In ACCA Manual D duct design, which calculation determines the friction rate used to size a residential duct system?
Duct Design And Sizing
Question · Medium
When sizing residential ducts with Manual D, the friction rate should generally fall within which range to avoid undersized or oversized ducts?
In Manual D, the total effective length (TEL) used to size a duct run is the length of which path?
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How is available static pressure (ASP) determined when designing a residential duct system per Manual D?
Question · Hard
A typical rule of thumb for residential cooling airflow is approximately how many CFM per ton of cooling capacity?
Question · Easy
In Manual D sizing, the equivalent length of a duct fitting represents what?
Which document provides the room-by-room heating and cooling loads that must be completed before a Manual D duct design can be performed?
Once the friction rate and required CFM are known, a duct sizing slide rule or ductulator is used primarily to determine what?
For a given airflow, increasing the cross-sectional area of a duct has what effect on air velocity and friction loss?
To convert a required round duct size to an equivalent rectangular duct that carries the same airflow at the same friction rate, a technician should use which reference?
What is the primary reason an oversized duct system, while quiet, can still be a poor design?
Compared with the friction rate, what does the velocity reduction from the supply trunk to branch runs help control in a well-designed system?
In residential duct design, which return-air strategy generally provides the best comfort and pressure balance?
Why must duct design CFM be calculated room by room rather than only for the whole house?
Which trunk-duct design uses a constant cross-section along its length, requiring balancing dampers at takeoffs to distribute air evenly?
Which sheet-metal duct joint is formed by sliding an S-shaped cleat and a drive cleat to connect two sections of rectangular duct?
Duct Installation And Fittings
Which seam is the common longitudinal corner lock used to form rectangular sheet-metal duct?
When installing flexible duct, which practice helps minimize airflow restriction and pressure loss?
Per common practice and ACCA guidance, the centerline radius of a flexible duct bend should generally be at least how large to limit pressure loss?
A radius (full) elbow versus a square (mitered) elbow with no turning vanes has what effect on pressure loss in a trunk duct?
Turning vanes are installed in which type of fitting to reduce turbulence and pressure loss?
Which takeoff fitting is commonly used to branch a round supply run off the side of a rectangular trunk while minimizing entry turbulence?
A boot fitting in residential duct installation serves what purpose?
When supporting horizontal metal ductwork, hangers should be spaced and sized so that the duct does not do what?
Which tool is used to fabricate a 90-degree groove in rigid fiberglass ductboard so it can be folded into a rectangular duct?
When connecting supply and return ducts to a furnace or air handler, why is a flexible canvas (flex) connector commonly installed at the equipment?
When installing a cooling coil with an upflow furnace, the coil is normally located where relative to airflow?
Why should supply and return plenum transitions avoid abrupt size changes directly at the air handler outlet?
Which hand tool is used to cut and trim sheet metal when fabricating rectangular duct, and is color-coded for straight, left, and right cuts?
A duct transition that changes from one rectangular size to a smaller rectangular size should ideally limit the slope of its sides to about what, to minimize loss?
What does total external static pressure (TESP) measured across an air handler indicate to an installer at startup?
Airflow And Static Pressure
Which instrument is used to measure static pressure in a duct in inches of water column?
Air velocity in a duct is measured to determine airflow; what is the relationship used to convert velocity to volumetric airflow (CFM)?
A pitot-tube traverse takes multiple readings across a duct cross-section primarily to account for what?
The temperature-rise (or temperature-drop) method estimates airflow using the equation CFM = (BTU/h) / (1.08 x temperature difference). The constant 1.08 is derived from which property of air?
If a duct system's measured total external static pressure is higher than the equipment's rated maximum, what is the likely result?
On a PSC (permanent split capacitor) blower motor, increasing duct static pressure has what effect on delivered airflow?
A constant-CFM ECM (variable-speed) blower responds to increased duct static pressure by doing what?
According to the fan laws, if a blower's speed (RPM) is increased by 10%, the airflow (CFM) changes by approximately how much?
When verifying airflow at commissioning, a common minimum target for residential cooling airflow is to avoid going below approximately what value to prevent coil icing?
A return-air drop that is significantly undersized relative to the supply most commonly causes what symptom?
Velocity pressure in a duct is related to air velocity in what way?
Which factor will NOT, by itself, increase a duct system's total external static pressure?
Static pressure readings should be taken at which locations to determine total external static pressure on a typical furnace with a cooling coil?
A flow hood (balometer) placed over a supply register directly measures what?
Which closure material is preferred for sealing rigid sheet-metal duct joints because it remains flexible and does not dry out and fail like ordinary cloth-backed tape?
Sealing And Insulation
Tapes and mastics used to seal flexible air ducts and connectors should be listed to which UL standard?
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