York Millennium YCAS 0693 Installation Operation & Maintenance Download

Page: 134 / 188

134

YORK INTERNATIONAL

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 func-
tions can easily be controlled by connecting user sup-
plied “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) con-
nected 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 8 m (25 ft.) 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 de-
vice must be suppressed with a sup-
pressor YORK Part Number 031-
00808-000 (60Hz models) or a stan-
dard RC suppressor (50Hz models)
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 clo-
sure will determine the amount of adjustment. Gener-
ally, this input is used for purposes of demand limit and
operates as follows:

Closing the input contact for a defined period of time
allows reset of the % Current Limit downward. Con-
tact closure of 1 - 11 seconds will allow % Current Lim-
iting to be adjusted downward from 105% by a maxi-
mum 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. Con-
tact closures of less than 1 second will be ignored. A
closure of 11 seconds is the maximum allowable clo-
sure 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)

(75% FLA)

}

CURRENT

10 sec

For example, after a 4 second pulse, the offset would
equal:

Remote Reset Curr = 105% FLA - {(4sec - 1 sec) X (75%FLA)}

10 sec

= 105% - 225%FLA sec

10 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 pro-
vided, 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 Option
Kit is connected to the micro. The Re-
mote Control Center will always de-
termine the setpoint.

MicroPanel Contents