York MILLENNIUM YCAS 250 Manual Download

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YORK INTERNATIONAL

FORM 201.18-NM3

Low Evaporator Temperature Cutout (R407c Only):

The Low Evaporator Temperature Cutout is to pro-
tect the evaporator from freeze-up with R-407c. This
safety uses the Cooler Inlet Refrigerant Temp Sen-
sors to monitor evaporator inlet refrigerant tempera-
ture on each system. These sensors are only installed
on R-407c units. If the refrigerant temperature falls
below 21°F (-6°C) in water cooling mode, the system
will be shut down. If the refrigerant temp falls 19°F
(11°C) below the leaving chilled liquid temp in gly-
col cooling mode, the system will shut down. Also, if
the cooler inlet refrigerant temp sensor reads out of
range low, the system will also shut down.

2.7

PRINTOUT ON FAULT SHUTDOWN

If an optional printer is installed, the contents of His-
tory Buffer 1 will be sent to the printer any time a fault
shutdown occurs. This will allow record keeping of
individual faults, even if they do not cause a lockout of
the system. This information may be useful to identify
developing problems and troubleshooting.

The No Run Permissive fault messages will not be
stored in the History Buffer and will not cause an auto
printout.

Due to extreme operating conditions
or systems where control deficiencies
are present, occasional faults may
occur with the corresponding auto-
matic printout. This is not a cause for
concern.

the MP contacts open. Manual reset is accomplished
by removing 115VAC control power from the micro
panel after the motor sensors have sufficient time to
cool. Details relating to operation of the Motor Protec-
tion Module can be found on page 16.

The External Motor Overload is responsive to motor
current. When the overload relay senses single phase
operation, locked rotor current in excess of 10 seconds,
or sustained current overloads in excess of 140% of RLA,
it will trip. This causes power to be removed from the
compressor contactors and shuts down the compressor.

Auto-restart will not be permitted since a manual reset
of the device is required to restart the compressor. Af-
ter the first fault, the micro will try two more restarts,
but with the External Motor Overload Relay tripped,
no restart can occur. The micro will then lock out the
system. In addition to manually resetting the External
Motor Overload Relay, the fault will also require reset
by turning the appropriate system switch OFF, then ON.

The OL relay setting should never be altered. If for some
reason the Overload Relay is replaced, the following
procedure is used for setup.

A/L Start:

Dial Setting = (1.1 x RLA) / 350

WYE-Delta Start:Dial Setting = (0.64 x RLA) / 350

The Mechanical High Pressure Cutout protects
against excessive refrigerant discharge pressure and is
set to 405 PSIG (28 bar). Auto-restart will be permitted
after shutdown on discharge pressure, when the pres-
sure drops below 330 PSIG (23 bar) and the cutout con-
tacts close. A fault lockout will result if safety thresh-
olds are exceeded three times in a 90 minute period.

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