I've just had the most bizarre experience with Sunlu. I bought their S2 Plus filament dryer.

It arrived, I threw some in (Green Bambu PLA), it managed to melt/fuse together after 2.5 hours. I had the set value at 50C.

I chalked that up to me being new and figured I just needed to lower the temperature. I moved the temperature to 45C and placed some other PLA I had (Black Bambu PLA) and checked it after 30 minutes. At that point, it had not completely fused, but is "tacking" to itself to the point where it kept jamming as it tried to unspool.

I pulled the filament out and turned the device off so it could cool off. An hour later, I checked it and it was still VERY hot. Further testing confirmed that it's not actually turning off, and I also discovered that no matter what I set the temperature at, it's staying as hot as it can, around 70C.

When I plug up the unit and leave it without turning it on, it stays cool to the touch. If I turn it on and then back off immediately, it will continue to heat up. The on/off seems to only be controlling the fan and the screen, but is not disengaging the heater element.

So, given that, I contacted support. I expressed my concern that it was a fire hazard and offered to send it back to them (instead of Amazon), because you'd think they'd want to inspect it. I know they have plenty of good reviews and I've read a lot of personal accounts praising the unit.

They got back in touch with me and asked me to take video of it contributing to hear up after being turned off. I also demonstrated how it ignored the set value and would keep heating up indefinitely.

I did this, answered some other questions, and then they asked me to try with another spool of filament and record my results. Seemed strange, but I've got an engineering and IT background, so I'm game for some troubleshooting. I asked again for clarification just to make absolutely sure that this is what they wanted me to do, and they confirmed…So I grabbed a fire extinguisher (just in case), and did so. This time, the spool melted. I was shocked. I sent the video, unplugged the unit, opened the window, and vacated my office for the night. Then they asked for me to take a temperature reading of it when it is on, to make sure that the temperature states is accurate… Which seems a bit pointless at this point, but I oblige.

Sunlu support then asked for a copy of my invoice (which was in the original email, but I went ahead and sent it again). Their response is to send it back to Amazon… Which I could have done in the first place. They don't plan on replacing my filament (one of which, THEY ASKED ME TO DESTROY TO PROVE TO THEM THAT THE UNIT WAS FAULTY).

I'm going to ask for the case to be elevated, but is Sunlu always like this? Has anyone else encountered this issue on one of their dryers?

Edit: one thing I forgot to include that was bizarre — after the spool melted, the support agent tried to tell me that the spool is not supposed to go in the dryer.