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

[akruse]

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.

 

[akruse]

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?

 

[PaulBr]

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.