Watlow® Start-Up Guide: Temperature Control Panels
A temperature control panel is essential for maximizing the performance and longevity of a thermal system, and proper installation is required to ensure safety, reliability and accuracy. If properly wired and installed, the control panel will help monitor and manage the heat output to maintain the top efficiency of your system.
Check the Power Lines
Begin the control panel set up by wiring the line side, or the side where the incoming power is connected. Then wire the load side or the side where the downstream loads are connected, back to the heater. As the wires are attached, tighten the torque on the power lines.
A common issue found in control panels that fail upon start-up is that the torque can quickly loosen up. It is essential to check the power lines to ensure the power cables are all at the correct torque. Verify the torque requirement in the installation and maintenance manual.
Check for Shorts
Once the power lines have been attached, perform a phase-to-phase check of the resistance followed by a phase-to-ground check. The goal during these checks is to look for shorts in the line and balance across the load. As part of the phase-to-phase check of the resistance, the hygroscopic ability of the magnesium oxide (MGO)—or the MGO’s ability to react to the moisture in the air—is tested.
If the power cables are tightened to the correct torque, and it has been determined there are no shorts, then the control panel is ready to be energized.
Tune-up the Control Panel
Proper tuning is necessary for the controller to reach peak performance and operate each Watlow® heating unit appropriately. Tuning sets the proportional, band, integral and derivative (PID) that allow the controller to ensure system reliability and longevity.
Controllers can be tuned using one of three methods:
If auto-tune is available on the Watlow control panel, the feature will automatically test and set the effective settings for PID control.
When auto-tuning is initiated, the controller alters the set point to 90% of desired to allow the process to cross this value four times. Once complete, the controller controls at the normal set point, using the new PID parameters. This process is the best way to tune the control panel.
Adaptive Tune (TRU-TUNE+®)
If the heater application requires frequent set point changes over a more extensive processing or temperature range, the adaptive tune feature should be used to tune the PID. Consider this method also if there will be increased material flow or variations in flow demand. If this is the case, adaptive tune, available with TRU-TUNE+®, is the best way to tune the controller.
TRU-TUNE+ works by employing a set of proprietary expert tuning rules to calculate and adjust the PID parameters without requiring more user adjustments.
Manual tune is directed when applications cannot reach PID standards using automatic methods. Manual tuning provides more control for the user because each parameter is set individually. There are several methods to provide a quick and effective result for manual tuning. These processes are best performed by resources with intimate knowledge and experience with PID tuning.
When users have issues with starting or restarting a control panel on site, one of a few checks can be performed to troubleshoot the startup.
Check the Wiring
Occasionally, the wires are installed backward and land on the wrong terminal blocks. If a control panel does not start immediately upon installation, check the drawings in the installation guide to make sure that the wiring has been properly installed.
Proper tuning will ensure that the system is brought slowly into operational status. By heating the system too quickly, the heater can be damaged.
By ensuring that the control panel is tuned correctly, the system will be able to appropriately control the heater and not allow the temperature to rise at a rate that the process cannot handle. Keeping the process under a tight restriction of control is critical for the useful operation of both the controller and the heater.
Cold flow is a phenomenon prevalent with stranded cables. During operation, current flow causes terminals to heat up, allowing the strands to move or “flow.” When the power is turned off, terminals cool down and settle in a different orientation. This directly affects the torque on the terminal. Unless re-torqued, the terminal will eventually burn out.
This drastic change interferes with the torque pressure, frequently causing it to loosen below the Watlow standard. The temperature change can also cause the cable to move, which becomes a maintenance issue that would need monitoring when the temperature is volatile.
Adhere to preventative maintenance cycles to avoid cold flow effects or the wear and tear of daily use of the heating unit.
Consult your installation and maintenance manual for a schedule of regular cycles. These include checking the torque on the wires, searching for wear and tear that could lead to long-term damage (such as worn wires) and verifying that external elements (the environment surrounding the unit) have not also caused additional damage. A recommended cycle of maintenance includes checking the torque once a week for the first four weeks after installation, then once a month for six months, followed by regular checks on a six-month rotation.