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electrical design trunking

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gareth davies

on 18 December 2012

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Transcript of electrical design trunking

trunking sizing installation design how do i decide what size trunking to install? how do i work out the spacing factor? round up of steps First we must gather all the information we can about the electrical design.

Can you think of what might be involved? What do the Regs say? For trunking it is recommended that a space factor be applied for calculation of the size of trunking to be installed.
Their must be a space ratio of

55% 0f the space must be air

while 45% of the space is taken up by cable follow me for an example 1 work out how many circuits there are

2 work out the space factor from the on site guide for each cable size.

3 round up the total of each cable factor

4 compare this cable factor total with the on site guide allowance how many circuits?

how many cables?

how big are the cables? objectives
what trunking is used for
rules and regs related to trunking
how to work out what size to install extra objectives to investigate
segregation considerations
environmental considerations
how to manufacture bends example
step 1 gather info for installation
2x lighting circuits
3x ring circuits
1x cooker circuit
3x three phase outlets step 2 work out the amount of cables used and size lighting cable size 1.5mm2 x 6 cables x 2 circuits ring circuit cable size 2.5mm2 x 6 cables x 3 circuits cooker circuit cable size 6mm2 x 3 cables three phase outlet cable size 4mm2 x 5 cables x 3 circuits step 3 use tables from the onsite guide for cable factors main objectives extras on site guide appendix E For each cable it is intended to use, obtain the appropriate factor from table E5 Add the cable factors together and compare the total with the factors for trunking given in table E6 the minimum size of trunking is that size having a factor equal to or greater than the sum of the cable factors Seek appendix E from the on site guide 1.5 mm2 cable = 8.6 x (the amount of cables) 12 =103.2 2.5mm2 cable = 12.6 x (the amount of cables) 18 = 226.8 6mm2 cable = 21.2 x 3 = 63.6 4mm2 cable = 16.6 x 15 = 249 the total space factor of cables is 103.2 + 226.8 + 63.6 + 249 = 642 use the cable factor total and apply this to table E6 in the on site guide step 4 have a look for your self and you suggest a size suitable for this installation look left for some ideas (look left for extra info) trunking uses essentially trunking is a wiring system used to distribute cables within a building while giving protection from damage to cables this can be made from galvanised steel stainless steel pvc give it a go
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