Trainees, Show Us Your Installs

[hightower]

Oi, I'm right her and I heard that!!!

I'm learning a few things tonight which is great. I have another question though, with the arrangement you have there with three wires in one MCB, why is that classed as a ring final with a spur and not as two circuits ie a ring final and a radial?

Isn't a circuit defined by having its own breaker? So this is one circuit, a ring with a spur. If it went on its own breaker then it'd be a radial.

Could be wrong

 

[Darkwood]

Oi, I'm right her and I heard that!!!

I'm learning a few things tonight which is great. I have another question though, with the arrangement you have there with three wires in one MCB, why is that classed as a ring final with a spur and not as two circuits ie a ring final and a radial?

The very definition of a circuit would mean you cannot have more than one out of an mcb, say you had a 20amp mcb with 3 cables going to 3 individual loads ( fridge socket, Alarm spur and boiler just for example) ..this is not 3 circuits, the mcb only provides 1 circuit way of which 3 loads are connected seperately. You can call it 3 radials if you want but it is still classed as one circuit. When Identifying a mcb it has a circuit no' and board no' if necessary so anything connected to it has only one circuit designation..... if you can get the jist of my explanation

 

[Leesparkykent]

Oi, I'm right her and I heard that!!!

I'm learning a few things tonight which is great. I have another question though, with the arrangement you have there with three wires in one MCB, why is that classed as a ring final with a spur and not as two circuits ie a ring final and a radial?

Its a spur at the origin of the circuit. To be a radial it would have to be on its own OCPD in this situation.

 

[Simonslimline]

Oi, I'm right her and I heard that!!!

I'm learning a few things tonight which is great. I have another question though, with the arrangement you have there with three wires in one MCB, why is that classed as a ring final with a spur and not as two circuits ie a ring final and a radial?

BS767 definitions - Circuit - An assembly of electrical equipment supplied from the same origin and protected against over current by the same protective device(s).

 

[Simonslimline]

Its a spur at the origin of the circuit. To be a radial it would have to be on its own OCPD in this situation.

Once again you beat me to it.

:shades_smile:

 

[Marvo]

So if you had two radial circuits supplied by a single OCPD it would only be classed as a single circuit...???

 

[Simonslimline]

So if you had two radial circuits supplied by a single OCPD it would only be classed as a single circuit...???

Technically yes.

What would it be in South Africa?

 

[Marvo]

If you were testing such a circuit and filling in the results on an EICR or whatever the form is you use, would you just enter one set of results for both radials tested as one or would you split the two radials and make two sets of tests?

It would be classed as two radial circuits on the same MCB in SA. We'd split them and do 2 sets of test with 2 sets of results on the paperwork.

By the way these aren't trick questions, I'm just interested in how you do things in the UK and why.

 

[davesparks]

If you were testing such a circuit and filling in the results on an EICR or whatever the form is you use, would you just enter one set of results for both radials tested as one or would you split the two radials and make two sets of tests?

It would be classed as two radial circuits on the same MCB in SA. We'd split them and do 2 sets of test with 2 sets of results on the paperwork.

By the way these aren't trick questions, I'm just interested in how you do things in the UK and why.

It's up to the discretion of the person testing it as to what they do.
It could be two lines on a results sheet or test both legs and record the highest measured value for impedances.

In an ideal world a radial would be wired such that there is only one outgoing cable from the mcb, and you'd normally design circuits that way, but you can't help what has been done by the people who've been there before you

 

[hightower]

To add on to Daves response, in our case we tested both legs and then recorded the highest figures (or lowest in case of IR)

 

[Marvo]

In an ideal world a radial would be wired such that there is only one outgoing cable from the mcb, ..........

I think this is the issue, where I am if there was a ring final with a spur that was from the CU we'd class it as two separate circuits ie a ring and a radial even if they both originate from the same MCB. Obviously this would be at odds with the 'circuit definition' given above which clearly would intend they were considered as one. If the origin of the spur was from somewhere along the length of the ring it would be classed as a single circuit here same as in the UK.

 

[Darkwood]

I think this is the issue, where I am if there was a ring final with a spur that was from the CU we'd class it as two separate circuits ie a ring and a radial even if they both originate from the same MCB. Obviously this would be at odds with the 'circuit definition' given above which clearly would intend they were considered as one. If the origin of the spur was from somewhere along the length of the ring it would be classed as a single circuit here same as in the UK.

Another way to look at it, you can spur off a ring at any point and its classed as a spur, breaking into the cable, additional wire at the socket etc, the mcb/rcbo is just a joint like any other socket or jb, just because it serves a different purpose doesn't change what adding and extra cable means, its thus still a spur albeit taken from the joint in the mcb/rcbo.

 

[Robson689]

CAD welding for part of an earth nest. It's hard to get decent pictures of the work I do!!

 

[Robson689]

Pitched roofs don't half make your ankles burn. I've worked on many of them over the past year and half but this was the first job with rosemary tiles where I felt confident enough to get properly stuck in. I felt a whole new sense of accomplishment finishing this job knowing that I had been trusted enough to do so many crucial parts of it.

 

[Leesparkykent]

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Pitched roofs don't half make your ankles burn. I've worked on many of them over the past year and half but this was the first job with rosemary tiles where I felt confident enough to get properly stuck in. I felt a whole new sense of accomplishment finishing this job knowing that I had been trusted enough to do so many crucial parts of it.

Do you have to carry out bonding to the lightning protection?