ELECSA Certification Scheme Elecsa Assessment

[ianphilip007]

hi guys

have my assessment coming up next month. have a question about the minimum mcb rating for an A3 radial (from outbuilding cu). Now the radial has one db socket and one single external socket. the radial has a very low loading (2kw max/9A). now i dont want to to be pulled up for using the wrong MCB. now usually i would just use a 20A mcb as stated in OSG for an A3 radial. problem is the garage has a buried 2.5mm (20A) supply fed from a RCD protected 20Amcb which i would like to utilise. so my question is would a 16Amcb for the A3 radial be acceptable due to the known low loading and the adequate protection offered by the 16Amcb. or has it got to be a 20Amcb as per OSG for an A3 radial with multiple socket outlets. As this is for assessment do you think it nessacary to supply via 6mm/32Amcb to allow for the 20A A3 radial and allow for discrimination?

 

[malcolmsanford]

No mate the OSG is a guide and so if you as the designer feels that a 2.5mm radial is best served by a 16amp MCB then there is no problem with that.

 

[ianphilip007]

so as long as i can explain to my assessor my reasoning for selecting the 16AMCB then there should be no problem?

 

[malcolmsanford]

No that should be fine. If your using an existing cable emphasise the fact that you tested it to make sure it was ok and point out the IR results.