Honeywell T775A Benutzerhandbuch

63-2489—2

10

There are seven error messages that can display in response 

to T775 software or hardware problems. The error Codes that 

can flash on the display are:

• SF: Sensor Failure

— A flashing SF indicates an out-of-range or defective 

sensor. Make sure that the sensors are connected 

properly. For T775A,C all loads de-energize when this 

error message flashes.

— For the T775B,D the loads controlled by the out-of-

range sensor de-energize. The display flashes 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) operate normally. Only the 

load(s) controlled by the defective, out-of-range, or 

unconnected sensor de-energize. 

NOTE: Sensor values below -40°F or above 220°F are 

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 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 

repaired. Replace the device.

To maintain temperature accuracy, use 18 AWG two-conductor 

sensor wires. If the length of the sensor wire exceeds 400 feet, 

recalibration will be necessary to maintain accuracy. Table 4 

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 programming instructions in the Programming section 

for entering temperature setpoints.

After the controller is installed and wired, apply power. Make 

initial adjustments and desired settings:

1. As shown in Fig. 10, record the sensed temperatures for 

both Sensor A and Sensor B as displayed on the device. 

Use the Select key to advance through the programming 

loop to determine and then write, on the Checkout Table 

(Fig. 10), the loads controlled by each sensor.

2. Write the operating mode (heat or cool) for each stage in 

the Checkout Table (Fig. 10).

3. Write the sensed temperature for each load on the 

Sensed Temp line.

4. Write the differential for each load on the Differential line. 

5. Write the setpoint for each stage (Off temperature). Cal-

culate the “On Temperature” for each stage.

NOTE: “On temperature” is setpoint plus differential for 

cooling, and it is setpoint minus differential for 

heating.

6. Plot the on and off (open/closed) values at which the 

device will energize and de-energize each output load, 

(Refer to the Device Programming Worksheet.) 

7. Verify which loads are energized by using the Checkout 

Table (Fig. 10). As shown in the example, the display 

indicates, in the lower right corner, energized stages. If 

no stages are energized, the words “stage energized” 

will not appear.

NOTE: If the sensed temperature is between the On 

and Off temperatures, the load may either be 

energized or de-energized. Refer to the Control 

Algorithm section (in Operation) for further 

explanation.

8. If an error message flashes, refer to the description of 

these messages. If SF flashes:

a. Check sensor connections.

b. If properly connected and SF continues to flash, 

check the sensor location to make sure it is located 

in an ambient condition that is within the sensor 

capability (-40° to +220°F).

9. If an error message other than SF flashes, the device 

cannot be field repaired. Replace the device.

0 to 399 ft

None required.

400 to 599 ft

1.0 degrees

600 to 799 ft

2.0 degrees

800 to 1000 ft

3.0 degrees