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 Post subject: ARC FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Wed Dec 19, 2018 9:38 am 

Joined: Fri Nov 16, 2018 11:01 am
Posts: 1
I am interested to know how people are interpreting the ARCH Flash requirements for a well maintained closed front/door, fused or non fused disconnect or safety switch. I have seen them Marked for Arch Flash PPE but it never delineates whether or not you can operate the closed switch with out PPE to shut down and lock out equipment. Anyone have some thoughts or guidance???


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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Thu Dec 20, 2018 12:40 pm 

Joined: Tue Feb 17, 2009 8:38 am
Posts: 43
Location: Westminster, MD
70E 2018 Table 130.5(C) Estimate of the Likelihood of an Arc Flash Incident... shows that as long as the equipment is in Normal Condition it is not likely to have an arc flash occurrence, so it can be operated without PPE.


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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Thu Dec 20, 2018 2:55 pm 
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Location: Rutland, VT
I have seen many non-fused disconnects in studies that are overdutied. This has to be considered when operating the switch as it is not installed according to manufacturer's instructions and violated NEC and OSHA. Normal Condition means it was installed per manufacturer's instructions.
But unless a study has been done, how do you know if using the tables that the device you are operating is not rated for the available short circuit?

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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Thu Dec 20, 2018 10:16 pm 
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Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
A study should be done even if PPE is not required to open the disconnect. The study will identify overdutied equipment. We normally put arc hazard labels on disconnects also, because this might be the place that voltage measurements are made to confirm that equipment is de-energized after opening the disconnect. The ability of operating the disconnect switch without PPE should be spelled out in the Electrical Safety Program and Training.


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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Mon Dec 24, 2018 1:31 pm 
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Location: North Carolina
According to data in IEEE 493 (not sure what the new 3000 series number is), the failure rates are at least an order of magnitude lower than circuit breakers for arcing faults, and really faults in general since for all practical purposes there's not much to them. And 70E has a fine print note that specifically states that normal operation of MCC's does not require arc flash PPE. MCC buckets use either a disconnect (and one not nearly as well built as safety disconnects) or a molded case circuit breaker or MCP so we can pretty easily reach a conclusion that safety disconnects are at least as safe if not safer than the disconnect mechanism for an MCC bucket.


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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Mon Jan 07, 2019 8:08 am 
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Joined: Tue Jul 01, 2014 8:40 am
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Hello, and greetings from North of the border. Below is the wording from the notes under the definition of "arc flash" in CSA Z462. As you are aware Z462 is technically harmonized with 70E:

The likelihood of occurrence of an arc flash incident increases when energized electrical conductors or circuit
parts are exposed or when they are within equipment in a guarded or enclosed condition, if a person is
interacting with the equipment in a manner that could cause an electric arc. An arc flash incident is not likely
to occur under normal operating conditions when enclosed energized equipment has been properly installed
and maintained.

We know that unless it is arc resistant switchgear, we cannot rely on the doors or covers to protect us from the effects of an arc flash, so possibly treat this as the doors being opened, however my thoughts are:
1) the age and the outside condition of the switch and handle (rust, covered in dust, dirt, etc). How does the equipment present itself?
2) Have I been here before and operated the switch? Or perhaps aware of the history of installation?
3) Would the installation meet code rerquirements?
4) Am I aware of the maintenance history? How well has the equipment been maintaned over the years?

If you can answer favourably to at least 3 of the above questions then operating the switch with standing to one side and facing away with a pair of good leather gloves (hand and wrist protection) on and safety glasses would be adequate


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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Mon Jan 07, 2019 4:15 pm 
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Joined: Sat Nov 21, 2009 10:23 pm
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Location: Ohio
wbd wrote:
I have seen many non-fused disconnects in studies that are overdutied. This has to be considered when operating the switch as it is not installed according to manufacturer's instructions and violated NEC and OSHA. Normal Condition means it was installed per manufacturer's instructions.
But unless a study has been done, how do you know if using the tables that the device you are operating is not rated for the available short circuit?


In most cases a non-fusible switch or molded case switch is 10kA. Most fusible switches are 200kA when used with a minimum of a Class r fuse.


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 Post subject: Re: ARCH FLASH REQUIREMENTS FOR SAFETY SWITCHES
PostPosted: Tue Jan 08, 2019 10:37 pm 
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Leonard wrote:
1) the age and the outside condition of the switch and handle (rust, covered in dust, dirt, etc). How does the equipment present itself?
2) Have I been here before and operated the switch? Or perhaps aware of the history of installation?
3) Would the installation meet code rerquirements?
4) Am I aware of the maintenance history? How well has the equipment been maintaned over the years?

If you can answer favourably to at least 3 of the above questions then operating the switch with standing to one side and facing away with a pair of good leather gloves (hand and wrist protection) on and safety glasses would be adequate


First off, what does the relative dirtiness of the equipment have to do with performance at all unless it's say NEMA 1? Nothing. In fact in many industries (oil and gas, iron & steel, mining) dirty is normal, and the incident rates as a whole are not higher than any other industry. In fact at least in U.S. mining, the average injury incident rate is much lower than the general industry average.

Second most plants would have trouble answering these questions, except the first one. Answering questions about installation requirements requires deep inspections or data that simply doesn't exist or is hard to get to. Similarly maintenance data... are you kidding me? Do you actually expect a summary of work order history to be attached to each work order or piece of equipment? I know what you are getting at but we need to be more practical here. OSHA 1910.269 Annex E has a much better suggested list of conditions to look for. I would argue that if the list of inspections cannot be performed by a qualified electrician working on site by visual external inspection alone, it is not a very practical condition. This is why everyone is so afraid of the "normal work" clauses in Z462 and 70E...because they are so wishy washy and poorly written that they basically give no guidance at all.


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