12
TABLE 2 – AIRFLOW DELIVERY VS NEGATIVE STATIC PRESSURE AS MEASURED FOR RETURN DUCT OR PLENUM (IN WC)
DUCT
LENGTH
0.05
0.10
0.15
0.20
0.25
0.30
FLEX
PIPE
FLEX
PIPE
FLEX
PIPE
FLEX
PIPE
FLEX
PIPE
FLEX
PIPE
10 FT
60
65
85
90
105
110
120
125
135
140
150
160
20 FT
55
60
80
85
100
105
115
120
130
135
140
150
30 FT
50
55
75
80
95
100
110
115
125
130
130
140
TABLE 3
Airflow Required >>
20
30
40
50
60
70
80
90
100
Airflow Delivered
KNOB SETTINGS (in minutes) FOR AIRFLOW DELIVERED vs AIRFLOW REQUIRED (1 HR CYCLE)
60
20
30
40
50
60
70
80
90
100
80
15
25
30
40
45
55
60
70
75
100
15
20
25
30
35
40
50
55
60
120
10
15
20
25
30
35
40
45
50
140
10
15
15
20
25
30
35
40
45
160
10
10
15
20
25
25
30
35
40
90-968A
STEP 2: DETERMINE THE FRESH AIR DELIVERY RATE
A. Measure the negative static pressure of the return system and consult
Table 2
below for approximate inlet airflow.
An airflow measuring device (Nailor-Hart, etc.) will give the airflow exactly.
B. For the table below, the flex duct is laid loose with 2 wide 90° bends, and the damper is fully open. For the rigid pipe, the
values are based on two 90° elbows, and the damper is fully open. For both cases the air intake is through a metal vent hood
with a bird screen. Adjust airflow accordingly for variations.
STEP 3: DETERMINE CYCLE TIME
A. The Cycle Period determines how often the dehumidifier should look to ventilate. This is
variable from 30 minutes to 3 hours (see
Figure 13
). Once the ventilation requirement is met,
ventilation will not occur until the start of the next Cycle Period.
B. The CYCLE TIME dial determines how long during every Cycle Period the damper will open
and ventilation will occur. The dial can be adjusted from OFF to between 1 to 60 minutes (see
Figure 14
). This will give outdoor air ventilation and HVAC fan operation from 1 to 60 minutes
every Cycle Period.
C. Refer to
Table 3
to determine the Cycle Time setting based on airflow delivered and airflow
required. The values listed in the table are for a 1 hour Cycle Period. For a 2 hour Cycle Period,
the Cycle Time would be set to twice the value (if in the white area of the table). The values
in the black portion of the table cannot be set due to the 60 minute Cycle Time limit.
FLOAT SWITCH
If the dehumidifier is installed in an attic or another location requiring
leak protection, the unit should be placed in a drain pan with a
normally closed condensate overflow safety switch (also known as a
float switch). The float switch should be wired to the float switch
terminals on the dehumidifier control board. See
Figure 18
. Remove
the jumper at the float switch terminals. The compressor is disabled
when the float switch is open. The dehumidifier will continue to
ventilate when the float switch is open.
CLOSED FLOAT SWITCH
LOW VOLTAGE NORMALLY
FL
O
A
T
S
W
IT
C
H
S
E
N
S
O
R
O
D
T
FIGURE 18
FIGURE 14
90-783C
FIGURE 13
4
3
2
1
O
N
TIMED
BLOWER
SYSTEM SETUP
ON
REMOTE
LOCAL
BLOWER-OFF
HOUSE
VENT-AUTO
REMOTE-OFF
O
N
1
2
3
4
2 HOUR
3 HOUR
30 MIN.
1 HOUR
CYCLE PERIOD
CYCLE TIME
TEST
60
MIN.
OFF
0
MIN
MIN.
30
MIN.
90-783C
4
3
2
1
O
N
TIMED
BLOWER
SYSTEM SETUP
ON
REMOTE
LOCAL
BLOWER-OFF
HOUSE
VENT-AUTO
REMOTE-OFF
O
N
1
2
3
4
2 HOUR
3 HOUR
30 MIN.
1 HOUR
CYCLE PERIOD
CYCLE TIME
TEST
60
MIN.
OFF
0
MIN
MIN.
30
MIN.
(shown set
to 1 hour)
(shown set to
30 minutes)
