Spiral Duct How Shape and a New Connection Technology

7/30/2019 Spiral Duct How Shape and a New Connection Technology

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Besides improving the energy efciency o

HVAC systems, round ductwork cuts installed

costs and adds aesthetic appeal. New

connection technology plays a key role.

High perormance has reached buzzword status in

the HVAC industry. With energy costs soaring, designers

and speciers are searching or ways to maximize

energy eciency in buildings. The search naturally

leads to consideration o HVAC systems, which account

or around 40 percent o the energy usage in a typical

building. Besides reducing costs, boosting the energy

eciency o HVAC systems helps building owners and

operators meet the latest sustainability requirements

such as those spelled out in LEED1, the internationally

recognized green-building certication system.

O course, one way to meet

sustainability objectives is to

speciy more ecient HVAC

equipment. So when designing

an HVAC system, engineers

oten ocus on the more costly

mechanical components such

as chillers and air handlers.

But theres another part o

the system that has a major

impact on perormance and

eciency: the ductwork.

Thats why todays smart HVAC

system designers and speciers

are careully considering their

ductwork options.

One choice that has much to oer in both new

construction and renovation o commercial buildi

spiral ductwork. Advantages o spiral ductwork inc

ecient air movement and minimal leakage, whic

can help reduce the energy needs o HVAC system

Spiral duct is also relatively inexpensive to install aprovides an aesthetic asset once in place. Many o

these benets are due at least in part to new sel-

sealing connection components that come with s

ductwork made by leading manuacturers.

Shape improveS airflow

In buildings, spiral ductwork can be a major asset t

an HVAC system, which requires power to drive th

or blower unit that moves air through the ductwo

various locations in the building. I the system ails

deliver the proper airfows, building occupants wil

temperature settings up or down more than shou

necessary to meet their comort needs, which in tu

boosts energy use and costs.

Such problems can be lessened by using spiral du

which produces equal internal pressure and allows

and ecient airfows. Studies have shown that rou

duct produces less airfow resistance than rectang

duct, which lowers energy use. With the seam ent

on the outside o the pipe, spiral duct also has a

smooth interior that minimizes riction losses.

www.smcduct.com 2011 Sheet Metal Connectors

Spiral Duct: How shape and a new connection technology

contribute to high-perormance HVAC systems

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Another key airfow issue concerns pressure. Air leaving

an air handler under high pressure drops to lower

pressures as it travels through straight ducts, bends and

diusers to its destination. In typical spiral duct systems,

this pressure drop is less than the one experienced by

air fowing through rectangular ductwork. By

decreasing the drop in air pressure and increasing

airfow e ciency, spiral duct allows the use o smaller,

less powerul and less expensive air-moving units.

minimiZeD air leaKaGe

In addition to airfow, air-duct leakage is a major

concern o building designers and owners. When

ducts leak, HVAC systems require larger and more

expensive ans to produce the required airfow. Ductleaks also make ans and other HVAC equipment work

harder to maintain the desired building temperatures,

increasing energy usage and reducing system

e ciency. Oten, engineers will speciy HVAC syste

with larger and more expensive ans to produce

the required airfow, simply to compensate or duc

leakage. An ine cient duct system can be easy tosee; i it s not sealed properly, blowback will build

outside o the ductwork, which is both ine cient

unsightly. Other undesirable eects o duct leakag

include lower indoor air quality and reduced com

or building occupants.

For these reasons, building designers and specie

strive to produce airtight HVAC systems. By

choosing spiral duct, they can meet or exceed the

highest industry air-leakage standardsi the righ

connection and sealing options are also selected.

Some leading manuacturers o spiral duct oer

special galvanized steel ttings eaturing double-

legged EPDM rubber gaskets that virtually elimina

leakage at connection points.

The gaskets are mechanically xed to the ttings

with a 180-degree hemmed edge, providing adde

rigidity to the ttings, which ensures the gaskets w

remain secure and create a sae rounded edge or

the installer. Unlike conventional sealing alternativ

that require the application o duct sealant to the

joints, these systems create an airtight connection

simply by means o pressure tting, when the end

two duct sections are pressed together. Made usin

lean manuacturing methods and state-o-the-art

equipment to maximize e ciency and minimize

costs, the ttings meet the requirements o ASHRA

and SMACNA Leakage Class 3.

By minimizing air leakage, these advanced sealing

systems reduce the an energy required to move a

downstream through the duct. As a result, they ca

help building owners pursuing LEED certication

optimize or energy perormance credits.

www.smcduct.com

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With the seam

entirely on the

outside of the pipe,

spiral ducts smooth

interior minimizes

friction losses.

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GASKET PROFILE BEFORE AND AFTER INSTALLATION


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eaSier anD leSS eXpenSive inStallation

Besides its per ormance-related eatures, spiral

ductwork oers other advantages that make it a

good choice or HVAC systems. Consider, or example,

the positive impact it can have on the installation

process. Strong

and rigid due to its

lockseam construction,

spiral duct needs

ewer supporting

components such

as stieners and

hangers, cutting both

product and labor

costs. Spiral duct also

requires ewer tools

to installa drill

and some screws.

In comparison,

rectangular duct

requires slips and drives, nuts and bolts, gaskets,

hammers and snips, as well as eld cuts and caulk.

The strength o spiral duct also allows it to be mad

o lighter-gauge, less costly metals than wouldotherwise be required. As a result, spiral duct can b

signicantly lighter than rectangular duct, making

installation easierso much easier, in act, that

sometimes it can be installed by just one person

rather than two.

In addition, spiral duct normally comes in 10-

oot lengths as opposed to ve-oot lengths

or rectangular duct, reducing the number o

connections needed by hal to create a duct syste

and thereby reducing installation time, labor and

equipment. Further savings in all these areas are

realized by users o advanced sel-sealing ttings,

which eliminate the need or caulking transverse

connections.

www.smcduct.com

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Spiral duct is manuactured rom a variety o metals, including

galvanized, stainless steel, aluminum, polyvinyl coated and

paint grip. Spiral duct machines wind a continuous strip

o sheet metal, about six inches wide, locking the edges

together and orming it into a continuous spiral tube. The

our-ply spiral lockseam serves as a continuous reinorcingrib, boosting the pipes crushing resistance to more than twice

that o longitudinal lockseam or welded pipe. The stronger,

more rigid construction also allows long lengths o spiral duct

to be made in a wide range o diameters, rom three to 96

inches and manuactured in lengths rom one to 20 eet.

Common methods o

sealing spiral ductwork

include standard slip-ft

connections which require

the application o caulk or

some other joint sealant.In addition, top ductwork

manuacturers now oer

actory-applied gaskets that eectively seal spiral duct

connections without the use o sealants.

Making spiral duct:

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aeSthetiC aDvantaGeS

The lack o messy caulked slip-t connections also

contributes to the aesthetic appeal o gasketed spiral

duct. When advanced sel-sealing ttings are used, all

sealing is internal, so duct seams are smooth and clean.

This enhances the attractiveness o exposed spiral

duct, which is in avor with designers and architects

because it gives buildings a contemporary look.

Today, spiral ductwork is requently ound in modern

commercial buildings with open-air designs. These

include restaurants, sports acilities, malls, stores and

warehouses. In addition, spiral duct is oten the choice

or public and institutional buildings such as churches,

community centers, hospitals and schools.

Conclusion

Over the last hal-century, spiral ductwork has take

commanding market-share lead in Western Europ

which has long been saddled with relatively high

energy costs. Though not nearly as common in the

U.S., spiral duct is gaining popularity among desig

and speciers struggling to keep up with the lates

trends and requirements complicating the job o

building construction. Current conditions have increa

the need or innovative, high-perormance HVAC syst

that reduce energy use and costs. Spiral ductwork

give users a signicant perormance, installation a

aesthetic edge, especially when it is paired with th

latest sel-sealing connection technology.


About SMC

Sheet Metal Connectors, Inc. is a abricator o standard and custom

commercial and industrial sheet metal products. SMC was ounded in

1969 to supply installers with slip and drive connectors. Since then, SMC

has expanded rom connectors to vane and rail, and urther to roundpipe, rectangular ductwork, spiral pipe and beyond. SMCs state o the art

manuacturing acility provides high quality systems at competitive cost.

A yellow label union shop, Sheet Metal Connectors supplies complete

ductwork systems or the HVAC industry, including, but not limited to,

ductwork, spiral pipe, fttings, custom welding, doublewall duct, dieorm

elbows, slips and drives, oval pipe, etc.

Sheet Metal Connectors, Inc. serves its customers rom two locations:

Minneapolis, Minnesota and Rockord, Illinois. For more inormation, contact

SMC at 763-572-0000 (toll ree: 800-328-1966) or visit www.smcduct.com

www.smcduct.co

5850 Main St. Minneapolis, MN 554

763.572.0000 800.328.19

5601 Sandy Hollow RoRockord, IL 611

815.874.4600 866.504.46

2011 Sheet Metal Connectors,

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Spiral Duct How Shape and a New Connection Technology

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