Ems/Bas Controls - York YCAS0098EB Installation Operation & Maintenance

Micro Panel Contents
1.10

EMS/BAS CONTROLS

The microprocessor system can accept remote signals
to Start/Stop the chiller, to adjust maximum allowable
running current for each compressor, and to adjust
the chilled liquid leaving temperature setpoint. These
functions can easily be controlled by connecting user
supplied "dry" contacts to the customer terminals in the
control panel. In addition, Alarm Contacts are provided
to remotely signal a fault with the chiller.
Remote Start/Stop
Remote Start/Stop can be accomplished using a time
clock, manual contact or other "dry" contact in series with
the flow switch (Terminals 13 and 14 of TB4) connected
to terminals in the logic section of the control panel.
The contact must be closed to allow the chiller to run.
Any time the contact opens, the chiller will shut down
and the NO RUN PERM message will be displayed.
The location of the flow switch connection is shown in
Section 1.12.
Never bypass a flow switch. This will
cause damage to the chiller and void
any warranties.
Wiring from remote "dry" contacts
(for stop/start reset functions) should
not exceed 25 ft. (8 m) and should be
run in grounded conduit that does not
carry any wiring other than control
wiring or shielded cable. If an induc‑
tive device (relay, contactor) is supply‑
ing these contacts, the coil of the device
must be suppressed with a suppressor
YORK Part Number 031‑00808‑000
across the inductive coil.
Remote Current Reset
The maximum allowable running current for each com-
pressor can be adjusted remotely to a lower value using
repeated timed closure of "dry" contacts connected to
Terminals 13 and 16 at the bottom center of the Micro-
processor Panel (See Section 1.12) in the logic section
of the control panel. The duration of the contact closure
will determine the amount of adjustment. Generally, this
input is used for purposes of demand limit and operates
as follows:
128
Closing the input contact for a defined period of time
allows reset of the % Current Limit downward. Contact
closure of 1 - 11 seconds will allow % Current Limiting
to be adjusted downward from 105% by a maximum
of 75%, i.e. to a minimum value of 30% FLA. EMS
Current Limiting operates independently of the High
Average Current Unload (See Section 8.2). The micro
will always look at the two Current Limit Setpoints and
choose the lower as the controlling value, whenever
Remote Current Limiting is utilized. Contact closures
of less than 1 second will be ignored. A closure of 11
seconds is the maximum allowable closure and provides
a Current Limit reduction of 75%. The remote reset
current can be calculated as follows:
REMOTE
= - {
RESET 105% FLA (Contact Closed Time -1sec)
CURRENT
For example, after a 4 second pulse, the offset would
equal:
Remote Reset Curr = 105% FLA - {(4sec - 1 sec) X (75%FLA)}
= 105% - 225%FLA sec
= 82.5% FLA
To maintain a given offset, the contact closure signal
must be repeated at not more than 30 minute intervals
but not less than 30 seconds from the end of the each
PWM signal. After 30 minutes, if no refresh is provided,
the setpoint will change back to its original value.
After an offset signal, the new Remote
Current Limit may be viewed on the
Remote EMS Limiting Display under
the Motor Current Key (see Section
3.5). However, if this display is being
viewed when the reset pulse occurs, the
setpoint will not change on the display.
To view the new offset, first press any
other display key on the keypad and
then press the Remote EMS Limiting
Display.
Remote EMS Reset will not operate
when a Remote Control Center Op‑
tion Kit is connected to the micro. The
Remote Control Center will always
determine the setpoint.
x
(75% FLA)
10 sec
10 sec
10 sec
JOHNSON CONTROLS
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