I use this product to control two 120 watt cartridge heaters. I've tried using autotuning but the results aren't very good. Instead, I continued with the manual process of setting the options. A search or two on the internet will find a lot of information about it. The reason I deducted a star is that while the relay works, it is not very well designed. The bottom plate of the relay (which should be in contact with the heatsink) is plastic as far as I can tell. It cuts too easily and the mounting holes are at an angle that would resemble an injection mold. The problem with this is that plastic doesn't transfer heat nearly as well as aluminum. I would have serious doubts about successfully passing 40 amps through it. In my case it's only 2 amps so it does the job. However, I didn't give it a lower rating because of the price. If you went to a professional online electronic parts retailer and bought a 40A solid state relay, the minimum cost for one of these parts would be around $50. You get what you pay for I guess.
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