York Millennium YCAS Series Installation Operation & Maintenance page 135

Wiring from remote "dry" contact (for
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 inductive device (relay,
contactor) is supplying these contacts,
the coil of the device must be sup-
pressed with a suppressor YORK Part
Number 031-00808-000 (60 Hz mod-
els) or a standard RC suppressor (50
Hz models) across the inductive coil.
Remote Setpoint Reset
The chilled liquid leaving temperature setpoint pro-
grammed into the micro can be remotely adjusted to a
higher value using repeated timed closure of "dry" con-
tacts connected to Terminals 13 and 17 of TB4 in the
logic section of the control panel (See Section 1.12).
The duration of the contact closure will decide the
amount of adjustment. This is achieved as follows:
The maximum allowable reset value can be programmed
from 1°C - 22°C (2°F - 40°F), as appropriate to the
application – see Section 6.4. Once the maximum reset
is programmed, an input contact closure of 11 seconds
provides the maximum reset. Closure for less than 11
seconds will provide a smaller reset. For noise immu-
nity, the micro will ignore closures of less than 1 sec-
ond. To compute the necessary contact closure time to
provide a required Reset, use the following steps:
Reset Temp ={ (Contact Closure - 1sec) X Programmed Max Reset}
Offset
For example, with a programmed setpoint of 7°C (44°F),
after a 4 second pulse and a programmed maximum off-
set of 22°C (40°F), the temperature offset would equal:
Reset Temp = (4 sec - 1 sec) X 4.4°F
10 sec
Reset Temp = 66.7°Csec
10 sec
= 6°C (12°F)
YORK INTERNATIONAL
10 sec
To determine the new setpoint, add the reset to the
setpoint programmed into memory. In the example
above, if the programmed setpoint = 7°C (44°F), the
new setpoint after the 4 second contact closure would
be 7°C (44°F) + 6°C (12°F) = 13°C (56°F). This new
setpoint can be viewed on the display by Pressing the
Remote Reset Temperature/Range key.
To maintain a given offset, the contact closure signal
must be repeated every 30 seconds - 30 minutes. The
refresh is not accepted sooner than 30 seconds from
the end of the last PWM signal, but must be refreshed
before 30 minutes has elapsed. After 30 minutes, if no
refresh is provided, the setpoint will change back to its
original value.
After an offset signal, the new Remote
Setpoint may be viewed on the Remote
Reset Temperature Range display.
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 Reset Tempera-
ture Range key. The new setpoint will
then appear.
Remote Setpoint Reset will not oper-
ate when a Remote Control Center
Option Kit is connected to the Micro.
The Remote Control Center will al-
ways determine the setpoint.
Wiring from remote "dry" contact (for
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 inductive device (relay,
contactor) is supplying these contacts,
the coil of the device must be suppressed
with a standard RC suppressor (50 Hz
models) across the inductive coil.
FORM 201.18-NM4
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