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Dad, What's a Circuit?

Zoomup
Well son that a long story.


In my dictionary a circuit is: roughly a circular route, a track for motor racing in the U.K., a regular journey around a district by a judge to hear cases, a system of conductors and components forming a complete electrical path. It comes from the Latin word "circuitus." (No doubt related to the Latin word "circulus," which means circle.


I can see why ebee's friend considers two lighting circuits connected to just one M.C.B.to be two circuits connected together. Two individual circuits connected in parallel in fact.


When we are taught about electrical circuits at school we are told that the circuit starts at the source, which could be a battery terminal , continues to a load, which could be a light bulb, through the load, and then returns back the the battery's second terminal. Or the same arrangement could be made using a transformer's secondary winding.


But B.S. 7671 defines a circuit as: "An assembly of electrical equipment supplied from the same origin and protected by the same overcurrent protective device(s)."


So, a 1.0 mm2 T&E cable supplying lighting connected to a 6 Amp M.C.B. is a circuit. In B.S. 7671 land if a second 1.0 mm2  T&E lighting cable is added to the same M.C.B. there is still only one circuit even though one lighting circuit may supply upstairs in a house, and the other downstairs. Or perhaps originally the two originated from two separate M.C.B.s.


So in B.S. 7671 land, 1 circuit plus 1 circuit = 1 circuit. How could it be any different?


I personally, still though, prefer to call that situation two circuits connected in parallel.


Z.

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    ebee:

    No Zoom. It will be one circuit !!!


     


    Not in Zoomland it won't. And as Mrs. Slocombe would say: "I am unanimous in that."


    Z.


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    OK, now tear yourself away from sleeping lion songs, as I think Blondie has just the song lyrics for those wondering where they should  terminate that cable for the outside light just installed in the porch, or for tracing that elusive fault.

    All the way from the 1970s....

    One way,   Or another....



    Mike.


    The chap and chappess at 3 min 28 remind me about new shower curtains and that I soon need a haircut...
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    The 100 m2 went a long time ago Mike, and 2 rings as described will have 1/2 the cable length, so 1/2 the voltage drop, each! Only one circuit through Zoomup, although 2 loops.
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    This current too has completed ' a circuit' of the wiring but not all of it has taken the same route.

    Mike.


    Yep that is the fly in the ointment, the elephant in the fridge, or the spanner in the works. A circuit comprises just one route which is roughly circular not multi-routed. Notice the singular implication of the word "circuit."


    Z.


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    No Zoom. It will be one circuit !!!


    Be it X rings or X radials.


    Ok to Muddy the waters ring(s) and radial(s) combined - so long as floor space served therefore intended loading is not an issue.


    Beats me how we reckoned 100 sq yds then it became 100 sq metres which is a good deal more (about 20% I think) for a ring
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    I am a new person. From now on in I shall change my ways. I will call an M.C.B. with multiple cables and circuits attached to it a "way". My consumer units will be multi-way. The ways will be numbered for identification. No more references to circuit 1 or 2. From now on it will be way 1 or way 2 etc. A way may feed more than one circuit. 


    Z.
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    There are 2 rings of sockets in 2 opposite directions but they both terminate in one CPD (32A, 4 wires). Would anyone like to comment on this?


    I'll bite.

    Perfectly fine, so long as the total load is respectable and neither branch is so long there is a volt drop issue.

    I may want a quick check of what exactly is being a served and that it really is two rings, just in case we exceed the 100m2 by miles or serve two busy kitchens or something silly, but as described, OK a bit unusual, but no sleep lost.


    Assuming it was already there and looked happy (no cooked cables or anything silly) I'd be in the leave well alone camp.


    Mike.
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    Its ok was just a throw away comment please don't think about it too much unless you want to of course
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    Kelly Marie Angel:

    Just watched the tight fit video reminds me I had a swimsuit like that happy holiday memories


    Having just watched the video too I am not sure what reply you expect to that. ?

    It is certainly odd what looking at various consumer units makes people think of. No wonder some folk were not fully concentrating on the maths lessons, but perhaps it does explain why they become electricians.


    Mike.


     


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    Zoomup:

    13th Edition definition. Circuit: "An arrangement of conductors for the purpose of carrying current." (See Final sub-circuit).


    14th Edition definition. Circuit: Not found. 

                                         Final sub-circuit: An outgoing circuit connected to a distribution board and intended to supply electrical energy to current using apparatus, either directly or through socket outlets or fused spur-boxes."


    15th Edition definition. "An assembly of electrical equipment from the same origin and protected against overcurrent by the same protective device (s). 


    So, it is the 15th edition that is to blame.


    Z.


    Indeed - it  like a living language and usage changes over time - it's almost as if "circuit" now just an abbreviation for "sub circuit".

       - Andy.


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