Manual 2100-738C
Page
41 of 73
FIGURE 29
Geothermal Compressor Logic Control Board
Jumper Designations
FIGURE 30
Modulating Water Line Control Board
compressor operation will be terminated; red fault
light illuminated. Logic control will then go through
5-minute delay on break plus random start sequence.
If no fault occurs on next run cycle, compressor will
continue operation. If fault reoccurs, hard lockout
occurs and fault signal is sent to L terminal.
NOTE Jumper wire is factory installed.
Over and Under Voltage Protection
When an under or over voltage condition exists, the
controller locks out the unit. When condition clears,
the controller automatically releases the unit to normal
operation and the compressor restarts after the random
start and anti-short cycle timings are met. The under
and over voltage protection starts at plus or minus
20% from nominal voltage and returns to operation at
plus or minus 10% from nominal voltage. All four LED
fault lights will flash when an over or under voltage
conditions occurs.
NOTE The over voltage protection can be disabled by
removing the O/V jumper on the geothermic
logic control board (see Figure 29).
Intelligent Reset
The geothermic logic control has an intelligent reset
feature after a safety control is activated. The controller
locks out the unit for 5 minutes; at the end of this
period, the controller checks to verify that all faults
have been cleared. If faults have been cleared, the
controller restarts the unit. If a second fault occurs, the
controller will lockout the unit until the control is reset
by breaking Y signal from thermostat. The last fault
will be kept in memory after a full lockout; this is only
cleared by cycling the unit power.
Modulating Water Line Control
On a call for cooling or heat pump (Y signal from
thermostat), the Y terminal has 24 volts applied and
YO output is energized. See Figure 30.
On a call for dehumidification (D signal from
thermostat, with no Y signal from thermostat), the D
terminal (input) is energized. Concurrently, the TWV
(3-way valve) terminal is energized.
When D is energized with no Y signal, the thermistor
connected to the board will start measuring the supply
air temperature at the leaving side of the indoor blower.
The board will modulate the water valve through a
signal sent from the SU and SC terminals to the valve
actuator.
When a cooling/heating call becomes active while the
system is operating in dehumidification mode, the
cooling/heating call becomes the default state. The
modulating water line board will have 24VAC at the
Y terminal starting a 75-second time delay. The time
delay will have to expire before the YO cooling/heating
signal becomes active. The purpose of the time delay
is to ensure the modulating valve is "full open" before
allowing the YO signal out of the board to initiate
cooling/ heating.
See
TROUBLESHOOTING MODULATING WATER
LINE CONTROL BOARD
on page 67 for further
information on modulating water line control.
MIS-4140
C
R
CONTROL BOARD
Y
Y0
SU
SC
R
C
TWV
D
MODULATING WATER LINE
THERMISTOR
MIS-4140
“WSD”
JUMPER
“TEST”
JUMPER
“O/V”
JUMPER
