Rheem RRPL-B - Cooling Mode Dehumidification; On Demand Dehumidification Airflow Adjustment

H. COOLING MODE DEHUMIDIFICATION
An Explanation of On Demand Dehumidification Use
“On-Demand Dehumidification” (ODD) is an optional feature of the ECM interface board. The
ODD allows the user to have automatic dehumidification in the cooling mode that is controlled
by the user’s dehumidifying thermostat or humidistat setting. The humidistat should be wired
between the ODD (grey) pigtail and the R (red) pigtail. (Note: no field wiring should be con-
nected directly to the ECM interface board.) When the humidity exceeds the humidistat set-
ting, the airflow is decreased by a preprogrammed amount. This results in higher latent
capacity and increases the level of comfort.
Use of the ODD feature is important if maximum latent removal is desired. These systems
typically have a latent capacity between 24% to 28% of total system capacity. ODD drops
c
ooling airflow to boost latent capacity without significantly reducing total system capacity.
Refer to the thermostat wiring section of this manual for recommended dehumidifying ther-
mostats.
IMPORTANT: Typical dehumidistats apply a 24V signal when humidity is high. This board
requires 24V when humidity is low. (See Table 10.)
I. ON DEMAND DEHUMIDIFICATION AIRFLOW ADJUSTMENT
Use switches 9 & 10 to lower cooling airflow as defined in the following table:
IMPORTANT: Selection A turns off the input of the ODD terminal. DO NOT USE SELECTION
A WITH A DEHUMIDIFYING THERMOSTAT OR HUMIDISTAT (refer to Figure 34).
EXPLANATION OF ABOVE SELECTIONS:
Selection A: Maximum Latent Removal
This selection lowers cooling airflow to maximize latent removal anytime there is a call for
cooling. This selection can be used in environments where there is always a high latent
load as in coastal and southern regions of the USA (see Table 11).
NOTE: Use of selection A in arid environments is not necessary and may cause unneces-
sary power consumption.
TABLE 10
ODD TERMINAL
INDOOR INPUT TO “ODD”
AMBIENT TERMINAL
CONDITION (FROM HUMIDISTAT)
HIGH HUMIDITY Ø VAC
LOW HUMIDITY 24 VAC
FIGURE 34
O
N
O
N
O
N
O
N
A
9
10
9
10
9
10
9
10
BCD
SWITCH 9 SWITCH 10
SELECTION
POSITION POSITION
COOLING AIRFLOW ADJUSTMENT
MAXIMUM LATENT REMOVAL
A OFF OFF
(WITHOUT ODD INPUT)
NONE
B ON OFF
(FACTORY SETTING)
ON DEMAND DEHUMIDIFICATION
C OFF ON
(WITH ODD INPUT)
D ON ON NONE
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