YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls
YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls
YVAA Style A Air-Cooled Screw Liquid Chillers ... - Johnson Controls
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FORM 201.28-NM1.1<br />
ISSUE DATE: 8/29/2012<br />
ing at 10% of the programmed cutout. If over the next<br />
30 seconds, the suction pressure does not stay above<br />
the ramped cutout, which ramps between 10% of the<br />
cutout and the programmed cutout over the 30 second<br />
period, the system will fault on low suction pressure.<br />
Low Motor Current Cutout Fault<br />
The Motor Current Cutout shuts the system down with<br />
a controlled ramped shutdown when the microprocessor<br />
detects the absence of motor current (less than 10%<br />
FLA), usually indicating that a compressor is not running.<br />
This safety is ignored for the first 10 seconds of<br />
operation.<br />
The status display fault message for this safety is<br />
shown below:<br />
SYS X YYYYYYYY LOW MOTOR CURRENT<br />
The X indicates the system and YYYYYYY indicates<br />
the system is in a “FAULT” condition and will restart<br />
when the 120 second anti-recycle timer times out or<br />
“LOCKOUT” and will not restart until the operator<br />
clears the fault using the keypad.<br />
High Differential Oil Pressure Cutout Fault<br />
The High Differential Oil Pressure Cutout protects the<br />
compressor from low oil flow and insufficient lubrication,<br />
possibly from a dirty oil filter. A system will fault<br />
and shut down with a controlled ramped shutdown<br />
when its Discharge to Oil Differential Pressure rises<br />
above the cutout of 4.48 bard (65 PSID). This safety is<br />
ignored for the first 90 seconds of run time. This safety<br />
measures the pressure differential between discharge<br />
and oil pressure, which is the pressure drop across the<br />
oil filter. The Status display fault message for this safety<br />
is shown below:<br />
SYS X YYYYYYYY HIGH DIFF OIL PRESSURE<br />
The X indicates the system and YYYYYYY indicates<br />
the system is in a “FAULT” condition and will restart<br />
when the 120 second anti-recycle timer times out or<br />
“LOCKOUT” and will not restart until the operator<br />
clears the fault using the keypad.<br />
Low Differential Oil Pressure Cutout Fault<br />
The Low Differential Oil Pressure Cutout protects the<br />
compressor from low oil flow and insufficient lubrication.<br />
A system will fault and shut down with a controlled<br />
SECTION 7 - OPERATION<br />
ramped shutdown when it’s differential between oil<br />
and suction pressure falls below the cutout. This safety<br />
assures that the compressor is pumping sufficiently to<br />
push oil through the oil cooling circuit and through the<br />
internal compressor lubrication system. The Status display<br />
fault message for this safety is shown below:<br />
SYS X YYYYYYYY LOW DIFF OIL PRESSURE<br />
The X indicates the system and YYYYYYY indicates<br />
the system is in a “FAULT” condition and will restart<br />
when the 120 second anti-recycle timer times out or<br />
“LOCKOUT” and will not restart until the operator<br />
clears the fault using the keypad.<br />
The safety is ignored for the first 60 seconds of run<br />
time. After the first 60 seconds of operation, the cutout<br />
is linearly ramped from 0 bard to 2.09 bard (0 PSID to<br />
30 PSID) in 5 to 10 minutes based on ambient temperature.<br />
See the following table for the ramp times for the<br />
given ambient temperatures.<br />
TABLE 7 - LOW DIFFERENTIAL OIL PRESSURE<br />
CUTOUT<br />
AMBIENT TEMPERATURE<br />
RAMP<br />
TIME<br />
more than 10°C (50ºF) 5 Minutes<br />
more than 7.2°C (45ºF) 6 Minutes<br />
more than 4.4°C (40ºF) 7 Minutes<br />
more than 1.6°C (35ºF) 8 Minutes<br />
more than 1.1°C (30ºF) 9 Minutes<br />
more than or equal to 1.1°C (30ºF) 10 Minutes<br />
A 30 second safety bypass below 50 Hertz is employed<br />
during rampdown. The bypass is primarily needed<br />
under conditions where another compressor is being<br />
brought on and the running compressor is being<br />
ramped down to 5 Hertz to add the additional compressor<br />
due to load requirements. Under these conditions,<br />
the slow speed of the running compressor(s) causes the<br />
oil differential to become very low, especially if the<br />
water temperature is high and the suction pressure is<br />
high. The bypass assures the compressor(s) will not<br />
trip on a nuisance low oil differential fault.<br />
High Discharge Temperature Cutout Fault<br />
The High Discharge Temperature Cutout protects the<br />
motor and compressor from overheating. A system will<br />
fault and shut down with a controlled ramped shutdown<br />
when its Discharge Temperature rises above 121°C<br />
JOHNSON CONTROLS 91<br />
7