Exhaust fan mounting

[DMartin]

10500 CFM gun range exhaust fan. Mounted to isolator springs but those are mounted to wood runners that are just sitting on rubber mats. Not attached to roof. I know deep inside me this is not good. But engineer is asking for code cite. There is nothing for a one off fan in IMC that I am finding. Manufufacturer made specifically for the application and cannot give a mounting spec. Any suggestions of a mounting code for exhaust fans. I would think this needs to be on curbs just like any other rooftop unit. Would love to post pictures but not sure how.

 

[cda]

10500 CFM gun range exhaust fan. Mounted to isolator springs but those are mounted to wood runners that are just sitting on rubber mats. Not attached to roof. I know deep inside me this is not good. But engineer is asking for code cite. There is nothing for a one off fan in IMC that I am finding. Manufufacturer made specifically for the application and cannot give a mounting spec. Any suggestions of a mounting code for exhaust fans. I would think this needs to be on curbs just like any other rooftop unit. Would love to post pictures but not sure how.

Become a Sawhorse, and you can direct post,,,, Or make it a link, or I think drop box works..

But supporting the forum would be great!!!!! I sign up two more people and I get a toaster.

 

[cda]

10500 CFM gun range exhaust fan. Mounted to isolator springs but those are mounted to wood runners that are just sitting on rubber mats. Not attached to roof. I know deep inside me this is not good. But engineer is asking for code cite. There is nothing for a one off fan in IMC that I am finding. Manufufacturer made specifically for the application and cannot give a mounting spec. Any suggestions of a mounting code for exhaust fans. I would think this needs to be on curbs just like any other rooftop unit. Would love to post pictures but not sure how.

And this will set on top of the roof?

 

[DMartin]

yes its on the roof.

 

[DMartin]

Photos https://www.flickr.com/photos/32042721@N05/

 

[cda]

They don’t have to meet Dorthy code???

Tornado wind standards?

 

[steveray]

I'd go with wind loading....We have seen RTU's sucked off of buildings and end up in the street and we are not super high winds...

 

[DMartin]

We only require being built to withstand 90mph wind load here. And yes that is enough to topple the unit. i can rock it by hand so I am sure this combined with the potential thrust is going to cause issues but the engineer is fighting me on it because they dont want to void the roof warranty by attaching the the roof. Not finding anything in code saying it must be attached though.

 

[Paul Sweet]

How are they waterproofing the duct? IBC Chapter 15 requires roofing materials to be installed in accordance with manufacturer's instructions. These usually bring in detailing at roof penetrations.

Building a curb shouldn't void the warranty if it is done in accordance with the manufacturer's instructions by a roofer certified by that manufacturer. Having a jackleg do it with materials on sale at a big-box store could jeopardize the warranty.

 

[Sifu]

1605.1 requires "buildings and other structures and portions thereof" to resist the loads. Is mechanical equipment a portion thereof? I am pretty shocked at the reluctance to provide anchorage and that the MFR wouldn't have mounting requirements.

 

[DMartin]

finally got Manufacturers to get me a spec together

1605.1 requires "buildings and other structures and portions thereof" to resist the loads. Is mechanical equipment a portion thereof? I am pretty shocked at the reluctance to provide anchorage and that the MFR wouldn't have mounting requirements.

Thanks for the cite. I can use this with the engineer. Manufacturer working on getting me some literature. They are not getting their final until this is resolved and I'm not backing down because I know it is wrong. The engineer I would think would want to resolve this because his name is all over this project.

 

[north star]

@ ~ @

See Section 301.15 in the `15 IMC: "Mechanical equipment, appliances
and supports that are exposed to the wind shall be designed and installed
to resist the wind pressures determined in accordance with the
International Building Code".

@ ~ @

 

[Sifu]

@ ~ @

See Section 301.15 in the `15 IMC: "Mechanical equipment, appliances
and supports that are exposed to the wind shall be designed and installed
to resist the wind pressures determined in accordance with the
International Building Code".

@ ~ @

I knew that was somewhere in the IMC, I just couldn't find it. That is a way more definitive citation. Nail on the head.

 

[tmurray]

When we get in this situation, we nicely ask the engineer to provide the calculations they completed that led them to believe that this will not be an issue, for our records. This is actually how our local professional engineering society told us to deal with these situations.