Re-tuning UDC3300 controller using “Accutune”
Due to wide variations in heating systems and heater capacities, Accutune works fine on some heating systems, but not well on others. Accordingly, try Accutune before re-tuning the controller manually. If it does not work as well as expected, try re-tuning it manually. Follow these steps to use Accutune:

1. Press the SET UP button repeatedly until the lower display shows ACCUTUNE.
2. Press the FUNCTION button to show FUZZY in lower display. Make sure upper display shows DISABL.
3. Press FUNCTION button until ACCUTUNE shows in lower display. Use arrow key so that TUNE shows in upper display.
4. Press LOWER DISPLAY button to return to main display. Make sure the letter A (auto) shows in the display.
5. Press LOWER DISPLAY button and up arrow button simultaneously. The letter T should appear in the upper display. This indicates that Accutune is underway. It could take from a few minutes to several hours. When it is complete the T will disappear and new values should appear for PROP BD, RATE MIN and RSET RPM. (You can abandon this tuning process by pressing the MANUAL/AUTO button.) If ACCUTUNE settings do not provide suitable operation, press the SET UP button until TUNING appears. Then proceed with manual re-tuning.

Re-tuning UDC3300 controller manually
To re-tune the controller manually, reset the values for the three tuning functions shown in Figure 4. This figure presently shows their initial preset values. These values are the same as shown on the laminated sheets of supplementary information furnished with your heater and duplicated in Figure 3. You will need to change these values.

Figure 4. Three key burner functions
Group Prompt	Function Prompt	Value or Selection
TUNING	PROP BD	10.0
	RATE MIN	1.00
	RSET RPM	5.00

Resetting the values of the three functions is a matter of trial and error. It may be possible to improve control by increasing the values of all three. However, the value of only one function should be reset at a time.

Start by increasing PROP BD to 15.0. Operate the heater at its new setting to see its effect before making any other changes.

If you think further improvement is needed, reset RATE MIN to 2.00. Again, operate the heater at its new setting to see its effect before making any other changes.

If you think further improvement is needed, reset RSET RPM to 8.0. Again, operate the heater at its new setting to see its effect before making any other changes.

If you think further improvement is needed after resetting all three, repeat the sequence of changing the values of each function, one at a time. Here are some values to try:

• For PROP BD try values from 2.0 to 15.0.
• For RATE MIN try values from 0.08 to 2.00 (0.08 or less disables this function)
• For RSET RPM try values from 3.00 to 8.00 (Setting it to 1.00 is too low)

You don’t have to know what these functions do and how they work to achieve satisfactory operation. However, some understanding of them should be helpful, so please read on for an explanation.

Understanding tune functions of the UDC3300 Controller
Understanding the three tuning functions mentioned above is helpful when re-tuning the controller. These three functions are widely known as PID or Proportional-Integral-Derivative.

When combined, the proportional, integral, and derivative actions provide quick response to error, close adherence to set point, and control stability. A brief overview of these three functions is shown in Figure 5.

Figure 5. Meaning of three key burner functions
PROMPT ON CONTROLLER	MEANING
PROP BD	A band of temperatures in which a change in the controller’s output is proportional to a change in temperature. The preset value for this band is a percentage of the process variable (PV) range. (PV range is the temperature range for the thermocouple used in the thermal fluid circuit.)
RATE MIN	A correction to the controller’s proportional output based on the difference in thermal fluid temperature and its set point and the rate it is changing. This correction is obtained using a mathematical derivative and uses the preset value as a factor in the equation.
RSET RPM	A correction to the controller’s output based on the difference in thermal fluid temperature and the set point and how long the difference has existed (integral time). The preset value for RSET RPM governs how many times or resets per minute the controller makes a correction.