You shall use Method B, but the values shall only be added to a lumped sum.

Please note that the latest Version of IEC/EN 60079-14 section 6.2.4 (and 60079-25) states that if the lumped sum of BOTH Li and Ci (of the instruments and not cables) is greater than 1% of Lo and Co, then the values of Lo and Co must be reduced to 50%.

Thank you for the answer.

I am very beginner with IS calculations. My basic understanding is Barrier should always be in Safe area.

Can barrier be in Hazardous area?

For example can we consider Strain/AC module as a barrier (Atex certificate: https://www.valvewatch.com/Global/ATEX/12ATEX1093X%20Issue%201.pdf) when used inside LDAU box (Atex certificate : https://www.valvewatch.com/Global/ATEX/11ATEX1229X%20Issue%201.pdf ) even though LDAU box is in Hazardous area.

I was told by vendor that the Strain/AC module is a barrier per definition in ATEX certificate, paragraph 15 and 17

Can you please help me remove my confusion

The links to certificates are to a non secure website, and I recomend anyone to be careful if you decide to download. I do not want to go into details about these products.

If you are all new to IS calculations I suggest that you take one of our courses "Exi basic" or "Exi for project personel" because if the calculations are not done correctly it may influence severly on the safety of the loop.I can give you the following answer to your questions:

If a barrier is to be placed in Hazardous area it must have additional proection. This could be inside an Exd or Exp encapsulation, and for Zone 2 applications the barrier itself can have a variant of the Exn protection method.

In Europe all equipment for use in Hazardous area should be marked with equipment category 1G/D, 2G/D or 3G/D. If any of theese are put in brackets, e.g. Ex II (2)G, the barrier is for use in non Hazardous area only.