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HVAC Design Criteria and Guidelines
EQUIPMENT, DUCTWORK, AND PIPING SUPPORT
Equipment Support:
1. Floor and Housekeeping Pad Installation: Floor-mounted equipment must always installed on
concrete housekeeping pad (or equivalent). Pads for air-handling units should be 6" high to allow
for drain pan traps, while pads for all other equipment should be 4" high. Equipment should be
anchored and grouted to housekeeping pads.
2. Structural Slab, Pier, or Foundation Installation: Cooling towers, tanks, chillers, and (sometimes)
boilers are typically heavy enough to require a structural slab, pier(s), or foundations for support.
Review each component with the project structural engineer to determine requirements.
3. Suspended Installation: For suspended equipment, structural steel framing to distribute the
imposed operating loads without stressing building structural elements or causing damage to the
building substrate is required This frame, which is then suspended from the building structure with
vibration isolators an appropriately sized all-thread rod, serves an equipment platform.
4. Rooftop Installation: Equipment may be mounted on structural steel supports (the preferred
method) or on continuous roof curb:
a. Structural steel supports must be as detailed on the Drawings and their design requires
the input of a structural engineer. The supports must allow for 36” clear space under the
equipment for roof maintenance and replacement and include appropriate service
walkways and handrails, steps, ladders, etc.
b Continuous roof curbs tops are required to be 17" above roof surface to prevent
leakage into the building in the event of roof flooding. Top of all roof curbs must be level,
with pitch built into curb when deck slopes 1/4 of an inch per foot or greater. Often,
structural steel reinforcement below roof to avoid stressing building structural elements is
required…review with the project structural engineer.
Ductwork Support:
1. Suspended Installation: SW master specifications require that ductwork hangers be fabricated
of sheet metal straps in accordance with SMACNA's HVAC Duct Construction Standards - Metal
and Flexible or of all-thread rod.
a. Section 5 of the SMACNA manual provides numerous details for duct hanger methods
with which the designer should become familiar.
b. Where multiple ducts are routed together, they may by supported by a common
trapeze hanger.
2. Vertical Shaft Installation: Vertical ducts must anchored and supported at each floor. See
Section 5 of the SMACNA manual.
3. Rooftop Installation: Horizontal ductwork installed above a roof must be supported by roof
support rails integrated with the building roof and structural members to both support the weight of
HVAC Design Guidelines
EQUIPMENT, DUCTWORK, AND PIPING SUPPORT
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HVAC Design Criteria and Guidelines
the duct and to provide vertical and horizontal anchoring against wind forces. Consult with the
project structural engineer to determine requirements and provide details on the Drawings.
Piping Support:
1. Suspended Installation: Piping systems and their support are classified as follows:
Classification
Type 1: Hot Systems
Temperature
Range
Type 1A:
120250°F
Type 1B: >250°F
Type
2:
Ambient
Systems
Type 3: Cold Systems
71-120°F
Type 3A: 32-70°F
Type 3B: <32°F
Typical
Service Applications
Hot Water, Low Pressure Steam (15 psig),
Steam Condensate, Low Pressure Boiler
Feedwater
High Pressure Steam (>15 psig), High Pressure
Boiler Feedwater
Condenser Water, Oil, Fuel Gas
Chilled Water, Cooling Condensate Drains,
Condenser Water with Waterside Economizer
Cycle
Liquid And Cold Gas Refrigerant, Chilled Water
with Ice Thermal Storage System
The guide master specifications establish requirements and offer options for each classification of
piping support and the designer must carefully review and edit these specifications to accurately
reflect project requirements.
2. Vertical Shaft Installation: Vertical piping must anchored and supported at each floor. [Note: In
tall, concrete structure buildings, provide expansion devices every other floor to account for long
term “creep” and shrinkage of the structure.]
3. Rooftop Installation: Horizontal piping installed above a roof must be supported by roof support
rails integrated with the building roof and piping supports.
Support in Seismic Zones: Review seismic requirements with the project architect/structural engineer.
See Chapter 55, 2015 ASHRAE Handbook-Applications for design guidance. Responsibility for the
design of manufactured equipment and/or field-fabricated components installed outdoors to
withstand seismic loading, including comprehensive engineering analysis by a qualified
professional engineer, using performance requirements and design criteria specified by the HVAC
designer, should be delegated to the Contractor by the project specifications. This is a very
specialized design process and is typically not within the skill set of most HVAC designers.
[Note: Seismic design criteria may trigger building code requirements for “special inspections” by a third
party for this portion of the work during the construction period.
Support and Bracing for Wind Loads: Responsibility for the design of manufactured equipment
and/or field-fabricated components installed outdoors to withstand wind loading, including
comprehensive engineering analysis by a qualified professional engineer, using performance
requirements and design criteria hereinafter specified by the HVAC designer, should be delegated to
the Contractor by the project specifications. This is a very specialized design process and is typically
not within the skill set of most HVAC designers.
HVAC Design Guidelines
EQUIPMENT, DUCTWORK, AND PIPING SUPPORT
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HVAC Design Criteria and Guidelines
1. Project specifications should require that equipment and/or field-fabricated components installed
outdoors must be fabricated and anchored to the ground or building structure, as applicable, to
withstand a wind load imposed on the largest vertical or projected surface area at the maximum
wind speed dictated by the applicable building code and based on the project location.
2. Outdoor piping and raceway is required to be anchored by using a U-bolt, strap, or other holddown device anchored at each support point.
3. Equipment and other components may be anchored by using structural frames, straps, or other
hold-down devices anchored to foundations, structural supports, or roof curbs, as applicable.
HVAC Design Guidelines
EQUIPMENT, DUCTWORK, AND PIPING SUPPORT
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