NFPA 70E compliance- automation programmimg engineers

JWB

Member
Location
Louisiana
What level of Arc Flash and Shock PPE are Automation Engineers required to wear when trouble shooting a PLC with a live <120VAC?
 

JWB

Member
Location
Louisiana
Arc Flash PPE for <120VAC

Arc Flash PPE for <120VAC

What level Arch Flash and Shock PPE is required when trouble shooting a PLC, VFD or MCC with live <120VAC?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Assuming no line voltage equipment in the panel, you would not need anything (No PPE Required) if you use the "Task Tables", because it falls under this rule:
Working on control circuits with
exposed energized electrical
conductors and circuit parts,
nominal 125 volts ac or dc,
or below without any other
exposed energized equipment
over nominal 125 volts ac or
dc, including opening of hinged
covers to gain access.
I personally use common sense precautions; long sleeve cotton shirt and safety glasses, because I've seen too many things happen.
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
Is the highest voltage in the area you are working 120V? I ask since you mention MCC and they are typically 480V. Are you in a cubicle where the 480V breaker is?

If only 120V, then you need non-melting clothing (cotton), safety glasses, Class 00 gloves plus the training. You should also be doing a hazard and risk analysis for the task you are performing
 

JWB

Member
Location
Louisiana
NFPA 70E compliance- automation programmimg engineers

Thanks for answering so quickly. I'm told that typically there's a 480VAC in the same PLC panel box. The 480VAC should be LOTO, which is why my only concern is the live 120VAC. I just hired an Electrical Safety trainer/consultant to train our guys in NFPA 70E. He's telling us that our guys need to at least have FR clothing, safety glasses and rubber gloves/leather outers (00), to open the panel and use voltmeter / trouble shoot the 120VAC. Where can I find the information you cited?
 

JWB

Member
Location
Louisiana
Arc Flash PPE for <120VAC

Arc Flash PPE for <120VAC

Thanks for answering so quickly. I'm told that typically there's a 480VAC in the same PLC panel box. The 480VAC should be LOTO, which is why my only concern in the PLC is the live 120VAC.
I recently hired an electrical safety trainer/consultant to train our guys in NFPA70E. He's telling us pretty much the same as you just said; FR clothing, safety glasses and rubber gloves (00) with leather outers to open the panel and use a voltmeter and trouble shoot the live 120VAC.

Does the 480V need to be live when trouble shooting a MCC?
 

JWB

Member
Location
Louisiana
NFPA 70E compliance- automation programmimg engineers

Jraef - I found the task table quote you mentioned. Thank you. So basically, my guys need to be protected from "shock" at 120VAC-live, rather than an Arc Flash. Correct?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Please don't cross post. I am closing the other thread because this probably belongs here.

In the original thread you didn't mention the MCC or VFD, that makes a difference. Locking off the breaker / disconnect of a panel does NOT make it totally safe to be in it without PPE, so long as the LINE SIDE of the equipment is sharing the same space. So in an MCC bucket, if you only lock off the UNIT disconnect, it doesn't qualify as not needing PPE if the REST of the MCC is still live, because an arc flash event elsewhere could still propagate the plasma and blast pressure right into your face; the bus bar barriers are NOT intended to withstand that. The only way to avoid having to wear PPE to work on an MCC bucket is to power down the ENTIRE MCC, or to remove the bucket and work on it on the bench. The same is true in a VFD enclosure; a dropped tool or insulation failure on the line side of the disconnect would still have you exposed to the dangers (I personally have lived through that one, but I was lucky). So that's why I had qualified my earlier statement to say IF THERE IS NO LINE VOLTAGE, you don't need PPE. that is NOT the case of there are line power devices and the line power is still hot anywhere in the panel.
 
Last edited:

jctj88

Member
Location
oklahoma
NFPA 70E 130.7(C)(15)(A)(b) Table

NFPA 70E 130.7(C)(15)(A)(b) Table

According to this table under equipment rated 240v and below you need a Arc Flash PPE Category 1. Arc Flash Boundary 19in.

if you go to Table 130.7(C)(16) you will see what type of Clothing and PPE you are required as Category 1 on the previous table.
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
According to this table under equipment rated 240v and below you need a Arc Flash PPE Category 1. Arc Flash Boundary 19in.

if you go to Table 130.7(C)(16) you will see what type of Clothing and PPE you are required as Category 1 on the previous table.
NFPA 70E-2018 is Table 130.7(C)(15)(a) which lists Category 1 for equipment rated 240V and below as long as the parameters of maximum available fault current is no greater than 25kA and the maximum clearing time is 2 cycles (0.03 sec) are met. So the OP would have to obtain the available, not infinite bus, fault current from the utility and model the system to the equipment to obtain the available fault current and then obtain the time current curve for the protective device upstream from that equipment to determine if it will trip in 2 cycles or less.

You need to pay attention to the parameters of the table to use the table method.
 
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