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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 'MOTOR
CURRENT' key.
Remote EMS reset will not operate
when a Remote Control Center Op-
tion Kit is connected to the micropro-
cessor. The Remote Control Center
will always determine the setpoint.
Wiring from remote 'voltage free' con-
tacts (for reset functions) should not
exceed 25 feet (7.5 meters), and should
be run in grounded conduit that car-
ries only control wiring. If an induc-
tive device (relay, contactor) is supply-
ing these contacts, the coil of the de-
vice must be suppressed with a stan-
dard RC suppressor across the induc-
tive coil.
1.13 REMOTE SETPOINT RESET
The chilled liquid leaving temperature setpoint pro-
grammed into the microprocessor can be remotely ad-
justed to a higher value using repeated timed closure of
'voltage free' contacts (Terminals 13 & 27). The dura-
tion of the contact closure will decide the amount of
adjustment.
This is achieved as follows:
The maximum allowable reset value can be programmed
from 2°F to 40°F (1°C to 22°C), as appropriate to the
application. Once the maximum reset is programmed,
an input contact closure of 11 seconds provides the maxi-
mum reset. Closure for less than 11 seconds will pro-
vide a smaller reset. For noise immunity, the micropro-
cessor will ignore closures of less than 1 second.
To calculate the necessary contact closure time to pro-
vide a required Reset, use the following steps:
36
RESET
TEMPERATURE = [(CONTACT CLOSURE - 1 SEC) X PROGRAMMED MAX RESET]
OFFSET
For example, with a programmed setpoint of 44°F
(7°C), after a 4 second pulse and a programmed
maximum offset of 40°F (22°C), the temperature
offset would equal:
RESET
TEMPERATURE
=
(4 sec - 1 sec) x 40°F (22°C)
OFFSET
RESET
TEMPERATURE
=
OFFSET
RESET
TEMPERATURE
=
OFFSET
To determine the new setpoint, add the reset to the set-
point programmed into memory. In the example above,
if the programmed setpoint = 44°F (7°C), the new
setpoint after the 4 second contact closure would be
44°F + 12°F = 56°F (7°C + 6.6°C = 13.6°C). This new
setpoint can be viewed on the display using the 'RE-
MOTE COOLING SETPOINTS' key.
To maintain a given offset, the contact closure signal
must be repeated every 30 seconds to 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 set-
point 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 COOLING
SETPOINTS' key. The new setpoint
will then appear.
Remote setpoint reset will not operate
when a Remote Control Center Option
Kit is connected to the microproces-
sor. The Remote Control Center will
always determine the setpoint.
FORM 201.25-NM1 (302)
10 SEC
10 sec
120°F (66°C) sec
10 sec
12°F (6.6°C)
YORK INTERNATIONAL
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