I came into the hot shop and found the little catering oven plugged in and super hot. I had already unplugged it when I realized how hot it was. Then when I tried to close the door, the latch wouldn’t work.
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Can’t tell from the pic, is the latch just misaligned with the catch? Linda looks like the door is sagging.
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Probably yes, but I couldn’t pop it back into alignment. It was so hot that I’ll admit I didn’t try super hard to investigate adjusting the door.
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Do you think it was just super hot because it had been left on for so long? You don’t think the contactor stuck again, do you?
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Dunno, sorry. That was the first and only time I was in the hot shop yesterday.
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I adjusted the upper hinge a little so it latches more easily
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The oven switch is faulty that’s twice in 10 days its been left on! The oven needs unplugged when done using it!
Till someone fixes it!
Maximum of 400 degrees is needed for powder coating.
The digital readout shows over 550 degrees its twice that inside where the coils are this is Totally unsafe to go off and leave UN monitored!
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I’ll take a look at it Sunday before or during the Electronics Meetup. I’ll post something afterward regarding what I discovered.
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By switch, do you mean the solid state relay?
I finally looked at the small oven, and yes, it was stuck on. The Solid State Relay (SSR) used as a heater on-off switch was shorted. All you had to do was plug it in, and even if the front panel switch was off, the heater would come on to 100% power. This is due to the “too simple” design of the control system, which does not indicate what is happening, or offer a way to do something about it.
I have ordered a new SSR to get us going again, and also some indicator lamps so users can understand what is going on. I will also start designing an improved control system for that oven, but that will take longer. To be continued.
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I’ve wondered about adding a thermal runaway circuit similar to what 3d printers use. Over the past couple years we’ve replaced the SSR a few times. It seems like adding some space between the control box and the oven itself helped, but maybe there’s a better system.
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Given the track record using solid state relays, would it be worth considering a conventional relay plus contactor type of setup?
Is there a MOV across the SSR contacts to absorb spikes?
Is the SSR in need of a cooler ambient temperature?
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I replaced the SSR last week and removed the out-of-order sign, so the oven is at least minimally repaired and back in operation. But then I got busy with other things and forgot to post the repaired status here until now. I’m holding off for a little while on the new indicator lamps (and the questions asked by mikeb) until I look into what it would take to upgrade the control system. To be continued.
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