Spurs off Spurs on radial circuit

[stratplus]

So you can spur off Spurs on a radial socket circuit, is this because the cable is protected via a 20amp breaker at the board compared to 32amp on a ring?

 

[Octopus]

What do you think? Similar to many lighting circuits!

 

[Andy78]

So you can spur off Spurs on a radial socket circuit, is this because the cable is protected via a 20amp breaker at the board compared to 32amp on a ring?

Think about the current carrying capacity of the cable. Are you a trainee ?

 

[stratplus]

Think about the current carrying capacity of the cable. Are you a trainee ?

I am a trainee yes Andy.
Been trying to get my head round rings/Spurs and radials/Spurs. I can understand if you spur off a ring that piece of cable can take potentially 26amps (two 13amp fuses). Now if you spur off that spur your current could be 52amps so overloading the cable.
Finding it difficult to understand how with a radial you can spur off spurs without overloading the cable.

 

[Pete999]

I am a trainee yes Andy.
Been trying to get my head round rings/Spurs and radials/Spurs. I can understand if you spur off a ring that piece of cable can take potentially 26amps (two 13amp fuses). Now if you spur off that spur your current could be 52amps so overloading the cable.
Finding it difficult to understand how with a radial you can spur off spurs without overloading the cable.

Radials usually covered by a 20amp breaker, cant see by extending the radial how you would overload the cable Appendix 15 BYB

 

[Andy78]

I am a trainee yes Andy.
Been trying to get my head round rings/Spurs and radials/Spurs. I can understand if you spur off a ring that piece of cable can take potentially 26amps (two 13amp fuses). Now if you spur off that spur your current could be 52amps so overloading the cable.
Finding it difficult to understand how with a radial you can spur off spurs without overloading the cable.

Well you said it yourself in your opening post. The OCPD is 20A which is less than the CCC of the cable. With a ring circuit the standard OCPD is 32A which is higher than the CCC of the cable in that leg and therefore the potential loading must not exceed that of the CCC of the cable.

See appx 4 for cable calculation procedure and appx 15 for standard circuit arrangements as your revision points for this.

 

[stratplus]

Radials usually covered by a 20amp breaker, cant see by extending the radial how you would overload the cable Appendix 15 BYB

Pete what do you mean by "can't see by extend"?

 

[stratplus]

Well you said it yourself in your opening post. The OCPD is 20A which is less than the CCC of the cable. With a ring circuit the standard OCPD is 32A which is higher than the CCC of the cable in that leg and therefore the potential loading must not exceed that of the CCC of the cable.

See appx 4 for cable calculation procedure and appx 15 for standard circuit arrangements as your revision points for this.

Ok, thank you Andy. Got it now. Every time I read and think I understand something, I read something else and have another ten questions! Read the same four pages for 2 months to understand lighting circuits!

 

[Pete999]

Pete what do you mean by "can't see by extend"?

If you are adding a new socket to a radial you are either extending the circuit, I'll clarify, by extending the radial, I assume you are adding a socket from the last point on the radial.
Read Appendix 15 BYB and get back to us if you don't understand anything.

 

[Paul.M]

Before spurring from a RFC or a radial you must work out what is on that circuit now, what will be on it afterwards and can the cable/protective device provide adequate distribution and protection?

 

[stratplus]

If you are adding a new socket to a radial you are either extending the circuit, I'll clarify, by extending the radial, I assume you are adding a socket from the last point on the radial.
Read Appendix 15 BYB and get back to us if you don't understand anything.

Hi Pete, not doing any electrical work just trying to understand the circuits.
Ok I understand that if you are adding a socket to the end of a radial you are extending. I was more thinking about a spur from a socket so you'd already have two cables in there, spurring would be adding a third cable.

 

[Andy78]

There is a dedicated trainee forum here that you could join if you are in training.

 

[Pete999]

Hi Pete, not doing any electrical work just trying to understand the circuits.
Ok I understand that if you are adding a socket to the end of a radial you are extending. I was more thinking about a spur from a socket so you'd already have two cables in there, spurring would be adding a third cable.

Nothing wrong with that, have you had a look at the BYB yet?

 

[stratplus]

Nothing wrong with that, have you had a look at the BYB yet?

I don't have the yellow book (apart from osg) but I do have the red one. I'll have a look now.

 

[Pete999]

I don't have the yellow book (apart from osg) but I do have the red one. I'll have a look now.

Not sure which Appendix it is in the BRB probably the same as the latest book

 

[Paul.M]

There is a dedicated trainee forum here that you could join if you are in training.

Thanks Andy but I dont think stratplus is a Trainee after reading through his threads over the past 3 years. Working sparky that dose not understand basic spurring? (appendix 15 btw, last page before the index).


May I suggest that members do not give a step by step guide, only positive prompting towards learning what he installs.

 

[stratplus]

Not sure which Appendix it is in the BRB probably the same as the latest book

Red book: Appendix 15 Ring and Radial final arrangements.

 

[stratplus]

Thanks Andy but I dont think stratplus is a Trainee after reading through his threads over the past 3 years. Working sparky that dose not understand basic spurring? (appendix 15 btw, last page before the index).


May I suggest that members do not give a step by step guide, only positive prompting towards learning what he installs.

Did my 2330 some years ago, I'm not a sparky. Electrics is something I have been interested in for a while but have no intention of doing electrical work outside of my own home. Just because I did my 2330 (NOT an nvq) doesn't make me a competent spark.
I am constantly coming back to reading my books to help my understanding.

 

[stratplus]

Thanks Andy but I dont think stratplus is a Trainee after reading through his threads over the past 3 years. Working sparky that dose not understand basic spurring? (appendix 15 btw, last page before the index).


May I suggest that members do not give a step by step guide, only positive prompting towards learning what he installs.

College evening class practical consisted of wiring certain circuits on a board and working through them as quickly as you could because you only had a couple of weeks (at two evenings a week) to complete the practical assignments. That was the easy bit. It's only later when you sit down and think about the circuits that you realise how little you REALLY understood. That's something I'm now trying to rectify.

 

[Paul.M]

College evening class practical consisted of wiring certain circuits on a board and working through them as quickly as you could because you only had a couple of weeks (at two evenings a week) to complete the practical assignments. That was the easy bit. It's only later when you sit down and think about the circuits that you realise how little you REALLY understood. That's something I'm now trying to rectify.

Whilst you typed the above I sent you a PM. Everything is cool and I hope my explanation of spurring is a benefit to you.