Location for Intrinsically Safe Barrier

[saluki_engineer]

I am working on a design for a mixer with a local control station that will be located in a Class 1, Div 2 area. We specify that the high-temp and moisture-sensing switches must utilize an IS barrier due to the classified nature of the room where it is located. The vendor submitted a design showing the IS barriers in a NEMA 4X rated local enclosure that includes the local HOA switch and will be located in the same room as the mixer.

My question is, is it ok to have the IS barrier in the classified area as long as it is in a NEMA 4X enclosure? I would assume that since we have an HOA switch with 120V control voltage coming to it, that this is ok, but another engineer has suggested to me that the relays can't be located in the classified area.

Thanks in advance for the help.

 

[petersonra]

I am working on a design for a mixer with a local control station that will be located in a Class 1, Div 2 area. We specify that the high-temp and moisture-sensing switches must utilize an IS barrier due to the classified nature of the room where it is located. The vendor submitted a design showing the IS barriers in a NEMA 4X rated local enclosure that includes the local HOA switch and will be located in the same room as the mixer.

My question is, is it ok to have the IS barrier in the classified area as long as it is in a NEMA 4X enclosure? I would assume that since we have an HOA switch with 120V control voltage coming to it, that this is ok, but another engineer has suggested to me that the relays can't be located in the classified area.

Thanks in advance for the help.

I don't see how the HOA switch with 120V on it can be located in a classified area unless it has hermetically sealed contacts, which is quite possible.

What relays are you asking about?

generally the barrier itself would be in a non-hazardous area.

it may be the intent of the supplier that the box be located outside of the classified area.

 

[saluki_engineer]

The more I look at their design, I think you are right about them expecting this box to be outside of the hazardous area. I was originally mistaken that NEMA 4x is explosion proof, but that isn't the case, so I think we will have to either specify that the control station is outside the room or re-think the layout of the system.

Thanks!