Mammoth 800 to 5500 CFM: Dedicated Outdoor Air System with Enthalpy Wheels (VHC) - Manual (Page 36)

MAMM-VHC-IOM-1A (JANUARY 2013) 36
Table I1: VHC-36, 42 and 50 Troubleshooting
Problem Cause Solutions
Compressor runs but stops quickly.
Overload, fuse burnout.
Check if voltage is too low, wiring is incorrect, wire
gauge is sized correctly; replace blown fuse.
Low or high pressure switch acti-
vated.
See solution for high pressure switch open and low
pressure switch open.
Compressor makes an abnormal
sound.
Reverse scroll operation.
Reverse any two phases on the three-phase com-
pressor.
Compressor quality issue. Replace compressor.
Excessive compressor vibration. Compressor screw is loose. Tighten the screw.
Compressor is running but there is
no pressure buildup.
Scroll reverse operation.
Reverse any two phases on the three-phase com-
pressor.
Compressor system is normal but
amps are too high.
Incorrect compressor voltage. Replace with correct voltage compressor.
High pressure switch is open in cool-
ing operation.
Lack of water flow (WSHP).
Check if the motorized water valve is opening complete-
ly and confirm loop water pumps are running.
Water flow rate is too small (WSHP). Check if pump sized correctly. If water strainer is in-
stalled in line, check if strainer is too dirty.
Condenser is too dirty (AC system). Clean condenser coil.
Refrigerant overcharge.
Charge correct amount of refrigerant.
Non-condensable air accumulates in
the coaxial coil.
Vacuum system, recharge refrigerant.
Coaxial coil scaled. Clean coaxial coil.
High pressure switch is open in heat-
ing operation.
Supply fan failure.
Check if wiring is correct, replace any failed compo-
nents.
Outside air damper not open.
Check outside air damper operation and replace actua-
tor if failed.
Dx coil is too dirty. Clean Dx coil.
Supply airflow is too small.
Check if components (coil, wheel, filter) are too dirty,
motor is running at low speed or not and check if there
is too much pressure loss in supply duct.
Refrigerant overcharge. Charge correct amount of refrigerant.
Low pressure switch is open in cool-
ing operation.
TXV failed in closed position. Replace TXV.
Supply blower failure. Replace TXV or filter drier.
Insufficient supply airflow.
Check if components (coil, wheel, filter) are too dirty,
motor is running at low speed or not and check if there
is too much pressure loss in supply duct.
Loss of refrigerant charge.
Check and repair any leaks in the piping and refill
refrigerant.
Low pressure switch is open in heat-
ing operation.
TXV failed in closed position. Replace TXV.
Blocked TXV or filter drier. Replace TXV or filter drier.
Lack of water flow (WSHP).
Check if motorized water valve is opening completely
and confirm loop water pumps are running.
Insufficient water flow (WSHP).
Check if pump is sized correctly or if water strainer is
blocked.
Water entering temperature too low
(WSHP).
Consult factory for operation out of application range.
Loss of refrigerant charge.
Check and repair any leaks in the piping and refill
refrigerant.