Voltage drop

pencilpusher · May 17, 2012

Hi all

If an outdoor circuit comprises 2.5mm SWA running to adaptable box where it then splits into 2 x 1.5mm SWA cables for lighting, socket etc. how is the VD calculated?

I presume the VD for the 2.5mm run is calculated up to the adpatable box and added to the 1.5mm VD for each additional cable run present?

I would normally calculate on the smallest cable size present as a worst case scenario but was wondering what the alternative way is for the cables present.

Thanks

PP

Knobhead · May 17, 2012

As you say work out the drop on the first section of 2.5 and add this to each of the individual 1.5’s

Rockingit · May 17, 2012

Supposing though that at the end of each leg of the smaller cable you had the same load, then wouldn't it be conductors in parallel? For arguments sake, if it was a 100W lamp, then wouldn't you be doing the calcs based on 200w down 3mm?? (also assumes both legs the same length).

Rockingit · May 17, 2012

Blaine said:
Mostly voltage are drop at your homes because of the more than load of energy when you use the energy overloaded then you face the drops of voltage

Please may we have that again, only in English this time?

pencilpusher · May 17, 2012

Blaine said:
Mostly voltage are drop at your homes because of the more than load of energy when you use the energy overloaded then you face the drops of voltage

I know what voltage drop is and why it occurs. I don't, however, understand a word of this!

pencilpusher · May 17, 2012

Rockingit said:
Supposing though that at the end of each leg of the smaller cable you had the same load, then wouldn't it be conductors in parallel? For arguments sake, if it was a 100W lamp, then wouldn't you be doing the calcs based on 200w down 3mm?? (also assumes both legs the same length).

Hmmm, this has got me thinking now! Views?

PP

Bosi · May 17, 2012

It gives the same VD...

Rockingit · May 17, 2012

Bosi said:
It gives the same VD...

haven't done the maths so happy to be corrected, but if you go by the BGB tables then they are non-linear, so not sure about that.

Bosi · May 17, 2012

Yes, in my tables the resistivity differs between 18.1-18.3 mΩmm²/m depending on the csa. But there is no meaning in trying to calculate the VD with a mV precision.

pencilpusher · May 17, 2012

Bosi said:
Yes, in my tables the resistivity differs between 18.1-18.3 mΩmm²/m depending on the csa. But there is no meaning in trying to calculate the VD with a mV precision.

Thanks but that is not the point though. My OP was about the correct way of doing it, not weather it was worth bothering with precision. I will stick with adding the VD up as previously mentioned.

Rockingit · May 17, 2012

^^^ agree entirely. But it's been a slow day here at Rockingham Towers, so......

SirKit Breaker · May 17, 2012

I thought voltage drop was what happens when the CU is upstairs, and all the sockets and lights are downstairs, so the volts all drop down the wires to the electrical stuff. Anyone know where my electric stopcock is?

Cheers.........Howard

telectrix · May 17, 2012

Anyone know where my electric stopcock is?

should be in the attic. water flows downhill as well as volts.

Bosi · May 17, 2012

Actually, it's the other way.

telectrix · May 17, 2012

Downhill. Proof.......

Voltage drop

pencilpusher

Knobhead

Rockingit

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Rockingit

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pencilpusher

pencilpusher

Bosi

Rockingit

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Bosi

pencilpusher

Rockingit

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SirKit Breaker

telectrix

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Bosi

telectrix

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