APPENDIX K. AIR MOVING EFFICIENCY

TABLE OF CONTENTS

K.l INTRODUCTION .................................................... K-1

K.2 METHODOLOGY ................................................... K-1

K.3 OVERALL AIR EFFICIENCY CURVES ................................. K-2

LIST OF FIGURES

Figure K.3.1 Airflow and Watts/CFM vs. Pressure for 3-Ton Non-Condensing FurnaceSingle-Stage, PSC motor ......................................... K-3

Figure K.3.2 BE vs. Pressure for 3-Ton Non-Condensing Furnace -

Single-Stage, PSC motor ......................................... K-4

Figure K.3.3 Air Horsepower (AHP) vs. Pressure for 3-Ton Non-Condensing Furnace -

Single-Stage, PSC motor ......................................... K-4

Figure K.3.4 Overall Blower Motor Efficiency vs. Pressure for 3-Ton Non-Condensing

Furnace - Single-Stage, PSC motor ................................. K-5

Figure K.3.5 Blower Efficiency vs. Pressure Curves for Non-Condensing Furnace -

Single-Stage Control, PSC Motor .................................. K-5

Figure K.3.6 Blower Efficiency vs. Pressure Curves for Condensing Furnace -

Single-Stage Control, PSC Motor .................................. K-6

Figure K.3.7 Blower Efficiency vs. Pressure Curves for Non-Condensing Furnace -

Two-Stage Virtual Control, ECM Motor, High Fire .................... K-6

Figure K.3.8 Blower Efficiency vs. Pressure Curves for Non-Condensing Furnace -

Two-Stage Virtual Control, ECM Motor, Low Fire .................... K-7

Figure K.3.9 Blower Efficiency vs. Pressure Curves for Condensing Furnace -

Two-Stage Virtual Control, ECM Motor, High Fire .................... K-7

Figure K.3.10 Blower Efficiency vs. Pressure Curves for Condensing Furnace -

Two-Stage Virtual Control, ECM Motor, Low Fire .................... K-8

 EE-RM/STD-01-350 COMMENT 164

APPENDIX K. AIR MOVING EFFICIENCY 

TABLE OF CONTENTS 

K.l INTRODUCTION .................................................... K-l 

K.2 METHODOLOGy ................................................... K-l 

K.3 OVERALL AIR EFFICIENCY CURVES . . .................. . ............ K-2 

LIST OF FIGURES 

Figure K.3.1 Airflow and Watts/CFM vs. Pressure for 3-Ton Non-Condensing FurnaceSingle-Stage, PSC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. K-3 

Figure K.3.2 BE vs. Pressure for 3-Ton Non-Condensing FurnaceSingle-Stage, PSC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. K-4 

Figure K.3.3 Air Horsepower (AHP) vs. Pressure for 3-Ton Non-Condensing FurnaceSingle-Stage, PSC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. K-4 

Figure K.3.4 Overall Blower Motor Efficiency vs. Pressure for 3-Ton Non-Condensing 

Furnace - Single-Stage, PSC motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. K-5 

Figure K.3.5 Blower Efficiency vs. Pressure Curves for Non-Condensing FurnaceSingle-Stage Control, PSC Motor .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. K-5 

Figure K.3.6 Blower Efficiency vs. Pressure Curves for Condensing FurnaceSingle-Stage Control, PSC Motor .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. K-6 

Figure K.3.7 Blower Efficiency vs. Pressure Curves for Non-Condensing FurnaceTwo-Stage Virtual Control, ECM Motor, High Fire . . . . . . . . . . . . . . . . . . .. K-6 

Figure K.3.8 Blower Efficiency vs. Pressure Curves for Non-Condensing FurnaceTwo-Stage Virtual Control, ECM Motor, Low Fire . ..... . .... ..... .. .. K-7 

Figure K.3.9 Blower Efficiency vs. Pressure Curves for Condensing FurnaceTwo-Stage Virtual Control, ECM Motor, High Fire . . . . . . . . . . . . . . . . . . .. K-7 

Figure K.3.10 Blower Efficiency vs. Pressure Curves for Condensing FurnaceTwo-Stage Virtual Control, ECM Motor, Low Fire .................... K-8 

K-i 
APPENDIX K. AIR MOVING EFFICIENCY

K.1 INTRODUCTION

The purpose of calculating the overall air-moving efficiency for the basic furnace models

used in the LCC analysis is to show typical efficiency levels for furnace air handlers.

K.2 METHODOLOGY

The overall air-moving efficiency is a ratio of the air power divided by the electric power

used by the blower motor:

AHP

77overall = BE

where:

77 overall

AHP

BE

Eq. I

overall air-moving efficiency,

air horsepower (watts), and

circulating air fan electrical energy consumption (watts).

Air power is the power embodied in the air due to its motion and pressure increase. Air

power at any operating condition can be calculated for any furnace from pressure, airflow, and

supply air outlet area. Air power (air horsepower or AHP) is calculated as':

.7 AHP = (745 6356) x Q X P +

z

4005 x AJ

where:

AHP =

Q =

(745.7)

6356)

4005 =

P =

air power (watts),

airflow (cfm),

a conversion factor to express air horsepower in watts

Eq. 2

,

a conversion factor to express the velocity pressure of standard air in

w.9.,'

external static pressure (in.w.g.), and

' The velocity pressure is the increase in pressure caused by the motion of air.

K-1

 EE-RM/STD-01-350 COMMENT 164

APPENDIX K. AIR MOVING EFFICIENCY 

K.l INTRODUCTION 

The purpose of calculating the overall air-moving efficiency for the basic furnace models 

used in the LCC analysis is to show typical efficiency levels for furnace air handlers. 

K.2 METHODOLOGY 

The overall air-moving efficiency is a ratio of the air power divided by the electric power 

used by the blower motor: 

where: 

'7overaU 

AHP 

BE 

17 werail = 

AHP 

BE 

= overall air-moving efficiency, 

air horsepower (watts), and 

Eq.l 

= circulating air fan electrical energy consumption (watts). 

Air power is the power embodied in the air due to its motion and pressure increase. Air 

power at any operating condition can be calculated for any furnace from pressure, airflow, and 

supply air outlet area. Air power (air horsepower or AHP) is calculated as·: 

where: 

AHP 

Q 

C45.

7

) 6356 

4005 

P = 

air power (watts), 

airflow (cfm) , 

a conversion factor to express air horsepower in watts, 

Eq.2 

a conversion factor to express the velocity pressure of standard air in 

1 w.g., 

external static pressure (in.w.g.), and 

I The velocity pressure is the increase in pressure caused by the motion of air. 

K-I 
A = cross-sectional airflow area of the supply -air outlet area (sq.ft.)

determined by equation 1 or 2 in Chapter 7, section 7.2.5..

The power consumption of the fan (BE) is calculated by multiplying the Watts/CFM by the

CFM at the operating point:

BE =

Watts

CFM"Q Eq. 3

where,

BE = circulating air fan electrical energy consumption (watts),

Watts/CFM = determined by equation 1 or equation 2 in Appendix J, and

Q = airflow (cfm) determined in Chapter 7, section 7.5.2.

K.3 OVERALL AIR EFFICIENCY CURVES

In order to generate the overall air moving efficiency curves we followed the following

procedure (a 3-ton non-condensing single-stage furnace is used as an example):

STEP 1: Using the coefficients in Appendix I and J generate the Airflow (CFM) vs. pressure and

Watts/CFM vs. pressure curves. See Figure K.3.1 for the sample 3-ton non-condensing

furnace (single-stage, PSC motor).

STEP 2: Using Equation 3, DOE multiplied the airflow times the Watt/CFM at each pressure from

Step 1 to calculate BE in terms of pressure. See Figure K.3.2 for the sample 3-ton noncondensing furnace (single-stage, PSC motor)..

STEP 3: Using Equation 2, DOE used the airflow (CFM) and pressure from Step 1 to calculate

the variables Q and P and used the equations in Chapter 7, section 7.2.5, to calculate the

A, the supply-air outlet area. These values were used to calculate AHP in terms of

pressure. See Figure K.3.3 for the sample 3-ton non-condensing furnace (single-stage,

PSC motor), where A is equal to 2.04 sq. ft. (at 75 kBtu input capacity).

STEP 4: Using Equation 1, finally DOE substituted BE and AHP from Step 2 and Step 3,

respectively, to calculate the overall air moving efficiency in terms of pressure. See

Figure K.3.4.

Figures K.3.5 through K.3.10 show the overall air moving efficiency vs. pressure curves for

single-stage non-condensing, single-stage condensing, two-stage non-condensing (high and low

fire), and two-stage condensing (high and low fire). Not all 25 basic design options are shown on

graphs, just 4 are shown: 2-ton at 50 kBtu, 3-ton at 75 kbtu, 4-ton at 100 kbtu, and 5-ton at 120 kbtu.

K-2

 EE-RM/STD-01-350 COMMENT 164

A cross-sectional airflow area of the supply-air outlet area (sq. ft.) 

determined by equation 1 or 2 in Chapter 7, section 7.2.5 .. 

The power consumption ofthe fan (BE) is calculated by multiplying the Watts/CFM by the 

CFM at the operating point: 

where, 

BE 

Watts/CFM 

Q 

BE 

Watts 

CFM x Q Eq.3 

circulating air fan electrical energy consumption (watts), 

determined by equation 1 or equation 2 in Appendix J, and 

airflow (cfm) determined in Chapter 7, section 7.5.2. 

K.3 OVERALL AIR EFFICIENCY CURVES 

In order to generate the overall air moving efficiency curves we followed the following 

procedure (a 3-ton non-condensing single-stage furnace is used as an example): 

STEP 1: Using the coefficients in Appendix I and J generate the Airflow (CFM) vs. pressure and 

Watts/CFM vs. pressure curves. See Figure K.3.1 for the sample 3-tonnon-condensing 

furnace (single-stage, PSC motor). 

STEP 2: Using Equation 3, DOE multiplied the airflow times the WattlCFM at each pressure from 

Step 1 to calculate BE in terms of pressure. See Figure K.3.2 for the sample 3-ton noncondensing furnace (single-stage, PSC motor) .. 

STEP 3: Using Equation 2, DOE used the airflow (CFM) and pressure from Step 1 to calculate 

the variables Q andP and used the equations in Chapter 7, section 7.2.5, to calculate the 

A, the supply-air outlet area. These values were used to calculate AHP in terms of 

pressure. See Figure K.3.3 for the sample 3-ton non-condensing furnace (single-stage, 

PSC motor), where A is equal to 2.04 sq. ft. (at 75 kBtu input capacity). 

STEP 4: Using Equation 1, finally DOE substituted BE and AHP from Step 2 and Step 3, 

respectively, to calculate the overall air moving efficiency in terms of pressure. See 

Figure K.3.4. 

Figures K.3.5 through K.3.1 0 show the overall air moving efficiency vs. pressure curves for 

single-stage non-condensing, single-stage condensing, two-stage non-condensing (high and low 

fire), and two-stage condensing (high and low fire). Not all 25 basic design options are shown on 

graphs, just 4 are shown: 2-ton at 50 kBtu, 3-ton at 75 kbtu, 4-ton at 100 kbtu, and 5-ton at 120 kbtu. 

K-2 
1400

1200

1000

U 800

9

0

t 600

400

200

0.2 0.4 0.6 0.8 1

Static Pressure (in. w.g.)

0

0

Fl- ,AWIflow

y M

1.4

1.2

C)

0.6 3

0.4

0.2

0

Figure K.3.1 Airflow and Watts/CFM vs. Pressure for 3-Ton Non-Condensing

Furnace - Single-Stage, PSC motor

 EE-RM/STD-01-350 COMMENT 164

1400 1.4 

-,-~,to-. __ ~ __ -~=---:--_ ___ _ __ ---1j:: -.'Airf10W -l 1.2 

•• > -' ~ .... ---.. ""Watts CFM I ·~"""74. _ _ . ....... ~ ... 

- ---- ----- - ---. - ---- - ____ _ ---- _ _ .c""" .!.... --.~-----+ 1 

1200 

1000 

, 

~ LL. 800 ---.------------- ---,, ------~ :.. '-~ 0.8 -

~ ~ ., ~ ~ 

~ 0 'E 600 ---·------- --- --- ---- .- - ---------j- 0.6 ~ 

:.;: - ~ 

400 ft:::::==~·=~ ... ... O==='1.== .= ~.F==~tF-- ~=::::!~-+ 0.4 

200 +----------- - - - --- -----------+ 0.2 

o ----- -,-, - - - - -,--, - ------,-- -----.------+ 0 

o 0.2 0.4 0.6 0.8 

Static Pressure (in. w.g.) 

Figure K.3.1 Airflow and Watts/CFM vs. Pressure for 3-Ton Non-Condensing 

Furnace - Single-Stage, PSC motor 

K-3 
600

400

300

w

200

100

0

0 0.2 0.4 0.6 0.8 1

Static Pressure (in. w.g.)

Figure K.3.2 BE vs. Pressure for 3-Ton Non-Condensing Furnace -

Single-Stage, PSC motor

100

90

80 - : ,- -

70

.;.

60

50

Q 40

30

.r

20

r

10 -

r.,-

0 0.2 0.4 0.6 0.8 1

Static Pressure (in. w.g.)

Figure K.3.3 Air Horsepower (AHP) vs. Pressure for 3-Ton Non-Condensing

Furnace - Single-Stage, PSC motor

K-4

 EE-RM/STD-01-350 COMMENT 164

W 

III 

200 --_._--- ------- ------ - ---- ---- --- -

100 +---- - --------------------- --------

0+----------,-----.---------,------,---------. 

o 0.2 0.4 0.6 0.8 

Static Pressure (in. w.g.) 

Figure K.3.2 BE vs. Pressure for 3-Ton Non-Condensing FurnaceSingle-Stage, PSC motor 

100 

90 

80 

70 

~ 60 £! 

~ 50 

a.. 

J: 

c( 40 

30 

20 

10 

0+----------,-----,---------,------,---------, 

o 0.2 0.4 0.6 0.8 

Static Pressure (in. w.g.) 

Figure K.3.3 Air Horsepower (AHP) vs. Pressure for 3-Ton Non-Condensing 

Furnace - Single-Stage, PSC motor 

K-4 
45%

40%

35%

30%

25%

20%

15%

10%

5% -I

0.2 0.4 0.6 0.8 1

Static Pressure (in. w.g.)

Figure K.3.4 Overall Blower Motor Efficiency vs. Pressure for 3-Ton

Non-Condensing Furnace - Single-Stage, PSC motor

Static Pressure (in. w.g.)

Figure K.3.5 Blower Efficiency vs. Pressure Curves for Non-Condensing

Furnace - Single-Stage Control, PSC Motor

K-5

 EE-RM/STD-01-350 COMMENT 164

45% 

40% +-------------------------------------------------------

35% -- ----- - - -----------.----------.. ------------- - ------

30% - ----- --- ------ ----- --------- .-------------------

~ 

;: 25% +--------------------------------------------,.~ .. -.. .O% ,.~.- ""<~.->" .... 

g -' :§ 20% ~"''''-.<''~>''''.'~ --- ----- ---

in "",,,,- ;j(" 15% \--------------- - ----- --------:-;?'~ .. ---------------------

.. ~"V' 

"'""'(; tt 

10% +-------------- ~: "~----------------------------------

5% +--- ~-~¢ ···-- ----------------------------------------- • .,.~1'~ . ..... 

.. ;. ..:;~ 

O% ----------,_--------~----------,_--------~-------___, 

o 02 0.4 0.6 0.8 

Static Pressure (in. w.g.) 

Figure K.3.4 Overall Blower Motor Efficiency vs. Pressure for 3-Ton 

Non-Condensin Furnace - Sin le-Sta e, PSC motor 

45% 

40% +-____ ~Ton ~-------------------------------------- ..... 4-Ton 

"" 3-Ton 

35% t-------L 2~~~on~--------------------------------------

30% +---------------------------------------------- -------=~ 

-rfe. 

;: 25% +------------------------------ ------ ~ u 

s::: 

Q) :§ 20% +-----------------------

in 

15% +----------------

10% +--------------- ----------------------------------

5% ---- ~~--------------------------------------

O% ----~-- ---------------- ----,----- --~---- -----

o 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Static Pressure (In. w.g.) 

Figure K.3.5 Blower Efficiency vs. Pressure Curves for Non-Condensing 

Furnace - Single-Stage Control, PSC Motor 

K-5 
45%

40%

35%

30%

15%

10%

5%

-+-5-Ton

-41-4-Ton

•3-Ton

2-Ton

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Static Pressure (in. w.g.)

Figure K.3.6 Blower Efficiency vs. Pressure Curves for Condensing Furnace

- Single-Stage Control, PSC Motor

0% +

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Static Pressure ( in. w.g.)

Figure K.3.7 Blower Efficiency vs. Pressure Curves for Non-Condensing

Furnace - Two-Stage Virtual Control, ECM Motor, High Fire

K-6

 EE-RM/STD-01-350 COMMENT 164

~ 

45% 

40% .. --- ...... 5-Ton ___ 4-Ton 

-*-3-Ton 

35% --- - . ·· L~:..!.T£!onu---.---- .. ... -----. 

30% 

--_._-----

;: 25% IJ 

I: 

III 'u 20% +----- if 

w 

15% 

10% +----- -- ~~-- -- ----------------

5% +---~~~--------------------------------

o 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Static Pressure (In. w.g.) 

Figure K.3.6 Blower Efficiency vs. Pressure Curves for Condensing Furnace 

- Sin le-Sta e Control, PSC Motor 

-

?Ie 

45% 

40% +------1 -+-S-Ton 1---- -------------- --- - '"*-4-Ton '~"" -Ton 

35% t--- -. 2~~~onu_ -- --------

30% +-------- -----

;: 25% +-- -----------. IJ 

I: 

III :§ 20% 

ffi 

15% 

10% +--- --------- -- ---------

5% +-- ~~----

O% +---,---.---.--~- ~--~--.---.---.--~ 

o 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Static Pressure (in. w.g.) 

Figure K.3.7 Blower Efficiency vs. Pressure Curves for Non-Condensing 

Furnace - Two-Stage Virtual Control, ECM Motor, High Fire 

K-6 
45%

40% -I

35% -

15%

10%

5%

5-Ton

::7-4 -Ton

a • 3-Ton

2-Ton j

0% i i I

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Static Pressure ( in. w.g.)

Figure K.3.8 Blower Efficiency vs. Pressure Curves for Non-Condensing

Furnace - Two-Stage Virtual Control, ECM Motor, Low Fire

45% -1

40% -I -0--5-Ton

35%

-4-Ton

3-Ton

2-Ton

30%

25% d

20% -I

15%

10% d

5%

0% I

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Static Pressure ( in. w.g.)

Figure K.3.9 Blower Efficiency vs. Pressure Curves for Condensing Furnace

- Two-Stage Virtual Control, ECM Motor, High Fire

K-7

 EE-RM/STD-01-350 COMMENT 164

45% 

40% 

35% 

30% 

~ " 

--5-Ton 

"';;:"'4-Ton . _---------

-

;: 25% (.) 

c: 

GI ·u 20% 

it: 

w 

15% 

10% 

5% 

0% I 

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Static Pressure (in. w.g.) 

Figure K.3.8 Blower Efficiency vs. Pressure Curves for Non-Condensing 

Furnace - Two-Sta e Virtual Control, ECM Motor, Low Fire 

.-. 

<f!. 

45% 

40% 1----1 __ 5-Ton 1------------------------

...... 4-Ton 

·· ... 3-Ton 

35% l----L ~2-~T~on~---------------------_= 4 

30% +-------------------- ~ . 

;: 25% (.) 

c: 

GI 

·u 20% 

ffi 

15% 

10% 

5% 

o 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Static Pressure (in. w.g.) 

Figure K.3.9 Blower Efficiency vs. Pressure Curves for Condensing Furnace 

- Two-Stage Virtual Control, ECM Motor, High Fire 

K-7 
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Static Pressure (in. w.g.)

0.8 0.9 1

Figure K.3.10 Blower Efficiency vs. Pressure Curves for Condensing

Furnace - Two-Stage Virtual Control, ECM Motor, Low

Fire

 EE-RM/STD-01-350 COMMENT 164

45% 

40% 

35% 

30% 

_____ ... ....... S·Ton 

....... 4·Ton 

~- 3·Ton 

-- •... -------- .. - .--.. -------.-.... . 

5% +- ----------------------------------

O% T--- ,---.---,---r---.---.---.---.---.--~ 

o 0.1 

Figure K.3.10 

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

Static Pressure (in. w.g.) 

Blower Efficiency vs. Pressure Curves for Condensing 

Furnace - Two-Stage Virtual Control, ECM Motor, Low 

Fire 

K-8 
REFERENCES

1. Lindeburg, M. R., Fans and Ductwork, Chapter 20. In Mechanical Engineering

Reference Manual for the PE Exam, Michael R. Lindeburg PE, Editor. Tenth ed. 1997.

Professional Publications, Inc.: Belmont, CA. p. 20-23

 EE-RM/STD-01-350 COMMENT 164

REFERENCES 

1. Lindeburg, M. R., Fans and Ductwork, Chapter 20. In Mechanical Engineering 

Reference Manualfor the PE Exam, Michael R. Lindeburg PE, Editor. Tenth ed. 1997. 

Professional Publications, Inc.: Belmont, CA. p. 20-23 

K-9