Difference between revisions of "Talk:CU"
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--[[User:John Rumm|John Rumm]] 02:58, 8 March 2009 (GMT) | --[[User:John Rumm|John Rumm]] 02:58, 8 March 2009 (GMT) | ||
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| + | == level of protection == | ||
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| + | I think this bit is missing the point really. | ||
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| + | Fault current protection is '''required''' at the origin of the circuit. Overcurrent protection is typically also provided at the origin, but is not actually required to be there. By design one may choose to delegate the overcurrent protection to somewhere else. (i.e. this is not just about inheriting sub optimal situations from old installations) | ||
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| + | For example two 16A radials connected to space heaters could legitimately be connected to one 32A MCB if it made more sense to have them controlled together (say both are in one room). If they were wired in 2.5mm^2 T&E then the 32A MCB would provide adequate protection in the event of a fault (e.g. damaged cable etc). However it would not provide protection from overload. In this circumstance the job has been delegated to the FCUs that connect the appliances. The maximum fuse that could be inserted in each is 13A, and the absence of any sockets or other FCUs prevents the maximum load on the circuit exceeding the nominal 26A | ||
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| + | --[[User:John Rumm|John Rumm]] 03:08, 8 March 2009 (GMT) | ||
Revision as of 03:08, 8 March 2009
I have done my edits in the other version of this, however I will add comments here where appropriate.
The upgrades section is already covered in more detail in the changing a cu article.
Same goes for the sections on Upgrading on TT, and working on a CU.
--John Rumm 02:58, 8 March 2009 (GMT)
level of protection
I think this bit is missing the point really.
Fault current protection is required at the origin of the circuit. Overcurrent protection is typically also provided at the origin, but is not actually required to be there. By design one may choose to delegate the overcurrent protection to somewhere else. (i.e. this is not just about inheriting sub optimal situations from old installations)
For example two 16A radials connected to space heaters could legitimately be connected to one 32A MCB if it made more sense to have them controlled together (say both are in one room). If they were wired in 2.5mm^2 T&E then the 32A MCB would provide adequate protection in the event of a fault (e.g. damaged cable etc). However it would not provide protection from overload. In this circumstance the job has been delegated to the FCUs that connect the appliances. The maximum fuse that could be inserted in each is 13A, and the absence of any sockets or other FCUs prevents the maximum load on the circuit exceeding the nominal 26A
--John Rumm 03:08, 8 March 2009 (GMT)