Free Practice Questions for NCARB PDD Exam

Understanding the Diagram

The diagram shows a 480Y/277V three-phase, four-wire wye-connected system with a neutral (N) and system ground.

480 V = Voltage between any two phase conductors (line-to-line)

277 V = Voltage between any one phase conductor and neutral (line-to-neutral)

Fluorescent Lighting Voltage Requirements

Standard commercial fluorescent lighting systems are typically designed for 277 V operation in the U.S. (in buildings with a 480Y/277V system).

To achieve 277 V, you connect one phase conductor (A, B, or C) to Neutral (N).

This is a single-phase line-to-neutral connection.

Which Conductors to Use?

In the given options, the correct pair must give 277 V.

C, N → 277 V line-to-neutral → Correct for fluorescent lighting.

Other options produce different results:

A, B = 480 V (line-to-line) — too high for fluorescent ballasts.

C, A, B = all three phases — used for three-phase loads, not lighting.

C, A, N — would give two circuits, but includes extra phase unnecessarily for single-phase lighting.

NCARB ARE 5.0 PDD Study Guide References:

Content Area: Electrical Systems — Power Distribution and Circuiting for Lighting

Source References:

Electrical Systems for Architects — Fluorescent lighting voltage selection

MEEB (Mechanical and Electrical Equipment for Buildings) — Chapter on Electrical Service and Lighting Systems

NEC (National Electrical Code) — Voltage to ground for wye-connected systems

Key Point:

For a 480Y/277V wye system, fluorescent lighting should be connected from any phase to neutral for 277 V operation.

The diagram shows a displacement ventilation system. In this system:

Cool supply air (about 65°F) is introduced at floor level at low velocity through floor diffusers.

Warm air rises as it picks up heat from occupants/equipment and stratifies near the ceiling, where it is returned or exhausted.

This creates a stratification layer with cooler, cleaner air in the occupied zone and warmer air above.

This is efficient for comfort, air quality, and energy use in spaces ≤12 ft high.

Why not other options:

A: This system uses a plenum return, not ducted supply and return for both.

C: It is efficient in summer since it uses warmer supply air and reduced fan energy.

D: Individual comfort control is possible via diffuser location/adjustment.

PDD Reference: ARE 5.0 PDD “Mechanical Systems—Air distribution types,” ASHRAE Fundamentals, displacement ventilation diagrams.

Per IBC Chapter 6 and Chapter 7, distillation involving flammable liquids requires a 2-hour fire-resistance-rated fire wall between H-occupancy (hazardous) and assembly use (A-2). Objective 1.3 of the PDD Handbook emphasizes understanding of life safety code implications in space planning.

The owner’s request for review of ASIs (Architect's Supplemental Instructions), RFIs (Requests for Information), RFPs (Requests for Proposals), and change orders relates to contract modifications.

Section 01 26 00 in the project manual typically covers Contract Modification Procedures, including timelines and processes for handling these changes.

AIA Document A201 is the general conditions but does not detail specific timelines.

Supplementary Conditions modify A201 but usually don't detail these timelines.

Section 01 35 16 is specific to alteration projects, not general contract mod procedures.

The arrow in the wall-floor assembly indicates a horizontal structural member attached to a wall, used to support the end of a floor joist. This is called a ledger.

Ledger: Typically a dimensional lumber or engineered wood member fastened to a wall that supports floor framing members (joists).

Fire block: Installed to limit fire spread in concealed spaces—often mid-wall or mid-stud cavity, not in this floor-to-wall position.

Girt: A horizontal framing member in a wall, usually in steel-frame or post-frame construction, not in conventional wood framing for floors.

Lateral shear plate: A metal plate for shear transfer, not applicable here.

PDD References:

ARE 5.0 PDD “Structural Systems—Wood framing details”

IBC §2308.4—Floor framing requirements

AWC (American Wood Council) “Wood Frame Construction Manual” Ledger attachment details

Step-by-Step Reasoning

1. Mezzanine Area Limitations — IBC Section 505.2.1

From the exhibit:

The aggregate area of a mezzanine within a room shall be not greater than one-third of the floor area of that room/space.

Given:

Main floor = 9,000 SF

Maximum mezzanine size = 1/3 × 9,000 SF = 3,000 SF

2. Openness Requirements — IBC Section 505.2.3

From the exhibit:

A mezzanine must be open to the room below unless it qualifies for one of the listed exceptions.

3. Relevant Exception for Enclosed Mezzanine

Exception 1:

Mezzanines (or portions thereof) are not required to be open to the room if the occupant load of the enclosed space is not greater than 10.

Exception 3:

Mezzanines (or portions thereof) are not required to be open to the room if the aggregate floor area of the enclosed space is ≤ 10% of the mezzanine area.

However — the scenario says:

The mezzanine will have one exit (so it’s not an open floor requiring multiple exits)

The architect notes there are adequate exits on the main floor to handle additional occupant load from the mezzanine → This means it could be enclosed if allowed by exceptions.

4. Evaluate Each Option:

A. 2,500 SF open lounge for 20 people

Size < 3,000 SF → OK on area.

Open mezzanine → Complies without needing an exception.

But 20 occupants means more than 10 occupant load, so it can’t be enclosed unless open — this one is already open, so fine.

This works, but the question asks for which method should the architect design, and the key is the one-exit enclosed scenario.

B. 2,750 SF enclosed business center for 15 people

Size < 3,000 SF → OK.

It is enclosed, and occupant load is 15, which is greater than 10. That means Exception 1 doesn’t apply.

But Exception 3 says: enclosed space can be allowed if enclosed area ≤ 10% of mezzanine area. Here:

10% of 2,750 SF = 275 SF.

If the enclosed portion is the business center itself (full area enclosed), then it fails Exception 3.

Wait: This would only be code-compliant as enclosed if the occupant load is ≤ 10 (Exception 1) OR enclosed area ≤ 10% of mezzanine (Exception 3).

This option might work only if the mezzanine is considered enclosed but the occupant load doesn’t require multiple exits and is allowed due to adequate exit capacity on the main floor — this appears to be the intended IBC Exception 1 scenario, but since OL = 15 > 10, it technically fails Exception 1.

The problem statement says “adequate exits available on main floor to pick up additional occupant load” — which would allow designing an enclosed mezzanine as long as total egress capacity is fine.

C. 3,250 SF open dining for 30 people

Size exceeds 3,000 SF → FAILS area limitation. Not allowed.

5. Conclusion

Given the constraints:

Must fit within 1/3 floor area rule (≤ 3,000 SF)

Must work with one exit and available exit capacity on main floor

Option C fails on size

Option A is possible but doesn’t use the enclosed condition in the prompt

Option B meets area limit, occupant load works with available exit capacity, and provides an enclosed use that matches the problem’s “program requirement” scenario

In a tropical climate, the interior is cooler and drier than the hot, humid exterior. The vapor drive is from outside → inside, so the vapor retarder must be installed on the warm/moist side of the assembly, which is below the insulation when the insulation is above the roof deck. This prevents moist exterior air from reaching cooler surfaces inside the insulation where condensation could occur.

PDD Reference: Psychrometrics & vapor drive principles, PDD “Thermal & Moisture Protection—Placement of vapor barriers,” ASHRAE Handbook recommendations.

In subsurface drainage system design:

The shape, size, and slope of drainage lines are selected primarily to achieve a desired flow velocity that prevents sedimentation and clogging but does not cause erosion.

Minimizing or maximizing flow is not the goal; the system must convey the design flow efficiently.

Velocity must be balanced — too low leads to sediment build-up; too high causes pipe damage.

Emergency egress requires minimum 5.7 sq ft clear opening (net).

Double-hung windows’ clear opening is about half the sash area. A 3'×5' nominal size gives ≈ 3×2.5 = 7.5 sq ft gross, ~6.25 sq ft clear → meets code.

North wall placement minimizes direct morning sunlight (vs. east wall).

A: 2'×2' awning → too small and awnings don’t count for egress in most cases.

B: Fixed windows do not meet egress operability requirements.

C: Two 3'×2' casements on east wall → each only 6 sq ft gross, and east wall gets morning sun, opposite client’s goal.

PDD Reference: IBC §1030 Emergency Escape and Rescue; ARE 5.0 PDD “Code compliance—Daylighting control & egress.”