Rewiring and digitizing an old GARE kiln

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  #1  
Old 10-26-11, 02:07 PM
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Rewiring and digitizing an old GARE kiln

Greetings all. Long time DYIer from car to home improvements... This week,however, I have found something that has me stumped. I am rewiring an old GARE kiln. 240v, 30a, single phase. The kiln was functioning prior to its gutting, but only on 2 of the 5 coils, since the others had broken. It originally had 5 switches for the coils wired in parallel. I have removed all switches, and brought them to a single 20a DTST switch. I have added an SSR (40a) and a CXTG-3000 series Intelligent digital controller. The descriptive of my schematic is:
L1 to the L1 on the switch.
L2 to the L2 on the switch.
L1 switch output runs to the coils and to the CXTG connector 2.
L2 switch output runs to the SSR connector 1 and to the CXTG connector 1.
SSR 2 runs to complete the coil circuit.
SSR 3 runs to CXTG connector 7.
SSR 4 runs to CXTG connector 6.
CXTG connectors run to the thermocouple.

Everything is getting power, the controller programs, but the wires are not heating.

I am stumped and looking for help. Anyone have familiarity?
Thanks!

Keith
 
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  #2  
Old 10-26-11, 05:47 PM
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What kind of temperature input sensor are you using? Could you please include a link to the installation manual for the controller? Also a diagram of EXACTLY how you have everything wired would be helpful.

BTW, if this unit draws more than 16 amperes then that 20 ampere switch on the input is too small.
 
  #3  
Old 10-26-11, 07:21 PM
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It is a type K thermocouple, regulated for up to 2600 degree F temps.
The link to the digital controller user manual is here:
http://www.dinicoinc.com/uploads/1.pdf
...however, it is incomplete. There are 5 other settings under the Cod 1 (on page 7) settings, that are not listed in the manual.

I have not yet removed the controller from the equation yet to see if there is an issue with it and the coils heat unregulated (as they did prior to the rewire).

I would not think that the switch would be the issue, given that the old switches that were in the kiln were each 10a switches, and the amps were not split amongst them coming in to the kiln.

Kiln diagram:
 
  #4  
Old 10-27-11, 12:55 AM
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First to the issues of the switch. If the original wiring had a switch for each of the heaters (coils) then each switch carried the current for only one heater. If the full load rating was 30 amperes at 240 volts that equals 7,200 watts and each heater would be 1/5 that amount or 1,440 watts which translates as 6 amperes per heater.

However, you now have all five heaters being switched by a single switch so that single switch needs to have a rating of no less than 30 amperes and a higher rating would be better.


What is the FULL model number of the controller? Are you certain that you have the unit with a time-proportioning relay output and not a voltage/current output?

I agree that the instructions leave a lot to be desired. I've worked with a lot of digital PID controllers over the years and I don't think I have ever seen a manual quite as bad as this one.

Do you have a multimeter for testing purposes?
 
  #5  
Old 10-27-11, 06:43 AM
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Yes, I have a multimeter.

I will get a higher ampere switch, but the 20amp switch I have would not explain no heat at all. Even getting 4 amperes (or even 1 ampere) per coil, there should be some heat from the coils. There is nothing at all.

Unless I am completely missing something.
 
  #6  
Old 10-27-11, 09:40 AM
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The switch rating isn't causing the problem right now, but Furd is pointing it out because it's a point of failure that may burn up once you get the heaters working.
 
  #7  
Old 10-27-11, 10:19 AM
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Oh, and the model is:

CXTG-3000-FK02-M*AN-NN
 
  #8  
Old 10-27-11, 11:43 AM
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Okay, that should be the proper controller for your application. Try disconnecting the leads from the solid state relay input and then measuring the output on terminals 6 and 7 while varying the set point above and below the temperature of the thermocouple. You should get voltage readings that are either on or off although you might get pulses depending on the settings of the PID parameters.

Try also connecting a DC source (a six volt lantern battery or a nine volt radio battery) to the input of the solid state relay. Be careful to mind the polarity. If the heaters work with the battery on the relay then you know the problem is in the controller but if the heaters do NOT work with the battery driving the relay then either your wiring is incorrect, the fuse in the line to the heaters is bad, the heaters are all bad or the relay is bad.

Post back with results.
 
  #9  
Old 10-27-11, 12:14 PM
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I had a thought.... What if the PID is not sending the signal to the SSR to open?

I am going to test connections and such later today or tomorrow. I will post results.

Thank you for assisting thus far.
 
  #10  
Old 10-27-11, 12:35 PM
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What if the PID is not sending the signal to the SSR to open?
That is why I suggested measuring the output of the controller while varying the setpoint above and below the ambient temperature of the thermocouple and also using a separate DC source (battery) to test the relay and heating circuit.

For testing purposes I recommend setting the proportional band to zero (on-off control) and also setting the integral and derivative functions off. Quite honestly, I wouldn't even consider derivative action in that operation and you probably don't need much in the way of integral action either.
 
  #11  
Old 10-28-11, 11:38 AM
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In the process of testing now. I am getting no voltage to 6 and 7 on the PID, but the ATU setting is at 0. I also see that there is an STU setting, but nothing in the manual for it.

When I set the ATU setting to 1, I get a clicking sound from the PID and the AT LED on the front of the PID starts flashing, but nothing else occurs. I am testing the SSR with a 9v battery next.
 
  #12  
Old 10-28-11, 12:16 PM
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Ok - battery test done. SSR gets signal (even has an LED that indicated such) and the coils started heating.

So, issue is with the controller or a setting on the controller.
 
  #13  
Old 10-29-11, 11:35 AM
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I'll need to go back and study the lousy instructions but try this first. If you got no voltage response on the output terminals of the controller (terminals 7 and 7) when varying the setpoint above and below the temperature at the thermocouple then try connecting your meter as an ohmmeter or continuity tester across the same output terminals and repeating the test of varying the setpoint above and below the ambient temperature.

If you get continuity (zero ohms resistance) when the setpoint is above ambient and no continuity (infinite ohms resistance) when the setpoint is below ambient then you have a non-powered relay output from the controller. If this IS what you have next try to wire the battery in series with the controller relay (terminals 6 and 7) and the solid state relay. If this works then you will need to come up with a DC supply for the system.

I'm going out in a bit and won't be able to review the manual until late tonight or perhaps tomorrow. Post back with the results of your testing.
 
  #14  
Old 10-30-11, 11:59 PM
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I was looking at the diagram and it kinda got my attetion as Furd addressed out on testing producre which the soild state relay the input { #3 et #4 } is DC feed not AC feed so what you did test with battery source and work so you will need to verify the digtail meter on DC volts and the red test lead will read postive while black lead is negtive { that is pretty much standard unless you have the test lead on backwards } and read the voltage on that if you get good reading on DC volts then it should work once you know which polorty it goes if you get straght AC volts on the #3 et #4 then you will need a full bridge recfier to run it properly.

And the last thing did you test the heating element by useing the ohmmeter? so that way you know which band of heating element is good and what not you can tell real quick when you read this in ohm scale { make sure there is no power source on this testing }

I will read more with installment instruction little later when I get more free time.

Merci,
Marc
 
  #15  
Old 10-31-11, 12:23 AM
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I'm thinking that this particular controller has dry relay contacts for the output, not time-proportioning control. If I am correct then you will need a separate DC supply to make the whole thing work.

Once Ken returns I will give some details on setting up the controller programming.
 
  #16  
Old 10-31-11, 09:23 AM
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Spoke with the Co. where I purchased the controller, and they stated that it has a built in relay.

I am either not seeing or missing where it indicates how to set this in the instructions.

Should I run a DC connect to terminals 6 and 7 on the controller?
 
  #17  
Old 11-01-11, 12:42 AM
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Yes, I know it has a built-in relay, the question is whether or not it has a powered output to control the solid state relay and I think it does not. I also suspect that it does not have a "time proportioning" action for that output relay.

I want you to set up some control parameters and do a couple of more tests. You do not need the controller to be connected to the solid state relay for this.

Read page four, section 3, Parameter setting mode through page 7 section 5, Setting of meter parameter mode There will be several options not available, several options to ignore and (I suspect) most of it will make little sense. Make the changes I direct and then the testing I will add at the end.

Power up the controller and let it warm up for a few minutes. You need to have the thermocouple connected properly before starting. Press the SET key and hold it in for 3 seconds to put the controller in set-up mode. (NOTE: If you do not press a key for 30 seconds the controller will automatically revert back to operate mode.) After holding the SET button for 3 seconds the upper display (PV= Process Value= temperature of the thermocouple) will change to strange symbols and letters. Use the chart on page 5 to decipher these symbols and letters. Press and release the SET button to advance to the next line of parameters.

Advance to the P and using the up and down arrow keys change the lower display (SV=Set Value (setpoint)=desired temperature of kiln) to 0 (zero) press and release the SET button to the I and again using the up and down arrow keys change the lower display to 0. Do this also with the d parameter. Nothing else should need changing. Either cycle the power or wait 30 seconds for the controller to return to the operate mode.

What these changes have done is set up the controller for an "on/off" mode of control. When the temperature of the thermocouple is above the setpoint (SV) the internal relay will be an open circuit and the heaters will be off. When the temperature of the thermocouple is below the setpoint the internal relay will be closed and the heaters will be on. To verify this action you need to connect your multimeter across the output terminals 6 and 7. Use the DC Volts setting on the multimeter and power up the controller. The upper display should be showing the temperature of the thermocouple at this point.

Read page 4 section 2, SV setting mode and momentarily press and release the SET button. Use the left arrow key (<) to move the decimal point to allow 2 digits to the left of the decimal and then the up and down arrows to set a temperature setting higher than the PV reading. Press and release the SET button to return to normal operation. At this point the OUTPUT light on the controller should be lit. Check the voltmeter connected to the output for the presence of a voltage somewhere near 12 volts DC. If the OUTPUT lamp is lit but no voltage is measured proceed with the next step.

Press and release the SET button and use the up and down arrow keys to change the setpoint to a temperature setting lower than the PV reading. Press and release the SET button to return to operate mode. At this point the OUTPUT light should be off and there should be no voltage reading on the meter.

Post back with the results.
 
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