psychrometic 101 - dc ashrae · hvac psychrometrics. psychrometric chart hvac psychrometrics. 30 40...
TRANSCRIPT
PSYCHROMETRICS 101NATIONAL CAPITAL CHAPTER ASHRAE
WEDNESDAY, OCTOBER 7, 2015
Jesse Fisher, PE
What is psychrometrics?
The field of engineering concerned with thedetermination of physical and thermodynamicproperties of gas-vapor mixtures.
Dry Air
• Mixture of gases.
• 78% Nitrogen
• 21% Oxygen
• Standard Temp = 59°F
• Standard Press = 14.7 psi
• Sensible Heat
• Heat of Vaporization isapproximately 1000BTU/lbm
• Maximum amount ofwater in dry air isfunction of temperatureand pressure.
• Saturation is the point ofequilibrium betweenmoist air and thecondensed water phase.
• Latent Heat
Water Vapor
The Psychrometric Chart
HVAC PSYCHROMETRICS
Psychrometric Chart
HVAC Psychrometrics
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Psychrometric Properties
HVAC Psychrometrics
Psychrometric Properties of Air
• Dry BulbTemperature
• Wet BulbTemperature
• Dew PointTemperature
• Relative Humidity
• Humidity Ratio
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Dry Bulb Temperature
-
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Dry Bulb Temperature (DBT)• Units: °F• T: Absolute temperature (R or K)• t: Relative Temperature (F or C)
Dry Bulb Temperature; °F
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Wet Bulb Temperature
-
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Wet Bulb Temperature (DBT)• NOT adiabatic saturation temp.• Units: °F
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Dew Point Temperature -
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Dew Point Temperature (DPT or DP)• Temperature when condensation
occurs.• Units: °F
De
wP
oin
tTe
mp
era
ture
;°F
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
50%
50%
50%
50%
50%
50%
50%
50%
50%
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Relative Humidity (RH)• Unit less measure• Ratio of W / WS
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Humidity Ratio -
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Humidity Ratio• Mass Ratio: Water Vapor to Air• Units: grains / lbm or lbm / lbm• W: Humidity Ratio• WS: Saturated Humidity Ratio
Hu
mid
ity
Ra
tio
;g
r/lb
m–o
r-lb
m/l
bm
“Other” Properties
HVAC Psychrometrics
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Enthalpy
-
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Enthalpy (BTU/lbm)• Total Energy; adiabatic saturation
temperature.• H = Sen + Lat• Lines are parallel
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Specific Volume
-
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Specific Volume• Cubic Feet Air / Pound Mass• Measure of Density
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
- SHR = 1.0
SHR = 0.6
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Sensible Heat Ratio• Defines the slop for the space
being served• QS / QT
Sensible Heat Ratio
Se
nsi
ble
He
at
Ra
tio
Determining State Points
HVAC Psychrometrics
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air: 95 DBT / 78 WBT
Return Air: 75 DBT & 50% RH
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Determining State Points• Any condition can be fixed
on the chart with just twoproperties.
• Every property can bedetermined once the statepoint is fixed on the chart.
Psychrometric ProcessesHVAC PSYCHROMETRICS
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Return Air
Outdoor Air
Mixed Air: 25% OA
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Mixing• Process line connection the two
state points being mixed.• Mixed state point is
proportionally along the mixingline.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Mixed Winter Air Heating Supply Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Heating• Q=1.08 x CFM x Delta T• Sensible Only Process
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Summer Mixed Air
Leaving Cooling Coil
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Cooling• QSEN=1.08 x CFM x Delta T• QTOTAL=4.45 X CFM x Delta h• Cooling is sensible only until the
air is cooled below the DPT.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Hot & Dry OA
Evaporatively Cooled Supply Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Adiabatic Saturation• Evaporative Cooling• Evaporative Humidification• Constant enthalpy process
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Winter: Dry Air
Winter: Humidified Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Humidification – Steam Injection• Adds both sensible and latent
heat to the airstream.• Exact slope varies by selection.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Summer: Entering EA Summer: Leaving EA
Summer: Entering OASummer: Leaving OA
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Energy Recovery: Sensible• OA: 95/78 to 83/75• EA: 75/63 to 89/67• DtOA = 12°F• DhOA = 3.3 BTU/lbm
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Winter: Entering EA
Winter: Leaving EA
Winter: Entering OA Winter: Leaving OA
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Energy Recovery: Sensible• OA: 10/9 to 49/34• EA: 70/53 to 33/32• DtOA = 39°F• DhOA = 9.1 BTU/lbm
Heat Recovery Performance
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Summer OA: Entering
Summer OA: Leaving
Summer EA: Entering
Summer EA: Leaving
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Energy Recovery: Total• OA: 95/78 to 83/71• EA: 75/64 to 89/74• DtOA = 12°F• DhOA = 6.7 BTU/lbm
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Winter OA: Leaving
Winter EA: Entering
Winter EA: Leaving
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Energy Recovery: Total• OA: 0/0 to 46/45.2• EA: 75/64 to 28.2/28.2• DtOA = 46°F• DhOA = 16.9 BTU/lbm
Enthalpy Wheel Performance
Psychrometrics of SystemsHVAC PSYCHROMETRICS
DRAWING A SYSTEM
HVAC Psychrometrics
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Drawing a System• Identify the Outdoor Air Condition• Identify the Return Air Condition
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air: 20% OA
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Drawing a System• Draw the mixing line between both
state points.• Locate the mixed air condition based
on OA percentage.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air: 20% OA
Leaving Cooling Coil
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Drawing a System• Draw the cooling coil curve
down to the leaving coolingcoil condition.
• Does not quite reachsaturation; mostpsychrometric charts havecooling coil lines.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air: 20% OA
- Supply Air Temperature
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Drawing a System• The leaving cooling coil
condition, in the draw throughsystem, is not the supply airtemperature.
• Fan heat is a sensible onlyheating process.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air: 20% OA
- Supply Air Temperature
Space Condition
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Drawing a System• Close the system.• Be careful and follow the
sensible heat ratio slope fromyour load calculations.
• DO NOT just close the systemloop.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air: 20% OA
- Supply Air Temperature
Space Condition
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Drawing a System• Iterate to determine system
conditions.• Sometimes you will find that
the space conditions areoutside acceptable designconditions.
AIR SIDE SYSTEM ANALYSIS
HVAC Psychrometrics
AIR SIDE SYSTEM ANALYSIS
Common Equations
QSensible = 1.08 x CFM x Dt [BTU/hr]
QLatent = 0.68 x CFM x Dw Change [BTU/hr]
QTotal = 4.45 x CFM x Dh [BTU/hr]
QTotal = Qsensible + QLatent
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air: 25% OA
- Supply Air Temperature
Space Condition
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Constant Air Volume (CAV):Design Day - Auditorium• High (60%) space RH at design
day.• Design loads are with lights on.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Return Air
- Supply Air Temperature
Space Condition- 50% Load SAT
50% Load Space Condition
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
CAV - Off Design: No Reheat• Lights turned off.• CAV adjusts SAT for temperature
control.• Results in 73% RH in the space.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Return Air
- -
Space Condition
50% Load SAT
-
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
CAV - Off Design: With Reheat• Lights turned off.• CAV adjusts SAT for temperature
control.• Reheat coil kicks in for humidity
control.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
TH
ALP
Y-
Btu
per
lb.o
fdry
air
and
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
UR
E- °
F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-I
NC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TU
RE
-°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
EH
EA
TR
AT
IO=
Qs
/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Mixed Air: 25% OA
LC Supply Air Temp
Rm T Return Temperature
Outdoor Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Air System – Plenum Return• Air Side Delta T increased.• Airflow decreased.• Same Coil Capacity.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Entering Cooling Coil
Leaving Cooling CoilLeaving Cooling Coil
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Face and Bypass Cooling Coil• Airstream splits through coil.• Mixing of fully condition and
unconditioned air.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Leaving Coil
Return Air
Leaving Coil
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Min OA Cooling Coil• Staged Coil Control• Cools and Dehumidifies OA
before Return Air• Provides dry supply air
temperatures at part load.
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Entering Coil
LCC Supply Temp
- Return Air
Exhaust Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Dedicated Outdoor Air Unit• Total Energy Recovery• Integral exhaust fan
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
OA: Post ERU
Return Air
Mixed Air
- SAT
Return Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Energy Recovery AHU• Total Energy Recovery• 25% Outdoor air
30 40 50 60 70 80 90 100 110 115
DRY BULB TEMPERATURE - °F
10 15 20 25
30
35
40
45
50
55
EN
THA
LPY
-B
tupe
rlb.
ofdr
yai
rand
asso
ciat
edm
oist
ure
ENTHALPY - Btu per lb. of dry air and associated moisture
10
15
20
25
30
35
40
45
50
55
ENTH
ALPY
- Btu
per l
b.of
dry
air a
ndas
soci
ated
moi
stur
eW
ETBU
LBTE
MPE
RAT
URE
- °F
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
HU
MID
ITY
RA
TIO
(orS
peci
ficH
umid
ity)
GR
AIN
SO
FM
OIS
TUR
EP
ER
PO
UN
DO
FD
RY
AIR
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.25
1.30
VA
PO
RP
RE
SS
UR
E-
INC
HE
SO
FM
ER
CU
RY
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
WP
OIN
TT
EM
PE
RA
TUR
E-
°F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
STANDARD AIR
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
=Q
s/Q
t
10% RELATIVE HUMIDITY
20%
30%
40%
50%
60%
70%
80%
90%
WET BULB TEMPERATURE - °F
20
25
3032
35
40
45
50
55
60
65
70
75
80
85
90
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
Outdoor Air
Return Air
Mixed Air Lvg Preheat
- Lvg Regen
Lvg Cooling Coil
Lvg WheelReturn Air
BAROMETRIC PRESSURE: 29.921 in. HG
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
High Latent Cooling AHU• Space Design: 68°F & 35% RH• Chilled Water: 45°F
