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Thread: How close a outdoor tranformer can be installed to a building

  1. #1
    Join Date
    Jan 2006
    Posts
    265

    How close a outdoor tranformer can be installed to a building

    My client asks me how close the utility tranformer can be to their building. They want to put the transformer as close to building as code allows. I have checked NEC450.22 that mentions at least 12in from conbustible materials of the building.

    Any thought is welcome.
    David Lin

  2. #2
    Join Date
    Sep 2006
    Location
    Massachusetts
    Posts
    361

    transformer

    In this area of So. Mass. the pad shall be located at a minimum of 5 feet of clearance, and it must conform to standard GS 0110. The POCO and the municipal inspedtors having jurisdiction shall aprrove the location. My advice is to get in contact w/ your local POCO.

  3. #3
    Join Date
    Nov 2004
    Location
    Las Cruces N.M.
    Posts
    1,090
    Our utility requires 3' from the building to the sides of the transformer without openings, and 6' for working space on the side(s) that open to electrical connectors.

    I looked in the NESC, but couldn't find a reference.

    Jim T

  4. #4
    Join Date
    Dec 2006
    Posts
    13
    There are also rules on padmount transformers (liquid filled) being placed in paths of egress, or a certain number of feet from operable windows, etc. You should definitely check with your local fire marshall, electrical inspector and local utility before installing the transformer near the building.

  5. #5
    Join Date
    Aug 2004
    Location
    Plainfield, IN
    Posts
    889
    How many kva is the transformer (this will give me an idea of how much oil it contains)? Will it contain mineral oil?

    The minimum separation depends on the type of oil, amount of oil in the tank, and how combustible the building is. I'll have more specifics tomorrow at the office.

  6. #6
    Join Date
    Aug 2004
    Location
    Plainfield, IN
    Posts
    889
    If the transformer is your standard utility transformer, the it probably contains mineral oil. Unless the transformer is going to be huge (over 1000 kva), then it probably contains less than 500 gallons of mineral oil. For fire resistant construction, minimum separation is 5 feet, for non-combustible building, min separation is 15 feet, and for combustible construction the min separation is 25 feet.

    This information is from a table in a Cooper Bulletin, and they say the table is a reproduction from the Factory Mutual Guide Loss Prevention Data (LPD) 5-4/14-8.

    Factory Mutual - so it is a requirement from an insurance company. Better check with the building owner's insurance to be sure.

    The serving utility may have their own standards as well, better check with them.

    I can't remember the exact number, but I think the definitions of fire resistant, non-combustible, and combustible construction is located in NFPA 220? I was surprised at how involved it was to determine the type of construction. It goes through each piece of the building assembly and gives requirements on what is considered fire resistant, non-combustible, and combustible.

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