Tips for locating a RTU

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9 comments

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    Jorge De La Rosa

    ARE-Wise, I wouldn’t know how to answer it. Real life-wise, I can tell you that the structural grid guides the location first to make sure the roof structure and columns can support it. Then, aesthetically, you don’t want it too close to edge of the roof because it may mean you need to increase the height of parapets ($) or build screenwalls to block it from the road (visually). Wind direction have never been an issue to me...maybe engineer would care about the rotation, but I have never heard of prevailing winds being an issue.

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    Joseph Osborn

    You also don't want to locate the outside air intake near a plumbing waste vent/ stack.

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    ANGELA FERRIGAN

    I think wind direction probably impacts it based on where the waste vent/stack is located. I'm trying to remember if there was a structural grid shown on the roof plan, but I don't think there was. I'll definitely check for it if it shows up again. Anyway, thanks for the help!

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    Anson Nickel

    Be wary of adjacent building heights. Most codes will have some guidance on distance from a lot line (ie - 10'-0" from a side lot line). I would think that the best placement would be away from vents, away from side lot lines, far enough away from front lot line to minimize visual impact, and close to any designed vertical shafts.

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    Luis Vargas

    The RTU needs to be 10' away from any dangerous level difference (edge of the roof).

     

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    ANGELA FERRIGAN

    Anson and Luis, can you tell me where I can find that information? There might be other helpful info within the same resource.

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    Anson Nickel

    Code-wise: https://codes.iccsafe.org/public/document/IMC2015/chapter-5-exhaust-systems



    Zoning-wise: Dependent on municipality.

    Fire-code: Dependent on municipality.

     

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    Kevin Griendling (Edited )

    Angela,

    The 10' away from parapet is actually in Chapter 10 - Means of Egress, even though on the roof it isn't technically an egress component. It is for fall protection. Section 1015 outlines all of the requirements for guards along your entire egress path, and roof fall protection basically follows the same guidelines and requirements. It is important to note the exception though. You can either have a 42" parapet, or add guard rails, or even add anchors for fall protection harnesses requiring neither a tall parapet nor a guard rail. The choice is yours.

    Make sure to read the entirety of section 1015 to truly understand it.

    IBC 2015

    Guards shall be provided where various components that require service are located within 10 feet (3048 mm) of a roof edge or open side of a walking surface and such edge or open side is located more than 30 inches (762 mm) above the floor, roof or grade below. The guard shall extend not less than 30 inches (762 mm) beyond each end of such components. The guard shall be constructed so as to prevent the passage of a sphere 21 inches (533 mm) in diameter. 

    Exception: Guards are not required where permanent fall arrest/restraint anchorage connector devices that comply with ANSI/ASSE Z 359.1 are affixed for use during the entire roof covering lifetime. The devices shall be reevaluated for possible replacement when the entire roof covering is replaced. The devices shall be placed not more than 10 feet (3048 mm) on center along hip and ridge lines and placed not less than 10 feet (3048 mm) from the roof edge or open side of the walking surface.
     
    All the best,
     
    Kevin Griendling, AIA
     
    edit: I only read the tail end of this conversation, so I focused on fall protection not RTU location. Well good news is, you now understand both!
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    ANGELA FERRIGAN

    Thanks everyone! Very helpful!

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