First Co EVBQ (Variable Speed) - Manual (Page 13)

Dehumidify Capability with Standard Dehumidistat Connection
Latent capacities for systems using the EVBQ Fan Coil are better than average systems. If increased latent capacity is an
application requirement, the field wiring terminal block provides connection terminals for use with a standard dehumidistat.
The fan coil will detect the dehumidistat contacts opening on increased humidity and reduce its airflow to approximately 80
percent of nominal cooling airflow. This reduction will increase the system latent capacity until the humidity falls to a level,
R
C1 (RCom)
EM
W1
O
Y2
Y1
G
CFM
FIRST CO. -- CB600
Y2 Y1 G O W1 W2 NC C1 R HUM
EM
HEAT
A
B
C
D
COOL
A
B
C
D
DELAY
A
B
C
D
ADJUST
-
NORM
+
TEST
DEHUMIDIFY
CUT TO ENABLE
which causes the humidistat to close its contacts. When the contacts close, the airflow will return to 100 percent of the
selected cooling airflow. To activate this mode, cut the resistor located on the lower right hand corner of the selection
control board and wire in a standard dehumidistat. (Refer to figure 9.)
PROCEDURE 10 –SEQUENCE OF OPERATION
The sequence of operation will depend what type of thermostat selected. The unit has the ability to be used as:
1. Single stage A/C cooling with single stage heat.
2. Two stage A/C cooling with single stage heat.
3. Single stage heat pump with auxiliary / backup heat.
4. Two stage heat pump with auxiliary / backup heat & emergency heat.
Refer to the thermostat installation instructions for more information.
A. Continuous Fan
The blower runs continuously at a reduced airflow.
B. A/C Cooling only with Hot Water Heat
Cooling Mode – If the indoor temperature is above the thermostat set point and the humidity is below the humidity set
point if a dehumidistat is installed, the thermostat sends a signal to the fan coil and compressor which delivers cooling
airflow. If the humidity is above the humidity set point, then the fan coil delivers the cooling airflow at 80% of the
nominal.
Heating mode – If the indoor temperature is below the thermostat set point, the thermostat sends a signal to the fan coil
to deliver hot water heating airflow.
C. Heat Pump Cooling / Heating with backup Hot Water Heat.
Cooling Mode – If the indoor temperature is above the thermostat set point and the humidity is below the humidity set
point if a dehumidistat is installed, the thermostat sends a signal to the fan coil and heat pump which delivers cooling
airflow. If the humidity is above the humidity set point, then the fan coil delivers the cooling airflow at 80% of the
nominal.
Figure 10 - Select Control Board
13