Would like to get a discussion going on C1 D2 boundary seal-off in outdoor installation.
In our application we are going from Ex-Proof Instrument (outdoor open area) to a Non-Ex-Proof Enclosure with terminals in C1D2 area (outdoor open area). Then we are going from a Non Ex-Proof Enclosure to Control panel via underground sleeve with gutter boxes at both ends.
As per NEC 501.15 B (1), the instrument is considered explosion proof enclosure and will need seal-off at instrument within 18 inch.
However for the C1D2 boundary there are items in Exception 2 and 4 that apply to our installation eliminating the need for boundary seals.
Please see below screen shot from code.
In our application we are going from Ex-Proof Instrument (outdoor open area) to a Non-Ex-Proof Enclosure with terminals in C1D2 area (outdoor open area). Then we are going from a Non Ex-Proof Enclosure to Control panel via underground sleeve with gutter boxes at both ends.
As per NEC 501.15 B (1), the instrument is considered explosion proof enclosure and will need seal-off at instrument within 18 inch.
However for the C1D2 boundary there are items in Exception 2 and 4 that apply to our installation eliminating the need for boundary seals.
Please see below screen shot from code.