Carwiz, got a minute?

[CarWiz]

Yikes! That's a bummer. Can't tell a lot from the pic but it looks like the side is out of the contactor. Are you sure all the connections were tight? A loose connection on the relay or mains will burn a contactor in a hurry. Rating on the contactor high enough? Can you see the mains contacts? Are they burned or did the unit just over heat?

[JTW37]

Yea, pic was really sucky. I'm going to remove contactor today and just ordered a new one this morning. I'll have a better look at it when I get it out. Not sure how it got that way. But I thought I had all wires tight (pretty funny about that stuff) but I know the oven got over 550 as the outside of it was hot enough that you couldn't lay your hand on it. I'll scan my diagram and attach it here, but everything seems to work, just not right. The wire that burned came from the PID.

[CarWiz]

It's not uncommon for Auto Mode to over-shoot on the first cycle. Once you exit Auto or turn off the power, everything it learned is gone. That's why I don't like using it. To help get around the first over-heat, you can lower the target or raise the overshoot parameter (Souf - 0036).

Once you get your contactor replaced, I'd set all the parameters back to default and run a straight SV=250 run and see what you get. Burning the relay coil wire is an exception so something was amiss with the old contactor. It may be worth while to put a 1A in-line fuse on that line.

[JTW37]

Originally Posted by CarWiz

It's not uncommon for Auto Mode to over-shoot on the first cycle. Once you exit Auto or turn off the power, everything it learned is gone. That's why I don't like using it. To help get around the first over-heat, you can lower the target or raise the overshoot parameter (Souf - 0036).

Once you get your contactor replaced, I'd set all the parameters back to default and run a straight SV=250 run and see what you get. Burning the relay coil wire is an exception so something was amiss with the old contactor. It may be worth while to put a 1A in-line fuse on that line.

Amazing, I thought the whole idea of the auto train mode was to do just that and then keep what it learned. Guess it's kind of like going to school, you don't keep everything you learn stored away. I have a fuse in that line on my other oven, so I suppose I better do that as well to this one.

[crowntech]

Sounds like I need to go ahead and install one and then try the auto tune and see what happens.........Got other projects going on but once it's in, I'll post results.

Thanks!

[JTW37]

New contactors arrived today. Will attempt to put them in and give em a whirl this weekend. Will see how it goes (fingers crossed)

[ed_denu]

Originally Posted by JTW37

Amazing, I thought the whole idea of the auto train mode was to do just that and then keep what it learned. Guess it's kind of like going to school, you don't keep everything you learn stored away. I have a fuse in that line on my other oven, so I suppose I better do that as well to this one.

I'm kind of late to this discussion but I think there are a few misconceptions stated here.

PID's are somewhat simple devices when used solely as heater element controls. Their only ability to control temperature is to switch the elements totally on or off via an SSR or contactor, there is no partial on/off. The 5 or 6 PID parameters are set to values that attempt to predict how quickly an oven environment will react to the elements being either on or off and to minimize as much as possible this on/off switching. This can vary from oven to oven and it is common for ovens to continue to increase in temperature for a period of time after the elements are switched off.

While I do not claim to be knowledgeable on every PID manufactured, most of the simple PID's like the TC-408 I use do not continue to learn and adjust settings over time. This is only accomplished by entering 'auto tuning' and letting the function run thru completion. When using 'auto tuning' the PID parameters will be adjusted based on the rise and fall of temperatures as observed from feedback of the thermocoupler. Once these values are changed they remain in effect until another auto tuning cycle is executed or they are manually changed. Power on/off of the PID does not impact these settings. If it did, then all setting would revert back to a default status(including Inty, Outy, SV, etc.) whenever the oven were to be powered off. If anyone doubts this then do a simple test on your PID.

[PhredAre]

Curious, do you have a circulating fan in this oven to help balance the oven temp accross the entire oven ? Fred

[JTW37]

Originally Posted by PhredAre

Curious, do you have a circulating fan in this oven to help balance the oven temp accross the entire oven ? Fred

Not sure who that question is directed at, Fred, but I shut mine off for the time being, as I believe it ihas caused some dust/debris in the finish. I have it mounted on the outside and I think it is pulling dust in from the side of the motor. Not sure, have to investigate this further.

Ed,
My thinking (as observed with my other oven) is that auto tune is just what you stated. If you read the prior posts, I was having extreme temps in the oven, which did not correspond with the PID. To the point that the heat cracked my glass and was hot to the touch (real hot).

After making some changes and several attempts to get the auto tune to do what it's supposed to, it finally burned up my contactor. One question that I have rolling around in my gray matter is, isn't there supposed to be ajumper wire on the PID from one terminal to another, in order for it to function with a contactor and meat the dialed in temps? I haven't had time to get back at the oven the past week-end, but plan to in the next day or two, hopefully today. My thermocouple is a "K" type and the PID TET-612 of which I posted a pic of the connectors.
JT

[ed_denu]

Originally Posted by JTW37

One question that I have rolling around in my gray matter is, isn't there supposed to be ajumper wire on the PID from one terminal to another, in order for it to function with a contactor and meat the dialed in temps? I haven't had time to get back at the oven the past week-end, but plan to in the next day or two, hopefully today. My thermocouple is a "K" type and the PID TET-612 of which I posted a pic of the connectors.
JT

Unfortunately the directions that come with all these lower priced PID's are very lacking and sometimes I feel contradictory.

To run 'auto tuning' on the TET-612 the instructions state "d) Power up the controller. When it reaches temp hold (>) to activate auto-tuning." It doesn't specifically state what 'When it reaches temp' means. I think I recall someone said this means SV? I find this somewhat illogical as the PID is attempting to learn the heat up characteristics of the oven, so why would you have the oven to SV before starting 'auto tuning'?

The instructions for the PID I use (TC-408) which looks to be identical has somewhat different instructions. It doesn't state that the oven needs to be 'at-temp' before starting 'auto-tuning'. Actually it defines the configuration parameter 'Atdu' as 'auto offset' and states the following:
"Note 2．The auto-tune offset will shift the SV value down by the Atdu value during the auto tune process. That will preventing the system from damaging from over temperature during the auto-tune."

The TET-612 manual doesn't specifically state what function 'Atdu' performs and defines it as 'Auto duration'. The permissible values however are the same as the TC-408 (0-200).

I would suggest that if you are running 'auto tuning' with a SV of 400 degrees that you set 'Atdu' to 100 and first run 'auto tuning' with the oven at room temperature. This would lower the SV to 300 degrees and allow the PID to run over the SV to learn the oven characteristics without over heating and causing damage. I can't imagine that you would risk any damage if you used these settings. This is exactly how I run mine, although I am using an SSR.

The attached file shows the auto tuning process as defined in the TC-408 manual. The top line is the SV and the wavy line is the PV.

Of the PID instructions I've looked at I do not recall any requiring jumpers between any of the pid terminals for contactor use. Ed