Specifying Air Handling Units to Endure High Wind Events

Overview

The paper starts with wind categories. On the Saffir-Simpson scale Cat 1 is 74-95 mph, Cat 2 96-110, Cat 3 111-130, Cat 4 131-155 and Cat 5 above 155 mph. Miami-Dade County High Velocity Hurricane Zone (HVHZ) product approval is the certification the paper uses as its benchmark; it covers FBC TAS 201 (impact), TAS 202 (static air pressure) and TAS 203 (cyclic pressure), plus ASTM E8 and E72 material and panel tests.

The second half explains pressure ratings. The roughly 20 HVHZ-certified cabinet designs listed range from 55 psf (146 mph) to 227 psf (301 mph). The psf figure quoted is the design pressure, equal to 67% of the overload pressure. The key caution is that psf does not map directly to mph: the building risk category and equipment elevation from the structural engineer have to be applied.

A table lists HVHZ-rated AHU cabinets from several manufacturers. It helps compare products, but selection depends on site wind speed, risk category and mounting height as well as the rating itself. As a manufacturer publication it does not replace an ASCE 7 calculation; it gives a starting specification for outdoor or rooftop air handlers.

Key points

1. Saffir-Simpson: Cat 1 74-95 mph, Cat 2 96-110, Cat 3 111-130, Cat 4 131-155, Cat 5 >155 mph.
2. Miami-Dade HVHZ approval covers FBC TAS 201 (impact), 202 (static pressure), 203 (cyclic pressure) plus ASTM E8 and E72.
3. About 20 HVHZ-certified designs are rated from 55 psf (146 mph) to 227 psf (301 mph).
4. Rated psf is design pressure, which is 67% of the overload pressure.
5. psf does not map directly to mph; risk category and equipment elevation come from the structural engineer.

Using it in design

• For sites in hurricane or tornado regions, require a wind-pressure rating (psf at design pressure) for outdoor mechanical equipment and derive the required psf from wind speed, risk category and mounting height.
• Add 'windPressureRating_psf' and 'HVHZ approved' fields to the catalog.
• Warn when rooftop AHUs or chillers lack an adequate rating.

Who should read it

Mechanical designers specifying outdoor or rooftop air handlers in hurricane regions.

Related standards

• Florida Building Code TAS 201/202/203
• ASCE 7
• ASTM E72
• ASTM E8

Publication details

Authors

Lee Magill

Publisher

Nortek Air Solutions

Year

2020

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation