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Thread: Tunnel SUMP PIT Classification

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    Tunnel SUMP PIT Classification

    Hello Folks -
    I am involved in a Tunnel project in NYC. The tunnel is for vehicles and trucks. The subject sump pump pit is in an underground concrete room that contains ventilation exhaust fans and combustible gas detection. Piping from roadway catch basins drain into the sump pit. It is thought that if a vehicle accident occurred that gasoline could also enter the pit.

    The AHJ shows the pit itself and the area 5’ from pit openings classified as C1D1 Grp D. Outside that area as C1D2.

    Comments?

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    Quote Originally Posted by Natfuelbilll View Post
    Hello Folks -
    I am involved in a Tunnel project in NYC. The tunnel is for vehicles and trucks. The subject sump pump pit is in an underground concrete room that contains ventilation exhaust fans and combustible gas detection. Piping from roadway catch basins drain into the sump pit. It is thought that if a vehicle accident occurred that gasoline could also enter the pit.

    The AHJ shows the pit itself and the area 5’ from pit openings classified as C1D1 Grp D. Outside that area as C1D2.

    Comments?
    is it up to the AHJ to make such decisions? If so, I don't see how you can object a whole lot to them.
    Bob

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    It how Would you classify it?

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    Quote Originally Posted by Natfuelbilll View Post
    It how Would you classify it?
    I think their fear that an accident could well end up with gasoline entering the pit is well founded. C1D1 in the pit is thus not an unreasonable thing to require if that actually happens. I would certainly want the pit to be C1D1 if I knew that gasoline was likely to enter the pit in any quantity.

    There will certainly be accidents. Whether any of them is likely to result in spilled gasoline making it to the pit is something else.
    Bob

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    My thoughts too considering risk.

    There however a strong comparison to Art 511.

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    Quote Originally Posted by petersonra View Post
    I think their fear that an accident could well end up with gasoline entering the pit is well founded. C1D1 in the pit is thus not an unreasonable thing to require if that actually happens. I would certainly want the pit to be C1D1 if I knew that gasoline was likely to enter the pit in any quantity.

    There will certainly be accidents. Whether any of them is likely to result in spilled gasoline making it to the pit is something else.
    I'm not sure I would use the term, "well founded". It is a possibility, but I don't know if it's likely, given modern car construction, Hollywood "physics" to the contrary notwithstanding. The usual definition for C1D1 is that the hazard is normally present. If it is only present due to a malfunction or accident, then it would be more properly C1D2.

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    Quote Originally Posted by gadfly56 View Post
    I'm not sure I would use the term, "well founded". It is a possibility, but I don't know if it's likely, given modern car construction, Hollywood "physics" to the contrary notwithstanding. The usual definition for C1D1 is that the hazard is normally present. If it is only present due to a malfunction or accident, then it would be more properly C1D2.
    I think that there is some definition as to how often the condition has to exist in a given year to require it to be C1D1. I seem to recall it is something like ten hours a year. Is it likely that there will be gasoline in the pit more than ten hours a year is maybe the real question to be answered.
    Bob

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    Quote Originally Posted by petersonra View Post
    I think that there is some definition as to how often the condition has to exist in a given year to require it to be C1D1. I seem to recall it is something like ten hours a year. Is it likely that there will be gasoline in the pit more than ten hours a year is maybe the real question to be answered.
    Neither duration nor frequency are part of the Division 1 definition. [Section 500.5(B)(1)]

    Read carefully, root definitions for NEC Divisions are in terms of possibility not probability. IEC Zones allude to, but do not specify exact durations except for “are present continuously” with respect to Zone 0. Otherwise they are vaguely defined in terms of probabilities. NEC Zone definitions are a forced-fit combination of NEC Divisions and IEC Zones.

    The problem is normal is undefined with respect to Hazardous (Classified) Locations. An interesting reference to normal with respect to motors is found in Section 500.8(B)(5).
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

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    Some comments:
    1. Read the Scope of Article 511 carefully; it doesn’t apply to tunnels.
    2. Whether the pit is Division 1 or 2 wouldn’t likely alter the equipment or wiring methods significantly.
    3. I would ask the AHJ what their basis for classification was.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2017 NEC unless otherwise noted.

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