York SSS 14L-B, Operation Manual

Page: 31 / 40

JOHNSON CONTROLS
31
FORM 160.00-O2
ISSUE DATE: 04/30/2019
6
SECTION 6 – START INHIBIT
HIGH TEMPERATURE
During the ramp up period, when starting current is
being conducted to the motor, the internal die of the
SCR becomes very hot. Since the SCRs become very
hot, they must be cooled before each start of the chiller
or they will fail. To ensure that the SCRs are cooled
before each start, a Start Inhibit threshold is used. This
threshold is 110°F. Under normal running conditions
of the LCSSS, the SCR temperature is typically great-
er than 110°F. So, when the chiller has completed a
coastdown, it is normal for the Start Inhibit message
of
“LCSSS - HIGH PHASE X HEATSINK TEM-
PERATURE – STOPPED” to appear on the OptiV-
iew Control Center display. The X in the message will
indicate which phase is above the threshold. The cool-
ant pump will continue to run as long as the Start In-
hibit is active. The Remote Ready Relay contacts will
be open during this condition. When the temperature
of all three phases has fallen below 109°F, the coolant
pump will stop running and the LCSSS will now be
able to start. Since the Start Inhibit is not a fault condi-
tion, no events are logged into the History Log.
To minimize the time it takes to cool down the SCRs,
and allow the chiller to restart sooner if the anti-recy-
cle has timed out, a condenser water pump control has
been added to the OptiView Control Center software.
This added feature is available only for Mod. ‘B’ start-
ers with the following OptiView Control Center soft-
ware. On a YK chiller, the software is C.MLM.01.04
or later. On a YT chiller, the software is C.MLM.02.01
or later. On a YS chiller, the software is C.MLM.03.01
or later.
This new condenser water pump control will continue
to run the condenser water pump after the chiller has
been placed into a coastdown, as long as the following
conditions are met. If any one of the three SCR as-
semblies thermistors indicates a temperature of greater
than 105°F, and if it has been less than one hour since
the chiller was last stopped. The condenser water pump
will also turn on, when power is restored after a power
fault, if any one of the three SCR assemblies thermis-
tors indicates a temperature of greater than 105°F, and
it has been less than one hour since the chiller was last
stopped or shutdown due to a safety or cycling shut-
down. Once the temperature of all three thermistors is
below 105°F, the condenser water pump will turn off,
and will not turn on until the next compressor start.