The inherent power supply in my workshop requires replacement? I believe from reading threads in these forums that what has previously been installed (not by me) is inadequate or just wrong? So from a 13amp fused spur inside the house, an SWA is connected to a plastic consumer unit in the shop. So is it the case that the consumer unit in this situation is pointless as the fuse in the spur will be first to react? I am open to changing to a direct connection to the main consumer unit and then to an appropriate metal-clad unit in the shop. As ever any advice will be valued Marcus.
Power Supply To Workshop
- Thread starter MarcusG
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Whilst waiting for a pro to correct me, my thoughts would be:
I dont think discrimination is relevant with fuse overload protection as it is with rcd.
My guess is that the 13a fuse may blow first in an overload situation because the voltage drop would, I guess mean a higher current draw at the house end.
The existing 13a fuse needs to protect the cable run -so the cable size would need to be able to cope safely with more than 13a (length is also a factor).
I suppose if your house CU is rcd then you wouldnt need one in the workshop, but if it isnt, then maybe the workshop CU could have rcd protection....
As an aside, with the new rules relating to metal consumer units, I have wondered if the metal could be subject to condensation in cold garages or sheds....just a thought.
I dont think discrimination is relevant with fuse overload protection as it is with rcd.
My guess is that the 13a fuse may blow first in an overload situation because the voltage drop would, I guess mean a higher current draw at the house end.
The existing 13a fuse needs to protect the cable run -so the cable size would need to be able to cope safely with more than 13a (length is also a factor).
I suppose if your house CU is rcd then you wouldnt need one in the workshop, but if it isnt, then maybe the workshop CU could have rcd protection....
As an aside, with the new rules relating to metal consumer units, I have wondered if the metal could be subject to condensation in cold garages or sheds....just a thought.
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Current in = current out
(@op - I think there is a very long list of questions to answer first. Don't have time to write them out now, but there is no quick answer.)
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If the supply to the workshop is fed through the main RCD in the house then :-
(1) a fault in the workshop that trips the house RCD will leave the house without power or lights.
(2) a fault in the house that trips the house RCD will leave the workshop without power or lights.
Plunging a work shop into sudden darkness is a serious hazard. Rotating equipment ( saws, drills, angle grinders etc etc ) do not stop instantly when their power is shut off.
Feed the shed from it's own MCB and RCD ( or combined in an RCBO ) in the house
Current is the same at all points along a single loop circuit
So the usage would be for power tools and lawnmower etc. There are 3 bayonet light fittings, 1 outside light and 3 double sockets. 12 metres from the house.
It sounds fine to me. Pics help.
A 16A MCB will trip before a 13A fuse.
A 16A MCB will trip before a 13A fuse.
Of course
Voltage drop over the length of the cable is I guess due to power loss due to cable resistance, so whilst the power output at the end is the less than the start, the current is the same.
The number of electron movements is the same both ends?
"lost power" heats the cable.
Further issues have developed. So a new metal clad consumer unit was fitted and connected up and immediately blew the fuse in the spur and tripped the main RCD. The sparky I used is claiming it's the SWA which must be damaged? He is insisting that it needs replacing? I am not convinced as I have checked the continuity and all is ok. Can I do anything else to check the cable before I agree to it being replaced?
Picture of this new CU, including the wiring inside ?
If the SWA was damaged, they should have found out long before any power was applied to it.
No problem I can add a photo tomorrow. I am not sure what checks he carried out? I just left him to it! Everything worked attached to the plastic CU however a gland wasn't used! So the changes were metal clad CU and this was attached with a gland.
Why? I already told you that that was not required and you thanked me for the information.
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