Error Messages; Setpoint Calibration - Honeywell T775A User Manual

T775A,B,C,D
DESCRIPTION/OPERATION
devices. At any time during the programming procedure, the
display will revert back to showing the sensed temperature
and stage status indication 60 seconds after the last key
closure.
For two sensor applications, the user has three options for
what is displayed. The display can be configured to indicate
Sensor A and Sensor B sensed temperature at a five second
rate or lock onto Sensor A sensed temperature or lock onto
Sensor B sensed temperature continuously.
This selection is accomplished by stopping at Sensor A
or Sensor B sensed temperature points in the Select screen
scrolling loop. To lock on to either sensor, the user must
scroll the Select key through the loop to the sensed tem-
perature prompt of interest. The display will remain at that
parameter until the Select key is activated to advance the loop.
When the loop is stopped at any other prompt, the display
will alternatively indicate Sensor A and Sensor B sensed
temperature after 60 seconds from the last key closure or
immediately after the Select key is pressed at the end of the
programming sequence.

Error Messages

There are seven error messages that can be displayed in
response to software or hardware problems with the T775.
The error Codes flashing on the display are:
SF—Sensor Failure
If the display shows a flashing SF, this indicates an out-
of-range or defective sensor. Make sure that the sensors are
connected properly. For T775A,C all loads will be de-
energized when this error message is flashing.
For the T775B,D the loads controlled by the out-of-
range sensor will be de-energized. The display will flash SF
to indicate which sensor is defective or in error. In the event
that only one sensor is defective, the remaining sensor and its
load(s) will operate normally. Only the load(s) controlled by
the defective, out-of-range, or unconnected sensor will be
de-energized.
NOTE: Sensor values below -40°F or above 220°F will be
out-of-range.
EF—EEPROM Failure
The values read back from the EEPROM are not the same
as written into the EEPROM. This error cannot be field
63-2489
repaired. Replace the device. The EEPROM is not intended
to be field repaired.
CF—Calibration Failure
A calibration resistor reading was not within the range of
the Analog to Digital converter. This error cannot be field
repaired. Replace the device.
OF—Stray Interrupt Failure
An unused interrupt occurred. This error cannot be field
repaired. Replace the device.
CE—Configuration Error
The device hardware was configured to a nonexistent
device. This error cannot be field repaired. Replace the
device.
OE—ROM Error
The internal Read Only Memory (ROM) of the micro-
processor is defective. This error cannot be field repaired.
Replace the device.
AE—RAM error
The internal Random Access Memory (RAM) of the
microprocessor is defective. This error cannot be field re-
paired. Replace the device.

Setpoint Calibration

To maintain temperature accuracy, sensor wires should
be 18 AWG two-conductor. If the length of the sensor wire
exceeds 400 feet, recalibration will be necessary to maintain
accuracy. The chart that follows shows the corresponding
temperature offset to use for different sensor wire lengths.
This temperature offset should be added to the desired
temperature setpoint for these applications. Refer to pro-
gramming instructions in the Programming section for enter-
ing temperature setpoints.
Sensor Wire Length
0 to 399 ft
400 to 599 ft
600 to 799 ft
800 to 1000 ft
10
Calibration Offset
None required.
1.0 degrees
2.0 degrees
3.0 degrees