RING AMP XL calc for SKT WIRE diameter

[srands]

Hi folks,the following are equations/xl formulas (SPREADSHEET ) of what SKT WIRE would you use for RING MAIN example with a known MAX in AMPS (Given recognised KIRCHOFF equation with 3 SKT EXAMPLE1 below, D is the SUPPLY/SOURCE/START of CIRCUIT/FUSEBOX MCB).

As per the example given in the NICEIC TECHNICAL MANUAL , of a RING circuit, calculated using the KIRCHOFF equation.

Here is a SPREADSHEET with formulas for the example in the NICEIC TECHNICAL MANUAL.

EXAMPLE1:

SKT D to A: 32A(TOTAL OF A+B+C), 20m's
SKT A: 12A, AtoB 15m's
SKT B: 14A, BtoC 20m's
SKT C: 6A, CtoD 5m's

SIMPLY, "IF" this was a RADIAL CIRCUIT were the WATTS/AMPS MAXIMUM was known (32A), the SKT WITE to be used/spec'd would suggest 4mm SKT WIRE.

QUESTION: SIMPLY, what SKT WIRE would "you" use here for the RING MAIN example (Given the recognised KIRCHOFF equation)? 3 SKTS EXAMPLE1 ABOVE.
Please show your workings, I have shown mine long hand in the SPREADSHEET, which is the short hand version of the KIRCHOFF equation. If you have a better spreadsheet I'm sure this of interest to all electricians and DIYERS.

Obviously the KIRCHOFF equation doesn't actually reduce the actual WATTS/AMPS used, it calculates the AMPAGE spread over the RING MAIN, as an approximate. But isn't the KIRCHOFF equation the recognised standard equation for calculating a RING MAIN.

ALSO I realise in addition to KIRCHOFF, the IEE 17th Edition Pg44 qoutes something like:
1.5mm (20A not ringed) or 2.5mm (27A not ringed) is approx 32A Ringed, <less then 100m's (# 20A x 1.6 or 27A x 1.2).
Hence on the 3rd tab of the spreadsheet, I guess this is how IEE reached 32A, or a sliding scale of multiplication as you can see in the pattern #, or unless they destructively tested socket wire in collaboration with socket wire manufactuers such as Prysmian, and the suggested figures were thought reasonable for permanent use for a great many years, well socket wire isn't going to twist and bend behind plastered walls.

Cheers

Stephan

RING AMP CALC: Add your comments/workings and upload/post

FUSEBOX MCB autocalc 3rd & 4th tab

ELEC GAS WATER autocalc 1st tab, scroll down


LONG HAND OF EXAMPLE1 with KIRCHOFF short hand:

SKT D to A: 32A(TOTAL OF A+B+C), 20m's, Cumlative Count 0A
SKT A: 12A, AtoB 15m's, Cumlative Count 12A
SKT B: 14A, BtoC 20m's, Cumlative Count 26A
SKT C: 6A, CtoD 5m's, Cumlative Count 32A

i) Metres of Skt wire X Cumlative Count of AMPs from skts in circuit:
20 X 0 = 0
15 X 12 = 180
20 X 26 = 520
5 X 32 = 160
0+180+520+160=860

TOTAL i) / LENGTH TOTAL - Cumlative Count of Amps in circuit = AMPs of SKT LENGTH
D to A = 860 / (20+15+20+5) - 0 = 14.33A
A to B = 860 / (20+15+20+5) - 12 = 2.33
B to C = 860 / (20+15+20+5) - 26 = -11.67
C to D = 860 / (20+15+20+5) - 32 = -17.67

SEE NICEIC TECHNICAL MANUAL Pg 5

Given this example if RADIAL then 32A would use 4mm SKT WIRE. So if RING circuit what SKT WIRE would you use, given the above? Please show workings.

If the above are totalled together: 14.33A + 2.33A + -11.67A + -17.67A = 19.3A
Does this equate to the AMPAGE spread over the SKT WIRE?
Hence 1.5mm SKT WIRE? 1.5mm SKT WIRE is rated to 20A. OR since the figure is very 20A, then the next biggest 2.5mm SKT WIRE which is rated to 27A? (Bigger is always better).

Cheers

Stephan

RING AMP CALC: Add your comments/workings and upload/post

FUSEBOX MCB autocalc 3rd & 4th tab

ELEC GAS WATER autocalc 1st tab, scroll down

​

 

[MFHEng]

The type "a"s must be for the 2.5mm radials with 32 Amp mcb protection, or the 40 amp 2.5 rings or the 1.5mm 32amp ring mains......

 

[malcolmsanford]

Ahhhhhhhhhh but if you were using MICC...................

 

[telectrix]

malcolm are you taking the micc?

 

[MFHEng]

I don't think he knows what Micc is, it would be interesting to know what he would call it though, if t&e is skt wire, is MICC "burny hot fire wire"...

 

[Paul.M]

He's forgot to mention if its on a TT system? Very important for anyone's ring.

 

[MFHEng]

Always check your ring.... You never know there might be another calculation spread sheet up there.

 

[armbands0]

We touched on Kirchoffs and ring finals at college, I prefered the pdf file to read.

I'll save the pdf and read through it again on a rainy day.

 

[srands]

If my question is so ridiculously easy for you professional electricians/diyers, I realise nobody has answered my question, given the example, which socket wire (twin & earth), would you RING for the following circuit? (Summary: 3 skts total 32A, Metres total 60M's):

SKT D to A: 32A(TOTAL OF A+B+C), 20m's, Cumulative Count 0A
SKT A: 12A, AtoB 15m's, Cumulative Count 12A
SKT B: 14A, BtoC 20m's, Cumulative Count 26A
SKT C: 6A, CtoD 5m's, Cumulative Count 32A
see Spreadsheet example:

SO WHAT SKT WIRE/CABLE/TWIN&EARTH WOULD YOU USE ON THIS CIRCUIT, FOR A RING MAIN?
I bet none of you "pro leccy's" haven't got a serious suggestion for this simple example.

The only real question here is what is adequate SOCKET WIRE (Twin & Earth) for specific RING circuitS, two options (most recognised standards):

i) IEE 17th Edition Pg 44, 1.5mm or 2.5mm RINGED is adequate UPTO 32A only.
Which maybe OK for some house KITCHEN RING, but many may be greater then 32A. 4mm RING, 6mm RING, are the terminals big enough? (Yes, I know if it isn't, a length of socket wire, supply, load, is that skt wire AMPAGE ok).
The only other popular ring is SHOWER RING, 8KWp/h(33.3A) to 15KW p/h (62.5A) (These are averages, but obviously greater then 32A), guess TERMINALS on showers are big guess 4mm+ RINGED fits ok. Not every building has 1 shower, hence bigger fusebox/rcd/mcb, & not every building has sml kitchen: hotels, colleges, restaurants, so 1 big KITCHEN RING circuit or many MCBs.

ii) If AMPAGE greater then 32A, then the KIRCHOFF equation to work out the AMPAGE SPREAD OVER THE RING, then see which SOCKET WIRE (TWIN & EARTH) is adequate, is too bigger AMPAGE, next MCB, etc. However some variables have to be known (Or variables made up, as may not be known at this point!) the AMPAGE MAXIMUM at each socket and METRES distance between SOCKETS.
see Spreadsheet example:

Cheers

Stephan

RING AMP CALC: Add your comments/workings and upload/post

FUSEBOX MCB autocalc 3rd & 4th tab

ELEC GAS WATER autocalc 1st tab, scroll down

 

[Penance]

Arrrr it is cable not wire

 

[MFHEng]

Have you tried tescos for a job

 

[Geordie Spark]

Does anyone have any idea what this bloke is blathering about?

If so, could you please enlighten me - preferably in Plain English (or Geordie)?

 

[rryles]

srands,

The reason no one is answering your question is because it doesn't make sense. You obviously don't know what you are talking about. The pdf document you refer to is only to do with calculating voltage drop. There are other things to consider when designing a circuit. To calculate the current distribution in a ring you need to apply Kirchhoff's Laws (both of them) and Ohm's Law.

 

[telectrix]

Always check your ring.... You never know there might be another calculation spread sheet up there.

i check my ring every morning.

 

[rryles]

i check my ring every morning.

I've split my ring.

 

[malcolmsanford]

I've split my ring.

oh no don't ..............................