35
Installation, Operation & Maintenance - HEH/HEV Series
DXM2 Control
- For detailed control information, see
DXM2 Application, Operation and Maintenance (AOM)
manual (part # 97B0003N15).
Field Selectable Inputs
- Test mode: Test mode allows
the service technician to check the operation of the
control in a timely manner. By momentarily pressing the
TEST pushbutton, the DXM2 control enters a 20 minute
test mode period in which all time delays are sped up
15 times. Upon entering test mode, the status LED
display will change, either flashing rapidly to indicate the
control is in the test mode, or displaying a numeric flash
code representing the current airflow if an ECM blower
is connected and operating. For diagnostic ease at
conventional thermostats, the alarm relay will also cycle
during test mode. The alarm relay will cycle on and off
similar to the fault LED to indicate a code representing
the last fault, at the thermostat. Test mode can be exited
by pressing the TEST pushbutton for 3 seconds.
Retry Mode
– If the control is attempting a retry of a
fault, the fault LED will slow flash (slow flash = one flash
every 2 seconds) to indicate the control is in the process
of retrying.
Field Configuration Options
–
Note: In the following
field configuration options, jumper wires should be
clipped ONLY when power is removed from the DXM2
control.
Water coil low temperature limit setting: Jumper 3 (JW3-
LT1 Low Temp) provides field selection of temperature
limit setting for LT1 of 30°F or 10°F [-1°F or -12°C]
(refrigerant temperature).
Not Clipped = 30°F [-1°C]. Clipped = 10°F [-12°C].
Alarm relay setting: Jumper 1 (JW1-AL2 Dry) provides
field selection of the alarm relay terminal AL2 to
be jumpered to 24VAC or to be a dry contact (no
connection).
Not Clipped = AL2 connected to R. Clipped = AL2 dry
contact (no connection).
JUMPERS (Set at Factory)
A0-2: Configure Modulating Valve or Variable-Speed
Pump
Set A0-2 jumper (Figure 26a) to “IOV” if using Internal
Modulating Motorized Valve or “PMW” if using Internal
Variable-Speed Pump.
DIP Switches
– Note: In the following field configuration
options, DIP switches should only be changed when
power is removed from the DXM2 control.
DIP Package #1 (S1)
– DIP Package #1 has 8 switches
and provides the following setup selections:
1.1
- Unit Performance Sentinel (UPS) disable: DIP
Switch 1.1 provides field selection to disable the UPS
feature.
On = Enabled. Off = Disabled.
1.2
- Compressor relay staging operation: DIP 1.2
provides selection of compressor relay staging operation.
The compressor relay can be selected to turn on with
a stage 1 or stage 2 call from the thermostat. This
is used with dual stage units (2 compressors where
2 DXM2 controls are being used) or with master/
slave applications. In master/slave applications,
each compressor and fan will stage according to
its appropriate DIP 1.2 setting. If set to stage 2, the
compressor will have a 3 second on-delay before
energizing during a Stage 2 demand. Also, if set for stage
2, the alarm relay will NOT cycle during test mode.
On = Stage 1. Off = Stage 2.
1.3
- Thermostat type (heat pump or heat/cool): DIP 1.3
provides selection of thermostat type. Heat pump or
heat/cool thermostats can be selected. When in heat/
cool mode, Y1 is the input call for cooling stage 1; Y2 is
the input call for cooling stage 2; W1 is the input call for
heating stage 1; and O/W2 is the input call for heating
stage 2. In heat pump mode, Y1 is the input call for
compressor stage 1; Y2 is the input call for compressor
stage 2; W1 is the input call for heating stage 3 or
emergency heat; and O/W2 is the input call for reversing
valve (heating or cooling, depending upon DIP 1.4).
On = Heat Pump. Off = Heat/Cool.
1.4
- Thermostat type (O/B): DIP 1.4 provides selection of
thermostat type for reversing valve activation. Heat pump
thermostats with “O” output (reversing valve energized
for cooling) or “B” output (reversing valve energized for
heating) can be selected with DIP 1.4.
On = HP stat with “O” output for cooling. Off = HP stat
with “B” output for heating.
1.5
- Dehumidification mode: DIP 1.5 provides
selection of normal or dehumidification fan mode. In
dehumidification mode, the fan speed relay will remain
off during cooling stage 2. In normal mode, the fan speed
relay will turn on during cooling stage 2.
DXM2 Controls
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