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FORM 150.75-NM2
59
YORK INTERNATIONAL
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
anti-recycle 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 demand
requires, and anti-recycle timers allow.
The Low Water Temperature Safety Cut-out is program-
mable by the user (Page 47). An example of the Low
Water Temperature Fault display message is shown be-
low:
Low Ambient Temperature Safety
The Low Ambient Temperature Safety assures that the
chiller does not run in low ambients where potential dam-
age could result due to low system pressures.
The Low Ambient Cut-out is programmable by the user
(Page 46). 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 po-
tential malfunction of system mechanical and electrical
components may result. Whenever the outdoor ambi-
ent 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 requires,
and anti-recycle timers allow.
The High Ambient Cut-out is programmable (Page 46)
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 sup-
ply failure, the chiller is shut down. Restart will occur
when power is restored. The microprocessor circuitry
is capable of operating at voltages 10% below the nomi-
nal 115 VAC 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. A set of flow switch
“dry” contacts are connected between terminals 13 &
14 (Fig. 15 & 18). One flow switch must be connected
to each Control Panel. If a flow switch opens, a chiller
module will shut down and the following status mes-
sage 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
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
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