We are having a debate about what type of clothing is required to work on PLC. Given a PLC panel with 120V IO, fused at 5 amps. From what I see in NFPA 70E 130.7(c)(9) to do live voltage testing I need to have a uniform with a arc rating of 4. Our electrcial folks have no problems with this as our standard uniforms are FR. The rub is we have other groups on site that work on the PLC's (instrument, analyers and controls system group). I'm telling them in order to work on the equipment they have to have the proper rated clothing or shut if off. The debate is why do they need arc flash rated clothing / protection when the arc flash hazard is below 1.2 cal/cm^2. I would appreciate your opinion.
NFPA 70E & PLC's
- Thread starter cornbread
- Start date
- Status
billsnuff
Senior Member
- Location
- East of 480sparky
if you have already completed an arc flash study and the labeling has been done, you can skip (c)(9) and go to (c)(10) and suit up according to the arc flash label on the equipment based on the HRC from the study.
that said, it sounds as if there in no energized work permit program in place and that task specific job risk analysis hasn't been completed. these are also required by 70E. Had these activities taken place, then employees would already know what is expected and required. If i am wrong and these activities have taken place, then i would move to disciplinary action, as necessary, for those who won't comply. JMSHO
that said, it sounds as if there in no energized work permit program in place and that task specific job risk analysis hasn't been completed. these are also required by 70E. Had these activities taken place, then employees would already know what is expected and required. If i am wrong and these activities have taken place, then i would move to disciplinary action, as necessary, for those who won't comply. JMSHO
Apprecaite the reply. We are currlently working on standard for working in / on 120V control cabinets and thsi is where the debate began. Unfortuntialy we have not completed our Arc Flash study for 120v circuits. We are falling back the exception no 1 under 130.2(C) "an Arc flash hazard analysis shall not be required where all of the following exist:
1. Circuit < 240
2. supplied by one xfmr
3. Xfmr < 125KVA.
Does this exception indicate the arc flash hazard is low enough not to worry about?
1. Circuit < 240
2. supplied by one xfmr
3. Xfmr < 125KVA.
Does this exception indicate the arc flash hazard is low enough not to worry about?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
There is no IEEE 1584 method for calculating arc flash incident energy on single phase circuits.
billsnuff
Senior Member
- Location
- East of 480sparky
cornbread,
i think i understand better what you are saying, in my case i supply HRC2*
shirt and pants to all mechanics and elec. (my dime, but they all wear them and they are safer).
In some of my cabinets, all 120, 'cept for 1 - 3 ph 480 mtr str, I moved the starter and added a small cabinet. now we can change a component by locking a single cabinet and not shut down the entire machine. can also test and trouble shoot with less hazard.
engineer what you can and train the rest so they can go home in one piece.
good luck
i think i understand better what you are saying, in my case i supply HRC2*
shirt and pants to all mechanics and elec. (my dime, but they all wear them and they are safer).
In some of my cabinets, all 120, 'cept for 1 - 3 ph 480 mtr str, I moved the starter and added a small cabinet. now we can change a component by locking a single cabinet and not shut down the entire machine. can also test and trouble shoot with less hazard.
engineer what you can and train the rest so they can go home in one piece.
good luck
With respect to this thread, and the wearing of PPE, what exactly does that mean?
weressl
Esteemed Member
Yes, level 0. Electrocution hazard still exist.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It means that you are limited to using NFPA70E 130.3(A)(1) for determining Arc Flash Protection Boundaries and 130.7(C)(9) for PPE selection, unless you meet the specific requirements in 130.3 Exception 1.
Aggreed on the electrcial hazard, but not real sure hazard catagory 0 would apply. Granted using catagory 0 would be the best practice, but one could agrue that the arc flash is below 1.2 cal/cm^2 so no arc flash PPE is required. I know there is going to be a debate about having to wear long sleeve shirts when ther is no arc flash hazard.
With all that said, we are pushing forward with our SOP to include using cat 0 clothing when working on 120 VAC system that fall unde the exception note.
As always...your replies are greatly appreciated!!!
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Category 0 PPE is for locations with less than 1.2 cal/cm?.
Just because a calorie level can not be determined by calculations does not mean one does not exist.
I believe you must follow the 'task tables' when dealing with 1-phase or DC circuits.
Just because a calorie level can not be determined by calculations does not mean one does not exist.
I believe you must follow the 'task tables' when dealing with 1-phase or DC circuits.
billsnuff
Senior Member
- Location
- East of 480sparky
don't forget your boundaries (table 130.2(C)
don't forget your boundaries (table 130.2(C)
note 2 single phase * 1.732 ph to gnd
don't forget your boundaries (table 130.2(C)
note 2 single phase * 1.732 ph to gnd
weressl
Esteemed Member
Isn't the:
1. Circuit < 240
2. supplied by one xfmr
3. Xfmr < 125KVA.
clarifies that?
I presumed that the PLC work ONLY would most likely fall under that blanket statement.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The items you listed are the exceptions to the requirement to conduct an arc flash analysis. They are not directly related to the selection of PPE based on tasks performed. Not all 120V single phase circuits come from transformers <=125KVA (even though the vast majority probably do).
weressl
Esteemed Member
I suggest that you begin placing a GFCI protected port on the outside of your cabinets. This along with a port to the processor will avoid unnecessary entry to the panel. A laptop tray on the outside is also really nice. It can fold down to protect the outlet.
Try the following:
Daykin Model No. LTFB-07 Z1183
500 VA Transformer Disconnect
NEMA 1 Enclosed
480 VAC, 60 HZ Primary, 120 VAC Secondary
200 kA SCCR
Furnished with (1) GFI Circuit Breaker on the Secondary
(No Duplex Receptacle)
List $ 918.00
Daykin Model No. LTFB-05 Z1183
Same as above except 1 kVA and furnished with receptacle.
List $1094.00
Try the following:
Daykin Model No. LTFB-07 Z1183
500 VA Transformer Disconnect
NEMA 1 Enclosed
480 VAC, 60 HZ Primary, 120 VAC Secondary
200 kA SCCR
Furnished with (1) GFI Circuit Breaker on the Secondary
(No Duplex Receptacle)
List $ 918.00
Daykin Model No. LTFB-05 Z1183
Same as above except 1 kVA and furnished with receptacle.
List $1094.00
- Status