Example 2: Use Of Outside Air Chart On A Warm Day - Honeywell Design and Application Technical Reference Manual

Section 1 - Ventilation

Example 2: Use of Outside Air Chart on a Warm Day

OUTSIDE
AIR
CHART
-29 C -23
-20 F -10
0%
10%
%
20%
mixed air temperature till it intersects
O
U
30%
T
40%
S
I
50%
D
E
60%
A
intersection draw a
70%
I
R
80%
90%
100%
-20 F -10
-29 C -23
The chart can also be used on a warm day
when the outside air temperature exceeds
both the return and the mixed air
temperatures. The first line drawn will slant in
Honeywell Economizers 63-8594-02
MIXED AIR TEMP
84 F
OUTSIDE AIR TEMP
MIXED and RETURN AIR TEMPERATURES
-18 -12 -7 -1
0 10 20 30
Measure the return air
temperature.
Draw a line straight down from the
the line that was just drawn.
6
At the point of
line to the left till
the percentage of
outside air is
indicated.
0 10 20 30
-18 -12 -7 -1
OUTSIDE AIR TEMPERATURE
75 F
(24 C)
RETURN AIR TEMP
(29 C)
4 10 16 21 27
40 50 60 70 80
1
5
3
Draw a line
from the return
air on top to the
outside air on
the bottom.
40 50 60 70 80
4 10 16 21 27
a different direction. Once again it is best to do
this test when there is a minimum of 10
degrees F difference between the outside and
return air.
14
71 F
(22 C)
32 38 43 49 C
90 100 110 120 F
0%
10%
4
20%
Measure the mixed
air temperature.
30%
This should be
done in 4 or more
40%
locations and
averaged.
50%
60%
Measure the
70%
outside air
temperature.
80%
2
90%
100%
90 100 110 120 F
32 38 43 49 C
%
O
U
T
S
I
D
E
A
I
R
M25276A