Air Balancing 4th year ILM 110405d Flashcards
What does HVAC stand for?
Heating ventilation and air-conditioning
What is the purpose of testing adjusting and balancing for HVAC?
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To make sure that air is delivered efficiently,quietly and safely throughout a building.
This instrument has an inner tube an outer tube measuring air pressures. What is it?
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A pitot tube
What readings does the velometer measure?
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Air velocities inside heating and venting ducts
What are the two types of anemometers used?
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Thermal and Rotating vane
The thermal anemometer uses what to help measure air velocity?
A method of measuring air velocities by measuring heat transfer from a small wire or film immersed in the air.
The rotating vane anemometer uses what to help measure velocity?
(Propeller) A rotating vane anemometer uses a small propeller-like device, also called a vane, to measure the velocity and direction of airflow.
What is another name for a Balometer?
A capture hood or a flow hood.
What is the benefit of using a Balometer?
Accurate measurement: Balometers are highly accurate instruments that provide precise measurements of air volume flow rate. This can be particularly important in HVAC systems, where accurate airflow control is essential for occupant comfort and energy efficiency.
Define static pressure.
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Potential energy at rest or busting pressure in a duct system
Define Total pressure.
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Is the sum of all the energy exerted by the airstream. This energy is exerted by static pressure and the velocity of the air.
Define Velocity pressure.
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Directional pressure or pressure exerted by the airstream in the direction in which it is flowing
When taking duct traverse readings, what is the recommended distance away from an
elbow or transition?
Make sure the duct is straight and about 6 duct diameters to 10 duct diameters downstream from any elbows,transitions or branches.
What is the minimum number of readings that is required for a proper duct traverse?
The minimum number of readings for any duct is 12.
Where should the pitot tube be pointed when taking air flow readings?
The pitot tube tip should always be pointing into the airstream.
Why is it important for the capture hood to fully cover the grill or diffuser?
Using a capture hood that fully covers the grill or diffuser during air volume flow rate measurements is crucial to obtaining accurate, reliable measurements that are essential for HVAC system performance, occupant comfort, indoor air quality, and regulatory compliance.
Where would the Ak factor be found?
The value of the Ak factor is typically provided by the manufacturer of the GRD and can be found in the product specification sheet or product catalog.
When measuring a typical diffuser with a velometer, the velometer probes locations and
flow factors come from where?*
The velometer probes locations and flow factors come from the manufacturer’s specifications.
Before balancing can be started there are many things to consider, what needs to be
done to the filters, coils, and the fan rotation?*
- Filters: Ensure that the air filters are clean and free from debris. Clogged filters can reduce airflow and cause inaccurate air volume flow rate measurements during the balancing process.
- Coils: Check that the evaporator and condenser coils are clean and free of dust and debris. Dirty coils can also reduce airflow and affect system performance.
- Fan rotation: Check the direction of rotation of the fans to ensure that they are rotating in the correct direction. The direction of rotation will affect the performance of the fans and the airflow through the system.
- Dampers: Check the position of all dampers in the system to ensure that they are open, closed or partially open as required. This will help to ensure that the correct amount of airflow is delivered to each area.
- Airflow measurement instrumentation: Ensure that all airflow measurement instruments, such as anemometers, capture hoods and balometers, are calibrated and in good working condition.
Why must the filters be checked and cleaned before any balancing is started?
Clogged filters can reduce airflow and cause inaccurate air volume flow rate measurements during the balancing process.
There are many different report forms used for a proper TAB project. Why is it
important to conduct a Calibration Report?*
In a Testing, Adjusting, and Balancing (TAB) project, a Calibration Report is an essential document that verifies and validates the accuracy and precision of all the airflow measurement instruments used during the project.
When balancing a completed system, what is the most important part of the mechanical
plans needed?
The design intent provides a roadmap for the balancing technician, helping them understand how the system is supposed to operate and what the expected air volume flow rates should be. This information is essential for determining the proper adjustments that need to be made to the system during the balancing process.
What does percent of design mean?
To balance the system.percent of design is calculated by dividing the preliminary cfm by the design cfm
What are the tolerances for the following:
a. Total quantity to each space.
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b. Two outlets are in a space.
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c. Three or more outlets in a space.
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d. Return and exhaust systems balanced to a total of:
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a. Total quantity to each space: The total quantity of air supplied to each space or zone of a building should be within ±10% of the design airflow rate.
b. Two outlets in a space: The difference in airflow between two outlets in the same space should be within ±15% of the lower airflow rate.
c. Three or more outlets in a space: The difference in airflow between three or more outlets in the same space should be within ±20% of the average airflow rate.
d. Return and exhaust systems balanced to a total of: The return and exhaust systems should be balanced to within ±5% of the design airflow rate.
