84
Enertech Global
IOM, ZS/ZT Models
SECTION 12: TROUBLESHOOTING
A: UNIT WILL NOT START IN EITHER CYCLE
Thermostat
Set thermostat on heating and highest temperature setting. Unit should run. Set thermostat on cooling and
lowest temperature setting. Unit should run. Set fan to On position. Fan should run. If unit does not run in
any position, disconnect wires at heat pump terminal block and jump R, G, Y. Unit should run in heating. If
unit runs, replace thermostat with correct thermostat only.
Loose or Broken Wires
Tighten or replace wires.
Blown Fuse/
Check fuse size, replace fuse or reset circuit breaker.
Check low voltage circuit breaker.
Tripped Circuit Breakers
Check fuse size, replace fuse or reset circuit breaker.
Low Voltage Circuit
Check 24 volt transformer. If burned out or less than 24 volt, replace. Before replacing, verify tap setting
and correct if necessary.
B: BLOWER RUNS BUT COMPRESSOR WILL NOT START (COMPRESSOR OVERLOAD, BAD CAPACITOR, HP FAULT)
Logic Board
Check if status light is on and logic board is working properly. Check fault lights. See LED Identification
chart in Controls Section
Defective Sensors
Check status/fault lights. Sensor is out of normal range for resistance values, open, or shorted. Compare
sensor resistance values with the charted resistance in Controls Section
Defective Capacitor
Check capacitor. If defective, replace.
Failed Compressor
See charts M and N for compressor diagnostic. If compressor still doesn’t run, replace it.
Low Pressure Switch
Low refrigerant charge. Check for pressure. Check for leaks.
C: BLOWER RUNS BUT COMPRESSOR SHORT CYCLES OR DOES NOT RUN
Wiring
Loose or broken wires. Tighten or replace wires. See A: Unit will not start in either cycle.
Blown Fuse
Check fuse size. Check unit nameplate for correct sizing. Replace fuse or reset circuit breaker.
Check low voltage circuit
breaker.
Temporarily bypass flow switch for a couple seconds. If compressor runs properly, check switch. If
defective, replace. If switch is not defective, check for air in loop system. Make sure loop system is
properly purged. Verify flow rate before changing switch. .
Defective Sensors
Check status/fault lights. Sensor is out of normal range for resistance values, open, or shorted. Compare
sensor resistance values with the charted resistance in Controls Section
Water Flow (Source Heat
Exchanger Freeze Fault)
Check status/fault lights. To check water flow remove the FS jumper (see Controls Section for location)
and jumper the two FS terminals (located between blue and violet wires on the right side of the
board) together to complete the flow switch circuit. Determine if the required water pressure drop is
present. If required pressure drop is present, check the resistance of T4 source sensor (15°F=41.39kΩ;
30°F=28.61kΩ) and temperature of the refrigerant line between the source heat exchanger and TXV.
High or Low
Pressure Switches
If heat pump is out on high or low-pressure cutout (lockout), check for faulty switches by jumping the high
and low-pressure switches individually. If defective replace. Check airflow, filters, water flow, refrigerant
pressures, and ambient temperature. WARNING: Only allow compressor to run for a couple of seconds
with the high pressure switch jumped.
Defective Logic Board Relay
Jump R to Y directly on lockout board. Check for 24V at Y. If no operation and no faults occur, replace
lockout board.
Hot Gas Temperature>220°F
Check status/fault lights. Check hot gas/discharge line temperature with a thermocouple type
thermometer. WARNING: Let the unit remain off for several minutes and touch the thermocouple to the
discharge line to check if it is cooled enough to strap/tape a thermocouple to it. Check the discharge line
temperature during the next operation cycle to compare the temperature to the lockout temperature of
220°F. Check water/air flow. If water/air flow is present, check the refrigerant pressures.
Condensate Overflow (CO)
Check status/fault lights. Check sensors for contact with water, debris, or a loose sensor touching metal.
Clean sensors if contacting debris. Flush drain lines if the drain pan is full. If no debris is present and drain
pan is empty, remove violet wire from CO terminal on lockout board (lower right). If CO lockout occurs
with violet wire removed replace the lockout board.
Over/Under Voltage
Make sure secondary/low voltage is between 20V and 29V. Check the transformer’s primary connections
for the correct voltage (Orange & Black = 230V; Red & Black = 208V). Correct any possible voltage drops
in the main voltage.
Load Heat Exchanger Frozen
Check status/fault lights. Check for reduced air flow due to dirty filter, obstructions, or poor blower
performance. Check T1 sensor for the proper resistance (30°F = 28.61kΩ).
D: UNIT RUNNING NORMAL, BUT SPACE TEMPERATURE IS UNSTABLE
Thermostat
Thermostat is getting a draft of cold or warm air. Make sure that the wall or hole used to run thermostat
wire from the ceiling or basement is sealed, so no draft can come to the thermostat.
Faulty Thermostat (Replace).
Troubleshooting Tips