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HVAC SYSTEMS > Fan Selection > Flashcards

Fan Selection Flashcards

1
Q

What is CFM?

A

Cubic Feet Per Minute. It’s a measure of volume of air over a time period

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2
Q

What is SP?

A

Static Pressure is a resistance to flow (energy added by the fan) measured in inches of water gauge in.wg.)

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3
Q

How is a fan selected?

A

A fan is selected based on CFM and ESP

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4
Q

What is BHP?

A

Brake Horse Power is a measurement of power consumption

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5
Q

What is HP?

A

Horse Power is used to indicate fan’s motor size

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6
Q

What is RPM?

A

Revolutions per minute is a measurement of motor speed

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7
Q

What is FRPM?

A

Revolutions per minute measuring fan speed

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8
Q

What is TS?

A

Tip speed is the speed of the fan impeller tip measured in feet per minute

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9
Q

How is Tip Speed Caluculated?

A

3.14 x RPM x impeller diameter / 720

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10
Q

What is a decibel?

A

A logarithmic measurement of magnitude

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11
Q

What is a Sone? What is considered quiet or loud?

A

A linear measurement of sound

1-2 is quiet. 5 is loud.

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12
Q

What are the three basic types of fans?

A

Axial, Centrifugal, and Mixed Flow

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13
Q

Describe Axial fans

A

airflow is parallel to the fan impeller. High CFM, most economical impeller. higher efficiencies at lower SP. Louder than centrifugal, mostly unducted applications

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14
Q

Describe Centrifugal fans

A

inline, utility set, plenum/plug fans, or dome. More expense than axial. Takes up more physical space. Lower sound levels. Moves air perpendicular to air inlet

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15
Q

Describe Mixed Flow fans

A

Hybrid between axial and centrifugal. Efficient air movement. High Volume or CFM flow. Lower sound levels

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16
Q

What are the two types of fan motor configuration?

A

Direct Drive and Belt Drive

17
Q

What are pros of Direct Drive fan motors?

A

Low maintenance and compact design

18
Q

What are the cons of Direct Drive fan motors?

A

Limited motor availability. Limited motor access and less performance flexibility.

19
Q

What are the pros of Belt Driven fan motors?

A

Performance flexibility. Easy access to motors. Work with VFDs. Motors are readily available.

20
Q

What are the cons of Belt Driven fan motors?

A

More maintenance. Takes up more space.

21
Q

How do you adjust the CFM flow on a belt driven motor?

A

Opening the pulley will decrease fan RPM and closing it will increase fan RPM.

22
Q

What is the rule of thumb for Belt Drive?

A

Normally above 2,000 CFM with a SP above .5” wg

23
Q

What is the rule of thumb for Direct Drive?

A

Normally below 2,000 CFM with a SP less than .5” wg

HVAC SYSTEMS (21 decks)

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