FORM 150.44-NM4
65
YORK INTERNATIONAL
RANGE and press the ENTER Key to store the new
value in memory.
Once the maximum reset is programmed, it will require
a contact closure of 21 seconds to achieve the maxi-
mum reset. Closure for less than 21 seconds will pro-
vide a smaller reset. For noise immunity, the micro will
ignore closures of less than 1 second.
To compute the offset for a given timer closed, use the
formula below:
1. Programmed max. reset = Reset per sec.
20 seconds
2. (Time Closed - 1 ) Reset per sec. = Reset
Example:
Programmed max reset = 30°; Time Closed = 9 sec.
1. 30° = 1.5° per sec.
20 sec.
2. (9 sec. - 1 sec.) 1.5° per sec. = 12° = Reset
To determine the new setpoints, add the reset to the
setpoint programmed into memory. In the example above,
if the programmed setpoint = 44°F, the new setpoint after
the 9 second contact closure would be 44°F + 12°F =
56°F. This new setpoint can be viewed on the display by
pressing the REMOTE RESET TEMP/RANGE key.
To maintain a given offset, the micro must be refreshed
every 30 seconds - 30 minutes with a contact closure
of the required time period. It will not accept a refresh
sooner than 30 seconds after the end of the last PWM
signal, but must be refreshed before a period of 30
minutes expires from the end of the last PWM signal.
After 30 minutes, if no refresh is provided, the setpoint
will change back to its original value. A refresh is noth-
ing more than a contact closure for the period required
for the desired offset.
NOTE: After an onset signal, the new setpoint may be
viewed on the REMOTE RESET TEMP
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 onset, first press any other display key
on the keypad and then press the REMOTE
RESET TEMP RANGE key. The new setpoint
will then appear.
Wiring from these contacts should not exceed 25 ft. and
should be run in grounded conduit that does not carry
any wiring other than control wiring. Additionally, if an
inductive device (relay, contactor is supplying these con-
tacts, the coil of the device must be suppressed with a
user supplied YORK P/N 031-00808 suppressor.
NOTE: Remote Setpoint Reset will not operate when
a Remote Control Center Option Kit is con-
nected to the Micro Panel. The Remote Con-
trol Center will always determine the setpoint.
REMOTE UNLOADING
The microprocessor is capable of remote unloading or
pulldown demand limiting in two steps. The first step
shuts down the lag system. The second step unloads
the lead system to its minimum step of capacity which
places the entire system at minimum possible capac-
ity.
To shut down the lag compressor, a dry contact should
be connected between terminals 13 & 16. See Fig. 11
for the location of these terminals. When the contact is
closed, the lag compressor will shut down.
Before the lead system can be unloaded to its mini-
mum step of capacity, the lag compressor must already
be disabled with a dry contact closure between ter-
minal 13 & 16 as described in the preceding paragraph.
With contacts on Terminals 13 & 16 closed, the lead
system can be unloaded to its minimum step of capac-
ity by closing a dry contact connected between termi-
nals 13 & 17. See Fig. 11 for location of this terminal.
The lead system; will remain totally unloaded as long
as the contacts remain closed on both 13 & 16 and 13
& 17. It should be noted that terminals 13 & 17 are
normally used for Remote Setpoint Reset. However, it
is assumed that if the lag system is purposely being
shut down, Remote Setpoint Reset and temperature
control is of no importance. This is generally true since
capacity control of the load is lost when a large portion
of the capacity is disabled.
CAUTION: Two cautions should be observed when us-
ing these functions. Observing these cau-
tions will assure that undesirable operation
does not result.
1.
Terminals 13 & 17 contact should always
be closed after or simultaneous with those
on 13 & 16, when unloading of the lead sys-
tem is desired. Otherwise, the micro-
processor may mistake the closed contacts
on 13 & 17 as a signal for a setpoint reset.
2.
Terminal 13 & 17 contact should always be
opened before or simultaneous with those
on 13 & 16 when loading is desired. Other-
wise, the microprocessor may mistake the
closed contacts on 13 & 17 as a signal for
a setpoint reset.