Outside Air Percentage Chart - Honeywell Design and Application Technical Reference Manual

Section 1 - Ventilation
-29 C
-20 F
0%
10%
%
20%
O
U
30%
T
40%
S
I
50%
D
E
60%
A
70%
I
R
80%
90%
100%
-20 F
-29 C
This chart can also be used for measuring the
percentage of outside air on an air handler.
The same three temperatures are measured
per the formulas on the preceding page. Lines
are drawn on the chart using a ruler. As with
the formulas this chart is most effective if there
is at least a 10 degree F difference between
the return and outside air. This will typically
require either a warm or cold day rather than
moderate weather. It is more accurate to
measure outside air percentage on a day
Honeywell Economizers 63-8594-02

Outside Air Percentage Chart

MIXED and RETURN AIR TEMPERATURES
-23 -18 -12 -7 -1
-10 0 10 20 30
-10 0 10 20 30
-23 -18 -12 -7 -1
OUTSIDE AIR TEMPERATURE
4 10 16 21 27
40 50 60 70 80
40 50 60 70 80
4 10 16 21 27
when the outside temperature is 10°F (-12°C)
rather than on a day when it is 70°F (21°C). If
the temperature difference between the return
and outside air is only a few degrees, a small
error in measurements can alter the results by
as much as 50% using this method. If the
temperature difference is 40 or 50°F (22 or
28°C) small errors in measurement do not
substantially affect the results of the
calculations.
12
32 38 43 49 C
90 100 110 120 F
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
90 100 110 120 F
32 38 43 49 C
%
O
U
T
S
I
D
E
A
I
R
M25274A