Fan motor amp. draw

Transcript Fan motor amp. draw

Arthur Miller, CMS, RCT HVACR Training Consultant www.kam-associates.com

OUTLINE

1. Air Flow Terminology 2. Classification of Duct Systems 3. Duct Design Methods 4. Fans 5. Ducts 6. Air Flow & Issues with Design of Ducts 7. Filters 8. Conclusion(s) & Solution(s)

A

’

PRACTICAL APPROACH

’

ALONG WITH SOME THEORY

3 ¼ x 12 wall stack

Who is Liable?

A. The contractor – from design to installation to service B. The filter manufacturer C. The building owner D. Nobody

AIR FLOW TERMINOLOGY

CFM

•

Volume or Quantity of air

•

measured in Ft 3 /min

FPM

•

Velocity of the air

•

measured in Ft/min

STATIC

•

Resistance to the air flow

•

measured in inches of water column (

“

w.c.)

Classification of Duct Systems 1.

Low Pressure System - up to 2 ” w.c.

Medium Pressure System - up to 6 ” w.c.

High Pressure System - up to 10 ” w.c.

Duct Design Methods 1. Velocity Method 2. Static Regain Method 3. Equal Friction Method

Velocity Method 1.

Select velocity for main and branch ducts.

Determine duct sizes.

Determine frictional pressure drops.

Select a fan.

Static Regain Method 1.

Select velocity for main ducts.

Velocities are selected so the static pressure at each take-off offsets the pressure loss of the preceding section of ductwork.

Select a fan.

Equal Friction Method 1.

Selection of friction loss.

Volume of air is known.

Duct is sized based on 1 and 2 above.

Select a fan or fan is selected.

FANS The

‘

HEART

’

of the air delivery system

Relationship between

STATIC

and

CFM

in respect to a FAN

Are they

A. a direct relationship B. an indirect relationship C. neither

STATIC CFM

two configurations of fans

1. AXIAL 2. CENTRIFUGAL

First, the

Axial Fans

Definition?

What makes an axial fan an axial fan?

ANSWER

Discharge Air Flow PARALLEL to shaft of motor/fan

(NO change in direction)

TYPES

1. tubeaxial 2. vaneaxial 3. propeller

TUBEAXIAL

operates at pressures up to 16 ” wc wheel turns faster than propeller fan efficiency up to 65%

VANEAXIAL

operates at pressures up to 20 ” wc uses guide vanes to improve efficiency and pressure most energy efficient fan

PROPELLER

operates at low speeds handles large volumes of air at low pressure and at free delivery efficiency is usually less than 50%

Performance of

PROPELLOR

Fans

PROPELLOR FAN

What is the LOADING component on a PROPELLOR fan?

A. CFM B. FPM C. STATIC

STATIC

This

‘

LOAD

’

is then imposed on the motor.

How will the motor respond?

STATIC AMPS

APPLICATION(S)

(1) The condenser conditioner is on very What will happen to the: an air dirty.

fan delivery in cfm?

fan motor amp. draw?

Fan delivery in cfm

Increases Decreases Remains the same

Fan delivery in cfm

Increases

Decreases

Remains the same

Fan motor amp. draw

Increases Decreases Remains the same

Fan motor amp. draw

Increases

Decreases Remains the same

(2) What about a filter on an ice machine condenser? What will happen to the: fan delivery in cfm?

fan motor amp. draw?

Fan delivery in cfm

Increases Decreases Remains the same

Fan delivery in cfm

Increases

Decreases

Remains the same

Fan motor amp. draw

Increases Decreases Remains the same

Fan motor amp. draw

Increases

Decreases Remains the same

(3) Consider a window fan. Is ductwork connected to the fan?

1. YES 2. NO

(3) Consider a window fan. Is ductwork connected to the fan?

1. YES 2. NO

Now, the

Centrifugal Fan

Definition?

What makes a centrifugal fan a centrifugal fan?

ANSWER

Discharge Air Flow PERPENDICULAR to shaft of motor/fan

Types of Centrifugal Wheels 1. Backward Inclined (BI) 2. Air Foil Wheels (AF) 3. Forward Curve Wheels (FC) 4. Radial Blade Wheel

Backward Inclined (BI)

Backward Inclined (BI) 1.

used with high pressure systems high flow high efficiency noisy

Air Foil Wheels (AF)

Air Foil Wheels (AF) 1.

used with high pressure systems high flow highest efficiency noisy

Forward Curve Wheels (FC)

Forward Curve Wheels (FC) 1.

used with medium pressure systems high flow best for moving large volumes against low static quiet

Radial Blade Wheel

Radial Blade Wheel 1.

used with high pressure systems medium flow best for moving air against high static and contaminated airstreams

Performance of

CENTRIFUGAL

Fans

CENTRIFUGAL FAN

What is the LOADING component on a CENTRIFUGAL fan?

A. CFM B. FPM C. STATIC

CFM

This

‘

LOAD

’

is then imposed on the motor.

How will the motor respond?

CFM AMPS

MOVIE TIME

APPLICATION(S)

How would following you questions answer the regarding CENTRIFUGAL fans?

(1) An addition has been added to a building and the duct system has been added onto include this addition. What will be the: A.

fan delivery in cfm?

fan motor amp. draw?

Fan delivery in cfm

Increases Decreases Remains the same

Fan delivery in cfm

Increases

Decreases

Remains the same

Fan motor amp. draw

Increases Decreases Remains the same

Fan motor amp. draw

Increases

Decreases

Remains the same

(2) As the air filter gets contaminated, what will be the: more A.

fan delivery in cfm?

fan motor amp. draw?

Fan delivery in cfm

Increases Decreases Remains the same

Fan delivery in cfm

Increases

Decreases

Remains the same

Fan motor amp. draw

Increases Decreases Remains the same

Fan motor amp. draw

Increases

Decreases

Remains the same

(3) You remove a supply air panel on a

‘

hot

’

day just to cool you off.

What will be the: A.

fan delivery in cfm?

fan motor amp. draw?

Fan delivery in cfm

Increases Decreases Remains the same

Fan delivery in cfm

Increases

Decreases Remains the same

Fan motor amp. draw

Increases Decreases Remains the same

Fan motor amp. draw

Increases

Decreases Remains the same

‘

CENTRIFUGAL

’

FAN PERFORMANCE

Fan Performance depends on (1) CFM (2) Outlet Velocity (3) Static Pressure (4) RPM (5) Brake Horsepower

Determining Fan CFMs (1) Using a Fan Curve (2) Using a Fan Chart (3) Using a Fan Law (4) Using Instruments

(1) Using a Fan Curve

Relationship between

STATIC

and

CFM

in respect to a fan

STATIC CFM

Relationship between

STATIC

and

CFM

in respect to the duct system

CFM STATIC

1 HP Original Operating Point 5 HP 3 HP New Operating Point

(2) Using a Fan Chart

PSC Motor

ECM Motor

And now, the new kid on the block.

Dec Star

Movie

Using a Fan Law

1. six fan laws 2. HVACR is affected by one of them

The physics of air flow dynamics dictates the following:

•

CFM – varies as the fan speed

•

Static – varies as the SQUARE of the speed

•

HP – varies as the CUBE of the speed

APPLICATION If we increase the cfm

’

s by 20%, what will be required of the motor speed( rpm )?

+ 20%

If we increase the cfm

’

s by 20%, what will happen to the static in the system?

+ 40%

If we increase the cfm

’

s by 20%, what will horsepower motor?

happen required to from the the

+ 80%

Using Instruments

1. Anemometer 2. Velometer 3. Manometer with Pitot Tube 4. Balometer

So why all the fuss about fans ?

Because they must deliver a volume of air that satisfies two requirements:

a. Equipment Efficiency b. Customer Satisfaction

AIR FLOW

So how much CFM can you

‘

shovel

’

into a duct?

That takes us to the

DUCT CALCULATOR

‘Rule of Thumb’ Design Static Pressures .10 (.08) for SUPPLY AIR duct .08 (.06) for RETURN AIR duct .08 (.06) for HEAT PUMP SUPPLY duct .06 (.04) for HEAT PUMP RETURN duct

Furnace Fan External Static Pressure .5

”

w.c.

for the furnace fan, then subtract any external components:

ACCA Manual D Component Static Pressure 1. Air conditioner coil = .25

”

w.c.

Filters = .10

”

w.c.

3. Electric heaters = .10

”

w.c. to .20

”

w.c.

4. Humidifiers = .10

”

w.c.

5. Supply Outlets = .03

”

w.c.

6. Return Inlets = .03

”

w.c.

7. Dampers = .03

”

w.c.

Example #1

• • • • • • •

Furnace fan = less AC coil = less air filter = less return grilles = less dampers = left for duct system = .50

- .25

- .10

less supply registers = - .03

”

w.c.

- .03

.06

” ” ” ” ” ”

w.c.

Example #2

• • • • • • •

Furnace fan = less AC coil = less air filter = less return grilles = less dampers = left for duct system = .50

- .00

- .10

less supply registers = - .03

”

w.c.

- .03

.31

” ” ” ” ” ”

w.c.

Designing the Duct System



Length of duct - measured



Fittings - Equivalent Length tables



Velocity Factor - Equivalent Length tables

Supply and Return Plenums

Take-off fittings

Fitting Velocity Factor EL Values 0 35 1 45 2 55 3 65 4 70 5 or more 80 20 30 35 40 45 50 65 75 85 95 100 110

CONCLUSION

The equivalent length(EL) of the duct system has a direct relationship to the

STATIC

FILTERS

Filters

in relation to the

SYSTEM

STUDY

•

ASHRAE

•

Published October 2012

•

by John Proctor, P.E.

Member ASHRAE

•

California Energy Commission field research

•

Two year old homes

•

Most common replacement filter used is a 1 in. pleated filter

•

Air Conditioning Contractors of America ’s Manual D

•

assumes pressure drop through a filter to be approx. 0.10 in. w.c.

Field installations showed PD far in excess of 0.10 in. w.c.

Static pressures for 34 split AC/furnaces

Static pressures for 34 split AC/furnaces Metric Mean: in. w.c.

Range: in. w.c.

Filter PD Return P S Total ESP 0.282

0.275 – 0.792

- 0.417

- 0.143 – - 0.928

0.887

0.533 – 1.21

Static pressures for 34 split AC/furnaces Metric Mean: in. w.c.

Range: in. w.c.

Filter PD Return P S Total ESP 0.282

0.275 – 0.792

- 0.417

- 0.143 – - 0.928

0.887

0.533 – 1.21

Static pressures for 34 split AC/furnaces Metric Mean: in. w.c.

Range: in. w.c.

Filter PD Return P S Total ESP 0.282

0.275 – 0.792

- 0.417

- 0.143 – - 0.928

0.887

0.533 – 1.21

Static pressures for 34 split AC/furnaces Metric Mean: in. w.c.

Range: in. w.c.

Filter PD Return P S Total ESP 0.282

0.275 – 0.792

- 0.417

- 0.143 – - 0.928

0.887

0.533 – 1.21

Research results of PD for 53 ducted systems.

Filter face area required for 0.05

”w.c. PD at 400 cfm/ton for one manufacturer ’s line of filters 16 x 25 = 400 in 2

Filter face area required for 0.05

”w.c. PD at 400 cfm/ton for one manufacturer ’s line of filters

•

The following two charts are tests performed by Kevin O ’Neill.

•

HVAC Service Manager

•

Carolina Clg. & Plbg.

•

Surfside Beach, SC

Filter Pressure Drop Table 20 in. x 20 in. x 1 in. – clean except as noted FILTER NAME Air flow hood and egg crate filter grille PRESSURE DROP (IN. W.C.) .03 in. Standard fiber glass filter Brand A Standard fiber glass filter Brand B Very dirty Brand A 1 in. thick pleated Brand C - clean .075 in. .08 in. .15 in. .2 in. 1 in. thick pleated Brand D - clean .2 in. Dirty 1 in. thick pleated Brand C @ 1 month .24 in. Dirty 1 in. thick pleated Brand C @ 3 months .32 in. AIRFLOW 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm

Filter Pressure Drop Table 20 in. x 20 in. x 1 in. – clean except as noted FILTER NAME Electrostatic filter Brand E Electrostatic filter Brand F Electrostatic filter Brand G PRESSURE DROP (IN. W.C.) .125 in. .14 in. .29 in. Electrostatic filter Brand H .35 in. Combination electronic, charcoal & fiber glass - clean .18 in. Same filter after 1 month of use Same filter after 3 months of use .34 in. .45 in. AIRFLOW 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm 800 cfm

CONCLUSION

every

system has air flow issues

CONCLUSION

Unfortunately there will always be those who: 1.

will not keep up with technology.

have always done it this way.

don ’t need to know that.

will do it the least expensive way.

SOLUTIONS

All designers of air flow systems need to check the manufacturer ’s specs.

of equipment designing a system.

before

SOLUTIONS

Filters may be a point of interest for poor performance of equipment and comfort.

SOLUTIONS

The consumer is getting smarter about our industry and making demands on us.

SOLUTIONS

Professionalism has to be promoted inside and outside the industry.

SOLUTIONS

Continuing Education