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Hi chaps and chapettes,
I have a buried 6mm SWA 32a radial circuit powering a single 32a commando/ceeform, i'm looking to add a 16a ceeform for convenience. Can I use a thermal-magnetic breaker to derate to 16a. There isn't space for a 2 way CU so would this be my best option?
Thanks.
 
Hi chaps and chapettes,
I have a buried 6mm SWA 32a radial circuit powering a single 32a commando/ceeform, i'm looking to add a 16a ceeform for convenience. Can I use a thermal-magnetic breaker to derate to 16/15a. There isn't space for a 2 way CU so would this be my best option?
Thanks.
 

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Yes you could, but I would not use the sort you pictured - it needs to be capable of breaking the worst case PFC/PSSC.

If you can fit in a garage CU or similar with a 16A MCB it will do the job, though you won't have any selectivity with the upstream one on a hard fault (but that probably does not matter here).
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I see you can't fit one - not at all?

Another option is an HRC fuse as often they can break well over a MCB's capabilites, but typically they have DIN-rail sized holders as well. You might get away with a 32mm x 6mm fuse in a panel holder.
 
Thanks, was mainly curious to whether those bimetallic breakers (with an IP rated boot) can be used as such (other than on appliances) and makes perfect sense to use an mcb in a suitable enclosure. In this case ill just expand the backboard on the stake post (this is all external) and mount an ip rated consumer unit.
Was just being cost conscious.
 
Thanks, was mainly curious to whether those bimetallic breakers (with an IP rated boot) can be used as such (other than on appliances) and makes perfect sense to use an mcb in a suitable enclosure. In this case ill just expand the backboard on the stake post (this is all external) and mount an ip rated consumer unit.
Was just being cost conscious.
Often when in an appliance they are backed up by the supply fuse which will limit the current, or the nature of the load/control arrangement has other current limiting properties.

You probably would be OK, as under a hard fault the upstream MCB probably will trip first so it never has to break more than a few times its rating. But for fixed wiring you should stick to the IET regs which requires any breaker to be capable of interrupting the worst case PFC/PSSC at that point in the installation.

If space is an issue you might be able to fit something like this:

With a suitable 38x10 HRC fuse it will easily cope with fault currents.
 

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