Maz Zs as per bs7671.

[cagedanimal2010]

Morning guys, (& girls)
quick one, i cant seem to find the max Zs's for bs3871's in the BGB.
any help would be helpful!!
Cheers.
Danny

 

[telectrix]

post corrected. typed before brain woke up.

 

[cagedanimal2010]

60898's dont come in 5, 15, and 30's?

 

[i=p/u]

i.e for 5A = 5 x 5 = 25A to cause operation so 230 / 25 = 9.2 ohms ,corrected of course.

 

[GaryM]

They're in GN3, p113 if you have access to it.

 

[telectrix]

as i=p/u says,if in doubt, work it out. type 1 2871 is equivalent to type b 60898.

 

[GaryM]

i.e for 5A = 5 x 5 = 25A to cause operation so 230 / 25 = 9.2 ohms ,corrected of course.

That works for a B type 60898 - 3-5 xIn

BS3871

Type 1 - 2.7 to 4.0 x In
Type 2 - 4.0 to 7.0 x In
Type 3 - 7.0 to 10.0 x In
Type 4 - 10.0 to 50.0 x In

To apply these to the calculation above, use the maximum figure for the type you're calculating for.

eg 30A BS3871 Type 2

230 / (30x7) = 1.09ohms (maximum uncorrected value)

 

[GaryM]

type 1 3871 is equivalent to type b 60898.

It's not:

Type 1 3871 - 2.7 to 4.0 x In

Type B 60898 - 3.0 to 5.0 x In
​

 

[telectrix]

sorry, gary, i should have said similar, not equivalent. values for both types ae given in table 2D , red osg. these are corrected values.

 

[GaryM]

I'm just going off a PDF I have for circuit breaker standards.
I'll have a look to see if I can host it online somewhere so you (and others) can have a look.

 

[GaryM]

I posted the link but have now removed it due to just finding that Lenny had previously posted a link to the very same document!

http://www.electriciansforums.net/i...ns/18439-circuit-breaker-info.html#post133310