# Calculate amperage based on variables wire length and max amps at sockets

• Hi I need an EXCEL spreadsheet to calculate the est. approx AMPAGE of the RING CIRCUIT socket wire (240V ac) from just the following?:
~ SKT WIRE lengths from skt to skt, and last skt to fusebox
~ MAXIMUM AMPAGE of each skt

Eg:
Skt A to B = 10M's
Skt B to C = 5M's
Skt C to D = 3M's
Skt D to A = 7M's

Skt A ampage = 5A
Skt B ampage = 3A
Skt C ampage = 10A
Skt D ampage = 7A

I'm aware of Kirchoff (http://www.voltimum.co.uk/file…00106819Kirchoff-Ring.pdf See Pgs 2-4), but I can't be bothered to do that everytime.

In summary I want just a simple spreadsheet :cool: to enter:
the METRES OF SOCKET WIRE and
the AMPAGE MAXIMUM AT EACH SOCKET,
to calculate the RING CIRCUIT AMPAGE of the SKT WIRE.

I know there is software to do this, but surely this can be sorted into XL formulas easily.

Cheers

Stephan

• Re: Calculate amperage based on variables wire length and max amps at sockets

see if this helps

## Files

• Re: Calculate amperage based on variables wire length and max amps at sockets

HELLO Pangolin, that's excellent, thanks, exactly what I meant.

Are you familiar with the use of the RING/KIRCHOFF equation to calc which socket wire to use for a specific ring circuit? I've altered the figures as per the Kirchoff example in the hyperlink below. But it's not obvious to me which diameter skt wire is to be used. Can you comment on this revised workbook? SPREADSHEET

Just wondering did you have that file? Or work it out from the example http://www.voltimum.co.uk/file…00106819Kirchoff-Ring.pdf

Cheers

Stephan

• Re: Calculate amperage based on variables wire length and max amps at sockets

for some reason unable to download your workbook.....if I remember correctly the Kirchoff equation requires some kind of optimisation techniques.....but unfortunately currently I do not have any textbook etc for solving that equation but if you have any worked out example then you may upload the same and I will try and come up with something for you........

• Re: Calculate amperage based on variables wire length and max amps at sockets

Hi Pangolin, file attached. Yes I agree the Kirchoff does need some optimisation techniques! An end equation because the end figures of the Kirchoff equation, not too sure what to do next with these!

Really looking for an end calc for the KIRCHOFF per skt ampages as per btm of pg4 of niceic tech manual) for RING mains to establish which socket wire to use! When:
~ AMPAGE maximum per socket is known and

~ METRES length between sockets is known.

Obviously spreading the AMPAGE load over a RING CIRCUIT, in theory in comparison to RADIAL, the RING circuit should be distributing the load. So lets say the IEE 17th Edition Pg44 was unknown, could you show your workings for 32A total in this example (see Spreadsheet example, see 1st tab), the only equation/formula/calculation that is referred to that I can see is KIRCHOFF, but given the instance in the NICEIC Tech Manual (At the end of Pg4) , this doesn't appear to be complete, that is how to calculate the AMPAGE TOTAL distributed equivalent? I have calculated 20A in cell B20, can you comment on this?

As I said above, I know the KIRCHOFF equation (, but surely this equation isn't complete, the end equation per skt includes NEGATIVE figures. If these KIRCHOFF end equation skt ampages, are added together, the TOTAL AMPAGE is less then the original total AMPAGE of all skts, is this AMPAGE figure thought to be the AMPAGE that the SKT WIRE is specified to? Obviously the electricity in WATTS or KILOWATTS consumed isn't less, but the flow of electric (The not visible electrons: anions - and cations +) is distributed over the skt circuit length and the ring return skt wire length. Hence the load may be less on the individual skt wires, hence in the example instead of using 4mm, possibly 2.5mm?

Also RING CIRCUITS, METRE LENGTH between SKTS maybe known, but for many circuits the AMPAGE TOTAL will be unknown, I guess an "AVERAGE" AMPAGE MAXIMUM PER SKT, instead of an actual figure.
Or how do you (or your offices calculate what skt wire to use in a RING circuit when AMPAGE MAXIMUM PER SKT is unknown? When I ask electricians they say they don't do that, the office does it all for them with a program, so they don't have to do any calcs onsite, so they say.

Many thanks.

Cheers

Stephan

## Files

• Re: Calculate amperage based on variables wire length and max amps at sockets

Hi Pangolin, PDF zip file of my recent xls file to you, attached.

The equation in your recent files weren't visible when I converted the file to xls.

Simply, at the end equation after Kirchoff I want to calc the distributed/spreaded AMPAGE of the RING CIRCUIT, as "A" single total.

Q. CAN YOU SHOW A SIMPLE CALC/FORMULA for distributed/spreaded AMPAGE? That is what equation, is needed to follow the Kirchoff end values/figures (14.33,2.33,-11.67,-17.67), that was in your original spreadsheet.

In the example the total amps is 32A, which would normally need 4mm SKT WIRE in a RADIAL circuit.
If for example the end conversion was an AMPAGE of say 20A, then either RINGED CIRCUIT of 1.5mm SKT WIRE or RINGED CIRCUIT of 2.5mm SKT WIRE.

Understand?

CABLE/WIRE GUIDE OF SKT WIRE (TWIN & EARTH):
SOCKET WIRE REFERENCE GUIDE for AC 240V1mm15A3600w1.5mm20A4800w2.5mm27A6480w4mm36A8640w6mm46A11040w10mm63A15120w16mm85A20400w

Cheers

Stephan

Cheers

Stephan

## Files

• Re: Calculate amperage based on variables wire length and max amps at sockets

assuming that skt wire length is stored in cells J8:J14 and ampage is in cells K8:K14 then this formula should help you =INDEX(J8:J14,IF(D2+SUM(F2:F5)<MIN(K8:K14),1,IF(D2+SUM(F2:F5)>MAX(K8:K14),ROWS(K8:K14),MATCH(D2+SUM(F2:F5),K8:K14,1)+1)))
here D2 is the sum total of ampage ( which is 32A in your example)...if I understand correctly the skt wire length should always be for the next higher ampage...hope this helps

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