York YCAV0157 Installation Operation & Maintenance page 201

VSD OPERATION AND CONTROLS (CON'T)
The VSD fan and glycol pump will run if any of the
following conditions listed below are true, provided
the VSD has been powered up for less than 30 seconds
and the pump has not run in the last 30 seconds. The 30
second limitations prevent pump motor overheating.
· 2 and 4 Compressor Baseplate temp is > Cutout
(218°F) – 10°F.
· 3 Compressor IGBT Baseplate temp is > Cutout
(232°F ) – 10°F.
· Pre-charge Enable 1 from the chiller Logic Board
is ON.
· Pre-charge Enable 2 from the chiller Logic Board
is ON.
· VSD Internal Ambient Temp > Cutout – 10°F.
· Any compressor is running.
· Service Mode Fan/Pump Run is enabled.
The VSD fan/glycol pump will turn off when ALL of
the following conditions are true:
· Compressor 1/3 IGBT Baseplate temp is < Cutout
– 15°F.
· Compressor 2/4 IGBT Baseplate temp is < Cutout
–15°F.
· Pre-charge Enable 1 from the chiller Logic Board
is OFF.
· Pre-charge Enable 2 from the chiller Logic Board
is OFF.
· VSD Internal Ambient Temp < Cutout – 15°F.
· No compressors are running.
· Service Mode Fan/Pump is disabled.
JOHNSON CONTROLS
In some cases, the condenser fans may
be turned on by the micro, when no
compressors are running, to keep the
power components and Control/VSD
Cabinet from overheating.
IGBT Module Baseplate Temperature Sensing
Each IGBT module has an internal 5Kohm thermistor
built in to measure the temperature of the module. Up
to 4 thermistors are connected to the VSD logic board
(one per compressor). The highest module temperature
of compressors 1 and 3 are sent to the logic board along
with the highest module temperature of compressors 2
and 4. If the temperature exceeds the software trip point,
the unit will shut down on a safety. See High Baseplate
Temperature Fault (P. 206) for details.
VSD Internal Ambient Temperature Sensing
A National LM34 temperature sensor located on the
VSD Logic Board is used to measure the internal ambi-
ent temperature of the Control Panel/VSD enclosure. It
has an output voltage that is linearly proportional to the
temperature in degrees Fahrenheit. If the temperature
exceeds the software trip point, the unit will shut down
on a safety. See High VSD Ambient Temperature Fault
(Page208) for details.
FORM 201.21-NM1 (1223)
8
LM 34
SENSOR
LD10636
201