Application, Operation, & Maintenance Manual | DXM2 UNIT CONTROLS | Heat Controller, Inc. |
Performance Troubleshooting
Symptom | Htg | Clg | Possible Cause | Solution | |
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| X | X | Dirty filter | Replace or clean | |
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| Rduced or no air flow | Check for dirty air filter and clean or replace | |
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| Check fan motor operation and airflow restrictions | |||
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| in heating | |||
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| Too high of external static - check static vs blower table | ||
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| Reduced or no air flow | Check for dirty air filter and clean or replace | |
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| X | Check fan motor operation and airflow restrictions | ||
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| in cooling | |||
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| Too high of external static - check static vs blower table | ||
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Insufficient Capacity/ |
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| Check supply and return air temperatures at the unit and at | |
X | X | Leaky duct work | distant duct registers if significantly different, duct leaks | ||
Not Cooling or Heating | |||||
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| are present | ||
Properly | X | X | Low refrigerant charge | Check superheat and subcooling per chart | |
| X | X | Restricted metering device | Check superheat and subcooling per chart - replace | |
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| X | Defective reversing valve | Perform RV touch test | |
| X | X | Thermostat improperly located | Check location and for air drafts behind stat | |
| X | X | Unit undersized | Recheck loads & sizing check sensible clg load and heat | |
| pump capacity | ||||
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| X | X | Scaling in water heat exchanger | Perform Scaling check and clean if necessary | |
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| X | X | Inlet water too hot or cold | Check load, loop sizing, loop backfill, ground moisture | |
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| Check for dirty air filter and clean or replace | |
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| Reduced or no air flow | Check fan motor operation and airflow restrictions | |
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| in heating | Too high of external static - check static vs blower table | ||
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| X | Reduced or no water flow | Check pump operation or valve operation/setting | |
High Head Pressure |
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| in cooling | Check water flow adjust to proper flow rate | |
| X | Inlet water too hot | Check load, loop sizing, loop backfill, ground moisture | ||
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| Air temperature out of range in | Bring return air temp within design parameters | |
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| heating | |||
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| X | Scaling in water heat exchanger | Perform Scaling check and clean if necessary | |
| X | X | Unit over charged | Check superheat and subcooling - reweigh in charge | |
| X | X | Vacuum system and reweigh in charge | ||
| X | X | Restricted metering device | Check superheat and subcooling per chart - replace | |
| X |
| Reduced water flow | Check pump operation or water valve operation/setting | |
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| Plugged strainer or filter - clean or replace | |||
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| in heating | |||
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| Check water flow adjust to proper flow rate | ||
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| Water temperature out of range | Bring water temp within design parameters | |
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Low Suction Pressure |
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| Reduced air flow | Check for dirty air filter and clean or replace | |
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| X | Check fan motor operation and airflow restrictions | ||
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| in cooling | |||
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| Too high of external static - check static vs blower table | ||
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| X | Air temperature out of range | Too much cold vent air - bring entering air temp within | |
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| design parameters | |||
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| X | X | Insufficient charge | Check for refrigerant leaks | |
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Low Dischage Air | X |
| Too high of air flow | Check fan motor speed selection and airflow chart | |
Temperature in Heating |
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| Poor performance | See “Insufficient Capacity” | ||
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| X | Too high of air flow | Check fan motor speed selection and airflow chart | |
High Humidity |
| X | Unit oversized | Recheck loads and sizing check sensible clg load and | |
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| heat pump capacity | |||
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| X | X | Thermostat wiring | Check G wiring at heat pump. Jumper G and R for fan | |
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| Jumper G and R for fan operation. Check for Line voltage | |
| X | X | Fan motor relay | across blower relay contacts. | |
Only Compressor Runs |
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| Check fan power enable relay operation (if present) | |
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| X | X | Fan motor | Check for line voltage at motor. Check capacitor | |
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| X | X | Thermostat wiring | Check thermostat wiring at or DXM2. Put in Test Mode | |
| and then jumper Y1 and W1 to R to give call for fan, | ||||
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| compressor and electric heat. | |
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| Set for cooling demand and check 24VAC on RV coil. | |
Unit Doesn't Operate in |
| X | Reversing Valve | If RV is stuck, run high pressure up by reducing water flow | |
| and while operating engage and disengage RV coil voltage | ||||
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Cooling |
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| to push valve. | |
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| X | Thermostat setup | For DXM2 check for “O” RV setup not “B”. | |
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| X | Thermostat wiring | Check O wiring at heat pump. DXM2 requires call for | |
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| compressor to get RV coil “Click.” | |||
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| Improper output setting | Verify the | |
Modulating Valve | X | X | No valve output signal | Check DC voltage between AO2 and GND. Should be O | |
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| when valve is off and between 3.3v and 10v when valve | ||
Troubleshooting |
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| is on. | ||
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| No valve operation | Check voltage to the valve | |
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| Replace valve if voltage and control signals are present at | |
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| the valve and it does not operate | |
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