Max Zs values at different ambient test temperatures Discussion ThreadMax Zs values at different ambient test temperatures Electrical Advice
Hi guys, I'm currently revising for my 2391 and kind of confused on the temperature factors for the Zs values
The BBB give Max Zs which are 100% values with a max operating temperature of 70c.
The OSG and GN3 give values to 80% which are when tested at ambient temp of 10c according to page 146 OSG. These values are the same if you x 0.8 of the BBB values.
There are correction factors on tables B8 and I2 on OSG
Q1. When using the 80% values which have ambient air temp of 10c do we have to apply the correction factor taken from table I2 OSG page 219 to the cable being tested? For example if I got a reading of say 0.56ohm on R1+R2 would I now need to divide that by 0.96 to reach the ambient temperature of 10c which will now be 0.58ohm R1+R2...
Under table I2 it says the rating factor may be applied in table I2 to the values to take into account of the ambient temp (for test purposes only)
Q2. Also, realistically the ambient temp is not always going to be 10c so lets says if it is 20c when testing circuits, would you then multiply the Zs of In x 1.04? So lets use B32 being 1.1ohm x 1.04 (correction) = 1.14ohm which will now be the Max permitted Zs for B32?
Q3. If the ambient testing temperature is 25c do we then apply a correction factor to both the protective device which will increase its max permitted Zs value by x1.06 as well as the measured R1+R2 readings which will decrease by 2% (1.02)?
So to break my questions down as simply as I can
Q1: if the testing ambient temperature is 10c do we apply the correction factors from table I2 page 219 OSG to the measured R1+R2 to meet the 10c test temperatures set out in B8 page 146 OSG
Q2: if the test temperature is higher or lower than 10c do we then multiply the 80% Max Zs values by the correction factors in table B8 page 146 OSG to meet the ambient temperature at the time of testing?
Q3. If the ambient testing temperature is 25c do we then apply correction factors to both protective device max Zs and R1+R2...
Read more
Max Zs values at different ambient test temperatures for the original thread on Electricians Forums
Hi guys, I'm currently revising for my 2391 and kind of confused on the temperature factors for the Zs values
The BBB give Max Zs which are 100% values with a max operating temperature of 70c.
The OSG and GN3 give values to 80% which are when tested at ambient temp of 10c according to page 146 OSG. These values are the same if you x 0.8 of the BBB values.
There are correction factors on tables B8 and I2 on OSG
Q1. When using the 80% values which have ambient air temp of 10c do we have to apply the correction factor taken from table I2 OSG page 219 to the cable being tested? For example if I got a reading of say 0.56ohm on R1+R2 would I now need to divide that by 0.96 to reach the ambient temperature of 10c which will now be 0.58ohm R1+R2...
Under table I2 it says the rating factor may be applied in table I2 to the values to take into account of the ambient temp (for test purposes only)
Q2. Also, realistically the ambient temp is not always going to be 10c so lets says if it is 20c when testing circuits, would you then multiply the Zs of In x 1.04? So lets use B32 being 1.1ohm x 1.04 (correction) = 1.14ohm which will now be the Max permitted Zs for B32?
Q3. If the ambient testing temperature is 25c do we then apply a correction factor to both the protective device which will increase its max permitted Zs value by x1.06 as well as the measured R1+R2 readings which will decrease by 2% (1.02)?
So to break my questions down as simply as I can
Q1: if the testing ambient temperature is 10c do we apply the correction factors from table I2 page 219 OSG to the measured R1+R2 to meet the 10c test temperatures set out in B8 page 146 OSG
Q2: if the test temperature is higher or lower than 10c do we then multiply the 80% Max Zs values by the correction factors in table B8 page 146 OSG to meet the ambient temperature at the time of testing?
Q3. If the ambient testing temperature is 25c do we then apply correction factors to both protective device max Zs and R1+R2...
Read more
Max Zs values at different ambient test temperatures for the original thread on Electricians Forums
