Hi all, Just wondering if anyone can shed some light on the max zs values in the OSG, they don’t seem to follow the 1.25 divisor stated in the note on page 126
For example BS 60898 circuit breaker, max zs at 70 degrees is 7.28, following the formula this should be 5.82 at 10 degrees which is what is in the niceic handbook, however looking at the tables in the OSG it is actually 5.87 which uses 1.24.
This does make sense as the simple way to work it out would 60 degree rise in temperature at simplified coefficient of 0.004 per degree which would equal 1.24, however this contradicts the formula on page 132 note 1 which is {1+0.004(ambient temp - 20)} / {1+0.004(10-20)} = 1.25
(Ambient temp being 70 degrees)
Just curious as to why the tabulated values in the OSG seemed to be calculated the simple way and not followed either the formula stated above or the 1.25 divisor stated in the first note page 126
They’re seems to be two different methods which both makes sense but both have different outcomes which is confusing me a bit.
What’s your opinions? Thanks in advance everyone.
For example BS 60898 circuit breaker, max zs at 70 degrees is 7.28, following the formula this should be 5.82 at 10 degrees which is what is in the niceic handbook, however looking at the tables in the OSG it is actually 5.87 which uses 1.24.
This does make sense as the simple way to work it out would 60 degree rise in temperature at simplified coefficient of 0.004 per degree which would equal 1.24, however this contradicts the formula on page 132 note 1 which is {1+0.004(ambient temp - 20)} / {1+0.004(10-20)} = 1.25
(Ambient temp being 70 degrees)
Just curious as to why the tabulated values in the OSG seemed to be calculated the simple way and not followed either the formula stated above or the 1.25 divisor stated in the first note page 126
They’re seems to be two different methods which both makes sense but both have different outcomes which is confusing me a bit.
What’s your opinions? Thanks in advance everyone.