Under NAC 624.380, which work is authorized for a Nevada C-21C sheet metal contractor but expressly excluded from the classification?
Ducts
Question · Easy
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Short
Why is lock-forming-quality galvanized steel the usual material for low-pressure HVAC supply and return ducts under UMC 2018 Chapter 6?
What is the relationship used to size HVAC duct airflow from a known cross-section and velocity?
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Which longitudinal seam is the standard shop-formed lock on rectangular galvanized HVAC duct?
On a low-pressure rectangular HVAC duct, which pair of fittings makes the ordinary transverse joint?
Six feet: a hard-hat anthem
Factory-made flexible air ducts used on a UMC 2018 HVAC system must be listed and labeled to which standard?
A C-21C installer is connecting a return-air duct to a central HVAC unit. From which of the following spaces does UMC 2018 prohibit taking return air?
Under UMC 2018 Section 603.4, factory-made flexible air ducts shall not do which of the following?
On an externally insulated cooling-supply duct, where is the vapor retarder installed?
When a galvanized HVAC duct passes through a fire-resistance-rated wall or floor, UMC 2018 requires which device unless an exception applies?
A 12-inch by 12-inch rectangular supply duct carries air at 800 feet per minute. What is the airflow?
Question · Medium
A 16-inch by 12-inch rectangular duct is designed for 900 feet per minute. What is the airflow?
On a nonresidential UMC 2018 HVAC job, what is the maximum length of a factory-made flexible air duct or connector?
A C-21C mechanic wants to use a 6-foot piece of UL 181 flex to make a 90-degree turn in a commercial supply main instead of a rigid square elbow. Does UMC 2018 allow that?
UMC 2018 limits the temperature of air conveyed in a factory-made air duct to not more than which value?
Unless it is installed as a liner inside concrete, tile, or metal pipe, a factory-made air duct must be kept at least how far from earth?
UMC 2018 prohibits using factory-made air ducts as vertical risers in air-duct systems that serve more than how many stories?
Under SMACNA HVAC Duct Construction Standards, Seal Class A requires sealing of which locations?
SMACNA recommends keeping the aspect ratio of a rectangular HVAC duct at or below which value when practical?
Why are turning vanes installed in a square-throat rectangular HVAC elbow?
How must a round metallic HVAC duct joint be mechanically fastened under the UMC/SMACNA practice used on the C-21C exam?
A C-21C shop is fabricating a domestic clothes-dryer exhaust. What construction does UMC 2018 require?
Where is fibrous glass duct liner prohibited?
When would a C-21C shop select TDC/TDF four-bolt flanges instead of S-slips and drive cleats?
Materials exposed within a ceiling or air-handling plenum used as an HVAC air path must generally meet which surface-burning limits?
A listed fire damper is installed in a galvanized supply duct at a 1-hour wall. What else must the C-21C installer provide?
A 20-inch by 10-inch rectangular duct carries air at 1,000 feet per minute. What is the airflow, rounded to the nearest CFM?
Question · Hard
A commercial supply main must deliver 2,400 CFM at a design velocity of 800 fpm. Which rectangular size provides that area?
What is the cross-sectional area of a 14-inch inside-diameter round duct, and the airflow at 1,000 fpm?
A 10-inch inside-diameter round branch is designed for 900 fpm. What is the airflow, rounded to the nearest CFM?
A specification calls for SMACNA 2-inch w.g. positive-pressure class on a rectangular supply main. What does that require of the C-21C fabricator compared with 1/2-inch w.g. class?
UMC 2018 requires duct-leakage testing of some installed HVAC systems. Which document is the referenced test method for that work?
A 2.00-square-foot supply main can be built as 24 × 12 or as 36 × 8. Why is 24 × 12 the better C-21C choice at the same CFM?
What is a Type B gas vent?
Chimneys Flues Vents
Which chimney and flue items are inside the Nevada C-21C sheet-metal scope?
A factory-built or masonry chimney for a residential-type or low-heat appliance must terminate how, relative to the roof and nearby construction?
What is the ordinary clearance from a listed Type B gas vent to combustible construction?
What is the ordinary clearance from single-wall metal vent-connector pipe to combustible construction?
A vent connector shall be installed without dips or sags and shall slope toward the vent or chimney not less than which amount?
A Type L vent is the listed product intended primarily for which appliances?
May a C-21C installer use Type B gas vent as the chimney for a wood-burning stove?
A mechanical-draft venting system shall terminate not less than 3 feet above a forced-air inlet that is located within what horizontal distance?
A factory-built metal chimney installed under C-21C must be listed to which standard and installed how?
What is the usual limit on the horizontal length of a single-wall vent connector serving a natural-draft appliance?
A listed gas-fired water heater and a listed gas furnace share a common Type B vent. Which statement is correct under UMC 2018?
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