Hi guys.
I've not had to look at discrimination since college so could do with a little refresher.
The job is to provide power to a domestic shed (30m away from CU) supplying a 32a ring (possible mig welding, milling machine etc..) and a 6a lighting circuit, all protected by an RCD.
My plan is to take from a Henley block to a new 2way CU (sub 1). A 40a MCB protects power to the shed via 30m of 6mm SWA (have yet to check cable calcs, may need 10mm on a 50a MCB) to the above 2 way CU in the shed (sub 2).
So back to discrimination. I understand how to check when you have two different types of breaker (main cut out BS3036 and MCB BS60898) but what I'm unsure about is where we have two of the same breakers in series like the 40a at sub1 and the 32a at sub2. Now according to page 301 of the regs there shouldn't be a problem but I've read before about doubling the circuit breaker to "ensure" discrimination. Is this just how lazy people work out discrimination from two different types of breaker or is this something I need to be considering even with two types of the same breakers?
Cheers,
Chris
I've not had to look at discrimination since college so could do with a little refresher.
The job is to provide power to a domestic shed (30m away from CU) supplying a 32a ring (possible mig welding, milling machine etc..) and a 6a lighting circuit, all protected by an RCD.
My plan is to take from a Henley block to a new 2way CU (sub 1). A 40a MCB protects power to the shed via 30m of 6mm SWA (have yet to check cable calcs, may need 10mm on a 50a MCB) to the above 2 way CU in the shed (sub 2).
So back to discrimination. I understand how to check when you have two different types of breaker (main cut out BS3036 and MCB BS60898) but what I'm unsure about is where we have two of the same breakers in series like the 40a at sub1 and the 32a at sub2. Now according to page 301 of the regs there shouldn't be a problem but I've read before about doubling the circuit breaker to "ensure" discrimination. Is this just how lazy people work out discrimination from two different types of breaker or is this something I need to be considering even with two types of the same breakers?
Cheers,
Chris