Table 23 - Compressor Operation - Load Limiting - York YCAL0012EC Installation Operation & Maintenance

FORM 150.66-NM2
ISSUE DATE: 09/25/2020
LOAD LIMITING
Load Limiting is a feature that prevents the unit from
loading beyond the desired value. Two compressor
units can be load limited to 50%. This would allow
only 1 compressor per system to run. No other values
of limiting are available.
TABLE 23 – COMPRESSOR OPERATION –
LOAD LIMITING
COMPRESSORS STAGE 1
IN UNIT
2
Simultaneous operation of Remote Load
Limiting and EMS­PWM Temperature
Reset (described on following pages)
cannot occur.
COMPRESSOR RUN STATUS
Compressor run status is indicated by closure of contacts
at CTB2 – terminals 25 to 26.
ALARM STATUS
System or unit shutdown is indicated by normally-open
alarm contacts opening whenever the unit shuts down on
a unit fault, locks out on a system fault, or experiences a
loss of power to the chiller electronics . System 1 alarm
contacts are located at CTB2 – terminals 29 to 30. The
alarm contacts will close when conditions allow the unit
to operate, or the fault is reset during a loss of power,
the contacts will remain open until power is reapplied
and no fault conditions exist.
EMS-PWM REMOTE TEMPERATURE RESET
EMS-PWM Remote Temperature Reset is a value that
resets the Chilled Liquid Setpoint based on a PWM
input (timed contact closure) to the microboard. This
PWM input would typically be sup plied by an Energy
Management System.
JOHNSON CONTROLS
STAGE 2
50% -
A contact closure on the PWM Temp Reset input at
CTB1 terminals 13 - 20, will reset the chilled liquid
setpoint based on the length of time the contacts remain
closed. The maximum temperature reset is achieved
at a contact closure of 11 seconds. This is the longest
contact closure time allowed. One second is the shortest
time allowed and causes the Chilled Liquid Setpoint to
revert back to the Local programmed value. The reset
value is always added to the Chilled Liquid Setpoint,
meaning that this function never lowers the Chilled
Liquid Setpoint below the locally programmed value,
it can only reset to a higher value. The microboard must
be refreshed between 30 seconds and 30 minutes. Any
contact closure occurring sooner than 30 seconds will
be ignored. If more than 30 minutes elapse before the
next contact closure, the setpoint will revert back to
the locally programmed value. The new chilled liquid
setpoint is calculated by the following equations:
Setpoint = local Chilled liquid Setpoint + °Reset
°Reset = (Contact Closure - 1) x (*Max. Reset Value)
Example:
local Chilled liquid Setpoint = 45°F (7.22°C).
*Max Reset Value = 10°F (5.56°C)
Contact Closure Time = 6 Seconds.
(English)
(6 sec. - 1) (10°F/10) = 5°F Reset
The new chilled liquid setpoint = 45°F + 5°F= 50°F. This
can be viewed by pressing the Cooling Setpoints key
twice. The new value will be dis played as "REM SETP
= 50.0°F."
(Metric)
(6 sec - 1) * (5.56°C/10) = 2.78°C
Reset Cooling Setpoint = 7.22°C + 2.78°C = 10.0°C
The new Reset Cooling Setpoint = 7.22 °C + 2.78°C = 10°C.
This can be viewed by pressing the Cooling Setpoints key
twice. The new value will be displayed as "REM SETP =
10.0°C."
* Max Reset Value is the "Max EMS-PWM Remote Temp. Reset" setpoint
value described in the program ming section under Cooling Setpoints.
Programmable values are from 2°F to 40°F (1.11°C to 11.11°C).
SECTION 8 - UNIT OPERATION
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