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 Post subject: Class 1 Division 1 non-permissible MCC
PostPosted: Tue Nov 23, 2010 11:26 am 

Joined: Mon Aug 06, 2007 10:21 am
Posts: 35
Location: Ellijay, GA
I had a customer ask me if there is an impact on PPE levels, distances or any of that if the electrical device is a non-permissible MCC in a Class 1 Division 1 environment. The question is related to IR thermography in that environment.

I would be inclined to believe that equipment would not be allowed to be exposed in that environment, but I'm not sure. Does anyone know?


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PostPosted: Thu Dec 02, 2010 10:18 am 
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Location: Connecticut
Class 1 is limited to 30 volts and 1000 va. (NEC 725.41), so I don't see how this applies to your question about PPE levels. :confused: If you are refering to Class I, Division 1 thats a different issue. The electrical equipment and devices are in explosion proof housings and shouldn't be exposed to the hazardous environment until the (confined) space is purged, tested and monitored before the devices are opened for the IR survey.


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PostPosted: Thu Dec 02, 2010 10:44 am 
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Joined: Mon Mar 29, 2010 11:52 am
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Location: Yankton SD/ Lead SD
For Cl 1 Div 1 locations you could install IR viewing ports on the equipment. Or you could possibly de-energize the equipment, depending on the processes that the MCC buckets control. You should not lose any appreciable heat in the short time frame between de-energizing and scanning.


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PostPosted: Thu Dec 02, 2010 9:07 pm 
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geh7752 wrote:
Class 1 is limited to 30 volts and 1000 va. (NEC 725.41), so I don't see how this applies to your question about PPE levels. :confused: If you are refering to Class I, Division 1 thats a different issue. The electrical equipment and devices are in explosion proof housings and shouldn't be exposed to the hazardous environment until the (confined) space is purged, tested and monitored before the devices are opened for the IR survey.


Confined space? Where is that mentioned in the original scenario? Just wonderrin...

One of the things to be cautious of when doing an IR scan in a Class 1 Div 1 area, would to also ensure that any UV/IR Fire Detectors in the area are bypassed... Not doing so, could result in an unexpected shutdown.


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PostPosted: Thu Dec 02, 2010 9:09 pm 
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cbauer wrote:
For Cl 1 Div 1 locations you could install IR viewing ports on the equipment. Or you could possibly de-energize the equipment, depending on the processes that the MCC buckets control. You should not lose any appreciable heat in the short time frame between de-energizing and scanning.


Not sure on how much recertifying of the equipment you'd have to do by adding the IR windows. Unless the manufacturer has a procedure and the products, modifyin a Div 1 MCC could be rather costly..


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PostPosted: Mon Dec 06, 2010 10:36 am 
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glen1971 wrote:
Confined space? Where is that mentioned in the original scenario? Just wonderrin...

One of the things to be cautious of when doing an IR scan in a Class 1 Div 1 area, would to also ensure that any UV/IR Fire Detectors in the area are bypassed... Not doing so, could result in an unexpected shutdown.


Poor chioce of words I guess. I was refering to areas that explosing proof equipment is required. BTW... Isn't it class I not class 1? :confused:


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PostPosted: Mon Dec 06, 2010 9:06 pm 
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geh7752 wrote:
Poor chioce of words I guess. I was refering to areas that explosing proof equipment is required. BTW... Isn't it class I not class 1? :confused:


For Electrical Area Classifications:

Class I, Div. 1 - Where ignitable concentrations of flammable gases, vapors or liquids are present within the atmosphere under normal operation conditions.

Class I, Div. 2 - Where ignitable concentrations of flammable gases, vapors, or liquids are present within the atmosphere under abnormal operating conditions.

Class II, Div. 1 - Where ignitable concentrations of combustible dusts are present within the atmosphere under normal operation conditions.

Class II, Div. 2 - Where ignitable concentrations of combustible dust are present within the atmosphere under abnormal operating conditions.

Class III, Div. 1 - Where easily ignitable fibers or materials producing combustible flyings are present within the atmosphere under normal operation conditions.

Class III, Div. 2 - Where easily ignitable fibers or materials producing combustible flyings are present within the atmosphere under abnormal operating conditions.

NOTE: Note in Canada there is no Div. 1 or Div. 2, but instead they are Zone 0, 1, and 2. Also , sorry for the assumption that everyone knew that the number 1 and the Roman Numeral I were the same thing...

For Wiring Methods:

Class 1 circuit is where the failure to operate of a remote-control circuit to a safety control device will introduce a direct fire or life hazard.

Class 2 circuits are considered inherently safe from a point of view of shock and fire initiation. Wiring methods are generally more lenient than other types of wiring.

Class 3 circuits, with higher voltage and power limits, are still considered safe from a fire initiation perspective but may present a shock hazard.

Hope that clears it up.... :)


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PostPosted: Wed Dec 08, 2010 11:35 am 
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geh7752 wrote:
Poor chioce of words I guess. I was refering to areas that explosing proof equipment is required. BTW... Isn't it class I not class 1? :confused:


You are correct.

Hazardous locations are categorized into Class I (gases, vapors and liquids), Class II (dust) and Class III (fibers/flyings) locations. These are defined in NEC chapter 5 - Special Occupancies.

Remote control, signaling or power-limited circuits are categorized as Class 1, 2 and 3 circuits and are defined in NEC article 725.


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PostPosted: Wed Dec 08, 2010 2:40 pm 
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Location: Scottsdale, Arizona
Here is an article I wrote about classified locations a few years back. Might be helpful. [url="http://www.brainfiller.com/documents/JimPhillipsPEHazardouslocations.pdf"]Classified Locations Article[/url]

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