Application, Operation, & Maintenance Manual | DXM2 UNIT CONTROLS | Heat Controller, Inc. |
DXM2 Controls
airflow for the current operating mode. For the first
30 seconds of blower operation, the target airflow will be 50% of the normal target airflow. For the next 90 seconds of blower operation, the target airflow will be 75% of the normal target airflow. For Constant Fan, Emergency Heat, and Test Mode operation, the Soft Start Ramping profile is bypassed, and the ECM immediately ramps up to the normal target airflow.
c)Blower Off Delays – For ECM blower off delays, the target airflow will be adjusted to 50% of normal target airflow before the beginning of the blower off delay.
d)Default Blower Operation – If the DXM2 configuration is incorrect or incomplete with an ECM Blower connected, the ECM will be operated using default target airflows and operating parameters, and an ECM configuration fault will be active.
Hot Water Generator Operation – When the DXM2 is configured to operate a hot water generator pump, the pump will be directly controlled by the K2 relay, based on the S3 dipswitch settings and the T5 (hot water temperature) and T6 (compressor discharge temperature) inputs. Hot water generator operating features include:
a)HWG operating setpoint selection
b)Temperature offset verification for efficient HWG operation
c)HWG test mode
Proportional Valve Operation – When the DXM2 is configured to operate a proportional valve (optional), the valve will be directly controlled by the DXM2. For controlling the proportional valve, the DXM2 monitors the entering water temperature and leaving water temperature. The valve is controlled in the following way:
a)Maintain the appropriate temperature difference across the water coil
b)Maintain the leaving water temperature below the appropriate Maximum Heating LWT and above the Minimum Cooling LWT limits.
SPECIAL DXM2 APPLICATION NOTES / ACCESSORY RELAYS
Generally the following applications are based upon configuring the accessory relays.
Cycle with Fan – If Accessory relay 1 is configured to “cycle with fan”, Accessory relay 1 will be on any time the Fan Enable relay, or ECM Blower is on.
Cycle with Compressor – If Accessory relay 2 is
configured to “cycle with compressor”, Accessory relay 2 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, and the DXM2 is not connected to a communicating thermostat configured for night setback, then the NSB and OVR inputs are automatically configured for “mechanical” operation. See Mechanical NSB operation below.
Note: Digital Night Setback feature requires a compatible thermostat. Contact the manufacturer for information on compatible thermostats.
Mechanical Night Setback – When the NSB input is connected to Ground “C”, all thermostat inputs (G, Y1, Y2, W, and O) are ignored. A thermostat setback Heating call can then be connected to the OVR input. If the OVR input becomes active, then the DXM2will 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 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
Humidifier – If Accessory relay 2 is configured for a Humidifier, the Accessory relay will be on any time the H input is active.
Hydronic Economizer – If Accessory relay 1 is configured to be used as a hydronic economizer, normal cooling operation will be modified.
If Accessory relay 1 is configured as a single stage hydronic economizer, when a first stage cooling demand is present and the H input is active, the accessory relay will be activated instead of the compressor output. All other heat pump operating modes will operate normally, and the accessory relay will be off in all other operating modes.
If Accessory relay 1 is configured as a hydronic economizer for both stages, when a first stage cooling demand is present and the H input is active, the accessory relay will be activated instead of the compressor output. When a second stage cooling demand is present with the H input active, the accessory relay will be activated in addition
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