Test Question disagreement

Test Question disagreement

  • (A) Class I, Div 1

    Votes: 9 90.0%
  • (B) Class I, Div 2

    Votes: 1 10.0%
  • (C) Class II, Div 1

    Votes: 0 0.0%
  • (D) Class II, Div 2

    Votes: 0 0.0%

  • Total voters
    10
  • Poll closed .

BPoindexter

Inactive, Email Never Verified
Location
MT Vernon, WA
Division 1 the ignitable concentration of flammable gases, vapors or liquids can exist all of the time and is anticipated that they are there all of the time. A higher design safety factor must be in place.

Division II the ignitable concentration of flammable gases, vapors or liquids are not likely to be present but intermittently they can be. Lower design safety factor.


Try reading the question as a two separate parts; A location in which hazardous concentrations of flammable vapors exist intermittently is designated as

Division 1 ignitable concentration always anticipated to be present. Higher safety factor required.

Division 2 vapors should never be present, only under intermittent conditions. Lower safety factor required.


Both scenarios are under normal conditions; Division 1 anticipated to be there all of the time, Division 2 not anticipated to be present all of the time, except intermittently.
You are rewording the NEC language and thus changing the meaning. Under normal conditions does not translate to always present or always anticipated to be present. That may be the case but is not necessarily true. Zone classification for instance makes the distinction between Zone 0 (always present) and Zone 1 (can exist under normal operations). In our classic system both are C1D1.

"Under abnormal conditions" in no way translates to "intermittent". In fact I would say just the opposite. Abnormal condition would be be a relief valve lifting, a spill, valve stem leaking, etc. You last statement is a direct contradiction of the NEC in that you state Div 2 is under "Normal" conditions. The code specifically states that it is under "Abnormal" conditions.

In the end it is up a to PE to make that determination using the appropriate API and IEEE standards. There is no way that I as an electrician or inspector would take on that responsibility or liability.
 
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Gregg Harris

Senior Member
Location
Virginia
You are rewording the NEC language and thus changing the meaning. Under normal conditions does not translate to always present or always anticipated to be present. That may be the case but is not necessarily true. Zone classification for instance makes the distinction between Zone 0 (always present) and Zone 1 (can exist under normal operations). In our classic system both are C1D1.

"Under abnormal conditions" in no way translates to "intermittent". In fact I would say just the opposite. Abnormal condition would be be a relief valve lifting, a spill, valve stem leaking, etc. You last statement is a direct contradiction of the NEC in that you state Div 2 is under "Normal" conditions. The code specifically states that it is under "Abnormal" conditions.

In the end it is up a to PE to make that determination using the appropriate API and IEEE standards. There is no way that I as an electrician or inspector would take on that responsibility or liability.
Where do you think the classifications come from that are created by and listed by OSHA and printed in the NEC .What I posted is the design criteria that each of those classifications are based on. What happen under normal operation for each catagory, Category 1 the ignitable concentration is anticipated to be there. Division 2 it is not expected to be there.
 

Smart $

Esteemed Member
Location
Ohio
Where do you think the classifications come from that are created by and listed by OSHA and printed in the NEC .What I posted is the design criteria that each of those classifications are based on. What happen under normal operation for each catagory, Category 1 the ignitable concentration is anticipated to be there. Division 2 it is not expected to be there.
...and intermittent under normal operating conditions is saying the presence of ignitable gases is expected. Whether present at one instance and not at another, i.e. intermittent, is moot. Continuous presence is not required for it to be Division 1.
 

BPoindexter

Inactive, Email Never Verified
Location
MT Vernon, WA
Where do you think the classifications come from that are created by and listed by OSHA and printed in the NEC .What I posted is the design criteria that each of those classifications are based on. What happen under normal operation for each catagory, Category 1 the ignitable concentration is anticipated to be there. Division 2 it is not expected to be there.
What design criteria are you are basing this on? API? That is playing semantics- saying that Div 2 is not there under normal condions vs present under abnormal conditions, and then defining that as intermittent.
 
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KentAT

Senior Member
Location
Northeastern PA
Where do you think the classifications come from that are created by and listed by OSHA and printed in the NEC .What I posted is the design criteria that each of those classifications are based on. What happen under normal operation for each catagory, Category 1 the ignitable concentration is anticipated to be there. Division 2 it is not expected to be there.
You are saying that OSHA created the hazardous area classifications and that the NFPA merely prints what OSHA comes up within their NFPA 70 (National Electric Code) Standard?
What basis do you have for this statement?

You need to read this http://www.osha.gov/doc/outreachtraining/htmlfiles/hazloc.html, which is an OSHA Outreach Training Publication, wherein OSHA offers their explanation to the classification system used by the NEC.

As you read the whole thing, please make particular note of the last paragraph in OSHA's publication:

The National Electrical Code is the "Bible" of the Electrical Industry, and the primary source of reference for hazardous locations. The NEC is also the basis for OSHA standard 1926.407, Hazardous (Classified) Locations. There are several OSHA standards that require the installation of electrical wiring and equipment in hazardous (classified) locations according to the requirements of Subpart K, Electrical. The NEC should be consulted as a supplement to the OSHA standards for additional background information concerning hazardous locations.
 
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Gregg Harris

Senior Member
Location
Virginia
You are saying that OSHA created the hazardous area classifications and that the NFPA merely prints what OSHA comes up within their NFPA 70 (National Electric Code) Standard?
What basis do you have for this statement?

You need to read this http://www.osha.gov/doc/outreachtraining/htmlfiles/hazloc.html, which is an OSHA Outreach Training Publication, wherein OSHA offers their explanation to the classification system used by the NEC.

As you read the whole thing, please make particular note of the last paragraph in OSHA's publication:

The National Electrical Code is the "Bible" of the Electrical Industry, and the primary source of reference for hazardous locations. The NEC is also the basis for OSHA standard 1926.407, Hazardous (Classified) Locations. There are several OSHA standards that require the installation of electrical wiring and equipment in hazardous (classified) locations according to the requirements of Subpart K, Electrical. The NEC should be consulted as a supplement to the OSHA standards for additional background information concerning hazardous locations.

I have read it on several occasions, perhaps I should have wrote "in conjunction with".
It still does not change the Division of the question. Perhaps changing the wording in the question from intermittent to "occasional" would make it easier to trace the answer to the NEC code section for division II.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
I have read it on several occasions, perhaps I should have wrote "in conjunction with".
It still does not change the Division of the question. Perhaps changing the wording in the question from intermittent to "occasional" would make it easier to trace the answer to the NEC code section for division II.
If the flammable concentration is expected to exist under normal operating conditions, then the area is Division 1. It does not matter how long or how often that concentration is at or above LEL.
 
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