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UNITROL MODEL 8400, 8401, 8406, 8450, 8451, 8456
a. The overload on the water pump MOTOR STARTER K1 has tripped. The blue reset
button on the overload can be pushed to reset the contactor. However the cause
should be found and corrected. Otherwise this contactor will continue to trip. Tripping
of the overload can be caused by one of the following conditions:
i. One line of the 3-phase incoming power has been lost causing "single phasing"
of the motor.
ii. The setting on the overload is too low. Check the pump motor nameplate for
amperage and set the rotary switch on the overload to the amperage value (for
the voltage of the chiller) on the pump nameplate X 1.25.
iii. Contacts on contactor K1 are arching causing an imbalance of voltage, on the
three phase motors. Replace the K1 contactor.
b. Contacts on the motor starter are not closing due to a defective contactor or burned
out contactor coil. Replace the K1 contactor.
5. The flow in the machinery is not sufficient to satisfy the minimum setting of the water flow
safety switch. Check to be sure that water valves and solenoid valves on the equipment
being chilled are open. An internal bypass has been factory installed to allow a low outside
flow, but will not allow operation if outside load uses less than about 20gpm.
6. Note that on models with the letter L, a much larger internal bypass has been installed to
allow the chiller to operate with virtually no outside water flow.
LOW FREON FAULT:
The Freon pressure in the sealed refrigeration system has fallen below the setting on the LOW
FREON safety switch. The water pump will continue to operate, but the refrigeration system will
not turn on.
This is usually caused by a Freon leak in the system. A certified refrigeration technician can
check the system, locate the Freon leak, repair and recharge the system.
A LOW FREON fault can sometimes clear by itself for a short time, but will come back rapidly.
You may hear the compressor turning ON and OFF rapidly. In this case, turn the chiller off to
prevent damage to the system and consult a certified refrigeration technician.
This problem can also be caused by a faulty expansion valve (TXV). This component controls
the flow of Freon in the evaporator.
HIGH FREON FAULT:
The Freon pressure in the sealed refrigeration system has gone above the setting on the HIGH
FREON safety switch. When this switch trips, the chiller will reset in several minutes.
This HIGH FREON FAULT can be caused by one of the following:
DIRTY AIR INTAKE FILTER: If the airflow across the condenser coil is below a minimum
requirement, the ability for heat to be removed from this coil will be greatly reduced. The
temperature of the Freon in this coil will continue to rise until the set pressure value has been
exceeded. This filter should be cleaned with soapy water once per week for normal factory
TROUBLE SHOOTING
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