Nevada C-1E Sheet Metal Contractor Examination

Under NAC 624.190, which installation is outside the Nevada C-1E sheet metal subclassification?

• AInstalling a patented metal chimney and flue
• BFabricating a stainless-steel commercial steam-table pan
• CFabricating and installing a galvanized supply duct
• DInstalling a packaged rooftop unit that uses refrigeration as an integral part of the sys…

What is the correct relationship among airflow (CFM), average velocity (FPM), and internal cross-sectional area (square feet) in a sheet-metal duct?

• AVelocity equals airflow divided by area (FPM = CFM / sq ft)
• BVelocity equals airflow multiplied by area
• CVelocity equals area divided by airflow
• DVelocity equals airflow plus area

A rectangular galvanized duct measures 24 inches wide by 12 inches high and carries 2,400 CFM. What is the average air velocity?

• A800 feet per minute
• B1,000 feet per minute
• C1,200 feet per minute
• D1,600 feet per minute

A 12-inch inside-diameter round spiral duct carries 1,000 CFM. What is the approximate average velocity?

• A800 feet per minute
• B1,020 feet per minute
• C1,270 feet per minute
• D1,530 feet per minute

A 16-inch by 10-inch rectangular branch must run at 900 FPM. What airflow does that duct carry?

• A800 CFM
• B900 CFM
• C1,000 CFM
• D1,200 CFM

A 20-inch by 12-inch rectangular main carries 1,800 CFM. What is the average velocity?

• A1,200 feet per minute
• B1,440 feet per minute
• C900 feet per minute
• D1,080 feet per minute

Per the 2018 Uniform Mechanical Code Section 601.2, blower-type heating, cooling, and ventilation duct systems shall be sized in accordance with which method?

• AOnly the International Residential Code Appendix M
• BOnly equal-friction charts printed on the fan carton
• CAny shop rule of thumb the installer prefers
• DACCA Manual D, or other approved methods

Under the 2018 UMC commercial length limitation for factory-made flexible air ducts and connectors used as an elbow at a terminal device, what is the maximum permitted length?

• A14 feet
• B25 feet
• C3 feet
• D5 feet

Per the 2018 UMC, plastic air ducts and fittings are limited to which installation and maximum design temperature?

• AGrease ducts serving Type I hoods, 250°F
• BExposed rooftop mains, 180°F
• CAbove-grade supply only, 200°F
• DUnderground installations only, 150°F

What minimum pipe stiffness does the 2018 UMC require for underground PVC plastic air duct when tested in accordance with ASTM D2412?

• A12 psi at 10 percent deflection
• B25 psi at 5 percent deflection
• C4 psi at 5 percent deflection
• D8 psi at 5 percent deflection

In SMACNA-style rectangular low-pressure duct, which transverse joint uses a flat S-slip on the long sides and drive cleats on the short sides?

• AWelded standing seam
• BTDC/TDF 4-bolt flange only
• CCompanion-angle bolted flange
• DS-and-drive (flat S-cleat) joint

Which shop-formed longitudinal seam is the most common lock used on rectangular galvanized HVAC duct?

• APittsburgh lock
• BGrooved lock used only on copper roofing
• CDovetail lock used only on round spiral
• DStanding-seam roof clip

SMACNA duct-design practice recommends keeping the aspect ratio of a rectangular duct at or below which value whenever space allows?

• A8 to 1
• B12 to 1
• C2 to 1
• D4 to 1

A 24-inch by 12-inch duct must deliver 2,500 CFM at 1,250 FPM. Does this size meet that design point?

• AYes; the area is 2.00 square feet and 2,500 ÷ 2.00 = 1,250 FPM
• BNo; a 24-by-12 has only 1.50 square feet
• CNo; 2,500 CFM at 1,250 FPM requires 3.00 square feet
• DYes, but only if the duct is round

When is a square (mitered) rectangular elbow required to have turning vanes for acceptable pressure loss?

• AOnly on return ducts under 400 FPM
• BOnly when the duct is aluminum
• CNever; vanes are decorative only
• DWhen a full-radius (about 1.5D) throat cannot be used and a square throat would otherwise…

What maximum hanger spacing does SMACNA HVAC Duct Construction Standards commonly allow for horizontal rectangular sheet-metal duct, unless a heavier construction table says otherwise?

• A4 feet
• B6 feet
• C10 feet
• D16 feet

How must a duct construction pressure class relate to the system’s design operating pressure?

• AAll ducts may be built to 0.5 inch w.g. regardless of fan rating
• BNegative-pressure ducts have no pressure class
• CThe construction class may be half the design pressure if the fan is downstream
• DThe construction pressure class shall equal or exceed the design operating pressure of th…

Which closure system is the listed method for sealing a UL 181 factory-made flexible air duct?

• AOnly soldering the inner liner
• BOnly sheet-metal screws through the vapor jacket with no sealant
• COrdinary cloth duct tape with no listing mark
• DA UL 181B-listed tape or mastic, plus a listed mechanical fastener

In conventional low-velocity HVAC design, supply mains are typically kept at or below about which velocity to control noise and friction?

• A4,000 feet per minute
• B6,500 feet per minute
• C400 feet per minute
• D2,000 feet per minute

An 18-inch by 8-inch rectangular duct carries 960 CFM. What is the average velocity?

• A1,080 feet per minute
• B1,440 feet per minute
• C720 feet per minute
• D960 feet per minute

Which longitudinal seam is formed by a lockformer as a button-punch snap lock rather than a Pittsburgh pocket?

• AA snap-lock (button-punch) seam that closes by snapping the male edge into a roll-formed…
• BA welded companion-angle flange
• CA standing-seam roof panel clip
• DA soldered flat-lock copper roof seam

A 14-inch by 14-inch square duct carries 1,600 CFM. What is the approximate average velocity?

• A820 feet per minute
• B1,000 feet per minute
• C1,180 feet per minute
• D1,600 feet per minute

When SMACNA requires a metal nosing on internal duct liner, which condition triggers nosing on every leading edge?

• AWhenever velocity exceeds 4,000 FPM, and also on any liner edge that faces incoming unlin…
• BOnly when the liner is 1/2 inch thick
• COnly on return ducts
• DNever; adhesive alone is always enough

If two rectangular ducts carry the same CFM, why does the smaller cross-section increase fan static and noise?

• ASmaller area raises velocity; friction and fitting losses rise roughly with the square of…
• BSmaller ducts always leak less, so the fan unloads
• CVelocity falls in a smaller duct, so only noise falls
• DArea does not affect friction

Which installation practice is required for factory-made flexible duct used as a runout?

• ARoute it through a fire-rated floor as a flexible air connector
• BSupport it only at the two ends on a 20-foot span
• CCompress extra flex into the run to allow future relocation
• DInstall it fully extended, supported, and with a generous bend radius per the listing

Which sheet-metal product listed in the C-1E scope is an air-intake or exhaust opening cover, not a duct fitting?

• AAn S-cleat
• BA drive cleat
• CA Pittsburgh lock
• DA louver (louvre)

Where a galvanized duct penetrates a fire-resistance-rated wall or floor, what additional device is typically required unless a listed exception applies?

• AA fire damper, smoke damper, or combination damper listed for the assembly
• BA canvas vibration connector only
• CAn extra S-and-drive joint in the wall
• DA plastic sleeve

A 20-inch by 16-inch main carries 2,000 CFM. What is the average velocity?

• A1,125 feet per minute
• B1,250 feet per minute
• C750 feet per minute
• D900 feet per minute

Why do fabricators cross-break or bead wide flat sides of rectangular duct?

• ATo convert the duct to a grease duct
• BTo eliminate the need for hangers
• CTo change the internal area used in CFM calculations
• DTo stiffen the panel, reduce oil-canning, and raise the panel’s resonant frequency

Trade practice for joining accessible round metal duct sections is to use at least how many equally spaced sheet-metal screws or rivets at each joint?

• AOne screw at the top only
• BTwo screws 180 degrees apart
• CThree screws or rivets equally spaced
• DTwelve screws regardless of diameter

An 8-inch inside-diameter round branch carries 400 CFM. What is the approximate average velocity?

• A650 feet per minute
• B800 feet per minute
• C1,150 feet per minute
• D1,800 feet per minute

Which material is the most common shop standard for comfort HVAC rectangular duct on a Nevada C-1E job?

• ALead sheet
• BType I grease-duct stainless used for every return
• CUncoated black iron with no zinc
• DLockforming-quality galvanized steel (typically ASTM A653)

A 10-inch by 10-inch square duct carries 800 CFM. What is the approximate average velocity?

• A800 feet per minute
• B960 feet per minute
• C1,150 feet per minute
• D1,440 feet per minute

A Type B gas vent may be used to vent which appliances?

• AListed gas appliances with draft hoods, or other gas appliances listed for Type B vents
• BWood-burning fireplaces
• CCoal-fired boilers
• DOil-fired appliances that are not listed for Type B

Which factory-built vent is listed for certain oil-fired appliances and typically uses a stainless-steel inner wall?

• AType B-W wall-furnace vent only
• BA single-wall stove pipe with no listing
• CType B aluminum-inner gas vent
• DType L vent (UL 641)

Which vent type does 2018 UMC Table 802.4 require for a listed vented gas wall furnace?

• AType B-W gas vent
• BType L oil vent only
• CAn unlisted masonry chimney with no liner
• DA plastic Category IV vent

Per 2018 UMC Section 802.6.2.2, Type B and Type L vents shall extend in a generally vertical direction with offsets not exceeding which angle, except that one offset of which larger angle is permitted?

• A60 degrees, with one 90-degree offset permitted
• B90 degrees with no limit on the number of offsets
• C30 degrees, with one 45-degree offset permitted
• D45 degrees, with one 60-degree offset permitted

For draft-hood appliances, the 2018 UMC limits the total horizontal distance of a Type B or L vent plus its horizontal connector to what fraction of the vent’s vertical height?

• A25 percent
• B50 percent
• C75 percent
• D150 percent

What is the 2018 UMC minimum upward slope of a gas-appliance vent connector toward the vent or chimney?

• ALevel is acceptable if the connector is short
• B1/8 inch per foot
• C1/4 inch per foot
• D1/2 inch per foot

What is the 2018 UMC minimum vertical height of a Type B or Type L gas vent above the highest connected appliance draft hood or flue collar?

• A12 feet
• B2 feet
• C5 feet
• D8 feet

What is the 2018 UMC minimum vertical height of a Type B-W gas vent above the bottom of the wall furnace it serves?

• A5 feet
• B8 feet
• C12 feet
• D15 feet

Using 2018 UMC Table 803.1.2(2), a single 120,000 Btu/h Category I appliance needs a 5-inch Type B vent at 10 feet of height and 5 feet of lateral. If three 90-degree elbows are required, what capacity adjustment does the UMC commentary method apply, and what happens to the vent size?

• ADouble the diameter for every elbow
• BIncrease tabulated capacity 10 percent and keep the 5-inch vent
• CReduce tabulated capacity 10 percent, which in the published example forces a 6-inch vent
• DIgnore elbows; tables already include any number of 90s

A gas vent larger than 12 inches, or any gas vent less than 8 feet from a vertical wall, shall terminate not less than which heights?

• A10 feet above grade regardless of the roof
• B1 foot above the roof only, with no wall rule
• C2 feet above the highest roof-penetration point and 2 feet above any portion of a buildin…
• D6 inches above the shingles

Per 2018 UMC Section 802.6.1.5, a gas vent that passes through a roof shall terminate with which device?

• AA masonry chimney pot scavenged from another job
• BAn open pipe with no cap
• CA listed vent cap or listed roof assembly
• DA window screen stuffed into the end

Per 2018 UMC Table 802.4, which venting systems may serve a Category I gas appliance?

• AType B gas vent, a chimney, single-wall metal pipe, or a special gas vent
• BType B-W only
• CAn unlisted PVC sewer pipe
• DA Type I grease duct