26
Capacity overrides can prevent some safety shutdowns caused by exceeding the motor amperage limit, evaporator refrigerant
low temperature safety limit, motor high temperature safety limit, and condenser high pressure limit. In all cases there are
2 stages of capacity control.
1. When the value of interest crosses the First Stage Set Point into the Override Region, the capacity are prevented from
increasing further, and the status line on the 19 Series PIC 5+ controller indicates the reason for the override. Normal
capacity control operation is restored when the value crosses back over the First Stage Set Point, leaving the Override
Region.
2. When the value of interest is in the Override Region and further crosses the Second Stage Set Point, the capacity shall
be decreased until the value meets the Override Termination Condition. The 19 Series PIC 5+ controls resume normal
capacity control operation after the override termination condition has been satised. (In the case of high discharge
superheat, there is an intermediate stage.)
Besides the above overrides, other types of override will not override control guide vane or VFD. Only override events are
reported.
High Compressor Discharge Temperature Override
If the COMP DISCHARGE TEMP is greater than the COMP DISCHARGE ALERT threshold then high discharge
temperature override will be displayed in the main screen until the COMP DISCHARGE TEMP is less than the COMP
DISCHARGE ALERT threshold – 2F.
High Compressor Bearing Temperature Override
For 19XR6/7 and 19DV, if one of the compressor bearing temperature is greater than the compressor bearing temperature
Alert threshold then High Bearing Temperature Override will be active until all of the compressor bearing temperature is
less than Comp Bearing Temp Alert minus 2F.
For 19XR2~E/V/D chiller, if the calculated bearing temperature is greater than the bearing temperature alert threshold,
then high bearing temperature override will be active until the calculated bearing temperature is less than the threshold
minus 2F.
Low Discharge Superheat Temperature Override
Ignore low discharge superheat override during rst 5 minutes after chiller startup completed. After 5 minutes elapse, for
two stage 19XRE chiller, keep ignoring it until the rst time (Cond pressure – Evap pressure)>10psid; for 19XR6/7, keep
ignoring it until the rst time Damper becomes not fully closed for a consecutive 20 seconds; for 19DV, Ignore low discharge
superheat override during rst 5 minutes after chiller startup completed.
CONDENSER
PRESSURE
> COND PRESS OVERRIDE
LOW
For low condenser type
140psig (90 - 157 psig)
> COND PRESS OVERRIDE
HIGH + 2.4 psi
< COND PRESS
OVERRIDE HIGH - 1 psi
CONDENSER
PRESSURE
> COND PRESS OVERRIDE
HIGH
For high condenser type
250 psig (200 – 265 psig)
> COND PRESS OVERRIDE LOW
+ 2.4 psi
< COND PRESS
OVERRIDE LOW - 1 psi
CONDENSER
PRESSURE
> COND PRESS OVERRIDE
DV 44
For low condenser
type20psig (18 - 25psig)
> COND PRESS OVERRIDE
HIGH + 2.4 psi
< COND PRESS
OVERRIDE HIGH - 1 psi
CONDENSER
PRESSURE
> COND PRESS OVERRIDE
DV 72
For high condenser type
55 psig (20 – 56 psig)
> COND PRESS OVERRIDE LOW
+ 2.4 psi
< COND PRESS
OVERRIDE LOW - 1 psi
CALC EVAP SAT TEMP
or
EVAP REFRIG LIQUID
TEMP
< EVAP SAT OVERRIDE
TEMP
EVAP SAT OVERRIDE
TEMP = EVAP TRIPPOINT +
EVAP OVERRIDE DELTA T
< EVAP SAT OVERRIDE TEMP – 1F
> EVAP SAT OVERRIDE
TEMP
COMP MOTOR
WINDING TEMP
> COMP MOTOR TEMP
OVERRIDE
200 F
150 to 200 F
COMP MOTOR WINDING TEMP
> COMP MOTOR TEMP
OVERRIDE + 10 F (5.6 C)
COMPR MOTOR
WINDING TEMP < COMP
MOTOR TEMP OVERRIDE
- 2 F (1.1 C)
PERCENT LINE
CURRENT
PERCENT LINE CURRENT
> 100%
or RECTIFIER OVERLOAD
(Only for 32VS VFD) > 100%
PERCENT LINE CURRENT >
105%
(If 32VS VFD is installed,
PERCENT LINE CURRENT or
RECTIFIER OVERLOAD > 102%)
PERCENT LINE
CURRENT <= 100%
Discharge Superheat < DSH REQUIRED + 1 < DSH REQUIRED – 3 > DSH REQUIRED + 2
Leaving chilled water
temperature (Heating
mode)
< LWT Protection Setpoint
(Protective Limit Cong)– 2F
> LWT Protection Setpoint
(Protective Limit Cong)– 2F
To Next Page
Loading...
