AB Flex Ex I.S. Installation - Interface to non-I.S. components

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nhee2

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An existing installation uses Allen Bradley Flex EX I/O to interface to field IO in a Class I Div 2 area (Flex Ex is in the Div 2 area, as are all of the field devices). The Flex-Ex is overkill for a Div 2 area, however it is what is installed.

The plant needs to interface with a non-i.s. solenoid, and proposes to install an interposing relay between a 1797-OB4D output and the device. The proposed relay is listed for Div 2 installation but is not marked IS.

I have stated that the relay is not listed for use on the I.S. installation, and is not a simple apparatus.

- Would a relay coil be considered 'simple apparatus?
- If I/S relay coil is required to connect to the 1797-OB4D module, does such a relay exist? I looked quickly at MTL and did not see anything.
 
as long as you can properly segregate the conductors I see no reason why every conductor coming off the I/O module has to be an IS circuit, unless the instructions say so. I didn't look at the way the module is wired so it may be impossible to properly segregate them.
 
petersonra said:
as long as you can properly segregate the conductors I see no reason why every conductor coming off the I/O module has to be an IS circuit, unless the instructions say so. I didn't look at the way the module is wired so it may be impossible to properly segregate them.
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petersonra-

Are you saying there may be a way for one channel or module on the system to be I.S. even if an adjacent module/channel is not i.s.? I'll have to look again through the module documentation, this is different from what I was thinking, but could be correct.

Assuming I.S. is a requirement, are you aware of a way to interface the output module with the non-I.S. circuit?
 
nhee2 said:
petersonra-

Are you saying there may be a way for one channel or module on the system to be I.S. even if an adjacent module/channel is not i.s.? I'll have to look again through the module documentation, this is different from what I was thinking, but could be correct.

Assuming I.S. is a requirement, are you aware of a way to interface the output module with the non-I.S. circuit?
Click to expand...

I took a quick look at the documentation and it says you can't have non-IS channels.


maybe something like this

https://media.wix.com/ugd/bf08dd_4dc18e8df9e14adfac2262c2f8aefda8.pdf

part of your problem is going to be where are you able to locate the relay.
 
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