LG AR-DR11-08A Installation And Operation Manual page 108

TROUBLESHOOTING
Table 67: Troubleshooting Blowers Table, continued.
Blower Symptom
Insufficient airflow.
Excessive airflow.
High airflow, low static pressure.
Low airflow, low static pressure.
Low airflow, high static pressure.
108
Probable Cause
Fan
Duct system
Filters
Coils
Recirculation
Obstructed fan inlets.
System
Fan
System, fan, or interpretation
of measurements.
System
Air density
Fan
System
System
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Action
Check if the fan is running backwards.
Check if the impeller is not centered in inlet collars.
Check if the fan speed is too slow.
Check if the actual system is more restrictive (there is
more resistance to flow) than expected.
Check if the dampers are closed.
Check if the registers are closed.
Check for leaks in supply duct.
Check if filter is dirty or clogged.
Check if coil is dirty or clogged.
Check for internal cabinet leaks in the bulkhead that
separates the fan outlet (pressure zone) from fan
inlets (suction zone).
Elbows, cabinet walls, or other obstructions are
restricting air flow. Inlet obstructions cause more
restrictive systems but do not cause increased
negative pressure readings near the fan inlet(s).
Fan speed may be increased to counteract the
effect of restricted fan inlet(s).
Check for oversized duct work.
Check if access door is open.
Check if registers or grilles are not installed.
Check if filters are not in place.
Check if backward-inclined impeller is installed
backward; horsepower will be high.
Check if fan speed is too fast; reduce fan speed
The static pressure measured in a "loose" or
oversized system will be less than the static pressure
in a "tight" or undersized system for the same airflow
rate.
In most systems, pressure measurements are
indicators of how the installation is operating.
These measurements are the result of airflow
and are useful indicators in defining system
characteristics.
System has less resistance to flow than expected. Fan
speed may be reduced to obtain the desired flow rate.
This will reduce horsepower (operating cost).
Pressures will be less with high-temperature gasses
or at high altitude.
Check if backward-inclined impeller is installed
backward; horsepower will be high.
Check if the fan speed is too high.
Check if the fan inlet or outlet conditions are not the
same as tested
Check for obstruction in system