nic cert

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stringy

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just been looking at some nic certs getting use to filling them out, there is one part which is varification of volt drop

now lets say your doing a pir and have no idear of the length of run of the circuit how are you surpose to calculate the volt drop?

or am i being thick? lol

cheers

 

stringy

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hi kme

sorry for sounding thick but im new to testing done a bit but i struggle to understand the rusults as this time.

you say i know the length by the r1+r2 can you explain a bit more please.

thanks mate

 

Nicky Tesla

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How is this done on a ring cct, who knows what is going to be plugged in?

 
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hi kmesorry for sounding thick but im new to testing done a bit but i struggle to understand the rusults as this time.

you say i know the length by the r1+r2 can you explain a bit more please.

thanks mate
OK......

You know the cable size......

For a moment, suppose a radial (lighting OR power)

When you do r1+r2 at the furthest point, you get the resistance of the cable between the two points. OSG gives resistance of a given size of conductor (per metre).

Therefore, you can determine the length of the circuit. This is also a way of determining length when commisioning; as the length is necessary to calculate voltage drop.

I don`t have OSG here at the mo, but I`ll post an example tomorrow, unless one of my colleagues beats me to it........

Hope that helps mate.

KME

 

maccarooni

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Evening all,

May i be bold enough to suggest taking a measurement of voltage at the cu, as you will be measuring Ze, psc, and then another measurement at the end of each circuit, on ring circuit, Zs will indicate furthest point, you will then be able to calculate if voltdrop exceeds the given %..

Must put on my ppe as I may get shot to piecesPray

Macca

Anyway have plenty of these to keep me going.

Guiness DrinkGuiness DrinkGuiness Drink

 
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Evening all, May i be bold enough to suggest taking a measurement of voltage at the cu, as you will be measuring Ze, psc, and then another measurement at the end of each circuit, on ring circuit, Zs will indicate furthest point, you will then be able to calculate if voltdrop exceeds the given %..

Must put on my ppe as I may get shot to piecesPray

Macca

Anyway have plenty of these to keep me going.

Guiness DrinkGuiness DrinkGuiness Drink
http://www.talk.electricianforum.co.uk/showpost.php?p=24727&postcount=2

Great minds mate............. ;)

 

maccarooni

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Sorry KME to duplicate

but i type rather slowly on a saturday night...Blushing

Something to do with these LOL

Guiness Drink

Macca

 

maccarooni

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Nic

your measurement will tel you if your volt drop exceeds the max % allowed. The Zs reading on the ring will tell you your furthest point, if the voltage at this point exceeds the max drop allowance it will indicate that the circuit has not been designed to allow for this. I dont believe it has any thing to do with what is plugged in to the circuit at a certain point

Macca

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Nicky Tesla

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Nicyour measurement will tel you if your volt drop exceeds the max % allowed. The Zs reading on the ring will tell you your furthest point, if the voltage at this point exceeds the max drop allowance it will indicate that the circuit has not been designed to allow for this. I dont believe it has any thing to do with what is plugged in to the circuit at a certain point

Macca

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If nothing is plugged in drawing any current, then the voltage will remain exactly the same as at the CU

 

maccarooni

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The voltage will not be the same further on in the installation. mV/a/m.

On a long run you WILL get volt drop. Verification of volt drop, means exactly what it says on the tin. Check that there is not excessivse voltage drop on each circuit.

Macca

 

Nicky Tesla

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There is a clue in wot you just wrote.....mV/a/m

mv per AMP per metre.....10mA x 0amps = 0 x 20metres = 0

No current NO DROP

 

maccarooni

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There is a clue in wot you just wrote.....mV/a/mmv per AMP per metre.....10mA x 0amps = 0 x 20metres = 0

No current NO DROP
??

VOLTAGE drop = (mV/A/m) X Ib X L

----------------

1000

Ib= design current

Does the a not refer to the rating of the circuit.

32A circuit

6A circuit

Macca:|

 

Nicky Tesla

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??VOLTAGE drop = (mV/A/m) X Ib X L

----------------

1000

Ib= design current

Does the a not refer to the rating of the circuit.

32A circuit

6A circuit

Macca:|
Not normally on a radial cct supplying fixed equip, it goes on the expected current, but a ring cct wot else but the rating can you go on? even though if 32A is flowing in one point of the ring it doesn't mean 32A is flowing at another and that other point may be the furtherst from the DB and so not have a problem with volt drop eg 20 sockets quite close to the DB and one at a distant

 
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