DXM Electronic
Heat Pump Control
Application, Operation and
Maintenance Guide
TABLE OF CONTENTS
Page 2
DXM Overview
3
Physical Dimensions and Layout
3
General Operating Parameters
4
Control Features
4
Field Selectable Inputs
4
Safety Features
6
Diagnostic Features
7
Unit Operation Description
8
Special Application Notes
9
Thermostat Inputs
10
Other Outputs
13
Typical Schematic
14
Product Design and Application Notes
15
Sensors / Thermistors
15
Thermostat Details
16
Troubleshooting
17
DXM / CXM Electronic Control Features Comparison
Basic Features
High and Low Refrigerant Pressure Protection
E/Mech
CMC-2001
CMC-2005
CMC-2010
S
S
S
S
Klixon
Klixon
Klixon
Klixon
Anti-Short-Cycle Time-Delay
O
S
S
S
Emergency Shutdown
O
S
S
S
Random Start
O
S
S
S
Night Setback with Override
O
S
S
S
Condensate Overflow Sensor
O
S
S
S
S
S
S
O
O
O
E
E
E
E
E
E
Low Water Flow Protection
Pump Restart
Alarm (dry contact output)
O
Outdoor Air Damper Control
Motorized Water Valve Control
T-Stat Inputs Compatible with Triacs
True 24 VAC Thermostat Signals
S
S
CXM
S
DXM
S
DXM-Lon
S
Thermistor Thermistor Thermistor
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
Advanced Features
Reduced Reversing Valve Operation
S
High/Low Fan Speed
S
S
S
S
S
O
S
S
Intelligent Reset
S
S
S
S
S
S
High and Low Voltage Protection
S
S
S
S
S
S
S
S
S
Air Coil Freeze Protection
Thermostat Type Select (Y,O or Y,W)
S
S
S
S
Hot Gas Reheat Control
S
S
Boilerless Electric Heat Control
S
S
2 Stage Compressor Capacity Control
S
S
Dehumidistat Input
S
S
Reversing Valve Mode Select (O or B)
S
S
Hydronic Economizer Control
S
S
S
S
3
S
3
CE Approval
S
S
S
Unit Performance Sentinel (UPS)
S
S
S
Electric Heat Control Outputs
Freeze Setpoint Select (water, antifreeze)
Multiple Units on One Thermostat
S
3
3
3
Service and Reliability Features
Service Test Mode
S
S
S
S
S
S
LED Fault and Status Lights
S
S
S
S
S
S
S
S
Removable Low Voltage Connector
Noise Immune Communication Protocol
Harness-Type Factory Wiring Connectors
Fully Noise-Tested Design
S
S
S
S
S
S
S
S
O
O
DDC / Energy Management Features
Echelon / LonMark compatible
S
Johnson Controls Metasys compatible
S
S
Leaving Water Temperature Display
S
S
S
S
Leaving Air Temperature Display
Demand Load Shed
Room Air Temperature and Setpoint Display
S = Standard
O = Optional
E = Either WV or OAD
S
S
S
S
S
S
Rev. 5/24/00 m
DXM-Lon: With LonMark Module
E/Mech = ElectroMechanical Controls
Page 3
DXM Overview
The DXM Electronic Control is a robust, microprocessor
based heat pump controller that is advanced and featureladen for maximum application flexibility. The DXM
control has all of the basic CXM control features plus
additional inputs and outputs which allow for extensive
system capability. The DXM control has relay outputs
for compressor, fan, fan speed, reversing valve, alarm
relay, and 2 configurable accessory outputs. There are 3
LED’s which provide status indication.
switch selection inputs, thermostat inputs, night setback
inputs, and emergency shutdown input.
There are also 2 communications ports: one for
communications with DXM dual compressor heat pumps,
and another for communications with DXM slaved heat
pumps.
CM Part Number:
17B0002N01
DXM Control Board
There are inputs for safety pressure switches, freeze
protection thermistors, condensate overflow sensor, dip
Physical Dimensions and Layout
Y1
P5
Com2
R
Y2
W1
C
C
P1
Sig
R
C
Sig
5"
Com
Fan
FanEnable
Enable
(240Vac)
(240Vac)
P4
Com1
N.O.
O/W2
G
Com
DXM 17P0002N01 Rev A
R
Fan Speed
(240Vac)
C
AL1
N.O.
N.C.
AL2
Alarm
Relay
R
NSB
JW4
AL2 Dry
Micro
Status 1
HP
HP
LP
LP
Fault
FP1
FP1
FP2
FP2
RV
RV
RV
Relay
CO
12 CO
C
Test
ESD
7"
OVR
H
P2
A
Micro
R
P7
NO1
NC1
Test Jumpers
JW3 - FP1 Low Temp
JW2 - FP2 Low Temp
JW1 - LP Norm. Open
COM
NO2
COM
3/8” standoff
R
P3
Facttory Use
NC2
Acc1
Relay
Off
On
EH1
4 EH2
P6
On
Comp
Relay
Acc2
Relay
CCG
CC
S1
1.62
5
Off
1 24Vdc
S2
5 1/2"
4 Mounting
Screws #6 sheet
metal screw 1” long
Page 4
6 1/2"
Factory low
voltage molex
connection for
unit harness
Factory low
voltage molex
connection for
electric heat
harness
General Operating Parameters
Advanced Control Features
The following are general operating parameters for the
DXM control:
• Two accessory relays configurable for multiple
applications
Operating Environment: -40°F to 176°F and up to 95%
relative humidity, non-condensing.
• Night setback with override capability
Storage Environment: -40°F to 185°F and up to 95%
relative humidity, non-condensing.
• Communications port for DXM dual compressor
applications
Power Requirements:
• Communications port for DXM slave heat pump
applications
DXM only power draw -
• Emergency shutdown capability
- Normally 8 VA draw at 24VAC
• Intelligent fan speed capabilities
- Maximum 12 VA draw at 24VAC. A dedicated
24VAC, 50-60Hz, 1Ph, 40VA transformer
minimum is required for typical WSHP application.
• Boilerless electric heat
Relay and Connection Contact Ratings:
The following relays are mounted on the DXM control:
• Removable thermostat connector for ease of
installation and service
• Accepts heat pump (Y,O) or heat/cool (Y, W)
thermostat types
Alarm Relay: 28VA at 24Vac
• Accepts heat pump thermostats with O or B reversing
valve control logic
Reversing Valve: 28VA at 24Vac
• Dehumidistat input for advanced functions
Compressor Relay: 40VA at 24Vac
Accessory Relay 1: 28VA at 24Vac
Accessory Relay 2: 28VA at 24Vac
Field Selectable Inputs
Fan Enable Relay: 1 HP at 240Vac
Test Mode – Test Mode allows the service personnel to
check the operation of the control in a timely manner. By
momentarily shorting the test terminals, the DXM control
enters a 20 minute Test Mode period in which all time
delays are sped up 15 times. During Test Mode, the Test
LED will turn on. For Diagnostic ease at the thermostat, 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.
NOTE: Code 1 indicates there is no fault in memory;
stated differently, the control has not faulted since the
last power-down to power-up sequence. Test mode can
be exited by shorting the test terminals for 3 seconds.
Test mode can also be entered and exited by cycling the
G input, 3 times within a 60 second time period.
Fan Speed Relay: 1 HP at 240Vac
Connection ratings on the DXM control:
‘A’ terminal: 20VA at 24Vac. Larger solenoid valve
draw should be used with accessory relays.
Grounding: The control board is grounded through two
of the metal standoffs.
Basic Control Features
• Anti-short cycle protection
• High and Low pressure cutouts
• High and Low voltage cutouts
• Water Coil freeze protection
• Air Coil freeze protection
• Random Start
• Status LED, Test LED, and Fault LED
• Reset Lockout at unit or disconnect
• Intelligent Reset
Retry Mode - If the control is attempting a retry of a fault,
the status LED will slow flash (slow flash=one flash every
2 seconds) to indicate the control is in process of retrying.
NOTE: In the following field configuration options,
jumper wires should be clipped ONLY when power is
removed from the DXM control.
• Test Mode
Water Coil Freeze Protection Limit Setting - Jumper 3
(JW3-FP1 Low Temp) provides field selection of
temperature limit setting for FP1 to be 30°F or 10°F.
• Electric Heat Outputs
Not Clipped=30°F. Clipped=10°F.
• Accessory Water Valve Connection
Air Coil Freeze Protection Limit Setting - Jumper 2
(JW2-FP2 Low Temp) provides field selection of
temperature limit setting for FP2 to be 30°F or 10°F.
• Condensate Overflow sensor
• Optional LonWorks Control
Not Clipped=30°F. Clipped=10°F.
Page 5
Alarm Relay Setting - Jumper 4 (JW4-AL2 Dry)
provides field selection of Alarm Relay terminal AL2 to
be jumpered to 24Vac or to be dry (no connection).
Not Clipped=AL2 connected to R. Clipped=AL2 dry
contacts (no connection).
Low Pressure Normally Open – Jumper 1 (JW1-LP
Norm Open) Provides field selection for Low Pressure
input to be Normally Closed or Normally Open.
Not Clipped = LP Normally Closed. Clipped = LP
Normally Open.
Dip Switches
NOTE: In the following field configuration options,
dip switches should only be moved when power is
removed from the DXM control to insure proper
operation.
Dip Package #1 (S1)
Dip Package #1 is 8 position and provides the following
setup selections.
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.
On=Normal fan mode. Off=Dehumidification mode.
DIP 1.6 Not Used - Dip 1.6 Is not used.
Boilerless Operation - Dip 1.7 provides selection of
Boilerless Operation. In Boilerless mode, only the
compressor is used for heating mode when FP1 is above
the temperature specified 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 FP1 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. If a thermal switch is being used in
place of the FP1 thermistor, then only the compressor
will be used for heating mode when the FP1 terminals are
closed. If the FP1 terminals are open, then the
compressor is not used and the control goes into
Emergency Heat mode.
On=normal. Off=Boilerless operation.
Unit Performance Sentinel Disable - Dip Switch 1.1
provides field selection to disable the UPS feature.
Boilerless changeover temperature - Dip 1.8 provides
selection of Boilerless changeover temperature setpoint.
On = Enabled. Off = Disabled.
On=50°F. Off=40°F.
Compressor Relay Staging Operation - Dip 1.2 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 DXM 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.
Thermostat Type (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 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).
On=Heat Pump. Off=Heat/Cool.
Thermostat Type (O/B) - Dip 1.4 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.
Page 6
Table 1. Accessory Relay 1 Configuration
Dip 2.1
Dip 2.2
Dip 2.3
Acc1 Relay Option
On
Off
On
On
On
On
Off
On
On
On
On
Off
Cycle with fan
Digital NSB
Water valve – slow opening
OAD
All other DIP combinations are invalid
Dip Package #2 (S2)
Dip Package #2 is 8 position and provides the following
setup selections.
Accessory1 relay personality - Dip 2.1 provides selection
of Acc1 relay personality. See Table 1.
Accessory1 relay personality -Dip 2.2 provides selection
of Acc1 relay personality. See Table 1.
Accessory1 relay personality -Dip 2.3 provides selection
of Acc1 relay option. See Table 1.
Accessory2 relay personality - Dip 2.4 provides selection
of Acc2 relay personality. See Table 2.
Accessory2 relay personality -Dip 2.5 provides selection
of Acc2 relay personality. See Table 2.
Accessory2 relay personality -Dip 2.6 provides selection
of Acc2 relay option. See Table 2.
Auto Dehumidification Fan Mode or High Fan Mode Dip 2.7 provides selection of Auto Dehumidification Fan
Mode or High Fan Mode. In Auto Dehumidification
Mode, the Fan Speed relay will remain off during
Cooling Stage 2 IF the H input is active. In High Fan
Mode, the Fan Enable and Fan Speed relays will turn on
when the H input is active.
On=Auto Dehumidification Mode. Off=High Fan Mode.
DIP 2.8 Not Used - Dip 2.8 not used.
Table 2. Accessory Relay 2 Configuration
Dip 2.4 Dip 2.5 Dip 2.6
On
Off
On
On
On
On
Off
On
On
On
On
Off
Acc2 Relay Option
Cycle with compressor
Digital NSB
Water valve – slow opening
OAD
All other DIP combinations are invalid
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 by the Fault LED.
Lockout - In Lockout mode, the Status LED will begin
fast flashing. The Fault LED will be flashing a code
representing the last fault, which occurred that caused the
lockout. The compressor relay is turned off immediately.
Lockout mode can be soft reset via the thermostat by
removing the call for compressor, or can be hard reset via
the disconnect. The last fault causing the lockout will be
stored in memory and is displayed by the Fault LED.
Lockout with Emergency Heat - If the DXM is
configured for Heat Pump thermostat mode (see dip 1.3),
the DXM is in Lockout mode, and the W input becomes
active, then Emergency Heat mode will occur during
Lockout.
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.
High Pressure Switch - When the High Pressure Switch
opens due to high refrigerant pressures, the Compressor
relay is de-energized immediately since the High
Pressure Switch is in series with the compressor
contactor coil. The High Pressure Fault recognition is
immediate as well. The Fault LED will immediately
begin flashing Code 2 when a High Pressure Fault
occurs.
High Pressure Lockout Code = 2
Example: 2 quick flashes, 10-sec pause, 2 quick flashes,
10-sec. pause, etc.
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 including the LP will be
monitored during the off time. If all operation is normal,
then if the compressor demand is still present, the control
will turn the compressor back on.
Fault Retry - In Fault Retry mode, the Status LED
begins slow flashing to signal that the control is trying to
recover from a fault input. The Fault LED will also
begin flashing a code representing the last fault, which
occurred. The DXM control will stage off the outputs
and then “try again” to satisfy the thermostat call for
compressor. Once the thermostat input calls are satisfied,
the control will continue on as if no fault occurred. If 3
Low Pressure Switch - The Low Pressure Switch must
be open and remain open for 30 continuous seconds
during a compressor “on” cycle to be recognized as a
Low Pressure fault. If the low pressure switch is open
for 30 seconds prior to compressor power up it will be
considered a low pressure (loss of charge) fault. The Low
Pressure Switch input is bypassed for the initial 60
seconds of a compressor run cycle. The Fault LED will
immediately begin flashing Code 3 when a Low Pressure
Fault occurs.
Low Pressure Lockout Code = 3
Water Coil Freeze Protection (FP1) - The FP1
thermistor temperature must be below the selected freeze
protection limit setting for 30 continuous seconds during
a compressor run cycle to be recognized as a FP1 fault.
The FP1 input is bypassed for the initial 60 seconds of a
compressor run cycle. The Fault LED will immediately
begin flashing Code 4 when a FP1 Fault occurs.
FP1 Lockout Code = 4
Page 7
Air Coil Freeze Protection (FP2) - The FP2 thermistor
temperature must be below the selected freeze protection
limit setting for 30 continuous seconds during a
compressor run cycle to be recognized as a FP2 fault.
The FP2 input is bypassed for the initial 60 seconds of a
compressor run cycle. The Fault LED will immediately
begin flashing Code 5 when a FP2 Fault occurs.
FP2 Lockout Code = 5
Condensate Overflow - The Condensate Overflow sensor
must sense overflow levels for 30 continuous seconds to
be recognized as a CO fault. Condensate Overflow will
be monitored at all times. The Fault LED will
immediately begin flashing Code 6 when a Condensate
Overflow Fault occurs.
CO Lockout Code = 6
Over/Under Voltage Shutdown - An Over/Under
Voltage condition exists when the control voltage is
outside the range of 19Vac to 30Vac. Over/Under
Voltage Shutdown is self-resetting in that if the voltage
comes back within range of 19Vac to 30Vac for at least
0.5 seconds, then normal operation is restored. This is
not considered a fault or lockout. If the DXM is in over/
under voltage shutdown for 15 minutes, the alarm relay
will close.
Over/Under Voltage Shutdown Code = 7
Page 8
Unit Performance Sentinel-UPS (patent pending) - The
UPS feature warns when the heat pump is operating
inefficiently. A UPS condition exists when:
a) In heating mode with compressor energized, if FP2 is
greater than 125°F for 30 continuous seconds, or
b) In cooling mode with compressor energized, if FP1 is
greater than 125°F for 30 continuous seconds, OR
FP2 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…
Unit Performance Sentinel Warning Code = 8
Diagnostic Features
The Status LED and Fault LED on the DXM control
advises service personnel of the current status of the
DXM control. The Status LED will indicate the current
mode that the DXM control is in. The Fault LED will
ALWAYS flash a code representing the LAST fault in
memory. If there is no fault on memory, then the Fault
LED will flash Code 1. See Table 3 for a complete
listing of codes.
Table 3. LED and Alarm Relay Output Table
Description of Operation
Normal Mode
Status LED green
On
Test LED yellow
Off
Fault LED red
Flashing Appropriate Code
Normal Mode with UPS
On
Off
Flashing Code 8
DXM is non-functional
Test Mode
Off
-
Off
On
Off
Flashing Appropriate Code
Night Setback
ESD
Invalid T-stat Inputs
No Fault in Memory
HP Fault
LP Fault
FP1 Fault
FP2 Fault
CO Fault
Flashing Code 2
Flashing Code 3
Flashing Code 4
On
Slow Flash
Slow Flash
Slow Flash
Slow Flash
Slow Flash
Off
Off
Off
Off
Off
Off
Flashing Appropriate Code
Flashing Appropriate Code
Flashing Appropriate Code
Flashing Code 1
Flashing Code 2
Flashing Code 3
Flashing Code 4
Flashing Code 5
Flashing Code 6
Over/Under Voltage
Slow Flash
Off
Flashing Code 7
HP Lockout
LP Lockout
FP1 Lockout
FP2 Lockout
CO Lockout
Fast Flash
Fast Flash
Fast Flash
Fast Flash
Fast Flash
Off
Off
Off
Off
Off
Flashing Code 2
Flashing Code 3
Flashing Code 4
Flashing Code 5
Flashing Code 6
Alarm Relay
Open
Cycle (closed 5 sec,
open 25 sec, …)
Open
Cycling Appropiate
Code
Open
Open
Open
Open
Open
Open
Open (closed after 15
minutes)
Closed
Closed
Closed
Closed
Closed
NOTES:
a)"Flashing Appropriate Code" means that the Fault LED will
ALWAYS flash a code representing the LAST fault in memory.
If there is no fault in memory, the Fault LED will flash code 1.
b) Codes will be displayed with a 10 second Fault LED off period.
c) Slow flash will be 1 flash per every 2 seconds.
d) Fast flash will be 2 flash per every 1 second.
Unit Operation Description
PowerUp
The unit will not operate until all the inputs and safety
controls are checked for normal conditions. NOTE: The
compressor will have a 5-minute anti-short cycle
delay at power-up.
Standby/Fan Only
In Standby mode, the compressor will be off. The Fan
Enable, Fan Speed, and RV relays may be on if
appropriate inputs are present. If there is a Fan 1
demand, then the Fan Enable relay will turn on
immediately. If there is a Fan 2 demand, then the Fan
Enable and Fan Speed relays will turn on immediately.
NOTE: Dip1.5 (Dehum Fan Mode Select) has no
effect upon Fan 1 and Fan 2 outputs.
The RV relay will not directly track the input demands
for RV, the DXM control will employ “smart RV”
control. This ensures that the RV will only switch
positions if the thermostat has called for a heating/
cooling mode change.
Heating Stage 1
In Heating Stage 1 mode, the Fan Enable and Compressor
relays are turned on immediately. If configured as Stage 2
(dip1.2=off), then the compressor and fan will not turn on
until there is Stage 2 demand. The Fan Enable relay and
Compressor relay are turned off immediately when the
Heating Stage 1 demand is removed. The control reverts
to Standby mode. If there is a Master/Slave situation or a
Dual Compressor situation, all Compressor relays and
related functions will track with their associated dip1.2.
Heating Stage 2
In Heating Stage 2 mode, the Fan Enable and
Compressor relays remain on. The Fan Speed relay is
turned on immediately.
The Fan Speed relay is turned off immediately when the
Heating Stage 2 demand is removed. The control reverts
to Heating Stage 1 mode. If there is a Master/Slave
situation or a Dual Compressor situation, all Compressor
relays and related functions will track with their
associated dip1.2.
Heating Stage 3
In Heating Stage 3 mode, the Fan Enable, Fan Speed and
Compressor relays will remain on. EH1 output is turned
on immediately. With continuing Heating Stage 3
demand, EH2 will turn on after 10 minutes. EH1 and
EH2 are turned off immediately when the Heating Stage
3 demand is removed. The control reverts to Heating
Stage 2 mode. During Heating Stage 3 mode, EH2 will
be off (or will turn off if already on) if FP1 is greater
Page 9
than 45°F AND FP2 is greater than 110°F (FP2 greater
than 110°F includes the condition that FP2 is shorted).
This condition will have a 30-second recognition time.
During Heating Stage 3 mode, EH1, EH2, Fan Enable
and Fan Speed will be on if the G input is not active.
Slave situation or a Dual Compressor situation, all
Compressor relays and related functions will track with
their associated dip1.2.
Emergency Heat
In Cooling Stage 2 mode, the Fan Enable, Compressor,
and RV relays remain on. The Fan Speed relay is turned
on immediately (see dip1.5). The Fan Speed relay is
turned off immediately when the Cooling Stage 2
demand is removed. The control reverts to Cooling
Stage 1 mode. If there is a Master/Slave situation or a
Dual Compressor situation, all Compressor relays and
related functions will track with their associated dip1.2.
In Emergency Heat mode, the Fan Enable and Fan Speed
relays are turned on. EH1 is turned on immediately.
With continuing Emergency Heat demand, EH2 will turn
on after 5 minutes. EH1 and EH2 are turned off
immediately when the Emergency Heat demand is
removed. The Fan Enable and Fan Speed relays will turn
off after a 60-second delay. The control reverts to
Standby mode. During Emergency Heat mode, EH1,
EH2, Fan Enable and Fan Speed will be on if the G input
is not active.
Cooling Stage 1
In Cooling Stage 1 mode, the Fan Enable, Compressor,
and RV relays are turned on immediately. If configured
as Stage 2 (dip1.2=off), then the compressor and fan will
not turn on until there is Stage 2 demand. The Fan
Enable and Compressor relays are turned off immediately
when the Cooling Stage 1 demand is removed. The
control reverts to Standby mode. The RV relay remains
on until there is a Heating demand. If there is a Master/
Special Application Notes
Generally the following applications are based upon
configuring the accessory relays.
Cycle with Fan - If an Accessory relay is configured to
“cycle with fan”, the Accessory relay will be on any time
the Fan Enable relay is on.
Cycle with Compressor - If an Accessory relay is
configured to “cycle with compressor”, the Accessory
relay will be on any time the Compressor relay is on.
Digital Night Setback - If an Accessory relay is
configured for Digital NSB, the Accessory relay will be
on any time the NSB input is connected to Ground “C”.
NOTE: If there are no Accessory relays configured for
Digital NSB, then the NSB and OVR inputs are
automatically configured for “mechanical” operation.
See Mechanical NSB operation below.
Mechanical Night Set Back - When the NSB input is
connected to Ground “C”, all thermostat inputs (G, Y1,
Page 10
Cooling Stage 2
Night Low Limit (NLL) Staged Heating
In NLL Staged Heating mode, the OVR input becomes
active and is recognized as a call for Heating. (OVR is
an alternate means of calling for Heating mode). In
NLL Staged Heating mode, the control will
immediately go into Heating Stage 1 mode. With an
additional 30 minutes of NLL demand, the control will
go into Heating Stage 2 mode. With another additional
30 minutes of NLL demand, the control will go into
Heating Stage 3 mode.
Y2, W1, and O/W2) are ignored. A thermostat setback
Heating call can then be connected to the OVR input. If
the OVR input becomes active, then the DXM will enter
NLL Staged Heating mode. NLL Staged Heating Mode
would then provide heating during the NSB period.
Water Valve/Slow Opening - If an Accessory relay is
configured for Water Valve/Slow Opening, the
Accessory relay will turn on 60 seconds prior to the
Compressor Relay turning on.
Outside Air Damper-If an Accessory relay is configured
for OAD, the Accessory relay will normally turn be on
any time the Fan Enable relay is on. But, following a
return from NSB (NSB input no longer connected to
Ground “C”) to Normal Mode, the Accessory relay will
not turn on for 30 minutes even if the Fan Enable relay is
on. After this 30-minute timer expires, the Accessory
relay will turn on if the Fan Enable relay is on.
NSB and Override - NSB is the input for Night
Thermostat Inputs
Table 10 displays inputs and output signals. Table 4
shows the resulting demand from differing combinations
of inputs.
Y1 - Y1 is the input for compressor stage 1 if dip1.3=on.
Y1 is the input for Cooling Stage 1 if dip1.3=off.
Y2 - Y2 is the input for compressor stage 2 if dip1.3=on.
Y2 is the input for Cooling Stage 2 if dip1.3=off.
W1 - If Y1 and Y2 are active and dip1.3=on, then W1 is
the input for Heating Stage 3. If Y1 and Y2 are not
active and dip1.3=on, then W1 is the input for
Emergency Heat. If dip1.3=off, then W1 is the input for
Heating Stage 1.
O/W2 - O/W2 is the input for Reversing Valve relay if
dip1.3=on and dip1.4=on. O/W2 is the input for Heating
Stage 2 if dip1.3=off. O/W2 is the input for “Heat
Mode” if dip1.3=on and dip1.4=off; this means that the
thermostat outputs a “B” call when in Heating mode and
does NOT have an “O” output. The DXM control will
employ “Smart RV” control. This ensures that the RV
will only switch positions if the thermostat has called for
a heating/cooling mode change.
G - G is the input for Fan Enable relay.
Setback mode. When Digital NSB is selected via the
Accessory relays dipswitch inputs and the NSB input is
connected to Ground “C”, then the appropriately
configured Accessory relay is turned on to signal the
digital thermostat to go to Night Setback Setpoints.
Stated differently, when configured for Digital NSB
mode, the Accessory relay directly tracks the NSB input.
When Digital NSB is NOT selected via the Accessory
relays dipswitch inputs and the NSB input is connected
to Ground “C”, then Y1, Y2, W1 and O/W2 and G are
ignored. During this time period, if OVR is momentarily
connected to 24Vac, then Y1, Y2, W1 and O/W2 and G
are once again monitored for 2 hours. After the 2 hour
Override period, the DXM reverts back to ignoring Y1,
Y2, W1 and O/W2 and G, assuming the NSB input is
still connected to Ground “C”. There will be a random
start timer when coming back from NSB mode.
NOTE: The maximum number of DXM controls with
daisy-chained "NSB" terminals is 75. Also, the
maximum total wire resistance of the "NSB" wiring is
500 ohms.
ESD - ESD is the input for Emergency Shutdown
mode. When the ESD input is connected to Ground
“C”, all inputs are ignored and all outputs are turned
off. There will be a random start timer when coming
back from ESD.
Table 4. Thermostat Inputs with resulting demands
Tstat Inputs
G
x
-
Y1
x
x
x
x
x
Y2
W1
Dip Switch
O/W2
x
x
x
x
x
x
x
-
x
x
x
x
-
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Stat (HP/HC)
Type
Dip 1.3
HP
HP
HC
HP
HP
HC
HP
HP
HC
HP
HP
HC
HP
HP
HP
HP
HP
HC
HC
HC
HC
HP
Stat
(O/B)Type
Dip 1.4
O
B
O
B
O
B
O
B
O
B
O
B
O
B
Resulting
Demand #1
Standby/Off
F1
C1
C1
C1
C2
C2
C2
H1
H1
H1
H2
H2
H2
H3
H3
EH
EH
Invalid
Invalid
Invalid
Invalid
Invalid
Invalid
Page 11
NOTE: The maximum number of DXM controls with
daisy-chained "ESD" terminals is 75. Also, the
maximum total wire resistance of the "ESD" wiring is
500 ohms.
OVR - OVR is the input for Night Setback Override or
Night Low Limit Staged Heating input (NLL). When
Digital NSB is NOT selected via the Accessory relays
dip switch inputs and NSB is connected to Ground “C”,
then if OVR is momentarily connected to 24Vac
(minimum 1 second) then the OVR input is recognized as
a Night Setback Override signal and the DXM control
reverts from Night Setback and begins monitoring
thermostat inputs for heating and cooling calls for a 2
hour override period. If NSB is connected to ground "C",
then if OVR is continuously connected to 24V AC, then
the OVR input is recognized as a call for NLL staged
heating and the control enters NLL staged heating.
H - The H input function is determined by the setting of
dip2.7. If dip2.7=on then the H input is defined as
Automatic Dehumidification Mode and is used as an
“automatic” counterpart to dip1.5, meaning if H is
connected to 24Vac then the Fan Speed Relay will not
turn on during Cooling Stage 2. If H is not connected to
24Vac then the Fan Speed Relay will turn on during
Cooling Stage 2.
If dip2.7=off then the H input is defined as High Speed
Fan input and is used as an input to call for High Speed
Fan. If the control is in normal operating modes such as
Standby, Cooling or Heating AND the H input is
connected to 24Vac, then the Fan Enable and Fan Speed
relays will be on at all times (this operation is very
similar to the G/Fan Enable operation).
Table 5. System Inputs with the resulting demand. Table 5 describes demand changes with differing system
input (ESD, NSB, OVR) and DIP input settings. Resulting Demand #1 is derived from Table 4
Resulting Demand #1
(From Table 4)
Invalid
All (excluding Invalid)
All (excluding Invalid)
C1, C2
Off, F, H1, H2, or H3
EH
All (excluding Invalid)
System Inputs
ESD
x
-
NSB Type
NSB OVR
-
M
x
x
x
x
(After ESD, NSB)
Mechanical
All (excluding Invalid)
x
M
Mechanical
C1, C2
Off, F, H1, H2, or H3
EH
All (excluding Invalid)
All (excluding Invalid)
C1, C2
Off, F, H1, H2, or H3
EH
x
x
x
x
x
x
x
x
x
x
x
Mechanical
Mechanical
Mechanical
Digital
Digital
Digital
Digital
Digital
"M" is momentary input
"X" is continuous input
Page 12
M
x
x
x
Resulting Demand #2
ESD
Invalid
All (excluding Invalid)
All (excluding Invalid)
Invalid
NLL Staged Heating
EH
Standby/Off
All for 2 hrs and then revert to
Standby/Off (excluding Invalid)
Invalid
NLL Staged Heating
EH
All (excluding Invalid)
All (excluding Invalid)
Invalid
NLL Staged Heating
EH
Table 6. "H" input with resulting demand modes. Table 6 describes demand changes with "H" input and DIP
2.1-2.3, and 2.7 settings. Resulting Demand #2 is derived from Table 5
Resulting Demand #2
(From Table 5)
H
Auto Dehum / F2
Standby/Off
x
Auto Dehum Mode
Standby/Off with Auto Dehum
enabled
Standby/Off
x
High Fan Mode
F2
F1
x
Auto Dehum Mode
F1 with Auto Dehum enabled
F1
x
High Fan Mode
F2
C1
x
Auto Dehum Mode
C1 with fan destage
C1
x
High Fan Mode
*Clg with High Fan
C2
x
Auto Dehum Mode
C2 with fan destage
C2
x
High Fan Mode
*Clg with High Fan
H1
x
Auto Dehum Mode
H1
H1
x
High Fan Mode
Htg with High Fan
H2
H3
EH
Invalid
x
x
x
-
-
H2
H3
EH
Invalid
Dip 2.7
Resulting Demand #3
(After DIP 2.1-2.3, 2.7 Logic)
* = signifies that High Fan is locked on regardless of any Dehum demands.
Page 13
Other Outputs
Table 10 displays input and output signals.
Electric Heat
Outputs EH1 and EH2 turn on whenever the DXM
control is in the following modes: Heating Stage 3,
Emergency Heat, and boilerless operation.
Status LED
The Status LED is green. The Status LED indicates what
mode the DXM control is in. See Table 3: “LED and
Alarm Relay Operation”.
Test LED
The Test LED is yellow. The Test LED will be on any
time the control is in Test mode. See Table 3: “LED and
Alarm Relay Operation”.
Fault LED
The Fault LED is red. The Fault LED ALWAYS flashes
the corresponding code for the last fault that has
occurred. If there is no fault in memory, then the fault
LED will flash Code 1. If the Fault type is “Primary”
(HP, LP, FP1, FP2, or CO) then the Fault type will
always be retained in memory (Primary faults will over
write Secondary faults). If the Fault type is “Secondary”
(Over/Under Voltage or UPS) then the Fault type will
only be retained if there are no “Primary” faults in
memory. The Secondary Fault types will not “overwrite”
the Primary fault memory. See Table 3: “LED and
Alarm Relay Operation”.
Communications
There are two communications ports (Com1 and Com2)
which provide robust communications to external DXM
control boards via a simple noise resistant low speed
protocol. Wiring to Com1 and Com2 does NOT require
the use of shielded wiring for operation; standard
thermostat wire can be used.
Com1
Com1 is used to communicate thermostat and external
calls to other DXM Master/Slave controls. In this
configuration, up to 3 heat pumps can be controlled by
one thermostat.
Page 14
Note: Each heat pump could potentially be a Dual
Compressor unit thus there could be up to 6 DXM
controls being controlled by one thermostat.
However, only 1 DXM control in each heat pump will
be daisy-chained on Com1. See schematic on page 15.
The Master DXM control is defined as the DXM control,
which is directly connected to the wall-mounted
thermostat, time clock, fire alarm, and humidistat. The
Master DXM communicates to the Slave DXM typical
signals such as: Y1, Y2, W1, O/W2, G, NSB, ESD,
OVR, and H. The Slave DXM controls should have no
direct connections to any exterior devices such as
thermostats, time clocks, fire alarms, humidistats, etc…
Com2
Com2 is used to communicate thermostat and external
calls to a second DXM control being used for Dual
Compressor Function. A heat pump with two
compressors will have a DXM control for each
compressor. The Master DXM control will handle all I/
O with external sources as well as monitor and control
operations of the Secondary DXM control. The Master
DXM control is defined as the DXM control, which is
directly connected to the wall-mounted thermostat, timeclock, fire alarm, and humidistat. The Master DXM
communicates to the Secondary DXM typical signals
such as: Y1, Y2, W1, O/W2, G, NSB, ESD, OVR, and
H. The Secondary DXM control should have no
connections to any exterior devices such as thermostats,
time clocks, fire alarms, humidistats, etc…
Since the Master and Secondary DXM controls share CO
sensor and water valve/pump restart operations, these 2
signals are shared via communications as well. If either
the Master or Secondary DXM control senses a CO fault,
both DXM controls will fault and/or lockout due to the
CO signal. Regarding water valve/pump restart control,
if either the Master or Secondary DXM control faults or
goes into lockout mode, it will continue to provide water
valve/pump restart operation for the other functioning
DXM control.
Compressor
S
Typical DXM Wiring Schematic
208-230/60/1
C
Blu
R
Cap
Blk
Rd
Blu
T1
Unit
Power Supply
208-230/60/1
T2
CC
L1
L2
G
Dual
Comp
DXM
Slave
Unit
DXM
R C S
S C
PSC
Fan Motor
Grn
Wh
Brn
Note 2
Blk
Transformer
Blk Com
Note 3
Wh
Orange 240V
CB33.2A 24V
H M L
C
3 Air flow Settings
(Fctry Setting - Med)
Blu
Yellow
Com
N.O.
Com1
R C S
Com2
R
Blue
S C P4
3
P5
1
2
Blk
24V
Red 208V
Cap
BE
Brn
N.C.
Com
N.O.
BS
LonWorks
Controller
N01
N02
Typical
T-stat
Y1
Y2
W
N03
N04
24 H
24 G
DI 1
DI 1Com
P7
1
2
P1
O
G
R
C
Y1
Y2
W1
3
O/W2
G
R
6
C
AL1
P2
AL2
L
Note 1
Red
4
5
JW4 - AL2 Dry
Violet
Orange
Brn
10
11
12
Alarm
LOC
Grey
Grey
Violet
7
8
9
RV
HP
Red
Blue
Brn
FP1
FP2
RV
Yellow
CO
R
NSB
C
Note: when connecting
to LonWorks controller
JW4 MUST be clipped.
Thru Air Coil
DXM
Microprocessor
Control Logic
ESD
OVR
H
G Status
Test
Y
R
Fault
A
P6
1
2
24VDC
P3
R
NO
NC
EH1
EH2
ACC1
3
To Optional
Electric Heat
4
COM
NO
NC
COM
RV
Not used
Yellow
CC
CCG
Test Pins
JW3-FP1 Low Temp
JW2-FP2 Low Temp
JW1-LP Norm Open
ACC2
R
DIP Switch 1
Off
On
Compressor
Brown
Compressor
DIP Switch 2
Off
On
UPS Disable/Enabled
Comp Stage2/1
Tstat HC/HP
RV B/O
Dehumid/Norm
Not Used
Boilerless/Norm
40°F/50°F
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
17B0002N01 Rev A
DXM PCB
CC
ACC1
ACC1
ACC1
ACC2
ACC2
ACC2
High Fan/Dehum
Not Used
Rev. 5/16/00 m
Legend
Ground
Relay ContactsN.O., N.C.
T
G
Thermistor
Light emitting diode - Green
Relay coil
Switch - Condensate overflow
Switch - High pressure
Switch - Low pressure
P
3
L1
Fuse
1
2
Factory low voltage wiring
Factory line voltage wiring
Field low voltage wiring
Field line voltage wiring
Optional block
DC Voltage PCB traces
Internal junction
Quick connect terminal
Wire nut
Field wire lug
A
A
Polarized connector
Screw terminal field connection
Option Jumper - field clipped
Test Pins-
BE BS CC CO ER1 thru 4 Fan F1, F2, F3 FP1 FP2 -
Blower enable power relay
Blower Speed Relay
Compressor contactor
Condensate overflow sensor
Electric Heat Relays
PSC Fan Motor
Fuses
Water freeze protection sensor
Air Coil freeze sensor
HP LOC RV SW1 -
High pressure switch
Loss of Charge low
pressure switch
Reversing Valve coil
DIP switch, 2 position
Notes:
1 - Check installation wiring information for specific thermostat hookup instructions.
2 - Shown with optional two speed fan control
3 - On 208/230V units, switch orange and red wires for 208V operation
Page 15
Product Design and Application Notes
Sensors
Table 8. 1% Sensor Calibration Points
Pressure Switches-
Minimum
Temp (°F) Resistance
(ohm)
All pressure switches are designed to be normally closed
during normal operating conditions, and to open upon
fault.
Condensate Sensor-
Thermistor Temperature SensorsThe thermistor is available in the following configurations
shown in Table 7. The thermistor is an NTC (negative
temperature coefficient) type. The sensor has a 1%
tolerance and follows the Table 8 and Chart 1 shown.
Table 9 shows the nominal resistance at any given
temperature and can be used for field service reference.
The sensor will use a minimum of 24 awg wire and be
epoxy embedded in the beryllium copper clip.
Nominal
Resistance
(ohm)
78.5
77.5
76.5
9523
9650
10035
9715
9843
10236
9619
9746
10135
75.5
33.5
32.5
31.5
30.5
1.5
10282
30975
31871
32653
33728
80624
10489
31598
32512
33310
34406
82244
10385
31285
32190
32980
34065
81430
0.5
83327
85002
84160
0.0
84564
86264
85410
Chart 1. Thermistor Nominal Resistance
90.0
80.0
70.0
Resistance (kOhm)
The condensate sensor input will fault upon sensing
impedance less than 100,000 ohms for 30 continuous
seconds. The recommended design uses a single wire
terminated with a male 1/4" quick connect located in the
drain pan at desired trip level. Upon a high condensate
level the water will short between the air coil and the
quick connect producing a resistance less than 100,000
ohms. Since condensate is free of impurities, it has no
conductivity. Only the impurities from the drain pan and
coil dust or dirt create the conductance. A second ground
wire with appropriate terminal to the drain pan can be
used with the control to replace the air coil ground path.
The condensate sensor can also essentially be any open
contact that closes upon a fault condition.
Maximum
Resistanc
e (ohm)
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
Temperature (degF)
Table 7. Replacement Thermistor FP1, FP2 Part Numbers
Thermistor
Type
FP1 (Gray)
FP2 (Violet)
Lead Length In.
Tube OD
3/8, 1/2
36
17B0005N06
48
N/A
96
17B0005N04
192
N/A
5/8, 7/8
N/A
N/A
17B0004N01
N/A
3/8, 1/2
N/A
17B0005N02
N/A
17B0005N05
5/8, 7/8
N/A
N/A
N/A
17B0004N02
Rev. 5/17/00 m
Page 16
Table 9. Nominal resistance at various temperatures
Temp (°C) Temp (°F)
-17.8
-17.5
-16.9
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
0.0
0.5
1.5
10.4
12.2
14.0
15.8
17.6
19.4
21.2
23.0
24.8
26.6
28.4
30.2
32.0
33.8
35.6
37.4
39.2
41.0
42.8
44.6
46.4
48.2
50.0
51.8
53.6
55.4
57.2
59.0
60.8
62.6
64.4
66.2
68.0
69.8
71.6
73.4
75.2
77.0
78.8
80.6
82.4
84.2
86.0
87.8
89.6
91.4
93.2
95.0
96.8
98.6
100.4
102.2
104.0
105.8
107.6
109.4
111.2
113.0
114.8
116.6
118.4
120.2
122.0
123.8
125.6
127.4
129.2
Resistance
(kOhm)
85.41
84.16
81.43
61.70
58.40
55.30
52.40
49.60
47.00
44.60
42.30
40.10
38.10
36.10
34.30
32.60
31.00
29.40
28.00
26.60
25.30
24.10
23.00
21.90
20.80
19.90
18.97
18.09
17.25
16.46
15.71
15.00
14.32
13.68
13.07
12.49
11.94
11.42
10.92
10.45
10.00
9.57
9.17
8.78
8.41
8.06
7.72
7.40
7.10
6.81
6.53
6.27
6.02
5.78
5.55
5.33
5.12
4.92
4.73
4.54
4.37
4.20
4.04
3.89
3.74
3.60
3.47
3.34
3.22
3.10
Temp (°C)
Temp(°F)
Resistance
(kOhm)
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
131.0
132.8
134.6
136.4
138.2
140.0
141.8
143.6
145.4
147.2
149.0
150.8
152.6
154.4
156.2
158.0
159.8
161.6
163.4
165.2
167.0
168.8
170.6
172.4
174.2
176.0
177.8
179.6
181.4
183.2
185.0
186.8
188.6
190.4
192.2
194.0
195.8
197.6
199.4
201.2
203.0
204.8
206.6
208.4
210.2
212.0
213.8
215.6
217.4
219.2
221.0
222.8
224.6
226.4
228.2
230.0
231.8
233.6
235.4
237.2
239.0
240.8
242.6
244.4
246.2
248.0
249.8
251.6
253.4
2.99
2.88
2.77
2.67
2.58
2.49
2.40
2.32
2.23
2.16
2.08
2.01
1.94
1.88
1.81
1.75
1.69
1.64
1.58
1.53
1.48
1.43
1.38
1.34
1.30
1.26
1.22
1.18
1.14
1.10
1.07
1.04
1.00
0.97
0.94
0.92
0.89
0.86
0.84
0.81
0.79
0.76
0.74
0.72
0.70
0.68
0.66
0.64
0.62
0.60
0.59
0.57
0.56
0.54
0.53
0.51
0.50
0.48
0.47
0.46
0.45
0.43
0.42
0.41
0.40
0.39
0.38
0.37
0.36
Thermostat Details
Thermostat Compatibility Most all heat pump and heat/cool thermostats can be
used with the DXM control.
Anticipation Leakage Current Maximum leakage current for "Y" is 50mA and for "W"
is 20mA. Triacs can be used if leakage current is less
than above. Thermostats with anticipators can be used if
anticipation current is less than that specified above.
Thermostat Signals • "Y1, Y2, W1, O/W2" and "G" have a 1 second
recognition time when being activated or being
removed.
• "R" and "C" are from the transformer.
• "AL1" and "AL2" originate from the alarm relay.
• "A" is paralleled with the compressor output for use
with well water solenoid valves.
Safety Listing
The control is listed under the UL 353 standard for Limit
Controls. A comparable listing is pending for CE at the
time of publishing.
Rev.: 5/23/00 m
Page 17
Troubleshooting Information
General
DXM board troubleshooting in general is best
summarized as simply verifying inputs and outputs.
After this process has been verified, confidence in
board operation is confirmed and the trouble must be
else where. Below are some general guidelines
required for developing training materials and
procedures when applying the DXM control.
compared to the chart shown in the thermistor section of this
manual based upon the actual temperature of the thermistor
clip. An ice bath can be used to check calibration of a
thermistor if needed.
Outputs
All inputs are 24VAC from the thermostat and can be
verified using a volt meter between C and Y1, Y2, W,
O/W2 and G. See the I/O Reference table below.
The compressor relay is 24VAC and can be verified using a
voltmeter. The alarm relay can either be 24VAC as shipped
or dry contacts (measure continuity during fault) for use with
DDC by clipping the J4 jumper. Electric heat outputs are
24VDC and require a voltmeter set for DC to verify
operation. When troubleshooting, measure from 24VDC
terminal to EH1 or EH2 terminals. See the I/O Reference
table below.
Sensor Inputs
Test Mode
All sensor inputs are 'paired wires' connecting each
component with the board. Therefore continuity on
pressure switches, and the condensate switch can be
checked at the board connector.
Test mode can be entered for 20 minutes by shorting the test
pins. For Diagnostic ease at the thermostat, 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
also be entered and exited by cycling the G input, 3 times
within a 60 second time period.
Field Inputs
The thermistor resistance should be measured with the
connector removed so that only the impedance of the
thermistor is measured. If desired this reading can be
Table 10. Input/Output Reference Table
Connection
R
C
Y1
Y2
W1
O/W2
G
AL1
AL2
A
Fan Enable
Fan Speed
CC
CCG
HP
LP
FP1
FP2
RV
CO
24VDC
EH1
EH2
NSB
OVR
ESD
H
Page 18
Input or
Output
I
I
I
I
I
O
O
O
O
O
O
O
I
I
I
I
O
I
O
O
O
I
I
I
I
Description
24 VAC
24 VAC (grounded common)
Connect to thermostat - Y1 output call for compressor stage 1
Connect to thermostat - Y2 output call for compressor stage 2
Connect to thermostat - W1 output call for Htg 3 or Emerg Ht
Connect to thermostat - 0 output call for reversing valve with cooling
Connect to thermostat - G output call for fan
Connect to thermostat fault light - 24VAC or dry alarm
Alarm Relay 24VAC or dry
Output for water solenoid valve - paralleled with compressor contactor coil
Fan enable relay
Fan speed relay
Connection for compressor contactor
Compressor contactor common connection
High Pressure Switch input terminals
Low Pressure Switch input terminals
Water Coil Freeze Protection Thermistor Input
Air Coil Freeze Protection Thermistor Input
Reversing Valve Output Terminals - direct connect from "O"
Condensate overflow input terminals
24 VDC supply to electric heat module
Output terminal for stage 1 electric heat
Output terminal for stage 2 electric heat
Night Setback input
Night Setback Over Ride Input
Emergency Shutdown Input
Dehumidification or High Speed Fan input (dip 2.7)
Troubleshooting Chart
Use the following troubleshooting flow chart to find appropriate troubleshooting strategies on the following pages for
the DXM control and most water source heat pump applications.
Start
DXM Functional
Troubleshooting Chart
Did Unit
Attempt to
Start?
No
Check Main
power (see power
problems)
Yes
Did Unit
Lockout at
Start-up?
No
See “Unit
short
cycles”
Yes
Yes
Unit Short
Cycles?
Check fault LED code
on control board
See HP
Fault
See
LP/LOC
Fault
No fault
shown
See FP1
Fault
Replace
DXM
No
See “Only
Fan Runs”
See “Only
Comp
Runs”
Yes
Yes
Only Fan
Runs?
See FP2
Fault
See
Condensate
Fault
See Over/
Under
Voltage
No
Only
Compressor
Runs?
No
See “Does No
not Operate
in Clg”
Did unit lockout Yes
after a period of
operation?
No
Does unit
operate in
cooling?
Yes
Unit is OK!
‘See Performance
Troubleshooting’ for
further help
Page 19
Functional Troubleshooting
Fault
Main power Problems
Htg Clg Possible Cause
X
HP Fault-Code 2
High pressure
Solution
X
Green Status LED Off
X
Reduced or no water flow
in cooling
X
Water Temperature out of range in
Bring water temp within design parameters
cooling
X
Reduced or no Air flow
in heating
Check Line Voltage circuit breaker and disconnect
Check for line voltage between L1 and L2 on the contactor
Check for 24VAC between R and C on DXM
Check primary/secondary voltage on transformer
Check pump operation or valve operation/setting
Check water flow adjust to proper flow rate
Check for dirty air filter and clean or replace
Check fan motor operation and airflow restrictions
Dirty Air Coil- construction dust etc.
Too high of external static. Check static vs blower table
X
X
X
X
X
LP/LOC Fault-Code 3
X
X
Low Pressure/Loss of Charge
X
FP1 Fault - Code 4
X
Air Temperature out of range in
heating
Bring return air temp within design parameters
Overcharged with refrigerant
Check superheat/subcooling vs typical operating condition
table
Bad HP Switch
Insufficient charge
Check switch continuity and operation. Replace
Check for refrigerant leaks
Compressor pump down at startup
Check charge and start-up water flow
Reduced or no water flow
Check pump operation or water valve operation/setting
in heating
Plugged strainer or filter. Clean or replace.
X
Inadequate anti-freeze level
Check antifreeze density with hydrometer
X
Improper freeze protect setting
(30°F vs 10°F)
Clip JW2 jumper for antifreeze (10°F) use
Water freeze protection
Check water flow adjust to proper flow rate
X
Water Temperature out of range
Bring water temp within design parameters
X
X
Bad thermistor
Reduced or no Air flow
in cooling
Check temp and impedance correlation per chart
Check for dirty air filter and clean or replace
Check fan motor operation and airflow restrictions
Too high of external static. Check static vs blower table
X
Air Temperature out of range
X
Improper freeze protect setting
(30°F vs 10°F)
Normal airside applications will require 30°F only
X
X
Bad thermistor
Check temp and impedance correlation per chart
X
X
Blocked Drain
Check for blockage and clean drain
X
X
X
Improper trap
Poor Drainage
X
Moisture on sensor
X
X
Under Voltage
Check trap dimensions and location ahead of vent
Check for piping slope away from unit
Check slope of unit toward outlet
Poor venting. Check vent location
Check for moisture shorting to air coil
Check power supply and 24VAC voltage before and during
operation.
Check power supply wire size
Check compressor starting. Need hard start kit?
X
FP2 fault - Code 5
Air Coil freeze protection
Condensate Fault-Code
6
Over/Under VoltageCode 7
(Auto resetting)
Too much cold vent air? Bring entering air temp within
design parameters
Check 24VAC and unit transformer tap for correct power
supply voltage
X
X
Over Voltage
Check power supply voltage and 24VAC before and during
operation.
Check 24VAC and unit transformer tap for correct power
supply voltage
Unit Performance
Sentinel-Code 8
No Fault Code Shown
Unit Short Cycles
Only Fan Runs
X
Heating mode FP2>125°F
Check for poor air flow or overcharged unit.
X
Cooling Mode FP1>125°F OR
FP2< 40°F
Check for poor water flow, or air flow
X
X
No compressor operation
See 'Only fan operates'
X
X
Compressor Overload
Check and Replace if necessary
X
X
X
X
X
X
Control board
Dirty Air Filter
Unit in 'Test Mode'
X
X
Unit selection
X
X
Compressor Overload
Reset power and check operation
Check and Clean air filter
Reset power or wait 20 minutes for auto exit.
Unit may be oversized for space. Check sizing for actual
load of space.
Check and Replace if necessary
X
X
Thermostat position
Insure thermostat set for heating or cooling operation
X
X
Unit locked out
Check for lockout codes. Reset power.
X
X
Compressor Overload
Check compressor overload. Replace if necessary.
X
X
Thermostat wiring
Check Y and W wiring at heat pump. Jumper Y and R for
compressor operation in test mode.
Rev. 5/17/00 m
Page 20
Functional Troubleshooting (cont.)
Only Compressor Runs
X
X
Thermostat wiring
Check G wiring at heat pump. Jumper G and R for fan
operation.
X
X
Fan motor relay
Jumper G and R for fan operation. Check for Line voltage
across BR contacts.
X
X
Fan motor
X
X
Thermostat wiring
X
Reversing Valve
X
Thermostat setup
X
Thermostat wiring
Check fan power enable relay operation (if present)
Unit Doesn't Operate in
Cooling
Check for line voltage at motor. Check capacitor
Check Y and W wiring at heat pump. Jumper Y and R for
compressor operation in test mode.
Set for cooling demand and check 24VAC on RV coil and at
DXM board.
If RV is stuck, run high pressure up by reducing water flow
and while operating engage and disengage RV coil voltage
to push valve.
Check for 'O' RV setup not 'B'
Check O wiring at heat pump. Jumper O and R for RV coil
'Click'.
Performance Troubleshooting
Performance
Troubleshooting
Htg Clg Possible Cause
Insufficient capacity/
X
Not cooling or heating
X
X
properly
High Head Pressure
Dirty Filter
Solution
Replace or clean
Reduced or no Air flow
Check for dirty air filter and clean or replace
in heating
Check fan motor operation and airflow restrictions
Too high of external static. Check static vs blower table
Check for dirty air filter and clean or replace
Check fan motor operation and airflow restrictions
Too high of external static. Check static vs blower table
Check supply and return air temperatures at the unit and at
distant duct registers if significantly different, duct leaks
are present
Check superheat and subcooling per chart
Check superheat and subcooling per chart. Replace.
Perform RV touch test
Check location and for air drafts behind stat
Recheck loads & sizing check sensible clg load and heat
pump capacity
X
Reduced or no Air flow
in cooling
X
X
Leaky duct work
X
X
X
X
X
X
X
Low refrigerant charge
Restricted metering device
Defective Reversing Valve
Thermostat improperly located
X
X
Unit undersized
X
X
Scaling in water heat exchanger
Perform Scaling check and clean if necessary
X
X
Inlet Water too Hot or Cold
Check load, loop sizing, loop backfill, ground moisture.
Reduced or no Air flow
in heating
Check for dirty air filter and clean or replace
Check fan motor operation and airflow restrictions
X
Too high of external static. Check static vs blower table
X
X
X
Low Suction Pressure
X
X
X
X
X
X
X
X
X
X
X
Low discharge air
temperature in heating
Check pump operation or valve operation/setting
Check water flow adjust to proper flow rate
Check load, loop sizing, loop backfill, ground moisture.
Bring return air temp within design parameters
Scaling in water heat exchanger
Unit Overcharged
Non-condensables insystem
Restricted metering device
Reduced water flow
in heating
Perform Scaling check and clean if necessary
Check superheat and subcooling. Reweigh in charge
Vacuum system and reweigh in charge
Check superheat and subcooling per chart. Replace.
Check pump operation or water valve operation/setting
Plugged strainer or filter. Clean or replace.
Check water flow adjust to proper flow rate
Water Temperature out of range
Bring water temp within design parameters
Reduced Air flow
in cooling
X
Air Temperature out of range
X
Insufficient charge
Check for dirty air filter and clean or replace
Check fan motor operation and airflow restrictions
Too high of external static. Check static vs blower table
Too much cold vent air? Bring entering air temp within
design parameters
Check for refrigerant leaks
Too high of air flow
Check fan motor speed selection and airflow chart
X
Poor Performance
Too high of air flow
X
Unit oversized
See 'Insufficient Capacity'
Check fan motor speed selection and airflow chart
Recheck loads & sizing check sensible clg load and heat
pump capacity
X
X
High humidity
Reduced or no water flow
in cooling
Inlet Water too Hot
Air Temperature out of range in
heating
Rev. 5/17/00 m
Page 21
Notes:
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
Notes:
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
7300 S.W. 44th Street
Oklahoma City, OK 73179
Phone: 405-745-6000
Fax: 405-745-6058
www.climatemaster.com
*97B0003N02*
Part #: 97B0003N02
ClimateMaster works continually to improve its products. As a result, the design and specifications of each product at the time of order may be changed
without notice and may not be as described herein. Please contact ClimateMaster’s Customer Service Department at 1-405-745-6000 for specific
information on the current design and specifications. Statements and other information contained herein are not express warranties and do not form the
basis of any bargain between the parties, but are merely ClimateMaster’s opinion or commendation of its products.
© ClimateMaster 1999
Rev.: 5/00