YORK INTERNATIONAL
52
AUTOMATIC RESET SAFETIES
An Automatic Reset Safety will shut the entire chiller
down on a fault when the safety threshold is exceeded
and allows automatic restart after the condition caus-
ing the shutdown clears. Restart will occur only after
antirecycle timers are satisfied and demand requires.
A reset hysteresis is built in so repetitive faulting and
clearing will not occur in a short time period. An ex-
ample would be if ambient temperature dropped below
the cut-out, temperature would have to rise 5°F above
the cut-out before the fault lockout would clear and re-
start can occur.
When the chiller is shut down on one of these safeties,
a message will appear on the STATUS display inform-
ing the operator of the problem. This is accessible by
pressing the STATUS key.
Details concerning each of the three Automatic Reset
Safeties follow.
Low Water Temperature Safety
The Low Water Temperature Safety assures that the
evaporator is not damaged from freezing due to improp-
erly set control points. Whenever the chilled liquid tem-
perature drops below the programmable cut-out, the
chiller will shut down. Restart will not occur until tem-
perature rises 5°F above the cut-out point, load de-
mand requires, and anti-recycle timers allow.
The Leaving Water Temperature Safety Cut-out is pro-
grammable by the user (Page 36). An example of the
Low Water Temperature Fault display message is
shown below:
Low Ambient Temperature Safety
The Low Ambient Temperature Safety assures that the
chiller does not run in low ambients where potential
damage could result due to low system pressures.
The Low Ambient Cut-out is programmable by the user
(Page 35). An example of the Low Ambient Tempera-
ture Fault display message is shown below:
High Ambient Temperature Safety
The High Ambient Temperature Safety assures that the
chiller does not run in ambients above 130°F where
potential malfunction of system mechanical and electri-
cal components may result. Whenever the outdoor am-
bient exceeds 130°F (non-programmable) the chiller
will shut down. Restart will not occur until temperature
drops to 2°F below the cut-out point, load demand re-
quires, and anti-recycle timers allow.
The High Ambient Cut-out is programmable (Page 35)
for chiller cut-out at temperatures below 130°F (100°
-130°F). An example of the High Ambient Temperature
Fault display message is shown below:
Under Voltage Safety
The Under Voltage Safety assures that the system is
not operated at voltages where malfunction of the mi-
croprocessor could result in system damage. When-
ever the microprocessor senses an onboard power
supply failure, the chiller is shut down. Restart will oc-
cur when power is restored. The microprocessor cir-
cuitry is capable of operating at voltages 10% below
the nominal 115VAC supply to the panel.
An example of the Under Voltage Safety display mes-
sage is shown below:
Flow Switch
The microprocessor monitors the closure of the flow
switch to assure that water flow is present in the evapo-
rator which prevents freeze-ups. The flow switch dry
contacts are connected between terminals 13 & 14 (Fig.
11). If the flow switch opens, the chiller will shut down
and the following status message will be displayed.
Closure of the flow switch, when flow is present, will
cause the message to disappear and auto-restart will
occur.
CAUTION:
NEVER
BYPASS A FLOW SWITCH. THIS
WILL CAUSE DAMAGE TO THE CHILLER
AND VOID ANY WARRANTIES.
C H I L L E R
F A U L T :
L O W
W A T E R
T E M P
C H I L L E R
F A U L T :
L O W
A M B I E N T
T E M P
C H I L L E R
F A U L T :
H I G H
A M B I E N T
T E M P
S Y S # 1
N O
R U N
P E R M
S Y S # 2
N O
R U N
P E R M
C H I L L E R
F A U L T
1 1 5 V A C
U N D E R
V O L T A G E