# Older conveyor dryer giving inconsistent results



## numberonenog (Dec 22, 2016)

Hey all,

I have a used Chaparral 3612 conveyor dryer that is still giving me grief, and I could really use some wisdom/advice.

Admittedly, the dryer is at least 15 years old, and we bought is second- or third-hand, so I don't know its complete medical history so to speak. Our problems began when we noticed that the dryer temperature would keep rising after the relay shut the IR panels off, and the relay wouldn't kick in until the chamber temperature was way below the target temp. This caused a 100°F swing in measured temperature, resulting in either under-cured ink or scorched garments.

My printer adjusted a few things on the PID and narrowed the temperature swing, but only by 20°F or so. Then the relay started burning up. Over the course of two months we replaced the PID and thermocouple (issued by Workhorse, buyer of Chaparral), the relay, and even had a technician come in to replace some of the charred wiring that he claimed was the cause of the relay burning out (it was literally smoking).

Now, our problem is that the thermocouple is reading the temperature too high, thus shutting off the relay way before we reach optimum temperature. For instance, my IR temp gun reads the surface of the panel at 450°F and the thermocouple probe that I'm holding in my hand and hovering directly below the panel is reading more than 1000°F. Curiously enough, when I swap out the new thermocouple for the old one, they both behave in exactly the same matter, which makes me think that the issue is not the thermocouple.

(I should note here that the thermocouple housing inside the panel is either not intact or degraded, because when removed from the housing, the thermocouple is coated in insulation—not a great scene, I know).

Though I am mechanically inclined, electricity is a dark art as far as I'm concerned. I wish I knew more and could troubleshoot this with more confidence. Naturally, it would make sense to find a "sweet spot" in the conveyor chamber where the thermocouple doesn't overheat to the point that the PID reads "error" but still gives a reading that will make our dryer run at a consistent temperature. I may end up doing just that, but such a solution sounds like a band-aid, and I'd really like to know what the root of the problem is.

I've also been on the phone with Workhorse more times than I wish to share, and we've reprogrammed the PID twice to no avail. They're out of ideas as to what is going on.

Any advice at all would be much appreciated and thanks in advance!

James

*One more note: The original dryer shipped with a mercury relay. The one we have in it now is a solid state relay that three (yes, 3) electricians have all said should work just fine.


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## coolpapafunk (May 26, 2017)

Did you ever find the solution? We are having a similar issue. Shirt temps will remain consistent for about an hour, then will shoot up be about 100 degrees. I'm about to take it behind the barn and shoot it!


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