Complex HVAC Systems

Question 1

List 4 types of systems

Answer 1

Air, water, air and water, DX

Question 2

What 3 components are part of the DCV control system?

Answer 2

BAS, motion, CO2

Question 3

What happens to the bypass air from a VAV system?

Answer 3

Returns to the AHU though the return

Question 4

What does the term Bucking refer to?

Answer 4

Operates inefficiently by heating and cooling the air at the same time

Question 5

What is a regular VAV system?

Answer 5

Does not change the speed of the fan but throttles air through a damper

Question 6

What is a true VAV system?

Answer 6

Changes the fan speed

Question 7

I’m an induction reheat terminal what temperature causes condensation problems?

Answer 7

Coil temps cooler than 50F

Question 8

What must be used if a DX coil is used in face bypass system?

Answer 8

Capacity control

Question 9

How does the air flow in a centrifugal fan?

Answer 9

The air flow is perpendicular to the fan

Question 10

How does the air flow in an axial fan?

Answer 10

It flows parallel

Question 11

What 3 types of axial fans are there?

Answer 11

Propeller, tube, and vane

Question 12

Describe propeller fans

Answer 12

They can move large volumes at low static pressure and have no ductwork. Elevator room exhaust fans.

Question 13

Describe tube axial fans

Answer 13

Heavy duct propeller fans. Operate at a higher static pressure than propeller.

Question 14

Describe a vane axial fan?

Answer 14

Much like tube axial fans except they have guide vanes to reduce turbulence. They are efficient and the vanes help promote laminar flow.

Question 15

What type of centrifugal fan is most efficient and which one is the most least efficient?

Answer 15

Airfoil blades is most, and cross flow is the least

Question 16

How are centrifugal fans constant displacement devices?

Answer 16

They move constant volume rather than constant mass. Despite the air density. Air velocity is fixed even though mass flow rate changes.

Question 17

Backward inclined flat blades

Answer 17

Has 10-20 blades and are less expensive and less efficient than backward curved blades. Needs a large shaft.

Question 18

Backward curved blade

Answer 18

Quieter, might produce humming sound. Moves high volumes at high static.

Question 19

The air foil fan blade

Answer 19

Like a airplane wing, rotation is counter clockwise, most efficient, 8”-10” static pressure moved

Question 20

Radial tip fan blades

Answer 20

Tips are perpendicular to the shaft. Moves large volumes of dirty air 2” to 7” static. Inducers, boilers, grain dryers.

Question 21

Radial blade

Answer 21

Flat blade perpendicular to fan shaft. Workhorse of exhaust fan. 10” static pressure. Paddle type.

Question 22

What percent of excess air is necessary for building systems?

Answer 22

5%