COPYRIGHT
_
DRI-EAZ PRODUCTS, INC. 1997
9
E S TIMA T IN G WAT E R RE MOV AL
The Dri-X can be very efficient as a dehumidi-
fier. Its rate of water removal depends on how
much drier the outdoor air is when compared to
the indoor air. The Water Removal Chart below
shows the unit's power. Using the chart allows
comparing the rate of dehumidification to that of
refrigerant or desiccant dehumidifiers. When justi-
fying rental rates, the unit's value as an air cleaner
should be added in.
To estimate the unit's removal of water from a
humid indoor environment, use a thermo-hygro-
meter plus the Dri-X Airchanger Calculator, or a
psychrometric chart, table or calculator and the
Water Removal Chart below.
(Numbers given in the examples are accurate
calculations. When using a psychrometric chart,
numbers will be less exact. Use larger and more
detailed charts for more precise estimates.)
Step 1.
Measure the temperature and the relative hu-
midity both indoors and outdoors, using a thermo-
hygrometer.
Example: You measure indoor condi-
tions at 70°F (21°C) and 70% Rh. Outdoors, your
readings are 59°F (15°C) and 40% Rh.
Step 2.
Convert your readings into grains per pound
using the Dri-X Airchanger Calculator, or a psy-
chrometric chart or calculator. This figure is often
called the specific humidity.
Example: Using the
example above, the indoor condition is 77 gpp.
The outdoor condition is 30 gpp.
Step 3.
Subtract outdoor from indoor gpp. Look up this
number on the bottom scale of the Water Removal
Chart. Move up to the graph line, then left to gal-
lons per day, or right to pints per day.
Example: In
this case, the difference between indoor and out-
door conditions is 77 gpp less 30 gpp, or 47 gpp.
(77 - 30 = 47.) Looking up 47 gpp on the graph,
you find that the water removal is 166 pints or
about 21 gallons per day.
IMPORTANT:
The outdoor gpp
must NOT be
higher
than that of the indoors. This would mean
that the outdoor air is more humid – it is holding
more
water vapor. Do not use the Dri-X Air-
changer in these conditions, because it will bring
additional water vapor indoors, which would
raise
indoor humidity.
Water Removal Chart
0
10
20
30
40
50
60
Gallons Per Day
0
50
100
150
200
250
300
350
400
450
0
10
20
30
40
50
60
70
80
90
100
110
120
Difference between Indoors and Outdoors, in GPP
Pints Per Day
Examples by Geographical Areas
Example 1.
During early stages of a job in
Minneapolis during the winter, indoor conditions
are 75°F and 85% Rh. From your calculator or
chart you find that indoor specific humidity is 111
gpp (grains per pound). Outdoor conditions are
20°F (-4°C) and 25% Rh, for a specific humidity
of about 4 gpp. The difference is 107 gpp (111-
4=107). Reading from the Water Removal Chart,
the Dri-X is removing 377 pints or 47 gallons per
day.
Example 2.
You're in Seattle. It's cool and
foggy outdoors where your measurements are
48°F and 85% Rh, or 42 gpp. Indoor conditions
are 70°F and 65% Rh, or 71 gpp. The outdoor air
is drier by 29 gpp (71-42=29). Water removal is
102 pints or 13 gallons per day, similar to a large
refrigerant dehumidifier used in the same room.
Example 3.
In a Miami summer, the outdoor
air is 85°F with 70% relative humidity. Thus it
holds 128 gpp of water vapor. Indoor conditions
are 70°F and 90% Rh, or 99 gpp. Don't be fooled