In the absence of the OP responding we are all guessing
Electric to outdoor utility room
- Thread starter Jupiter01
- Start date
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Indeed, and in the absence of further input from OP, I would say that to assume (guess) that we're talking about a fused spur because the OP had proposed to use 2.5mm² cable would seem to be particularly unwise.
Could the CU in the utility room avoid the house fuse tripping?
In the majority of cases no
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I am happy to come out of the ring in the house into a FCU and then from here outdoors with a SWA (2.5 or 4mm?). I would then add a CU in the utility of it meant that any overload/fault will be handled here, rather than trip the circuit in the house.
If you goes through a (13A) FCU then, as has been said, 2.5mm² cable would be adequate unless the run was very long (in which case 'voltage drop' issues might conceivably arise) - but, as has also been said, that would limit the supply to 13A, not really enough to run, say, your proposed dryer and WM at the same time.
As has also been said, with an upstream 13A fuse, a CU would really not be either necessary or useful. The circuit in the house would not be expected to ever get tripped by an overload, since the 13A fuse in the FCU ought to 'blow' before the 32A breaker in the CU tripped.
A 2nd CU will not guarantee anything other than extra costs to install.
What rating MCB at source would benefit from a CU?
Depends on the load on the circuit, the length of the cable AND the installation method
Thought you said you couldn’t get from the CU
Your home ?
Not really. What rating of MCB in the CU would you be contemplating, and what do you think it would achieve?
In fact, if (with a 13A fuse in the spur, if the source MCB (in house CU) were 16A then that would be much more likely to trip (in the case of an overload) than would be the 32A one.
If there's a 13A fuse in the spur, then the rating of the 'source' MCB is essentially irrelevant - although, as I've just written, the lower the rating of the MCB, the more likely that it would trip (rather than the fuse blowing) in the event of an overload.
I thought we were now talking about a 13A fused spur - in which case 2.5mm² cable of any length and any installation method would be OK (unless it was so long that Zs became an issue) - and, in any event, the considerations you mention would have no bearing on the rating of the MCB upstream of the FCU
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