Test Balance Final

Question 1

What is a Parallel Fan Powered VAV?

Answer 1

Parallel: 2 separate parallel chambers, primary cool air flow, ceiling return air flow. With or w/o reheat. A fan in the return air chamber powering the return air flow

Question 2

What are the two types of Fan Powered VAVs and how do they work?

Answer 2

Series: have fans in primary air stream and operate continuously. Blend col primary air and warm plenum air maintaining constant flow while adjusting temps. Interlocked with central fan, higher operating costs

Question 3

What does the acronym for AMCA mean and what do they do?

Answer 3

Air Movement and Control Association

Question 4

What is AMCA Standard 210 state?

Answer 4

Defines procedures and conditions of fan testing so ratings published by manufactures can be compared

Question 5

What does Diversity Factor mean?

Answer 5

Sum of total ind. Max loads / Max Demand Load for System. If the size of the cooling, heating, and air distribution equipment is selected based on a lower actual max occupied simultaneous load, rather then a higher design, there is a diversity factor.

Question 6

What is a General Information Report and what is on it?

Answer 6

Describes the type of systems with key information. Lists job location, type of systems, manufacturer, instruments of measure used, building and system completion check

Question 7

After balancing, with what formula do you use to determine how much to increase RPM for the correct amount of CFM?

Answer 7

RPM and CFM are directly proportional. RPMnew = RPMold x CFMnew / CFMold

Question 8

What heating or cooling condition should most systems be put in before balancing?

Answer 8

Max flow through cooling coil by setting t-stat to 55 degrees. In winter, may have to leave t-stat at current setting

Question 9

What is the range for a High Pressure system?

Answer 9

2000 fpm and up, 6 in. WC and up

Question 10

What is the CFM formula?

Answer 10

CFM = Duct Size / 144 x fpm or CFM = A x V

Question 11

What is a Velometer and what does it measure?

Answer 11

Instantaneous direct reading for velocity in fpm and pressures in in. WC. Great for SA at ceiling diffusers. Also reads exhaust velocities at grilles, hoods and duct openings, currents in open spaces, etc.

Question 12

What does misalignment cause in fans with Inlet Cones?

Answer 12

Sharp loss of air volume and cycling within the fan

Question 13

What is a Rotating Vane Anemometer and what does it measure?

Answer 13

Reads velocities in fpm at grilles, louvers, exhaust hood openings, duct openings, etc. Operates as a windmill with timed counts

Question 14

What are the pressure ranges for a Medium Pressure System?

Answer 14

2000 fpm and up, 2-6 in. WC

Question 15

What is a VAV system and how does it work?

Answer 15

Auto varies air flow to spaces proportionately to current space needs at a constant temp. Usually, constant 55 degrees, programmed min and max damper settings. For heating, cool air reduced then air is heated with hot coil, RA used, or induction units used. Static pressure sensor maintains proper flow

Question 16

What is Fan Break Horse Power?

Answer 16

Horsepower absorbed by the fan, not just the motor. A fan will deliver deliver a constant volume of air at a constant RPM in a constant system regardless of density of air, but static and hp change with density

Question 17

What does an Oriface Plate do?

Answer 17

Creates a temporary pressure drop across the plate in in. WC and correlated against flow in gpm. Placed straight length of pipe and read with a Dial Type differential pressure gauge.

Question 18

How does a Photo Tachometer work and what does it measure?

Answer 18

Light beam directed a shaft or pulley and reads 120-19,999 rpm. The rotating item must be marked for it to count

Question 19

What is Standard Air?

Answer 19

air at 70 degrees F and 50% RH at 14.7 psi atmosheric pressure

Question 20

What is on an Outlet Balance Report?

Answer 20

Info from blueprints, shop drawings, schematics and grille schedule from manufacturer. Gives models, size, AK, velocity, cfm, and final measurements

Question 21

What is the temperature rating for a VAV system?

Answer 21

55 degrees

Question 22

What are the calibration parameters for Anemometers?

Answer 22

About once a year, sent to a factory, or checked against another unit

Question 23

What is a Shunt Motor Control?

Answer 23

Connected in parallel to allow for variable speed control of the motor in response to heat loads in the space. Can also alter dampers to aid

Question 24

What is the most efficient way to balance?

Answer 24

Proportional Balancing

Question 25

How do you balance a single zone system?

Answer 25

1. Pitot Total Air at fan, in mains, and branch ducts, use outlets if other not possible. 2. Add air flow in all branches and compare with fan CFM. 3. Compare each branch with design for the branch, adjust dampers as needed. 4. Reread branch flows with pitot. 5. Read outlets from near fan to furthest, reduce excessive flow at each outlest. 6. Make another pass if inbalance exists still. 7. Add all outlet CFM and compaire to fan CFM. Take amp and static pressure

Question 26

How is a Rotating Anemometer positioned to measure a grille?

Answer 26

Most accurate is to divide grille into equal sections and take multiple readings and average them. Also could sweep in an S curve across the grille one or more times (takes less time)

Question 27

What are the basic belt tensioning rules?

Answer 27

Alignment: belt 100% straight from sheave to sheave. Tension: 1/2” - 1” deflection on top side in center for one or two belt sheaves 2 - 4’ apart. Check manufacturer for higher horsepower (1/64” per inch from center of sheave to sheave)

Question 28

How do you calculate the OA % actually entering the building?

Answer 28

% of Outside Air: OA% = Tra - Tma / Tra - Toa

Question 29

What is an Air System Recap Report and what is on it?

Answer 29

Tie everything together and keep track of balancing progress. System, location, status, CFM, RPM, S.P. inches, AMPS

Question 30

What is meant by Traversing?

Answer 30

Taking several air velocity readings in a duct over a cross sectional area of air flow and averaged out

Question 31

How do you change a VAV to a Constant Volume System?

Answer 31

All terminals are set maximum or minimum flow settings

Question 32

What is meant by Capture Velocity of an exhaust system?

Answer 32

Velocity required to pick up contaminants from their source area. It must overcome spillage, air, and heat currents, and contaminants’ weight and velocity

Question 33

How do you change CFM?

Answer 33

Run calculation: RPMnew = RPMold (CFMnew / CFMold) & DIA Fan Sheave = DIA Motor Sheave (RPM motor / RPM fan)

Question 34

What is the most accurate way of measuring a flow on a Hydronic system?

Answer 34

Reading the actual flow (oriface plate flow meter, venturi flow meter, pitot flow meter, etc.)

Question 35

How do you connect and use a Manometer and Pitot Tube together?

Answer 35

Velocity Pressure: traverse with both tubes hooked up to pitot tube in the discharge duct. Total Pressure: hook up bottom connection to left side (+) Static Pressure: parallel pitot connection to right side (-) manometer

Question 36

How do you use a Flow Hood?

Answer 36

Place over outlet. Good if Ak Factor not known for diffusers and grilles. Set range and traverse it

Question 37

What are the classifications of Residential Systems?

Answer 37

Constant Volume Variable Temperature Low Velocity. 200-1200fpm, 1/2” to 1 1/2”

Question 38

Name all of the benefits of balancing.

Answer 38

Reduced energy, lower operating costs, safer systems, reduction or elimination of service callbacks, preventions of premature wear, healthier air, customer satisfaction, improved reputation, and profitability

Question 39

When balancing a High Pressure System, what components need to be set for what?

Answer 39

Auto Dampers to 100% OA, no recirculation of RA, close all doors and windows, max AC, all outlets open

Question 40

What is the formula for Max Leakage, from ASHRAE?

Answer 40

Max sys leakage (in CFM) / Feet of ductwork - 1% max allowed

Question 41

What are the components of a Grille?

Answer 41

Vanes only, no dampers

Question 42

What are the components of a Register?

Answer 42

Vanes and a control damper

Question 43

How do Tubular Inline Fans operate and what is their sequence?

Answer 43

Centrifugal fan wheel in tubular housing with inlet cone and vanes. Air discharged parallel to flow, unlike most fans.

Question 44

How do VAVs measure static pressure?

Answer 44

2/3 downstream the main duct is where the Static Pressure Sensor monitors. Directs fan volume controller to adjust proportionately

Question 45

How do you determine duct leakage?

Answer 45

1. Test one section of duct at a time 50 - 150’ long (length can’t exceed instruments ability). 2. Determine Max Allowable CFM leakage and determine allowed leakage for each section. 3. Seal both ends of segment and all tees. 4. Connect Testing Rig. 5. Start Blower and gradually open damper at inlet until Test Pressure is reached. Allow to run at test pressure for one minute. Air entering system is = to air leakage out. Pressure drop across oridace plate measure leakage with U Manometer

Question 46

How do you hook up a Manometer with a Pitot Tube?

Answer 46

Left side of manometer is Positive, right side is Negative. Total Pressure on the bottom of pitot to (+) and Static Pressure on side port (-)

Question 47

What is the formula to set OA based on MA Temp?

Answer 47

Outside Air Balance: Tma = (OA% x Toa) + (RA% x Tra)