NEBB Fundamental Formulas

A = Area (ft²) IP, (m²) SI M = Mass (lb) IP, (kg) SI

ACH = Air Changes per Hour ma = Mixed Air

Ak = Effective Area m = meter (metre)

AV = Average m³/s = Volumetric Flow: Cubic Meters Per Second

BHP = Brake Horsepower (IP) HP NLA = No Load Amperage

BP = Brake Power (SI) kW NPSHA = Net Positive Suction Head Available

Btu = British Thermal Unit oa = Outside Air

Btu/h = Btuh = BTUH = BTU/Hour % oa = % of Outside Air

= Center Distance (used in belt formula) Ω = Ohm

°C = Degrees Celsius, °C P = Pressure

C = Friction Loss Coefficient (For Duct Fittings) Pa = Atmospheric Pressure

CCF = 100 Cubic Feet Pab = Absolute Pressure (Atmospheric Pressure + Gauge Pressure)

CFM = Volumetric Flow: Cubic Feet Per Minute Pa = Pascals, Pressure SI

Cp = Specific Heat π = 3.14

Cv = Flow Constant (IP) PD = Sheave Pitch Diameter

ρ = Density (lb/ft³) IP, (kg/m³) SI P = Pressure at Pump Centerline

d = Diameter (in.) IP, (mm) SI ppm = parts per million

Δ = Difference or Change (Final - Initial) psi = Pounds Per Square Inch

dimp = Impeller Diameter psia = Pounds Per Square Inch Absolute

E = Volts psig = Pounds Per Square Inch Gauge

Eff = Efficiency Pvp = Absolute Vapor Pressure

EP = Pump Efficiency Q (flow) = Volumetric Fluid Flow Rate: (i.e. CFM, GPM, m³/s, l/s, etc.)

°F = Degrees Fahrenheit, °F Q (heat) = Heat Flow Rate (BTU/Hour) IP, (W or kW) SI

f = Friction Factor °R = °Rankin = Degrees Rankin, °R

FLA = Full Load Amps r = Radius (in) IP, (mm) SI

fpm = Feet per Minute (fpm) % ra = % of Return Air

ft = Foot R = Resistance

g = Acceleration of Gravity ra = Return Air

gal = Gallons rad = Radians

GPM = Gallons Per Minute (GPM) RH = Relative Humidity

h = Enthalpy (BTU/lb dry air) IP, (kJ/kg dry air) SI RPM = Revolutions Per Minute

H = Head (in wc, ft wc, psi) IP, (Pa, kPa) SI Rvalue = Thermal Resistance

Hg = Mercury s = second

hma = Mixed Air Enthalpy SHR = Sensible Heat Ratio

hoa = Outside Air Enthalpy SME = Sash Movement Effect Performance Rating (SME-XX yyy)

HP = Horsepower SP = Static Pressure

hr = Hour Sp Gr = Specific Gravity (for water use 1.00)

hra = Return Air Enthalpy T = Temperature

HT = Height (in) IP, (mm) SI Ta = Absolute Temperature (460˚ + T) or °R

I = Amps Tma = Mixed Air Temperature

J = Joules Toa = Outside Air Temperature

K = Kelvin, K TP = Total Pressure

Kv = Flow constant (SI) Tra = Return Air Temperature

kg = Kilogram TS = Tip Speed (fpm) IP, (m/s) SI

kJ = Kilojoule U = Heat Transfer Coefficient

kPa = Kilopascal µ = viscosity, dynamic

kW = Kilowatt = 1000 Watts V = Velocity

l = Liter (Litre) VP = Velocity Pressure

l/s = Volumetric Flow: Liters Per Second W = Watt

lb = Pounds WD = Width (in) IP, (mm) SI

lm = Lumens wg = wc = water gauge = water column

ln = natural log WHP = Water Horsepower (IP)

LG = Length (in) IP, (mm) SI WP = Water Power (SI)

lx = Lux ω = Humidity Ratio (lb or grains of water/lb of dry air) (g H2O/kg dry air)

NEBB Fundamental Formulas

Approved NEBB - May 1, 2017 of 8 Version 1.3

Airflow & Velocity Equations

Q V A Q VxA

TP VP SP TP VP SP

V 4005 √VP V 1.66 VP

V 1096VP

V 1.414VP

ACHQ 60

LGxWDxHT ACH

Q 3600 LGxWDxHT

Areaπ

d2

144π r144

Areaπ

d2

1,000,000π r

1,000,000

Area /HT WD144

Area /HT WD1,000,000

Area

HTxWD πHT2

144Area

HT WD πHT2

1,000,000

Air Temperature Equations

1.8 32° 32 1.8

°R 460 K 273

T % T % T h % h % h

%T TT T

100 %h hh h

100

Heat Transfer Calculations

Q 4.5 CFM ∆h Q 1.2 l s ∆h

Q 60 Cp ρ CFM ∆T Q Cp ρ l s ∆T

Q 1.08 CFM ∆T Q 1.23 l s ∆T

Q 0.69 CFM ∆ Q 3.0 l s ∆

Q 4840 CFM ∆

SHR Q Q Q Q Q

Q A U ∆ Q A U ∆

Fan Equations

CFMCFM

RPMRPM

l sl s

m sm s

rad srad s

PP

CFMCFM

PP

l sl s

m sm s

BHPBHP

CFMCFM

kWkW

l sl s

m sm s

TipSpeed TSπ d rpm

12TipSpeed TS

π d rpm60



Sheave Equations

RPMPDPD

RPM RPMRPM

PDPD

FanBeltLength 2 1.57 PD PDPD PD

4

Electrical Equations

Power E I 1 kW 1000Watts

I E Ω Ω E I

1HP 746Watts 1Watt 3.413Btu/hr

Power Equations

BHP E I PF Eff

746PF PowerFactor

kW E I PF1000

PF PowerFactor

BHP E I PF Eff 1.732

746PF PowerFactor 0.8&Eff 0.9;ifnotgiven

kW E I PF 1.732

1000

BHP HPI NLA 0.5FLA NLA 0.5

FLAFLA E

E

FanHPCFM TP SpGr

6356 Eff

Resistance

SeriesCircuit:totalresistance:Ω R ParallelCircuit:totalresistance:Ω R

R R R R ⋯ R 1

R1R

1R

⋯1R

E I E I VoltageDrop I R

Conversions

kilowatts Kw Btu/hr 3413

horsepower HP Btu/hr 2545

joules Btu/hr 0.000948

kilogramcalories Btu/hr 3.968

tonsofcooling chiller Btu/hr 12000

tonsofcooling coolingtower Btu/hr 15000

gallonsU.S. water poundsU.S. lb. 8.33

millimeters inchesU.S. 25.4

centimeters inchesU.S. 2.54

bar poundspersquareinch PSI 14.5

inchesofwater poundspersquareinch PSI 0.036

inchesofMercury Hg poundspersquareinch PSI 0.491



Hydronic

Pump Equations

GPMGPM

RPMRPM

l sl s

m sm s

rad srad s

GPMGPM

d

d

m sm s

d

d

HH

GPMGPM

HH

mh

mh

rad srad s

BHPBHP

GPMGPM

BPBP

m sm s

rad srad s

WHPGPM H SpGr

3960

SpGr 1.0, unlessgiven, EPuse0.7ifnotgiven

WP 9.81 m s H SpGr

WPl s H SpGr

1002

BHPGPM H SpGr

3960 EP


BPWPEP

EP %WHP 100

BHPEP %

WP 100BP

Hydronic Calculations

Coil∆P:GPM GPMPP

Coil∆P: m hm

hPP

CGPM SpGr

∆PK

mh SpGr

∆P

GPMC ∆P

SpGrSpGr 1.0, unlessgiven, EPuse0.7ifnotgiven

mh

C ∆P

SpGrSpGr 1.0, unlessgiven, EPuse0.7ifnotgiven

∆P SpGrGPMC


∆P SpGrm

hK


NPSHA P PV2g

P P

Heat Transfer Calculations

h ρ ∆ ρ ∆

h 500 ∆ 4190 ∆

4190 ∆

Boiler Calculations

OutputBtu InputBtu %Eff FireRateInputBtu

FuelBtu

BoilerOperatingCost FireRate hrsBurned $Costgal Btu lbofwater 500 ∆T



Metric Equivalents

acceleration m/s2 meterspersecondsquared 1m/s2 3.281ft/sec2

airflowvolumetricflowrate

m3/s cubicmeterspersecond 1m3/s 2118.88cfm

l/s literspersecond 1l/s 2.12cfm

m3/hr cubicmetersperhour 1m3/hr 0.589cfm

aream2 squaremeter 1m2 10.764ft2

mm2 squaremillimeters 1mm2 0.0016in2

atmosphericpressure

kPa kiloPascals 101.325kPa 29.92inHg 14.696psi

Bar Barometers 1Bar 100kPa 29.53inHg 14.504psi

distance.length,ordistance

m meter 1m 3.281ft

m meter 1m 39.370in

mm millimeter 1mm 0.039in

lightingintensitylx Lux 1lx 0.093fc

lm/m2 Lumens/squaremeter 1lm/m2 0.0931fc

pressurekPa kiloPascals 1000Pascals 1kPa 0.296inHg 0.145psi

Pa Pascals 1Pa 0.004inwg

temperature °C degreesCelsius °C °F‐32 /1.8

velocity m/s meterspersecond 1m/s 196.9fpm

volume m3 cubicmeters 1m3 35.31ft3

1Btu Energyrequiredtoheat1lbofH2Ofrom39˚Fto40˚F

1CCF 100000Btu

1ft inches 12

1ftwc 0.434psi

1ftHg 5.89psi

inches ftx12

1mmHg 0.535inwc

1inHg 1.133ft

1kW/hr 3413Btu

1lb moisture 7000grains

1psi 2.307ftwc

1psi 27.681inwc

1psi 2.036inHg

1Tonrefrigeration 12000Btu/hr

Atmospheric.Press 29.92inHgor14.69psi

DensityofAir Std 0.075lb/ft3

DensityofWater Std 62.4lb/ft3or7.49gal/ft3or8.33lb/gal

Onefootofmercury Hg column 5.89lb/in2 psi

Oneinchofmercury Hg column 13.6inches inwg 1.13ftwg

SpecificHeat Cp ofdryair 0.24Btu/lbx˚F@68°F

SpecificHeat Cp ice 0.50Btu/lbx˚F@68°F

SpecificHeat Cp vapor 0.45Btu/lbx˚F@68°F

SpecificHeat Cp water 1.00Btu/lbx˚F@68°F

SpecificVolumeofAir Std 13.33ft3/lb



-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130

DRY BULB TEMPERATURE - °F

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ENTH

ALPY

- BT

U P

ER P

OU

ND

OF

DR

Y AI

R

0

5

10

15

20

25

30

35

40

45

50

ENTH

ALPY

- BT

U PE

R PO

UND

OF

DRY

AIR

SATU

RATI

ON

TEM

PERA

TURE

- °F

-50

05

510

1015

1520

20 25

25 30

3035

35 40

40 45

45 50

50 55

55 60

6065

6570

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85 WET BULB TEMPERATURE - °F

85

90

15%

25%

2 %

4 %

6 %

8 %

1 0 % R E L A T I V E H U M I D I T Y2 0 %

3 0 %

4 0 %

5 0 %

60%

70%

80%

90%

12.0

12.5

13.0

13.5

14.0 SPECIFIC

VOLU

ME ft³/lb O

F DR

Y AIR

14.5

15.0

15.5

HU

MID

ITY

RAT

IO -

GR

AIN

S O

F M

OIS

TUR

E PE

R P

OU

ND

OF

DR

Y AI

R

PSYCHROMETRIC CHARTBAROMETRIC PRESSURE 29.921 inches of Mercury

Linric Company Psychrometric Chart, www.linric.com

.1

.2

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.4

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.7

.8

.9

1

1.1

1.2

1.3

VAPO

R P

RES

SUR

E - I

NC

HES

OF

MER

CU

RY

-20 0

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DEW

PO

INT

- °F

0

1.0 1.0

2.0

84.0- 8.

- -8.04.0-2 0.-1.0- -0.540.-0.3-0.2-0.1

0.10.20.3

0.4

0.50.6

0.8

-2000-1000

0.0

50.0

1000

1500

2000

3000

5000

-

SENSIBLE HEAT QsTOTAL HEAT Qt

ENTHALPYHUMIDITY RATIO

hW



lmaiani

Rectangle

5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

DRY BULB TEMPERATURE - °C

-30 -20 -10 0 10 20 30 40 50 60 7080

90

100

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EN

THA

LPY

- K

J P

ER

KIL

OG

RA

M O

F D

RY

AIR

-30

-20

-10

0

10

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30

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60

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90

100

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120

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ENTH

ALPY

- KJ

PER

KIL

OG

RAM

OF

DRY

AIR

1.02.03.04.05.06.07.08.09.010.011.012.013.014.015.016.017.018.0

19.020.021.0

22.0

23.0

24.0

25.0

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27.0

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PO

R P

RE

SS

UR

E -

MM

OF

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RC

UR

Y

-10

-5

0

5

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15

20

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30

35

DE

W P

OIN

T TE

MP

ER

ATU

RE

- °C

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

0.45

0.400.350.300.250.20

SENSIBLE HEAT RATIO = Qs / Qt

SE

NS

IBLE

HE

AT

RA

TIO

= Q

s / Q

t

2

4

6

8

10

12

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18

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28

30

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36

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15%

25%

2%

4%

6%

8% RELATIVE HUMIDITY

10% RELATIVE HUMIDITY20%

30%

40%

50%

60%

70%

80%

90%

-30 -25 -20 -15-15 -10

-10 -5

-5

05

510

10

15

15

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25

25

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35 WET BULB TEMPERATURE - °C

35

0.76

0.78

0.80

0.82

0.84

0.86

0.88 VOLU

ME - C

UBIC

METER

PER KG

DR

Y AIR0.90

0.92

0.94

0.96

0.98 1.00

1.02

HU

MID

ITY

RA

TIO

- G

RA

MS

MO

ISTU

RE

PE

R K

ILO

GR

AM

DR

Y A

IR

0

1.0 1.0

-

2.04.08.0-8.0-4.0-2.0-1.0-0.5

-0.4-0.3-0.2-0.1

0.10.20.3

0.4

0.50.6

0.8

-4.6

-2.3

0.0

1.2

2.3

3.5

4.7

7.0

11.7

-

SENSIBLE HEAT QsTOTAL HEAT Qt

ENTHALPYHUMIDITY RATIO

hW

-35 -30 -25 -20 -15 -10 -

PSYCHROMETRIC CHARTPSYCHROMETRIC CHART - METRICNORMAL TEMPERATURENORMAL TEMPERATURESI UnitsSI Units

SEA LEVELSEA LEVELBAROMETRIC PRESSURE: 101.325 kPaBAROMETRIC PRESSURE: 101.325 kPa



Sea Level 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

29.92 28.86 27.82 26.82 25.84 24.90 23.98 23.09 22.22 21.39 20.58

407.50 392.80 378.60 365.00 351.70 333.90 326.40 314.80 302.10 291.10 280.10-40° 1.26 1.22 1.17 1.13 1.09 1.05 1.01 0.97 0.93 0.90 0.87-0° 1.15 1.11 1.07 1.03 0.99 0.95 0.91 0.89 0.85 0.82 0.7940° 1.06 1.02 0.99 0.95 0.92 0.88 0.85 0.82 0.79 0.76 0.7370° 1.00 0.96 0.93 0.89 0.86 0.83 0.80 0.77 0.74 0.71 0.69

100° 0.95 0.92 0.88 0.85 0.81 0.78 0.75 0.73 0.70 0.68 0.65150° 0.87 0.84 0.81 0.78 0.75 0.72 0.69 0.67 0.65 0.62 0.60200° 0.80 0.77 0.74 0.71 0.69 0.66 0.64 0.62 0.60 0.57 0.55250° 0.75 0.72 0.70 0.67 0.64 0.62 0.60 0.58 0.56 0.54 0.51300° 0.70 0.67 0.65 0.62 0.60 0.58 0.56 0.54 0.52 0.50 0.48350° 0.65 0.62 0.60 0.58 0.56 0.54 0.52 0.51 0.49 0.50 0.45400° 0.62 0.60 0.57 0.55 0.53 0.51 0.49 0.48 0.46 0.44 0.42450° 0.55 0.56 0.54 0.52 0.50 0.48 0.46 0.45 0.43 0.42 0.40500° 0.58 0.53 0.51 0.49 0.47 0.45 0.44 0.43 0.41 0.39 0.38550° 0.53 0.51 0.49 0.47 0.45 0.44 0.52 0.41 0.39 0.38 0.36600° 0.50 0.48 0.46 0.45 0.43 0.41 0.40 0.39 0.37 0.35 0.34700° 0.46 0.44 0.43 0.41 0.39 0.38 0.37 0.35 0.34 0.33 0.32800° 0.42 0.40 0.39 0.37 0.36 0.35 0.33 0.32 0.31 0.30 0.29

60° 150° 200° 250° 300° 340°1.046 1.070 1.090 1.110 1.150 1.165

Sea Level 250 500 750 1000 1250 1500 1750 2000 2500 3000

101.33 98.30 96.30 93.20 90.20 88.20 85.10 83.10 80.00 76.00 71.90

0° 1.08 1.05 1.02 0.99 0.96 0.93 0.91 0.88 0.86 0.81 0.76

20° 1.00 0.97 0.95 0.92 0.89 0.87 0.84 0.82 0.79 0.75 0.71

50° 0.91 0.89 0.86 0.84 0.81 0.79 0.77 0.75 0.72 0.68 0.64

75° 0.85 0.82 0.80 0.78 0.75 0.73 0.71 0.69 0.67 0.63 0.60

100° 0.79 0.77 0.75 0.72 0.70 0.68 0.66 0.65 0.63 0.59 0.56

125° 0.74 0.72 0.70 0.68 0.66 0.64 0.62 0.60 0.59 0.55 0.52

150° 0.70 0.68 0.66 0.64 0.62 0.60 0.59 0.57 0.55 0.52 0.49

175° 0.66 0.64 0.62 0.62 0.59 0.57 0.55 0.54 0.52 0.49 0.46

200° 0.62 0.61 0.59 0.57 0.56 0.54 0.52 0.51 0.49 0.47 0.44

225° 0.59 0.56 0.56 0.54 0.53 0.51 0.50 0.48 0.47 0.44 0.42

250° 0.56 0.55 0.53 0.52 0.50 0.49 0.47 0.46 0.45 0.42 0.40

275° 0.54 0.52 0.51 0.49 0.48 0.47 0.45 0.44 0.43 0.40 0.38

300° 0.51 0.50 0.49 0.47 0.46 0.45 0.43 0.42 0.41 0.38 0.36

325° 0.49 0.48 0.47 0.45 0.44 0.43 0.41 0.40 0.39 0.37 0.35

350° 0.47 0.46 0.45 0.43 0.42 0.41 0.40 0.39 0.38 0.35 0.33

375° 0.46 0.44 0.43 0.42 0.41 0.39 0.38 0.37 0.36 0.34 0.32

400° 0.44 0.43 0.41 0.40 0.39 0.38 0.37 0.36 0.35 0.33 0.31

450° 0.41 0.40 0.38 0.37 0.36 0.35 0.34 0.33 0.32 0.31 0.29

500° 0.38 0.37 0.36 0.35 0.34 0.33 0.32 0.31 0.30 0.28 0.27

15.5° 65.5° 93.2° 121° 148.7° 170.9°

Water Temperature °FFeet head differential per inch Hg differential

Air Density Correction Factors (US Units) Standard Air Density (Sea Level & 70°F) = 0.075 lb/ft3 @ 29.92 in Hg

Air Temperature °F

Altitude (ft)

(in wg)

Barometer (in Hg)

Water Temperature °C

Air Density Correction Factors (Metric Units) Standard Air Density (Sea Level & 20°C) = 1.204 kg/m3 @ 101.325 kPa

Altitude (m)

Barometer (kPa)

Air Temperature °C



NEBB Fundamental Formulas

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