Latent capacities for systems using the FK4B Fan Coil are better
than average systems. If increased latent capacity is an application
requirement, the FK4B can be wired to provide this requirement by
adjusting its airflow in response to standard humidistat input. Fig.
22 illustrates the wiring connections to activate de-humidify mode.
Carefully consult product airflow data for cooling and dehumidi-
fying mode.
FK4C and FV4A
The FK4C and FV4A are similar to the discontinued FK4B as they
have both integrated controls and motor (ICM2) and their own
special circuit board. The difference is in the software of the
ICM2. Adjustments have been made in the CFM to enhance the
different modes of operation, such as, increased dehumidification.
Set up of desired airflow is obtained by the selections made on
Easy Select circuit board. The motor delivers requested airflow as
defined by signals received from Easy Select Board and the ICM2
software programming.
If a Thermidistat is used, additional CFM adjustments are made
through the ICM2 for super dehumidification in cooling mode.
Unlike fan coils using induction motors where static pressure
affects airflow, the FK4C and FV4A are constant airflow units.
The blower delivers requested airflow regardless of static pressure.
Consult FK4C and FV4A Product Data for static pressure limits.
The ICM2 is pre-programmed and contains airflow tables for all
modes of operation. Blower characteristics (requested airflow,
torque, and speed) are known from laboratory testing. If any 2
characteristics are known, the third is defined.
Requested airflow is known from Easy Select board configuration
and thermostat signals. Torque is known because it is directly
related to stator current which is measured by motor control. Speed
is measured by counting back EMF pulses from stator windings.
This information is entered into an expression which calculates
torque from speed and airflow numbers. If calculation does not
match stored blower characteristics, torque is adjusted until
agreement is reached. This calculation and adjustment is per-
formed every 0.8 sec while motor is in operation. There is no direct
measure of static pressure, but unit does react to a change in static
to maintain constant airflow. A change in pressure will result in a
change in stator speed and torque. The motor will begin to adjust
on the next sampling, calculate new desired speed and torque, and
adjust as necessary.
IX.
INTEGRATED CONTROLS AND MOTOR (ICM2)
An ICM2 is fed high voltage AC power through the 5-pin
connector. (See Fig. 23.) The AC power is then rectified to DC by
a diode module. After rectification, DC signal is electronically
communicated and fed in sequential order to 3 stator windings.
The frequency of these commutation pulses determines motor
speed. The rotor is permanently magnetized.
An ICM2 is powered with high voltage at all times. The motor will
run with high voltage alone. Low voltage must be applied to
control plug to run motor.
X.
PCB LAYOUT AND DESCRIPTION
NOTE:
Layout of actual PCB is depicted in Fig. 24 and 25.
The PCB interfaces a variable-speed ICM2 with other system
components.
Power for system is supplied from a 230-vac, 60-Hz line. Class 2
voltage (24 vac nom.), used for thermostat connections, is derived
from transformer located in close proximity to PCB. The primary
and secondary of transformer are connected to PCB. The 24-vac
secondary circuit includes 5-amp automotive-type fuse in SEC2
circuit.
Connection to heater panel is made through 12-circuit connector
P1. Connections to thermostat are made at screw terminals.
Twenty-one pin terminals comprise field select taps for motor.
Fuse Data: 5-amp automotive-type ATC/ATO (tan)
32v
200 percent current opening time of 5 sec maximum
A.
Electrical Connections
Twenty-one 0.110-in pin terminals are used to provide program-
ming selections for operating modes of ICM2. The 6 selection
modes are listed below. For additional information, refer to Easy
Select Configuration Taps section.
AUX Heat Range—(Violet Wire)
AC/HP Size—(Blue Wire)
Type—(Orange Wire)
AC/HP CFM Adjust—(Black Wire)
AC/HP Time Delay—(Grey Wire)
Continous Fan—(Yellow Wire)
XI.
SEQUENCE OF OPERATION
A.
Continuous Fan Mode
The thermostat closes circuit R to G. The G signal is sent directly
to ICM2.
B.
Cooling Mode—Single Speed or 2-Speed High
Thermostat closes circuits R to Y/Y2 and R to O (heat pump only)
for single speed. A circuit from R to Y1 is also required for
2-speed high.
C.
Cooling Mode—Two-Speed Low
Thermostat closes circuits R to Y1 and R to O (heat pump only).
The Y1 & O signals are sent to ICM2.
D.
Cooling Mode—Super Dehumidification Call
from Thermidistat
Thermidistat closes circuits R to Y/Y2 and R to O (heat pump
only) for single speed. A circuit from R to Y1 is also required for
2-speed high. Thermidistat call for super dehumidification opens
→
Fig. 21—KFAIR0101ACR Relay Kit
Wiring Schematic
A98625
24 VAC RELAY
FAN COIL
230 VAC OR
115 VAC BRANCH CKT
AUX1
(C)
AUX2
(G)
GND HOT NEUT
GRN
BLK
WHT
NO
COM
BLK
BLK
RED
RED
WHT
TO EAC
Fig. 22—Humidistat Wiring for De-Humidify Mode
A93215
HUMIDISTAT
TO PCB TERMINAL
MARKED 'RED'
RED WIRE
FROM ICM2
MOTOR
HUMIDISTAT WIRING FOR
DE-HUMIDIFY MODE
—28—
