Ze Values? HELP

Discuss Ze Values? HELP in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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Underpaid

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As a guide in the 17th the max Ze readings for the following =
Tns = 0.8
Tncs = 0.35
TT = 200

I Recently got a Ze reading of 0.15 on a Tns system, as its higher than 0.8 in the 17th should i be worried?
If its ok, what Ze readings would you consider high for each of the systems? e.g time to call the DNO.
Also filling out a certificate with a higher Ze reading than recommended in bs7671, allowed?
 
Underpaid said:
As a guide in the 17th the max Ze readings for the following =
Tns = 0.8
Tncs = 0.35
TT = 200

I Recently got a Ze reading of 0.15 on a Tns system, as its higher than 0.8 in the 17th should i be worried?
If its ok, what Ze readings would you consider high for each of the systems? e.g time to call the DNO.
Also filling out a certificate with a higher Ze reading than recommended in bs7671, allowed?
Click to expand...
with maths like that, you'll never make a scouse wheel thief. you'd nick1 and say it was more than 4!
 
Give the OP a break, most prob a brain fart moment....
 
Good grief!

Where exactly on BS7671 did you get that lot from?

There is no guideline maximum for Ze on a TT system, and if there was it's hardly going to be 200ohms is it!
Oh and 80 is higher than 15!
 
Underpaid said:
As a guide in the 17th the max Ze readings for the following =
Tns = 0.8
Tncs = 0.35
TT = 200

I Recently got a Ze reading of 0.15 on a Tns system, as its higher than 0.8 in the 17th should i be worried?
If its ok, what Ze readings would you consider high for each of the systems? e.g time to call the DNO.
Also filling out a certificate with a higher Ze reading than recommended in bs7671, allowed?
Click to expand...

Stop making out that scousers are thick
 
Hi,dude, You will have to grow a sense of humour,as you have only had 20% of the 100% normally given,which is,after all,only one seventh....:conehead:
 
0.80 implies greater accuracy than value than 0.8
Click to expand...

Could it be that it was 0.8 exactly, with the zero dropped as it would be irrelevant, to the outcome calcs.
Sorry I'm trying to get my head around this, not disrespecting your post.
 
newtothis said:
Could it be that it was 0.8 exactly, with the zero dropped as it would be irrelevant, to the outcome calcs.
Sorry I'm trying to get my head around this, not disrespecting your post.
Click to expand...

The zero is relevant to the outcome of the calculation as it will have an impact on its accuracy.
0.8 x 0.320 = 0.3
0.80 x 0.320 = 0.26
0.800 x 0.320 = 0.256

0.8 is a value anywhere between 0.75 and 0.84 wheras 0.80 is a value between 0.795 and 0.804
 
davesparks said:
The zero is relevant to the outcome of the calculation as it will have an impact on its accuracy.
0.8 x 0.320 = 0.3
0.80 x 0.320 = 0.26
0.800 x 0.320 = 0.256

0.8 is a value anywhere between 0.75 and 0.84 wheras 0.80 is a value between 0.795 and 0.804
Click to expand...

...Your calculator needs re-calibrating...:icon12:
 
newtothis said:
Could it be that it was 0.8 exactly, with the zero dropped as it would be irrelevant, to the outcome calcs.
Sorry I'm trying to get my head around this, not disrespecting your post.
Click to expand...

Yes mate. If the 2nd, 3rd 4th etc decimal place is not required, dont need to use it or it would become 0.800000 or 0.8 X 10 to the power of minus 6 :wink: (level 3 maths, you will see)

^^ that is correct isn't it gents? Been a long time since writing this form of equation and it does not look right?
 
This is getting too in depth,anyone know if my maths are right,I seem to keep getting e=mc squared
icon11.png
 
Paul.M said:
Yes mate. If the 2nd, 3rd 4th etc decimal place is not required, dont need to use it or it would become 0.800000 or 0.8 X 10 to the power of minus 6 :wink: (level 3 maths, you will see)

^^ that is correct isn't it gents? Been a long time since writing this form of equation and it does not look right?
Click to expand...

Yes you do, the number of decimal places displayed is significant in any calculation as it defines the accuracy of the end result. There's no point using a good quality tester which reads to 2dp then only recording the result to 1dp, you might as well use a less accurate tester.

Oh and 0.8 x 10 to the -6 would be 0.000008 ;)

(Or it might even be 0.00000008, thanks Mr styrofoam)
 
Last edited:
...This is why that Mars lander bounced off in to the yonder....

"By calculation", 0.8 x 0.320 = 0.256 not 0.3

By restraint of scale,rounding down etc,yes,but NOT by calculation,which by its' description,is definitive.

0.8 x 10 to the -6 is 0.0000008 or 8 to the -7 , the power of -6 being a millionth,micro or multiple of 0.000001.

...And,as my maths teacher was inclined to ask,after a grueling,set of calcs,"We know friction makes heat?...and heat boils water?...So how long will it take a donkey to ---- a bucket of water,so we can have a cup of tea?" :icon12:
 
PEG said:
...This is why that Mars lander bounced off in to the yonder....

"By calculation", 0.8 x 0.320 = 0.256 not 0.3

By restraint of scale,rounding down etc,yes,but NOT by calculation,which by its' description,is definitive.

0.8 x 10 to the -6 is 0.0000008 or 8 to the -7 , the power of -6 being a millionth,micro or multiple of 0.000001.

...And,as my maths teacher was inclined to ask,after a grueling,set of calcs,"We know friction makes heat?...and heat boils water?...So how long will it take a donkey to ---- a bucket of water,so we can have a cup of tea?" :icon12:
Click to expand...

about 15 minutes if the donkey's on ------,
 
davesparks said:
Ok I should have said 0.8ohms x 0.320 =0.256

In any scientific calculation an answer cannot be more accurate than the least accurate input value.
Click to expand...

Indeed, but you shouldn't make any assumptions about accuracy based only on the number of decimal places or significant figures used.

See my post here: http://www.electriciansforums.co.uk...0424-three-phase-calculation.html#post1079853

My multimeter shows values to 4 significant figures. Can I assume that it's accurate to plus/minus half of the final digit? No! But I still might write down the value I see on the display.

Here's another (silly) example: Would a shop selling something for £1.49 accept a "one pound" coin (0 decimal places), since it's not labelled as a "£1.00" coin?
 
HandySparks said:
Indeed, but you shouldn't make any assumptions about accuracy based only on the number of decimal places or significant figures used.

See my post here: http://www.electriciansforums.co.uk...0424-three-phase-calculation.html#post1079853

My multimeter shows values to 4 significant figures. Can I assume that it's accurate to plus/minus half of the final digit? No! But I still might write down the value I see on the display.

Here's another (silly) example: Would a shop selling something for £1.49 accept a "one pound" coin (0 decimal places), since it's not labelled as a "£1.00" coin?
Click to expand...

Around about now my dear old physics teacher would be tearing a few strips off you!
 
davesparks said:
The zero is relevant to the outcome of the calculation as it will have an impact on its accuracy.
0.8 x 0.320 = 0.3
0.80 x 0.320 = 0.26
0.800 x 0.320 = 0.256

0.8 is a value anywhere between 0.75 and 0.84 wheras 0.80 is a value between 0.795 and 0.804
Click to expand...

Thanks for replying - it's appreciated, I'm a bit confused cos my calcs show the number of zeros is irrelevant.
I suspect it's expressed as 0.8 because that's what it is. If it was 0.802 then this would have to be noted
that 0.8 is correct to x decimal places. ??

0.8x 0.320 = 0.256
0.80=0.320 = 0.256
0800x0.320 = 0.256
 

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