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Does your company allow turning on and off a fused switch <100A without ER gloves?
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Author:  THE CABLE GUY [ Wed Oct 21, 2009 9:43 am ]
Post subject:  Does your company allow turning on and off a fused switch <100A without ER gloves?
There are some that say a device like a fused safety switch less then 100A and having a fault current not exceeding 35kA can not be operated without using electrical rated gloves with leather covers and FR clothing. Do you believe that industry workers are doing this?

I am willing to bet that most plant nonqualified workers turn on and off these devices everyday without any special PPE.
Also, if you have an opinion on this let me know.
Author:  Zog [ Wed Oct 21, 2009 10:12 am ]
Post subject: 
THE CABLE GUY wrote:
There are some that say a device like a fused safety switch less then 100A and having a fault current not exceeding 35kA can not be operated without using electrical rated gloves with leather covers and FR clothing. Do you believe that industry workers are doing this?

I am willing to bet that most plant nonqualified workers turn on and off these devices everyday without any special PPE.
Also, if you have an opinion on this let me know.


AS long as there are no exposed live parts the rubber gloves are not required. The arc rated PPE will depend on the task table or the results of the arc flash study and should be labeld on the switch.

The 100A has nothing to do with it.
Author:  THE CABLE GUY [ Wed Oct 21, 2009 1:05 pm ]
Post subject: 
Thanks Zog
Author:  Canuck01 [ Wed Oct 21, 2009 1:42 pm ]
Post subject: 
Zog wrote:
AS long as there are no exposed live parts the rubber gloves are not required. The arc rated PPE will depend on the task table or the results of the arc flash study and should be labeld on the switch.

The 100A has nothing to do with it.


I guess I should throw my two bits in...
There is a general misconception about the risk involved with throwing the switch that I'd like some comments on.
Some people in my organization interpret "Normal Operation of Electrical Equipment" as throwing the disconnect handle therefore not a risk and not subject to PPE requirements. I'm on the fence because of previous conversations including one from Zog recently. There is a black or white answer to this one - can anyone point me to specifics?
Author:  Zog [ Wed Oct 21, 2009 5:50 pm ]
Post subject: 
Canuck01 wrote:
I guess I should throw my two bits in...
There is a general misconception about the risk involved with throwing the switch that I'd like some comments on.
Some people in my organization interpret "Normal Operation of Electrical Equipment" as throwing the disconnect handle therefore not a risk and not subject to PPE requirements. I'm on the fence because of previous conversations including one from Zog recently. There is a black or white answer to this one - can anyone point me to specifics?


Depends on the system, if you are within the limits of the tables you can use those HRC's, depending on the type of equipment you are talking about, I assume this is low voltage, then most likely this is a HRC-0. But HRC o is not the same as no PPE.

If you are outside the limits you need to do an analysis, and your Ei will likely be higher and require more PPE. There is no way to tell what the requirements are based on the info provided so far.
Author:  Vincent B. [ Thu Oct 22, 2009 7:53 am ]
Post subject: 
I agree with you Zog, and that's what I tell my costumers.

A question I sometimes receive is, "What is the normal operation of electrical equipment that doesn't require PPE"?

My take on this is:
- Operation of a manual disconnect (safety switch, main equipment disconnect, local motor disconnect): no
- Manual resetting of a tripped overload: no (especially if the panel door must be opened, but even door closed)
- Programming a VFD with the local keypad: no
- E-stop: yes
- Pushbuttons controlling a contactor (3 wire control): yes
- Other pushbuttons: yes
- HMI: yes
Author:  willcoc [ Thu Oct 22, 2009 8:00 am ]
Post subject: 
Same question but with more details

I had this question asked and not sure how to repsond so asking for some help.

Zog was wanting some more specific's so hope that this enough. Operator needs to open a 30 fused disconnect switch in a A-B MCC unit to lock out a peice of equipment. Door is closed with the screws. The label has 4 cal/ cm energy rating. They are not working on the electrical side of the equipment so don't need to verify "zero volts". Question is "does he require arc flash PPE" to open the disconnect switch?
Author:  Canuck01 [ Thu Oct 22, 2009 8:23 am ]
Post subject: 
Vincent B. wrote:
I agree with you Zog, and that's what I tell my costumers.

A question I sometimes receive is, "What is the normal operation of electrical equipment that doesn't require PPE"?

My take on this is:
- Operation of a manual disconnect (safety switch, main equipment disconnect, local motor disconnect): no
- Manual resetting of a tripped overload: no (especially if the panel door must be opened, but even door closed)
- Programming a VFD with the local keypad: no
- E-stop: yes
- Pushbuttons controlling a contactor (3 wire control): yes
- Other pushbuttons: yes
- HMI: yes


Here's a list of possible scenarios of "normal operation"(I'll assume I.E. +10 cal in all situations), all equipment in good condition:
Operator needs to lock out a machine for maintenance, 480V MCC, 30 amp disconnect. PPE?
Operator needs to lock out a machine for maintenance, 480V MCC, 200 amp disconnect. PPE?
Operator needs to lock out a machine for maintenance, 4160V MCC, 400 amp starter with disconnect handle. PPE?
Electrician opening or closing a 13.8 KV breaker using the local switching device. PPE?
All situations assume door is closed properly.
We do require people to suit up if the door is opened, for testing, or for any energised work already...
Author:  Zog [ Thu Oct 22, 2009 9:23 am ]
Post subject: 
willcoc wrote:
I had this question asked and not sure how to repsond so asking for some help.

Zog was wanting some more specific's so hope that this enough. Operator needs to open a 30 fused disconnect switch in a A-B MCC unit to lock out a peice of equipment. Door is closed with the screws. The label has 4 cal/ cm energy rating. They are not working on the electrical side of the equipment so don't need to verify "zero volts". Question is "does he require arc flash PPE" to open the disconnect switch?


Yes, PPE rated >4 cal/cm2. THere is no derating factor for having the doors closed. You analysis has identified a 4 cal/cm2 hazard.
Author:  Zog [ Thu Oct 22, 2009 9:25 am ]
Post subject: 
Vincent B. wrote:
I agree with you Zog, and that's what I tell my costumers.



Getting ready for Halloween?
Author:  THE CABLE GUY [ Thu Oct 22, 2009 9:42 am ]
Post subject: 
Canuck01,
I suppose I would have to ask what the reason the devices are being turned off.
Example, turning off the disconnect to shutdown equipment and go home?
Or, turning off for maintenance on the equipment with lock out, or turning off to do maintenance on the MCC, turning off a low HRC disconnect to plug or unplug a three phase device.

>10 cal/cm is really high for a 30A disconnect. I suppose that high of IE would be labeled as a high HRC. Method used to be sure the equipment is switched off; hmm, well an operator would not do that unless they are qualified. What about pressing a control but to see if the equipment operates? Not everything is ac motor control circuits either so that may be a problem. For me evaluation of the HRC and task risk goes beyond what the calculation result is. Sort of an educated assumption you might say.

Good discussion points to learn from. I hope to see some interesting comments.
Author:  THE CABLE GUY [ Thu Oct 22, 2009 11:16 am ]
Post subject: 
Gee, I understand I seen what Zog said and put it all together. The problem I suppose is in Arc Flash we consider door open/closed the same rating. If someone is interacting with the switch and the HRC is 0 the operator should be in FR clothing I believe this is the concensus.
Author:  Canuck01 [ Thu Oct 22, 2009 11:27 am ]
Post subject: 
THE CABLE GUY wrote:
Canuck01,
I suppose I would have to ask what the reason the devices are being turned off.
Example, turning off the disconnect to shutdown equipment and go home?
Or, turning off for maintenance on the equipment with lock out, or turning off to do maintenance on the MCC, turning off a low HRC disconnect to plug or unplug a three phase device.

>10 cal/cm is really high for a 30A disconnect. I suppose that high of IE would be labeled as a high HRC. Method used to be sure the equipment is switched off; hmm, well an operator would not do that unless they are qualified. What about pressing a control but to see if the equipment operates? Not everything is ac motor control circuits either so that may be a problem. For me evaluation of the HRC and task risk goes beyond what the calculation result is. Sort of an educated assumption you might say.

Good discussion points to learn from. I hope to see some interesting comments.

The issue arises from what is "normal operation of equipment". We run 24/7 doing maintenance when required. The non-electrical worker is required to lock out at the MCC when they work on the equipment (changing belts, screen panels, pumps, etc). They need to test during the LOTO by trying the local start button - we have remote/maintenance switches on most of our plant equipment. Once the machine is tested by pressing the local start button while the circuit is maintenance mode, the machine is locked out then re-tested by pressing the start button to confirm lockout. We consider that procedure an effective lockout for mechanical work. In my mind, I see that procedure as "normal operation of equipment" therefore the worker doesn't need Arc Flash gear even though the I.E. might be well in excess of 1.2cal. Why do we require workers to dress to the required PPE level to operate the disconnect handle when they are not interacting with the equipment electrically, just performing a regular lockout?
What kind of risk can you assign other than using a black or white standard? Either no special PPE is required or it's PPE to the I.E. on the label??
I have to say the whole thing doesn't make alot of sense and is costly to administer in PPE, training and labeling.
Author:  THE CABLE GUY [ Thu Oct 22, 2009 11:50 am ]
Post subject: 
However, the way I understand if the exposure is less then 1.2 cal/cm2 the thermal hazard is not enough for an operator to have to wear any special clothing.
Is this right?
Author:  Canuck01 [ Thu Oct 22, 2009 1:07 pm ]
Post subject: 
No PPE may not be correct. It is more like 100% natural fibers with HRC 0.

Everyone at this facility is dressed in 6.5 oz protera minimum. The coveralls and pants are 8.0 oz but the shirt is 6.5 oz

Still want to know why they need the Arc Flash clothing when doing general lockouts etc...
Author:  willcoc [ Thu Oct 22, 2009 1:15 pm ]
Post subject: 
Energy is not that low

In our case with the energy level being 4 cal (for this example), we would then require FR garment and the other PPE to complete a level 1. That is going to be a hard sell for the folks that have been doing it for years without issue. But if that is the way it is, then it they must comply.
Author:  THE CABLE GUY [ Thu Oct 22, 2009 1:57 pm ]
Post subject: 
Canuck01, sorry I was typing at the same time. The way I understand, it is arc flash PPE is required to the calculated rating listed on the label unless the IE is below 1.2 Cal/cm2 when turning on/off a LV disconnect.

What is making your LV disconnect so high in IE? Is the upstream fuse or CB is so large? Most LV (480) would be fused less the 500a should be fairly low in IE.

The way I understand the hazard is like this:
An operator does his job cleaned the machine, and general PM work but during that process created a dead short across a large 3 phase connection on the load side of the main disconnect (probably never happen but this is a dream) the operator never suspects a problem and turns on the main disconnect. The dead short creates some problem in the disconnect maybe the fuse interrupt capacity is wrong and the fuse explodes in flames and blows the door out and fire shoots out the devices openings.

Let me give you a real world scenario that happened to me the other day.
I turned off a 600A main fused switch to make some checks. When I turned it back on the insulator on the knife throw assembly came out of position someway. The knife on the throw touched and arch to the metal rod on the throw handle. The upstream fuse blew at the bus duct and the arc was limited. The door had a black spot on it but the IE was <less then 1.0 cals. I suppose some companies may have had the line side of a much higher IE and then the situation could have been dangerous.

Zog has some pictures of some equipment that has failed when turning on. You may find by doing a search in this forum.

I am not sure if Zog or others have pictures on LV disconnects blown out but I would think it to be possible under the right conditions.

So, I assume NFPA 70E group felt that if a issue comes up they have done the safer thing by stating that an Arc Flash can occur by the remarks in Art 100, FPN#1 An arc flash may exist in enclosed conditions.

Clear as smoke but that’s the way I see the reasoning. Simplified, I am sure there more complex reasoning’s .
Author:  Zog [ Thu Oct 22, 2009 4:33 pm ]
Post subject: 
LV MCC bucket, doors closed

http://www.youtube.com/watch?v=exA0sHO-cZM
Author:  THE CABLE GUY [ Thu Oct 22, 2009 6:00 pm ]
Post subject: 
Thanks Zog
Author:  THE CABLE GUY [ Fri Oct 23, 2009 6:09 am ]
Post subject: 
ZOG, when you speak of a remote controlled throw on a switch in some cases from other postings. Is this for a molded case circuit breaker? Like a remote test pushbutton to trip the breaker?

I cannot find a link to industrial 3 ph safety switches that contain a remote throw device. :( Maybe it's a miss-understanding in my understanding of what exactly is a remote controlled throw switch. I know of using a bus plug switch elevated with a handle so the switch can be operated with a pull chain or a hot stick device attached to the handle.

If you or anyone else know of such a device as a remote controlled throw for a safety switch 30-600A could you attach a link.

Question, would a remote controlled throw turn on and off a switch. If nothing like this is available I'll have to create one. :)
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