Measuring ZS

[woko27]

Hello, Help please.

Which table do you use for Max EFLI? in BS7671 table 41B2 says Max efli for a type B 32amp MCB is 1.5 ohms but table 2D in GN3 says 1.2 ohms

Anyone else have this problem or am I being blonde

Thanks in advance.

 

[Lectrician]

One is the corrected to the rule of thumb, re: temp during fault.

You should record the max UNCORRECTED value on forms, but compare your measured value to the CORRECTED chart. If you exceed the corrected chart, it's calculation time

BTW, I recall the regs use 75% as rule of thumb, where as the NIC publish 80% figures.

 

[Adam_151]

one is the actual maximum, the other is a 80% rule of thumb value, you can measure it and say, yeah less than 1.2 ohms, fine, rather than compensating for the temperature of the cable at the time your are measuring, etc, etc

 

[woko27]

Thanks a lot

 

[dingbat]

BTW, I recall the regs use 75% as rule of thumb, where as the NIC publish 80% figures.

The 80% figures also appear in the IEE On Site Guide. (The NIC don't make up their own rules as many seem to believe.)