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Is safety relay a NFPA79 requirement for E-stop circuits?

Is safety relay a NFPA79 requirement for E-stop circuits?

Is safety relay a NFPA79 requirement for E-stop circuits?

(OP)
I am confused about whether a safety relay is required in an emergency stop circuit.  I recently had a salesman tell me that NFPA 79 requires a level of control reliability for an E-stop that is essentially Category 3.  If this is the truth, can someone point me towards the sections of code that imply this?

I agree that it is good practice to use a safety relay.  However we currently have some machines that have low levels of risk.  The E-stop button opens a single contactor on the line side of the drives.  Is this an acceptable practice according to NFPA 79?  Or is the use of a safety relay implied for all E-stop applications?

Sorry if this is a common topic for discussion.  I tried to browse the many old threads about emergency stop circuits but I didn't see anything that addresses my specific question.  Thanks.
 

RE: Is safety relay a NFPA79 requirement for E-stop circuits?

(OP)
I'll bump this thread one time and then let it die if no one is interested.  Even if you're not sure about the code requirements, how do you typically approach an E-stop design?  Would it be a red flag for you if you saw a machine that did not use a safety relay?

RE: Is safety relay a NFPA79 requirement for E-stop circuits?

NFPA 79 is available online:
http://www.nfpa.org/onlinepreview/online_preview_document.asp?id=7907#
Site probably will ask you to register before letting you access its documents.
You may study paragraph 9.2.5.4.1 Emergency Stop. It does not states that every machine has category 3 risk. It requesting that risk assesement needs to be perfromed. Based on this proper emergency stop configuration needs to be selected.

PaulBr.
 

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