Heat Controller DXM2 manual Performance Troubleshooting, Symptom Htg Clg Possible Cause Solution

Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.

Performance Troubleshooting

Symptom	Htg	Clg	Possible Cause	Solution
	X	X	Dirty filter	Replace or clean
			Rduced or no air flow	Check for dirty air filter and clean or replace
	X
				Check fan motor operation and airflow restrictions
			in heating
				Too high of external static - check static vs blower table
			Reduced or no air flow	Check for dirty air filter and clean or replace
		X		Check fan motor operation and airflow restrictions
			in cooling
				Too high of external static - check static vs blower table
Insufficient Capacity/				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
				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
		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
	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
				Check for dirty air filter and clean or replace
	X		Reduced or no air flow	Check fan motor operation and airflow restrictions
			in heating	Too high of external static - check static vs blower table
		X	Reduced or no water flow	Check pump operation or valve operation/setting
High Head Pressure			in cooling	Check water flow adjust to proper flow rate
		X	Inlet water too hot	Check load, loop sizing, loop backfill, ground moisture
	X		Air temperature out of range in	Bring return air temp within design parameters
			heating
		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	Non-condensables insystem	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
				Plugged strainer or filter - clean or replace
			in heating
				Check water flow adjust to proper flow rate
	X		Water temperature out of range	Bring water temp within design parameters
Low Suction Pressure			Reduced air flow	Check for dirty air filter and clean or replace
		X		Check fan motor operation and airflow restrictions
			in cooling
				Too high of external static - check static vs blower table
		X	Air temperature out of range	Too much cold vent air - bring entering air temp within
				design parameters
	X	X	Insufficient charge	Check for refrigerant leaks
Low Dischage Air	X		Too high of air flow	Check fan motor speed selection and airflow chart
Temperature in Heating
	X		Poor performance	See “Insufficient Capacity”
		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
				heat pump capacity
	X	X	Thermostat wiring	Check G wiring at heat pump. Jumper G and R for fan
				operation.
				Jumper G and R for fan operation. Check for Line voltage
	X	X	Fan motor relay	across blower relay contacts.
Only Compressor Runs				Check fan power enable relay operation (if present)
	X	X	Fan motor	Check for line voltage at motor. Check capacitor
	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,
				compressor and electric heat.
				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
Cooling				to push valve.
		X	Thermostat setup	For DXM2 check for “O” RV setup not “B”.
		X	Thermostat wiring	Check O wiring at heat pump. DXM2 requires call for
				compressor to get RV coil “Click.”
			Improper output setting	Verify the AO-2 jumper is in the 0-10V position
Modulating Valve	X	X	No valve output signal	Check DC voltage between AO2 and GND. Should be O
				when valve is off and between 3.3v and 10v when valve
Troubleshooting
				is on.
			No valve operation	Check voltage to the valve
				Replace valve if voltage and control signals are present at
				the valve and it does not operate

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