York MILLENNIUM YCAS Installation Operation & Maintenance page 103

Wiring from remote "dry" contact (for
reset functions) should not exceed 25
ft. (8 m) and should be run in grounded
conduit that does not carry any wir-
ing other than control wiring or in
shielded cable. If an inductive device
(relay, contactor) is supplying these
contacts, the coil of the device must
be suppressed with a standard RC sup-
pressor (50Hz models) across the in-
ductive 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 & 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 (2ºF - 40ºF), as appropriate to the ap-
plication - 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 (44ºF),
after a 4 second pulse and a programmed maximum
offset of 22°C (40ºF), the temperature offset would
equal:
Reset Temp = (4 sec - 1 sec) X 22ºC
Reset Temp = 66°C sec
YORK INTERNATIONAL
10 sec
10 sec
10 sec
= 6ºC (12ºF)
To determine the new setpoint, add the reset to the
setpoint programmed into memory. In the example pre-
ceding, if the programmed setpoint = 7°C (44ºF), the
new setpoint after the 4 second contact closure
would be 7°C (44ºF)+ 6°C (12ºF) = 13°C (56ºF).
This new setpoint can be viewed on the display by Press-
ing 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 dis-
play. To view the new offset, first press
any other display key on the keypad
and then press the Remote Reset Tem-
perature 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 8m
(25 ft.) and should be run in grounded
conduit that does not carry any wir-
ing other than control wiring or in
shielded cable. If an inductive device
(relay, contactor) is supplying these
contacts, the coil of the device must
be suppressed with a standard RC sup-
pressor (50Hz models) across the in-
ductive coil.
FORM 201.18-NM2
9
103