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Brian Wong Shui 07-19-2020 07:18 AM

Hi Franklin

The Numbers looks a little off with Pb looking too small for a furnace. Here is a procedure from watlow that Ive used to manually tune.

Franklin Sankar 07-19-2020 09:47 PM

Thanks Brian. I was using the following which I found in the watlow 93 site
I will try yours tomorrow.

1. Apply power to the Series 93 and enter a set point. Set Operation parame- ters as follows: [``Pb] to [```1], [``rE] / [``It] to [`)00], [``rA] / [``dE] to [`)00], [``Ct] to [``%0], [`CAL] to [```0], [`AUt] to [```0].
2. Proportional Band Adjustment: Gradually increase [``Pb] until the upper display temperature stabilizes to a constant value. The process tem- perature will not be right on set point because the initial reset value is 0.00 repeats per minute. (When [``Pb] is set to 0; [``rE] / [``It] and [``rA] / [``dE] are inoperative, and the Series 93 functions as a simple on-off con- troller.) The [`HSC] parameter determines the switching differential value.
3. Reset/Integral Adjustment: Gradually increase [``rE], or decrease [``It] until the upper display temperature begins to oscillate or "hunt." Then slowly decrease [``rE] or increase [``It] until the upper display sta- bilizes again near the set point.
4. Cycle Time Adjustment: Set [``Ct] as required. Faster cycle times sometimes achieve the best system control. However, if a mechanical contac- tor or solenoid is switching power to the load, a longer cycle time may be de- sirable to minimize wear on the mechanical components. Experiment until the cycle time is consistent with the quality of control you want. [``Ct] will not appear on units with a process output.
5. Rate/Derivative Adjustment: Increase [``rA] / [``dE] to 1.00 minute. Then raise the set point by 11 to 17C, or 20 to 30F. Observe the system's approach to the set point. If the load temperature overshoots the set point, in- crease [``rA] / [``dE] to 2.00 minutes.
Raise the set point by 11 to 17C, or 20 to 30F and watch the approach to the new set point. If you increase [``rA] / [``dE] too much, the approach to the set point is very sluggish. Repeat as necessary until the system rises to the new set point without overshooting or approaching the set point too slowly.

Franklin Sankar 07-20-2020 10:21 AM

I tried auto tune one more time and it worked.
I dropped 200 from the set point then started the auto tune and it worked like magic. I feel the next time I start up the settings will not work at start up temp but will do a work around if that happens.
I will note the parameters used so next time I will be ok.
Thanks for all the help

Franklin Sankar 07-20-2020 10:31 AM

P= 7 I=.1 d=.47
It will be interesting to see what happens next startup.

Brian Wong Shui 07-21-2020 08:42 PM

Thats great.

Next time the furnace is up, check to see how the furnace behaves when you upset it from steady state (i.e opening and closing the door when gathering glass). Look at output percentage. As soon as it detects the temperature is falling, you should see the output jump to 100% right then. It should overshoot the setpoint and then fallback to slightly under and then converge on the setpoint. The output percentage should be fairly steady once it finds the setpoint and not erratically jumping around.

If it takes too long to get back, try reducing the d a little. (You did record the values, right?). Too much d makes the system slow. Ideally you want the system slightly underdamped to critically damped. This will have the fastest response back to the setpoint.

Franklin Sankar 07-22-2020 09:46 AM

Thanks will do. Values recorded above

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