
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 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
Remote Current Reset must never be used to control temperature. These contacts are to be used only for peri- odic demand limiting purposes.
Remote Setpoint Temperature 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” contacts connected to Terminals 13 and 17 of TB4 located in the logic section of the control panel (See Section 8.1.12). The duration of the contact closure will determine the amount of adjustment. This is achieved as follows:
The maximum allowable reset value can be programmed from 2°F - 40°F (1°C - 22°C), 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 immunity, the micro will ignore closures of less than 1 second. 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 | 10 sec |
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 Temp = (4 sec - 1 sec) X 40°F
10 sec
Reset Temp = 120°Fsec
10sec
=12°F (6°C)
To determine the new setpoint, add the reset to the setpoint programmed into memory. In the example above, if the programmed setpoint = 44°F (7°C), the
FORM
new setpoint after the 4 second contact closure would be 44°F (7°C)+ 12°F (6°C) = 56°F (13°C). 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 (refreshed) 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 by pressing the Remote Coding Setpoint Key. 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 Cooling Setpoint Range key. The new setpoint will then appear.
Remote Setpoint Reset will not operate when a Remote Control Center Option Kit is connected to the Micro. The Remote Control Center will always determine the setpoint.
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 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 suppressor YORK Part Number
Remote Setpoint Reset must never be used to control temperature. These contacts are to be used only for occasional temperature setback due to outside ambient, changes in building occupancy, or ice storage.
8
YORK INTERNATIONAL | 129 |