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equation

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  1. CG_Sparks

    BRE 489 wind Loads equation

    Hi. I'm having a bit of trouble trying to do the calculation in BRE 489 for solar pv wind loads. I understand the equation; F = qs x Cp, net x Ca x Aref But what i don't understand, is what to do with the number at the end. Do i look in say a schuco mounting rail...
  2. S

    adiabatic equation help!

    Hi all i was wondering if anybody could shed some light on this equation or part of it. I think i understand how to work out the equation its self but its this part i dont understand. In order to apply the adiabatic equation we first need to calculate the value of I (fault current) using this...
  3. Kamikaze

    Knowledge is Power

    First the basics Knowledge is Power Time is Money and as every electrician knows, Power is Work over Time. So, substituting algebraic equations for these time worn bits of wisdom, we get: K = P (1) T = M (2) P = W/T (3) Now, do a few simple substitutions: Put W/T in for P in equation (1), which...
  4. R

    Adiabatic equation calc

    can anyone help I want to calculate a main earthing conductor for a three phase supply using the old adiabatic equation. I'm struggling to work out what value of I to use. If you use 230V/0.35 (for a TN-C-S) then you get 657 amps.... if it turns out that Ze is lower, the fault current is going...
  5. 2

    Adiabatic Equation

    Hi Is it acceptable to use the adiabatic equation to work out the size Main Earthing conductor to install in a standard domestic property for a consumer unit change. Ive always been under the impression that its 25mm tails and 16mm main earth for a tns or tncs system, but a colleague...
  6. W

    Adiabatic equation help

    Hi chaps, Can someone please give me a quick lesson on adiabatics? When to use the equation, detailed description of what it is etc. Been scouting any literature i have here but not been able to pin something down. Thanks B
  7. P

    adiabatic equation reg 543.1.3

    Can any one help please on a tncs system (PME) 100amp main fuse bs1361 100amp I am trying to work out the maths for the earthing is there a simple way all looks a little confusing S is the csa of the conductor 25mm I is ??? t is page 244 the table says 630A K = ?? so 630A squared x 5 (5sec...
  8. C

    MCB tripping time equation?

    Evening, Can someone tell me what the equation is to work out how quick a CB will trip from the Amps its getting? I know there are tables in 7671, but I'm sure there is a formula where you can work it out from the fault current amps etc? Thanks in advance Craig
  9. S

    PIR codes, help please

    Hi guys. Just wanted to ask what code you would give an old wylex fuse board with wooden enclosure. It does have the plastic (plexolin I think it's called) plate at the back. Also 2.5 T+E with 1.0mm CPC used for a ring main on a 3036 fuse. Thanks in advance. Steve
  10. C

    Voltage drop on a ring?

    Morning, Just a quick question? In the OSG (2008) (page 44), it says that you can have 106 metres of 2.5 T&E with a 32A type B cb. Any ideas how they are working this out? My understanding of vd on a ring is mvam x half of length x half of ib / 1000 So 18 x 53 x 16 / 1000 = 15.2 v?? I assume...
  11. G

    Example of use of Adiabatic Equation.

    Many thanks to 'Dave_' for posting this example originally in a thread. Minimum Size of CPC Here I will calculate the minimum size of CPC in accordance with regulation 541.1.3 of BS7671. Primarily I will need to calculate the minimum size of CPC (or confirm the armouring is adequate) of...
  12. J

    Capacitor equation

    Can anyone help with this college equation? 3 x capacitors in parallel - 10pF (To the power of -12), 15 uF (-6), 25 nF (-9). What does Ct = ? Tutor says 10 (-6), I think 10 (-14). Thanks:confused:
  13. B

    cable sizing equation

    when determining cable size and you want to include the following thermal insulation(Ci) and circuits grouped (Cg) what tables do you use for the rating factors many thanks
  14. T

    Adiabatic Equation

    does anyone know what the current limiting class 3 means on an mcb, for eg does this mean a max of 3ka let through energy ? if it does it makes a difference when using the adiabatic equation for sizing cpc`s
  15. M

    help on equation please

    the current in a coil changes from 5amps to 2amps in 0.05s and induces a voltage of 30v in the coil, the inductance of the coil is
  16. M

    help on equation

    the current in a coil changes from 5amps to 2amps in 0.05s and induces a voltage of 30v in the coil, the inductance of the coil is
  17. H

    Size of Conductor for TT Installation

    I am hoping to use my own house for my assessment to join either NICEIC/Elecs/NAPIT however I have a question over the size of the earth conductor. Most people give me the stock answer of 16mm as the Tails are 25mm however I do not believe that this has to apply to a TT system although I am...
  18. ses

    adiabatic equation

    Can someone please tell me if i have done this correct. Got a fuseboard change and the tails are 16mm sinlges fed from an 800kmf with a 6mm single main earth. Board is other side of house to meter so a pain to upgrade main earth. Done the adiabitic and it comes out as follows. Supply is tnc-s...
  19. T

    adiabatic equation, help / advice

    Hi folk’s adiabatic equation, help / advice S = Size of earth bonding conductor required. I = pfc in amps. t = disconnection time in seconds. K = values in table 43.1. I am trying to work out if a 6mm main earth is adequate on a TN-C-S system Is the 6mm cpc in the 16mm T&E allowed? Have been...
  20. J

    Adiabatic equation Question

    I have just done a periodic on a flat that is supplied by 16.0mm pvc T&E (6.0 mm cpc only earth conductor) on a 60A 1361 switch fuse on a TN-S system. The DB Ze at the flat is 0.21 No matter what way i'm doing my sums i cant seem to get what i think is the right answer. I get 3.01mm minimum...

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