NEBB Testing, Adjusting and Balancing Certified Professional (CP) flashcards
NEBB Testing, Adjusting and Balancing Certified Professional (CP) · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fan law: flow vs speed
- Airflow (cfm) varies directly with fan speed (rpm) when system resistance and air density remain constant; doubling speed doubles flow.
- Fan law: pressure vs speed
- Fan static or total pressure varies with the square of fan speed; doubling speed quadruples pressure, assuming constant density and system.
- Fan law: power vs speed
- Fan brake horsepower varies with the cube of fan speed; doubling speed increases power eightfold, so verify motor capacity before speed changes.
- Pump affinity laws
- For a centrifugal pump, flow varies directly with speed, head with speed squared, and power with speed cubed, similar to fan laws but for water.
- Velocity pressure formula
- Velocity pressure (in. w.c.) equals (velocity in fpm divided by 4005) squared for standard air at 0.075 lb/ft³ density; solve for velocity as 4005 times square root of VP.
- Pitot tube traverse
- A grid of velocity pressure readings across a duct cross-section, taken at equal-area points, averaged to determine average velocity and airflow; requires straight duct length.
- Balancing hood
- A flow capture device placed over an air terminal to measure cfm directly; accuracy typically ±3% of reading when properly sealed and sized.
- Proportional balancing method
- A systematic technique that adjusts dampers to achieve design flow ratios at each terminal without repeated full-system measurement, starting with the farthest terminal.
- Air density correction
- Velocity and static pressure readings must be corrected for actual air density using temperature and barometric pressure to obtain true airflow in cfm.
- Fan total pressure
- The algebraic difference between total pressure at the fan outlet and total pressure at the fan inlet; used to determine fan performance and motor load.
- Fan static pressure
- Fan static pressure equals fan total pressure minus velocity pressure at the fan outlet; it represents the static resistance the fan must overcome.
- System effect
- The loss of fan performance caused by adverse inlet or outlet conditions, such as elbows or obstructions near the fan, not accounted for in catalog ratings.
- Duct leakage test
- A pressure test of ductwork at a specified static pressure to measure leakage cfm; acceptance criteria are based on leakage class and duct surface area.
- SMACNA leakage class
- A standard classification of allowable duct leakage in cfm per 100 square feet of duct surface at a given test pressure, used to specify and verify duct tightness.
- Terminal unit balance
- Adjusting the damper or reheat coil of a terminal box to achieve design airflow; verify minimum and maximum settings and control sequence operation.
- VAV box minimum flow
- The lowest airflow setpoint for a variable air volume terminal, typically set to maintain ventilation and avoid coil freeze; measured during balancing.
- Water flow measurement
- Use a calibrated flow meter or pressure differential across a known device (valve, coil, orifice) to determine gpm; verify with pump curve and balance valve settings.
- Balance valve
- A valve with a calibrated orifice and pressure ports used to measure and set water flow; its setting is recorded and locked after balancing.
- Coil pressure drop
- The difference in water pressure across a coil, used with the manufacturer's curve to determine water flow; also indicates fouling or air binding.
- Pump curve
- A graph of pump head versus flow at a given speed; the operating point is where the pump curve intersects the system resistance curve.
- System resistance curve
- A curve showing pressure loss versus flow for a piping or duct system; it rises with the square of flow and determines the pump or fan operating point.
- Static pressure setpoint
- The duct static pressure maintained by a supply fan controller, typically measured two-thirds down the main duct; used to control fan speed in VAV systems.
- Duct static pressure profile
- A series of static pressure readings along a duct run used to locate restrictions, verify fan performance, and confirm design pressure at terminals.
- Temperature difference test
- Measurement of entering and leaving air or water temperatures across a coil to verify capacity and sensible/latent performance during TAB.
- Outside air measurement
- Determination of outdoor air intake airflow using pitot traverse, flow station, or hood; critical for ventilation compliance and building pressure control.
- Building pressure control
- Adjusting relief or exhaust airflow to maintain a slight positive pressure (typically 0.02–0.05 in. w.c.) relative to outdoors, preventing infiltration.
- Exhaust fan balance
- Setting exhaust airflow to design values by adjusting dampers or fan speed, while coordinating with makeup air to avoid negative building pressure.
- Return air plenum
- A ceiling cavity used as a return air path; balancing requires measuring return grille flows and ensuring plenum pressure does not cause leakage.
- Test instrument calibration
- Verification of measurement devices against a known standard before and after TAB; records must be traceable and within manufacturer's accuracy tolerance.
- TAB report contents
- Documentation of design versus measured values for airflow, water flow, pressure, and temperature, plus instrument calibration records and deficiency list.
- Pre-balance checklist
- Verification that fans run correctly, filters are clean, dampers open, controls operational, and design conditions exist before starting balancing measurements.
- Proportional balance ratio
- The ratio of measured airflow to design airflow at each terminal; dampers are adjusted so all ratios are equal, then the system is set to design.