Lights Supplied by 30 Amp Ring Final. B.S. 3036 Fuse.

Zoomup:

AJJewsbury:

521.8.2 does not apply, as I am only dealing with ONE final circuit, that of the lighting circuit feeding a single timer extractor fan. No probs. here.

BS 7671 definition of a circuit means that any overcurrent protective device starts a new circuit (see part 2) - in this case the L and SL are by definition different circuits as the are protected by different fuses. As they both directly connect to current using equipment they'd be classed as final circuits.


Oddly enough there's nothing in the definitions that means that one final circuit can't supply another final circuit (despite the name).


   - Andy.

Circuit definition. "An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)." Notice the plural used here DEVICES.
But your permanent Line and switched Line cables must be on different circuits because they are protected by different devices

"Same origin." Yes the lighting circuit M.C.B., say a B6 or B10.
DIfferent origins- 2x BS1362 fuses

"An assembly of electrical equipment."  Yes, Lights, shaver outlet and fan.
Fan only- supplied by two circuits

We could argue about the fuses used to protect the fan are just there for fault protection and not overcurrent protection as the fixed fan load can not overload the supply cables in normal use.
 think you are confusing overcurrent (exceeding the rated value) protection with overload protection (which occurs in a mechanically sound circuit), a fault current can be an overcurrent if large enough, see definitions in part 2

"Protective device(s)" can be included in one final circuit. So we can have more than one protective device in a final circuit.

 Yes, if in series, not parallel.


Z.


 

If you were fitting a boiler to an existing fcu on a ring final circuit, would you record the OCPD as 32A mcb or 3A fuse on any MWEIC?


Also the label reg i was thinking of is 514.11.1 it does say not capable of being isolated by a single device, and you could argue the 6A mcb does this, but then so does the main switch and cut out. I think the intention is that it warns of a possible danger of live parts if one of the fuses blows and the fan dont work. 


Back to the OP, I thought my idea of an fcu behind the switch i posted earlier was good, but seems to have been overlooked :)

 

Zoomup:

AJJewsbury:

521.8.2 does not apply, as I am only dealing with ONE final circuit, that of the lighting circuit feeding a single timer extractor fan. No probs. here.

BS 7671 definition of a circuit means that any overcurrent protective device starts a new circuit (see part 2) - in this case the L and SL are by definition different circuits as the are protected by different fuses. As they both directly connect to current using equipment they'd be classed as final circuits.


Oddly enough there's nothing in the definitions that means that one final circuit can't supply another final circuit (despite the name).


   - Andy.

Circuit definition. "An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)." Notice the plural used here DEVICES.
But your permanent Line and switched Line cables must be on different circuits because they are protected by different devices

"Same origin." Yes the lighting circuit M.C.B., say a B6 or B10.
DIfferent origins- 2x BS1362 fuses

"An assembly of electrical equipment."  Yes, Lights, shaver outlet and fan.
Fan only- supplied by two circuits

We could argue about the fuses used to protect the fan are just there for fault protection and not overcurrent protection as the fixed fan load can not overload the supply cables in normal use.
 think you are confusing overcurrent (exceeding the rated value) protection with overload protection (which occurs in a mechanically sound circuit), a fault current can be an overcurrent if large enough, see definitions in part 2

"Protective device(s)" can be included in one final circuit. So we can have more than one protective device in a final circuit.

 Yes, if in series, not parallel.


Z.


 

If you were fitting a boiler to an existing fcu on a ring final circuit, would you record the OCPD as 32A mcb or 3A fuse on any MWEIC?


Also the label reg i was thinking of is 514.11.1 it does say not capable of being isolated by a single device, and you could argue the 6A mcb does this, but then so does the main switch and cut out. I think the intention is that it warns of a possible danger of live parts if one of the fuses blows and the fan dont work. 


Back to the OP, I thought my idea of an fcu behind the switch i posted earlier was good, but seems to have been overlooked :)