I have two 1500's, one about ten years old, one very new. They're a bit different and needed slightly different settings to work optimally. As mentioned above, stuff sometimes messes with them. My old one is basically bulletproof and just didn't care very much about breezes or anything else. Not the case with the newer one. I leave them on now all the time, have them plugged into a clean power setup, and turn off the AC and ceiling fan when I run them.
That said, even with all of the above, any of the Chargemasters are an absolute game changer, especially during load development. I probably could have gotten a LITE as I don't really use any of the features in the 1500.
You *might* have to mess with the factory speed settings but there are numerous Youtube tutorials. I think it varies slightly from machine to machine.
