Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Conduit in concrete

  1. #1

    Conduit in concrete

    I have a question on conduit in concrete. Under definition's of "location wet" Installations in concrete slabs are considered a wet location. Does the slab have to be in direct contact with the earth. Is it only called a "slab" if it in direct contact with the earth. If there is concrete on the fourth floor would it be considered a wet location. The conductors are not a concern as most are dual rated. I ask this because for years it has been debated in my code classes. Many say the concrete is wet when poured and that it retains moisture. I say that emt set screw type fittings are listed as concrete tight and are not water tight. I think that there are to many "or's" in the definition. What do you say?

  2. #2
    Join Date
    Dec 2004
    Location
    Fort Collins, CO NEC: 2014
    Posts
    15,472
    I say the fourth floor slab is not a wet location. I think the concrete and masonry are grouped.

  3. #3
    Join Date
    Jan 2008
    Location
    Raeford, NC
    Posts
    3,494
    Quote Originally Posted by HEYDOG View Post
    I have a question on conduit in concrete. Under definition's of "location wet" Installations in concrete slabs are considered a wet location. Does the slab have to be in direct contact with the earth. Is it only called a "slab" if it in direct contact with the earth. If there is concrete on the fourth floor would it be considered a wet location. The conductors are not a concern as most are dual rated. I ask this because for years it has been debated in my code classes. Many say the concrete is wet when poured and that it retains moisture. I say that emt set screw type fittings are listed as concrete tight and are not water tight. I think that there are to many "or's" in the definition. What do you say?
    This is what I have been told by our state inspectors. If the concrete is on grade then it is considered a wet location and unless there is another protective coating on EMT it cannot be use. PVC must be used. Then,as you have stated,if it were on the fourth floor then EMT with the correct connectors can be use with out a protective coating.
    Organized people are people that are just too lazy to look for their stuff

  4. #4
    Join Date
    Aug 2006
    Location
    Miami Fla.
    Posts
    6,894
    Quote Originally Posted by HEYDOG View Post
    If there is concrete on the fourth floor would it be considered a wet location.
    No.

    Location, Wet.
    Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.

  5. #5
    Join Date
    Dec 2006
    Location
    Eastern Oregon
    Posts
    2,729
    Quote Originally Posted by HEYDOG View Post
    I have a question on conduit in concrete. Under definition's of "location wet" Installations in concrete slabs are considered a wet location. Does the slab have to be in direct contact with the earth. Is it only called a "slab" if it in direct contact with the earth. If there is concrete on the fourth floor would it be considered a wet location. The conductors are not a concern as most are dual rated. I ask this because for years it has been debated in my code classes. Many say the concrete is wet when poured and that it retains moisture. I say that emt set screw type fittings are listed as concrete tight and are not water tight. I think that there are to many "or's" in the definition. What do you say?
    I thought only the compression type were concrete tight...?

  6. #6
    Join Date
    Feb 2003
    Location
    San Francisco Bay area
    Posts
    638
    Quote Originally Posted by ceb58 View Post
    This is what I have been told by our state inspectors. If the concrete is on grade then it is considered a wet location and unless there is another protective coating on EMT it cannot be use. PVC must be used. Then,as you have stated,if it were on the fourth floor then EMT with the correct connectors can be use with out a protective coating.
    I disagree [I think...depending upon exactly what you are saying].

    NEC Handbook comment...reciting the UL Guide for Elect. Equipment [White Book] - to paraphrase... Galvanized steel EMT installed in concrete, above grade, generally requires no supplementary corrosion protection.

    This is not about wet, it is about the corrosive effects of concrete...as long as the EMT is steel and galvanized...UL accepts EMT in concrete above grade.

    Regular, uncoated, ungalvanized EMT in concrete would not be permitted...IMO.

    As an inspector, I do not allow regular EMT to be embedded in concrete above grade.

  7. #7
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    19,255
    Quote Originally Posted by dana1028 View Post
    I disagree [I think...depending upon exactly what you are saying].

    NEC Handbook comment...reciting the UL Guide for Elect. Equipment [White Book] - to paraphrase... Galvanized steel EMT installed in concrete, above grade, generally requires no supplementary corrosion protection.

    This is not about wet, it is about the corrosive effects of concrete...as long as the EMT is steel and galvanized...UL accepts EMT in concrete above grade.

    Regular, uncoated, ungalvanized EMT in concrete would not be permitted...IMO.

    As an inspector, I do not allow regular EMT to be embedded in concrete above grade.

    I would say that regular EMT permitted in concrete above grade is permitted. Where are you finding uncoated or non-galvanized EMT?
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

  8. #8
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    19,311
    DYIX.GuideInfo Rigid Ferrous Metal Conduit


    Galvanized rigid steel conduit installed in concrete does not require supplementary corrosion protection.
    Galvanized rigid steel conduit installed in contact with soil does not generally require supplementary corrosion protection.
    In the absence of specific local experience, soils producing severe corrosive effects are generally characterized by low resistivity (less than 2000 ohm-centimeters).
    Wherever ferrous metal conduit runs directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.


    FJMX.GuideInfo Electrical Metallic Tubing


    Galvanized steel electrical metallic tubing installed in concrete on grade or above generally requires no supplementary corrosion protection. Galvanized steel electrical metallic tubing in concrete slab below grade level may require supplementary corrosion protection. In general, galvanized steel electrical metallic tubing in contact with soil requires supplementary corrosion protection. Where galvanized steel electrical metallic tubing without supplementary corrosion protection extends directly from concrete encasement to soil burial, severe corrosive effects are likely to occur on the metal in contact with the soil.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  9. #9
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    19,311
    Quote Originally Posted by dana1028 View Post
    Regular, uncoated, ungalvanized EMT in concrete would not be permitted...IMO.

    As an inspector, I do not allow regular EMT to be embedded in concrete above grade.
    As far as I know there are only two types of EMT on the market, galvanized steel and aluminum.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  10. #10
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    19,255
    Quote Originally Posted by don_resqcapt19 View Post
    As far as I know there are only two types of EMT on the market, galvanized steel and aluminum.
    My thought as well. Regular old steel EMT that I get off the rack at the supply house is permitted in concrete above grade without any additional protection.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •