor to a circuit using a B type mcb would silly yes? one socket for a kettle then a b fine?

Sorry but where does B type and a large motor come into the equation?

I was asking about 6KA versus 10KA MCBs, I also mentioned that all circuits were single phase only as this was a HMO.

 

[yellowvanman]

Just to give an update, I did ask the question to the technical support guys at Elecsa.

The guy was happy with the 6KA MCBs as the upfront 1361 Type II fuse had rated short circuit capacity of 16.5KA

 

[Chr!s]

Just to give an update, I did ask the question to the technical support guys at Elecsa.

The guy was happy with the 6KA MCBs as the upfront 1361 Type II fuse had rated short circuit capacity of 16.5KA

That's no Guarantee, its not as straight forward as that unless you are utilizing UK Annex ZA

 

[Knobhead]

Maybe, but i'm a great believer in providing the correct rated OCPD's. I've only seen the result of using grossly under rated Breakers once, (and there was other issues) but that breaker was missing almost half of it's casing and bit's of it's internals and busbar all over the DB, with quite a few damaged adjacent breakers to boot!! lol!!!! The upstream protection did trip, but not fast enough to prevent some expensive damage to the DB...

As an example, i always make sure that small power final DB's in our project S/S rooms are provided with MCB's rated at 25KA...

Not many will find themselves installing MCB’s so close the source.

One reason all our panels were fitted with BS88 fuses between the main busbars and the various small power boards in the panel. They were only to feed the various substation services but so close to the transformer a bit of help was considered necessary. Belt and braces it may have been, we were happy with it. 40KA MPFC at the main bars needs some toning down. Happy to say, it was never needed.

 

[Engineer54]

Not many will find themselves installing MCB’s so close the source.

One reason all our panels were fitted with BS88 fuses between the main busbars and the various small power boards in the panel. They were only to feed the various substation services but so close to the transformer a bit of help was considered necessary. Belt and braces it may have been, we were happy with it. 40KA MPFC at the main bars needs some toning down. Happy to say, it was never needed.

Agree, i was only using this as an example.

BTW, we haven't used HRC fuses in Main Switchboards and Main Distribution boards for a good many years now. All are now high rated Schneider (MG) ACB's/MCCB's.

 

[Sintra]

Just to give an update, I did ask the question to the technical support guys at Elecsa.

The guy was happy with the 6KA MCBs as the upfront 1361 Type II fuse had rated short circuit capacity of 16.5KA

That statement shows he doesn't fully understand what he's talking about lol.

 

[MDJ]

Sorry but where does B type and a large motor come into the equation?

I was asking about 6KA versus 10KA MCBs, I also mentioned that all circuits were single phase only as this was a HMO.

First of all if you are under any impression I am trying to give you a hard time you are mistaken so chill out. My point was when designing a circuit you will be aware what is going to be connected on it and you can install a suitible MCB for that designed circuit. I appreciate your circuit and your thoughts regarding a 6KA Btype MCB, I was just trying to suggest if you know what is on it then you will be able to know whether the device connected is suitible. Obviously if you did a zs and the reading didn't comply with the device you had there then a rethink need to be considered.