Heat Controller DXM2 User Manual
APPLICATION, OPERATION
& MAINTENANCE MANUAL
DXM2 Digital
Heat Pump Controller
Heat Controller, Inc. • 1900 Wellworth Ave. • Jackson, MI 49203 • (517)787-2100 • www.heatcontroller.com
Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.
Table of Contents
DXM2 Electronic Heat Pump Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
DXM2 Physical Dimensions & Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
DXM2 Layout and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
DXM2 Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
DXM2 Service & Application Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Basic Troubleshooting Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Advanced Troubleshooting and Confi guration Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Troubleshooting Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DXM2 Wiring Diagram with Motorized Modulating Water Valve - Optional 96B0005N62 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
DXM2 Wiring Diagram (Standard Installation) - 96B0005N56 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Functional Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Performance Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
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Heat Controller, Inc. DXM2 UNIT CONTROLS Application, Operation, & Maintenance Manual
DXM2 Electronic Heat Pump Controls
DXM2 OVERVIEW
The manufacturer’s next generation control board, DXM2,
is the geothermal industry’s fi rst two-way communication.
The DXM2 electronic control is a robust, microprocessor
based heat pump controller that is advanced and featureladen for maximum application fl exibility. The DXM2
Control has relay outputs for Compressor, Compressor
Speed, Reversing Valve, Alarm Relay, and 2 confi gurable
relays for Fan, Fan Speed, HWG Pump, and Loop Pump,
and 2 confi gurable accessory relay outputs. For on board
diagnostics, there are 2 LED’s to provide status indication.
There are inputs for safety pressure switches, low
temperature protection thermistors, condensate overfl ow
sensor, DIP switch selection inputs, thermostat inputs, night
setback inputs, and emergency shutdown input. Additional
confi gurable temperature sensor inputs are available that
may be used for hot water, compressor discharge, leaving
air, leaving water, and entering water temperature sensors.
The DXM2 has an RS485 communications port to interface
with a communicating thermostat or other compatible
controls.
DXM2 Controller Part Number:
17B0002N02 DXM2 Control Board
General Operating Parameters
The following are general operating parameters for the
DXM2 Control:
• Operating Environment: -40°F to 176°F and up to 95%
relative humidity, non-condensing.
• Storage Environment: -40°F to 185°F and up to 95%
relative humidity, non-condensing.
Power Requirements
DXM2 only power draw -
• Normally 8 VA draw at 24VAC
• Maximum 12 VA draw at 24VAC. A dedicated 24VAC,
50-60Hz, 1Ph, 40VA transformer minimum is required for
typical WSHP application.
Grounding
The control board must be grounded from one of the C
terminals.
Basic Control Features
• Single or two–stage compressor control
• Anti-short cycle protection
• High pressure cut-out
• Loss of charge cut-out
• High and low voltage cut-outs
• Water coil low temperature cut-out
• Air coil low temperature cut-out
• Random start
• Status LED and Fault LED
• Reset lockout at unit or disconnect
• Condensate overfl ow sensor
• Intelligent fault retry
• Test Mode
• Multiple blower confi guration options
• Electric heat outputs
• Accessory water valve connection
Advanced Control Features
• Direct control of ECM blower
• Intelligent hot water generator control
• Two accessory relays confi gurable for multiple
applications
• Internal Flow Center output
• Proportional valve output
• Night setback with override capability
• Emergency shutdown capability
• Removable thermostat connector for ease of installation
and service
• Accepts conventional heat pump (Y,O) or heat/cool (Y,W)
thermostat types
• RS–485 port to interface with a communicating
thermostat or other compatible controls
• Boilerless electric heat
• Confi gurable inputs and outputs for advanced functions
Relay and Connection Contact Ratings
The following relays are mounted on the DXM2 Control:
• Compressor Relay: 40VA at 24VAC
• Compressor Speed Relay: 28VA at 24VAC
• Alarm Relay: 28VA at 24VAC
• Reversing Valve: 28VA at 24VAC
• Accessory Relay 1: 28VA at 24VAC
• Accessory Relay 2: 28VA at 24VAC
• Fan Enable / Loop Pump Relay: 1 HP at 240VAC
• Fan Speed / HWG Pump Relay: 1 HP at 240VAC
• Connection ratings on the DXM2 Control:
• ‘A’ terminal: 20VA at 24VAC. Larger solenoid valve draw
should be controlled with accessory relays.
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Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.
DXM2 Physical Dimensions & Layout
5"
C
Gnd
B-
P1
Y1
Y2
W
O
G
R
C
AL1
R
P2
AL2
R
NSB
C
7"
ESD
OVR
H
A
P3
R
NO1
NC1
COM
NO2
NC2
COM
R
COH
COM
Alarm
Relay
Factory Use
JW1
Acc1
Relay
Acc2
Relay
Off On
P11
AO2
Fault
S3
1 2 3 4
Off On
Gnd
P4
A+ 24V
P5
(240Vac)
Com
Micro
U1
Status
Off On
1 2 3 4 5 6 7 8
S2
A0-1 A0-2
S1
T1
T2 T2 T3 T3 T4 T4
N.O.
Fan Enable
Test
JW3
1 2 3 4 5 6 7 8
Relay
P10
CCH
(240Vac)
Fan Speed
P12
RV
Relay
Comp
Relay
P9
T5
T5
N.C.
N.O.
T6 T6
12
1
1
4
P8
12V
IN
OUT
Gnd
NC
HP
HP
LP
LP
LT1
LT1
LT2
LT2
RV
RV
CO
CO
P7
24Vdc
EH1
EH2
P6
CCG
CC
6 1/2"
Factory low
voltage molex
connection for
unit harness
Factory low
voltage molex
connection for
electric heat
harness
3/8” standoff
Note: There is only
one T1 connection
1.5
5 1/2"
Use 4 mounting screws
#6 sheet metal screw 1” long
4
Heat Controller, Inc. DXM2 UNIT CONTROLS Application, Operation, & Maintenance Manual
DXM2 Layout and Connections
Conventional
stat connection
Cabinet
temperature
sensor
(with variable
speed pump)
Communications
and HWG
Settings
Accessory
relays refer
to DXM2 AOM
for configuration
P1
Y1
Y2
W
O
G
R
C
AL1
P2
AL2
R
NSB
C
ESD
OVR
H
A
P3
R
NO1
NC1
COM1
NO2
NC2
COM2
R
COH
COM
Service tool
connection
C
R
JW1
Alarm
Relay
Acc1
F
Relay
sU yrotca
e
Acc2
Relay
Communicating
stat connection
Gnd
B-
A+ 24V
P5
Fault
Status
Off On
1 2 3 4
S3
Off On
1 2 3 4 5 6 7 8
S1
P11
T1
Gnd
AO2
P4
(240Vac)
N.O.
Com
Fan Enable
Test
Micro
U1
Off On
S2
A0-1 A0-2
JW3
1 2 3 4 5 6 7 8
CCH
Relay
P10
T2 T2 T3 T3 T4 T4
(240Vac)
Fan Speed
P12
RV
Relay
Comp
Relay
P9
T5
T5
N.C.
N.O.
T6 T6
12
1
1
4
P8
12V
IN
OUT
Gnd
NC
HP
HP
LP
LP
LT1
LT1
LT2
LT2
RV
RV
CO
CO
P7
24Vdc
EH1
EH2
P6
CCG
CC
Test Button
to Speed up
Time Delays
ECM Motor
Connection
Water Coil
Low Temp
Limit Setting.
JWT-LT1 jumper
should be clipped
for low temp
(antifreeze)
operation
Factory low
voltage molex
connection for
unit harness
Electric heat
connection
Configure
Confi gure
modulating valve
Modulating V alve
or variable
(Optional)
speed pump
24V to compressor
second-stage solenoid
for Y2/full
load capacity
Variable
speed pump
water temp
Entering
water temp
5
air temp
Leaving
Leaving
Entering Hot water
Compressor Discharge
Temperature
Use 4 mounting screws
temperature
#6 sheet metal screw
1” long
Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.
DXM2 Controls
THERMOSTAT COMPATABILITY - IT IS STRONGLY RECOMMENDED THAT A COMMUNICATING THERMOSTAT (7602-443)
BE USED WITH GEOMAX COMMUNICATING SYSTEMS FOR:
1. Four-wire connections between the thermostat, compressor section (HTS), and air handler (WDG).
2. Confi guring, monitoring and diagnosing the system in
PLAIN ENGLISH on the thermostat.
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 and Fault LED displays will change.
The Status LED will either fl ash rapidly to indicate the
control is in the test mode, or display a numeric fl ash
code representing the current airfl ow if an ECM blower is
connected and operating. The Fault LED will display the
most recent fault condition in memory. Note: A fl ash code
of 1 indicates there have been no faults stored in memory.
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.
The test mode can be exited by pressing the TEST
pushbutton for 3 seconds. The test Mode can also be
entered and exited by cycling the G input, 3 times within a
60 second time period.
During Test Mode, the control monitors to see if the LT1
and LT2 thermistors are connected and operating properly.
If the control is in Test Mode, the control will lockout, with
Code 9, after 60 seconds if:
a) the compressor is On in Cooling Mode and the LT1
sensor is colder than the LT2 sensor. or,
b) the compressor is On in Heating Mode and the LT2
sensor is colder than the LT1 sensor.
Retry Mode: If the control is attempting a retry of a fault,
the Fault LED will slow fl ash (slow fl ash = one fl ash every 2
seconds) to indicate the control is in the process of retrying.
Field Confi guration Options - Note: In the following fi eld
confi guration options, jumper wires should be clipped
ONLY when power is removed from the DXM2 control.
Note: Jumper 3 must not be clipped prior to adding
antifreeze to the water loop. Antifreeze protection to
10°F required. Clipping JW3 without antifreeze may
result in freeze damage and will void the unit warranty.
Water coil low temperature limit setting: Jumper 3 (JW3-
LT1 Low Temp) provides fi eld selection of temperature limit
setting for LT1 of 30°F or 10°F [-1°F or -12°C] (refrigerant
temperature).
Not Clipped = 30°F. Clipped = 10°F.
Alarm Relay Setting - Jumper 1 (JW1-AL2 Dry) provides
fi eld selection of alarm function when Alarm Relay is
energized.
Not Clipped = AL1 connected to R (24VAC) with Alarm
Relay active.
Clipped = Dry contact connection between AL1 and AL2
with Alarm Relay active.
JUMPERS (Set at Factory)
A0-2: Confi gure Modulating Valve (Optional)
Set A0-2 jumper (see Figure on page 5) to “IOV” if using
Internal Modulating Motorized Valve (optional).
DIP SWITCHES
Note: In the following fi eld confi guration options,
DIP switches should only be moved when power is
removed from the DXM2 Control to ensure proper
operation.
DIP Package #1 (S1)
DIP Package #1 is 8 position and provides the following
setup selections.
DIP 1.1: Unit Performance Sentinel Disable - Provides fi eld
selection to disable the UPS feature.
On = Enabled. Off = Disabled.
DIP 1.2: Compressor Relay Staging Operation - Provides
selection of Compressor Relay staging operation. The
Compressor Relay can be selected to turn on with 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. 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.
DIP 1.3: Thermostat Type (Heat/Cool) - Provides selection
of thermostat type. Heat Pump or Heat/Cool thermostats
can be selected. When in Heat/Cool Mode, Y1 is input call
for Cooling Stage 1, Y2 is input call for Cooling Stage 2,
W1 is input call for Heating Stage 1, and O/W2 is input call
for Heating Stage 2. In Heat Pump Mode, Y1 is input call
for Compressor Stage 1, Y2 is input call for Compressor
Stage 2, W1 is input call for Heating Stage 3 or Emergency
Heat, and O/W2 is the input call for RV (heating or cooling
dependent upon DIP 1.4).
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Heat Controller, Inc. DXM2 UNIT CONTROLS Application, Operation, & Maintenance Manual
DXM2 Controls
On = Heat Pump. Off = Heat/Cool.
DIP 1.4: Thermostat Type (O/B) - Provides selection of
thermostat type. Heat pump thermostats with “O” output on
with Cooling or “B” output on with Heating can be selected.
On = HP Stat with O output with cooling. Off = HP Stat with
B output with heating.
DIP 1.5: Dehumidifi cation Mode - Provides selection of
normal or Dehumidifi cation Fan Mode. In Dehumidifi cation
Mode, the fan speed will be adjusted for Cooling. In Normal
Mode, the fan speed will be normal during Cooling.
On = Normal Fan Mode. Off = Dehumidifi cation Mode.
DIP 1.6: DDC Output at EH2 - DIP Switch 1.6 provides
selection for DDC operation. If set to DDC Output at EH2,
the EH2 terminal will continuously output the last fault code
of the controller. If set to EH2 normal, then the EH2 will
operate as standard electric heat output.
On = EH2 Normal. Off = DDC Output at EH2.
DIP 1.7: Boilerless Operation - Provides selection
of Boilerless Operation. In Boilerless Mode, only the
compressor is used for Heating Mode when LT1 is above
the temperature specifi ed by the setting of DIP 1.8. If DIP
1.8 is set for 50°F, then the compressor is used for heating
as long as LT1 is above 50°F. Below 50°F, the compressor
is not used and the control goes into Emergency Heat
Mode, staging on EH1 and EH2 to provide heating.
On = normal. Off = Boilerless operation.
DIP 1.8: Boilerless Changeover Temperature - Provides
selection of boilerless changeover temperature setpoint.
On = 50°F. Off = 40°F.
DIP Package #2 (S2)
DIP Package #2 (S2) - A combination of dip switches 2.1,
2.2, 2.3, and 2.4, 2.5, 2.6 deliver confi guration of ACC1
and ACC2 relay options respectively. See Table 2 for
description and functionality.
DIP 2.7: Auto Dehumidifi cation Fan Mode or High Fan
Mode - Provides selection of Auto Dehumidifi cation Fan
Mode or High Fan Mode. In Auto Dehumidifi cation Mode,
the Fan Speed will be adjusted during Cooling IF the H
input is active. In High Fan Mode, the Fan will operate on
high speed when the H input is active.
DIP Package #3 (S3)
DIP Package #3 is 4 position and provides the following
setup selections.
DIP 3.1: Communications confi guration: Provides selection
of the DXM2 operation in a communicating system. The
DXM2 may operate as a communicating master or slave
device depending on the network confi guration. In most
confi gurations, the DXM2 will operate as a master device.
On = Communicating Master device (default). Off =
communicating Slave device.
Table 1: Accessory Relay 1 Confi guration
DIP 2.1 DIP 2.2 DIP 2.3 ACC1 Relay Option
ON ON ON Cycle with fan
OFF ON ON Digital night setback
ON OFF ON Water valve – Slow opening
ON ON OFF Outside air damper
OFF ON OFF
OFF OFF OFF option – Humidistat
OFF OFF ON Hydronic Economizer – 1st Stage
ON OFF OFF
All other DIP combinations are invalid
Whole House Dehumidifi cation
option – Dehumidistat
Hydronic Economizer – Both
Stages
Table 2: Accessory Relay 2 Confi guration
DIP 2.4 DIP 2.5 DIP 2.6 ACC2 Relay Option
ON ON ON Cycle with compressor
OFF ON ON Digital night setback
ON OFF ON Water valve – Slow opening
OFF OFF ON Humidifi er
ON ON OFF Outside air damper
All other DIP combinations are invalid
DIP 3.2: HWG Test Mode: Provides forced operation of the
HWG pump output, activating the HWG pump output for up
to fi ve minutes.
On = HWG test mode. Off = Normal HWG mode (default).
DIP 3.3: HWG Temperature: Provides the selection of the
HWG operating setpoint.
On = 150°F [66°C]. Off = 125°F [52°C] (default).
On = Auto Dehumidifi cation Mode (default). Off = High Fan
Mode.
DIP 2.8: Factory Setting - Normal position is On. Do not
change selection unless instructed to do so by the Factory.
DIP 3.4: HWG Status: Provides HWG operation control.
On = HWG mode enabled. Off = HWG mode disabled
(default)
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Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.
DXM2 Controls
SAFETY FEATURES
The following safety features are provided to protect
the compressor, heat exchangers, wiring and other
components from damage caused by operation outside of
design conditions.
Anti-Short Cycle Protection - The control features a 5
minute anti-short cycle protection for the compressor.
Note: The 5 minute anti-short cycle also occurs at
power up.
Random Start - The control features a 5-80 second
random start upon power up. The random start delay will
be present after a control power up and after returning from
Night Setback or Emergency Shutdown modes.
Extended Compressor Operation Monitoring - If the
compressor relay has been on for 4 continuous hours, then
the control will automatically turn off the compressor relay
and wait the short cycle protection time. All appropriate
safeties will be monitored during the off time. If all operation
is normal, and if the compressor demand is still present,
the control will turn the compressor back on.
Fault Retry - In Fault Retry Mode, the Fault LED begins
slow fl ashing to signal that the control is trying to recover
from a fault input. The DXM2 Control will stage off the
outputs and then “try again” to satisfy the thermostat call for
compressor. Once the thermostat input calls are satisfi ed,
the control will continue on as if no fault occurred. If 3
consecutive faults occur without satisfying the thermostat
call for compressor, then the control will go to Lockout
Mode. The last fault causing the lockout will be stored in
memory and is displayed at the Fault LED by entering the
Test mode.
CAUTION!
CAUTION!
remedy of faulting condition. Equipment damage may occur.
the DXM2 is in Lockout Mode, and the W input becomes
active, then Emergency Heat Mode will occur during
Lockout. For Emergency Heat, the fan and auxiliary heat
outputs will be activated.
Fault Code 2: High Pressure Switch – When the High
Pressure switch opens due to high refrigerant pressures,
the compressor relay is de–energized immediately. The
High Pressure fault recognition is immediate (does not
delay for 30 continuous seconds before de–energizing the
compressor). When the Test mode is activated, the Fault
LED will display a fault code of 2 for a High Pressure fault.
Fault Code 3: Loss of Charge Switch – The Loss of
Charge Switch must be open and remain open for 30
continuous seconds during a compressor “on” cycle to
be recognized as a Loss of Charge fault. If the Loss of
Charge switch is open for 30 seconds prior to compressor
power up it will be considered a Loss of Charge fault. The
Loss of Charge Switch input is bypassed for the initial 120
seconds of a compressor run cycle. When the Test mode
is active, the Fault LED will display a fault code of 3 for a
Loss of Charge fault.
Fault Code 4: Water Coil Low Temperature Cut-Out
Limit (LT1) - The control will recognize an LT1 fault, during
a compressor run cycle if:
a) the LT1 thermistor temperature is below the selected
Do not restart units without inspection and
low temperature protection limit setting for at least 50
seconds, AND
Note: LT1 and LT2 faults are factory set for one try, so
there will be no “retries” for LT1 and LT2 faults. The
control will only try one time for these faults.
FAULT CODES
Lockout
fl ashing. The compressor relay is turned off immediately.
The fan output will be turned off after the current blower off
delay unless auxiliary heat is active. The Lockout Mode
can be “soft” reset via the thermostat by removing the call
for compressor, or by a “hard” reset (disconnecting power
to the control). The fault code will be stored in non-volatile
memory that can be displayed by the Fault LED by entering
the Test mode, even if power was removed from the
control.
Lockout with Emergency Heat - If the DXM2 is
confi gured for Heat Pump thermostat Mode (see DIP 1.3),
- In Lockout Mode, the Fault LED will begin fast
b) the LT1 thermistor temperature is rising (getting
warmer) at a rate LESS than 2°F per 30 second time
period.
The LT1 input is bypassed for the initial 120 seconds of a
compressor run cycle. When the Test mode is active, the
Fault LED will display a fault code of 4 for a LT1 fault.
Fault Code 5: Air Coil Low Temperature Cut-Out
(LT2) - The control will recognize an LT2 fault, during a
compressor run cycle if:
a) the LT2 thermistor temperature is below the low
temperature protection limit setting for at least 50
seconds, AND
b) the LT2 thermistor temperature is rising (getting
warmer) at a rate LESS than 2°F per 30 second time
period.
The LT2 input is bypassed for the initial 120 seconds of a
8
Heat Controller, Inc. DXM2 UNIT CONTROLS Application, Operation, & Maintenance Manual
DXM2 Controls
compressor run cycle. When the Test mode is active, the
Fault LED will display a fault code of 5 for a LT2 fault.
Fault Code 6: Condensate Overfl ow - The Condensate
Overfl ow sensor must sense overfl ow levels for 30
continuous seconds to be recognized as a CO fault.
Condensate Overfl ow will be monitored at all times
during the compressor run cycle. When the Test mode
is active, the Fault LED will display a fault code of 6 for a
Condensate Overfl ow fault.
Fault Code 7: Over/Under Voltage Shutdown - An
Over/Under Voltage condition exists when the control
voltage is outside the range of 18VAC to 31.5VAC. Over/
UnderVoltage Shutdown is self-resetting in that if the
voltage comes back within range of 18.5VAC to 31VAC for
at least 0.5 seconds, then normal operation is restored.
This is not considered a fault or lockout. If the DXM2 is in
over/under voltage shutdown for 15 minutes, the Alarm
Relay will close. When the Test mode is active, the Fault
LED will display a fault code of 7 for an Over/Under Voltage
Shutdown.
Fault Code 8: Unit Performance Sentinel – UPS – The
UPS feature warns when the heat pump is operating
ineffi ciently. A UPS condition exists when:
a) In Heating Mode with compressor energized, if LT2
is greater than 125°F for 30 continuous seconds, or
b) In Cooling Mode with compressor energized, if LT1
is greater than 125°F for 30 continuous seconds, OR
LT2 is less than 40°F for 30 continuous seconds.
If a UPS condition occurs, the control will immediately go
to UPS warning. The status LED will remain on as if the
control is in Normal Mode. (see “LED and Alarm Relay
Operation Table”). Outputs of the control, excluding Fault
LED and Alarm Relay, will NOT be affected by UPS. The
UPS condition cannot occur during a compressor off cycle.
During UPS warning, the Alarm Relay will cycle on and off.
The cycle rate will be On for 5 seconds, Off for 25 seconds,
On for 5 seconds, Off for 25 seconds, etc. When the Test
mode is active, the Fault LED will display a fault code of 8
for an UPS condition.
Fault Code 9: Swapped LT1/LT2 Thermistors - During
Test Mode, the control monitors to see if the LT1 and LT2
thermistors are connected and operating properly. If the
control is in Test Mode, the control will lockout, with Code
9, after 60 seconds if:
a) the compressor is On in Cooling Mode and the LT1
sensor is colder than the LT2 sensor. Or,
b) the compressor is On in Heating Mode and the LT2
sensor is colder than the LT1 sensor.
When the Test mode is active, the Fault LED will display a
fault code of 9 for a Swapped Thermistor fault.
Fault Code 10: ECM Blower Fault – When operating
an ECM blower, there are two types of ECM Blower fault
conditions that may be detected.
a) An ECM blower fault will be detected and the control
will lockout after 15 seconds of blower operation with
the blower feedback signal reading less than 100
RPM.
b) An ECM blower fault will be detected when the ECM
confi guration is incorrect or incomplete. For this
fault condition, the control will continue to operate
using default operating parameters.
When the Test mode is active, the Fault LED will display a
fault code of 10 for an ECM Blower fault.
Fault Code 11: Low Air Coil Pressure Switch (Whole
House Dehumidifi cation Units Only) – When the Low
Air Coil Pressure switch opens due to low refrigerant
pressure in the cooling or reheat operating mode, the
compressor relay is de–energized immediately. The Low
Air Coil Pressure fault recognition is immediate (does not
delay for 30 continuous seconds before de–energizing
the compressor). When the Test mode is activated, the
Fault LED will display a fault code of 11 for a Low Air Coil
Pressure fault. Note: Low Air Coil Pressure fault will keep
the unit from operating in the cooling or reheat modes, but
heating operation will still operate normally.
Fault Code 12: Low Air Temperature (Whole House
Dehumidifi cation Units Only) – The control will recognize
an Low Air Temperature fault, during cooling, reheat, or
constant fan operation if the LAT thermistor temperature
is below 35 degrees for 30 continuous seconds. When
the Test mode is activated, the Fault LED will display a
fault code of 12 for a Low Air Temperature fault. Note: Low
Air Temperature fault will keep the unit from operating in
the cooling, reheat, or constant fan modes, but heating
operation will still operate normally.
Diagnostic Features
The green Status LED and red Fault LED on the DXM2
Control advise service personnel of the current status of
the DXM2 Control. The LED’s will indicate the current
operating status of the DXM2, as well as the LAST fault in
memory. If there is no fault in memory and the fault display
is selected, the Fault LED will fl ash Code 1. See Table 3 for
a complete listing of codes.
UNIT OPERATION DESCRIPTION
Power Up - The unit will not operate until all the inputs and
safety controls are checked for normal conditions.
9
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