×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

HVAC equipment dead load

HVAC equipment dead load

HVAC equipment dead load

(OP)
Hello all,

Will looking at a set of prints, architectural, they called for a roof dead load of the HVAC equipment at 4 PSF.
Please correct me if I am wrong here but Pounds Per Square foot is calculated by weight / area in feet. So if the rooftop unit had a weight of 1000 lb and had a dimension of 8’x 5’ the PSF would be 25 PSF.

My question is “Did I calculate something wrong here?” By my calculations I would only be able to install something the size of a residential condenser on this roof.

This is an 8,000 square foot store that’s parts of a strip mall. What am I missing here?
There are currently no mechanical drawings.

Thanks

RE: HVAC equipment dead load

This could be a uniform load over the whole roof for such equipment (it may be anticipating piping, duct work, and that kind of thing rather than a single big unit).  There could also be a concentrated load allowance somewhere in there for the load case you describe.  Might be worth a call to the engineer in question if it's not clear.

RE: HVAC equipment dead load

That's correct - the 4 psf is an overall weight that primarily affects the larger members that support large areas of roof.  

For specific units that weigh higher, there should be some indication on the plans as to where these units can be located - usually with special, stronger framing to support them.  If you don't see anything indicated for the heavier units (like what JStephen suggests) then call the engineer.

RE: HVAC equipment dead load

Best to use the rule of thumb, that anything heavier than a person needs to be specifically agreed with the structural engineer.

RE: HVAC equipment dead load

For a typical retail or commercial bldg design, the assumed 4psf for MEP collateral loads is typical or std. procedure for design of the roof framing. It is because this load (4psf) is blanketed across the entire roof structure that it is actually smaller than the 25psf load that you came up with in your example.

When significantly larger unit weights come into play, such as those frequently encountered with industrial bldg. or industrial platform or mezzanine designs, then the method of collateral load determination must be looked at more closely, and will lean toward the more intuitive method that you used initially (i.e. 25psf).

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now
The Great Project Profitability Debate
A/E firms have a great opportunity to lead the world into the future, but the industry’s greatest asset—real-time data—is sitting wasted in clunky, archaic ERP platforms. Learn how real-time, fully interactive dashboards in a modern ERP allow you to unlock data that will shape the future of the world. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close