Multiple Cables in a single circuit breaker

[Knobhead]

For gods sake!

Go back to sleep!

 

[Pete999]

For gods sake!

Go back to sleep!

Living up to you avatar I see lol

 

[7029 dave]

With respect,
I think the definition of an electrical circuit needs to be clarified before anyone can justify calling two separate circuits a single circuit.
If I am reading comments correctly,
2 independently wired circuits are being supplied from a single mcb.
That doesn't make them 1 circuit.
Surely if there are 2 feeds and 2 returns connected across, and supplying different loads.
They are inherently 2 circuits ??
That would be how I see it anyway, but am open to being convinced otherwise. :icon12:

Sorry should explain my reference is with regards to the OP's first post.
I feel his 2 circuit description on 1 mcb is an accurate description.

It is one circuit, because it's on one ocpd.

 

[baldsparkies]

It is one circuit, because it's on one ocpd.

I can see if you read the definition on what's a circuit in BS7671 you could or may interpret that way, and that's fine if you don't want to think about it any further.
All I am saying is if I showed you 2 radial circuits supplying different loads.
And I then placed them into a single breaker without altering or re configuring the wiring in any way.
They would by definition be 2 circuits fed from 1 breaker.
That's why all over many electrical forums (yes there are others) and amongst members of the trade.
You will see comments and debate on the pro's and cons of wiring 2 circuits to one mcb.
If it was truly considered 1 circuit the issues and discussions would not exist.
And please don't get irate based on an alternate opinion.
I could actually have a point here if you think about it :icon12:

 

[davesparks]

They would by definition be 2 circuits fed from 1 breaker.
:

By what definition? Can you cite a reference for this definition?

 

[7029 dave]

I can see if you read the definition on what's a circuit in BS7671 you could or may interpret that way, and that's fine if you don't want to think about it any further.
All I am saying is if I showed you 2 radial circuits supplying different loads.
And I then placed them into a single breaker without altering or re configuring the wiring in any way.
They would by definition be 2 circuits fed from 1 breaker.
That's why all over many electrical forums (yes there are others) and amongst members of the trade.
You will see comments and debate on the pro's and cons of wiring 2 circuits to one mcb.
If it was truly considered 1 circuit the issues and discussions would not exist.
And please don't get irate based on an alternate opinion.
I could actually have a point here if you think about it :icon12:

What ever you say chap. Im happy.

 

[spark 68]

Let battle commence! lol

I thought the bloke with the train set had left the station

 

[baldsparkies]

By what definition? Can you cite a reference for this definition?

Well possibly,

If we consider a radial circuit (and a lighting circuit is a radial circuit) as being a final circuit.

Then would

Regulation 314.4 Apply

Which states,


Where an installation comprises more than one final circuit, each final circuit shall be connected to a separate way in a distribution board. The wiring of each final circuit shall be electrically separate from that of every other final circuit, so as to prevent the indirect energising of a final circuit intended to be isolated.

So is it really correct to say connect your final circuits to one breaker and problem solved because now there one circuit.

 

[Darkwood]

I can see if you read the definition on what's a circuit in BS7671 you could or may interpret that way, and that's fine if you don't want to think about it any further.
All I am saying is if I showed you 2 radial circuits supplying different loads.
And I then placed them into a single breaker without altering or re configuring the wiring in any way.
They would by definition be 2 circuits fed from 1 breaker.
That's why all over many electrical forums (yes there are others) and amongst members of the trade.
You will see comments and debate on the pro's and cons of wiring 2 circuits to one mcb.
If it was truly considered 1 circuit the issues and discussions would not exist.
And please don't get irate based on an alternate opinion.
I could actually have a point here if you think about it :icon12:

2 or more wires in one mcb regardless of destinations would be classed as one circuit and one circuit only, if you take 2 radials on 2 separate mcb's then doubled them up into one then this becomes one circuit, it always has been and to read the regulation any other way is a mis-interpretation and if you have read otherwise they also are mis-informed.

To define a circuit would be a single, double or triple way OCPD protecting a circuit, the number of wires into said mcb has no bearing on the fact it will still be 1 circuit, consider a lighting circuit and as commonly is done, a E/M is wired direct to the same mcb for convenience of say having a key switch by the DB, the E/M is not a separate circuit but the same as the lighting.

Same applies if I have a radial socket and then add a joint anywhere down the cable for an extra socket, now that joint can be the terminals of the socket to the terminals of the mcb and any where in between but just because you use the mcb to create the joint it does not change the nature of it been just one circuit..

Golden rule is if a regulation has ambiguity then apply common sense!

 

[baldsparkies]

Over the years I have often heard comments from sources such as electrical consultants, electrical design engineers, and NICEIC assessors.
They have referred to exactly this scenario as 2 circuits in 1 mcb and sighting it as bad practice.
As said maybe regulation 314.4 relates to just such a scenario, along with its wording.
If forum members are concluding that 2 become 1 when connected to a single mcb.
Then so be it.
Doesn't hurt to put these things to question from time to time. :icon12:

 

[Silly Sausage]

Over the years I have often heard comments from sources such as electrical consultants, electrical design engineers,
I was starting to take you seriously, until this ---->>> and NICEIC assessors.

........

 

[baldsparkies]

NICEIC assessor !!!!!! Yes I see your point.

 

[Darkwood]

Over the years I have often heard comments from sources such as electrical consultants, electrical design engineers, and NICEIC assessors.
They have referred to exactly this scenario as 2 circuits in 1 mcb and sighting it as bad practice.
As said maybe regulation 314.4 relates to just such a scenario, along with its wording.
If forum members are concluding that 2 become 1 when connected to a single mcb.
Then so be it.
Doesn't hurt to put these things to question from time to time. :icon12:

If in doubt I also have the spice girls to back me up!..

Its just one of those things that gets mis-interpreted so often it becomes believeable, but if you were right in your thinking then the whole design and layout of test certs would allow for multiple results from one OCPD if you think about it, ignore all the pen pushes half of them don't have a clue trust me I've corrected many of them before, if your in any doubt consult the IET themselves.

 

[SimpleSimon]

2 or more wires in one mcb regardless of destinations would be classed as one circuit and one circuit only, if you take 2 radials on 2 separate mcb's then doubled them up into one then this becomes one circuit, it always has been and to read the regulation any other way is a mis-interpretation and if you have read otherwise they also are mis-informed.

To define a circuit would be a single, double or triple way OCPD protecting a circuit, the number of wires into said mcb has no bearing on the fact it will still be 1 circuit, consider a lighting circuit and as commonly is done, a E/M is wired direct to the same mcb for convenience of say having a key switch by the DB, the E/M is not a separate circuit but the same as the lighting.

Same applies if I have a radial socket and then add a joint anywhere down the cable for an extra socket, now that joint can be the terminals of the socket to the terminals of the mcb and any where in between but just because you use the mcb to create the joint it does not change the nature of it been just one circuit..

Golden rule is if a regulation has ambiguity then apply common sense!

Just based on this Darkwood, if you came across an MCB with two conductors, one served the lighting system, one served the doorbell. Would you label the circuit on the test schedule as lighting & door bell or just lighting?

 

[Darkwood]

Just based on this Darkwood, if you came across an MCB with two conductors, one served the lighting system, one served the doorbell. Would you label the circuit on the test schedule as lighting & door bell or just lighting?

You enter both to denote its use and clear confusion but it does not mean it is 2 circuits, it still is classed as 1 circuit, same if you took a spur of a ring main to feed a boiler, you could write it as ring main + boiler but it is still one circuit regardless if it is jointed at the mcb terminals or via a spur.