Heated Bed 220VAC USA 2phase hot wires wiring question
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@jens55 That was pretty awesome explanation. I never connected AC and DC like the battery example. I am a software engineer, so all the electronic stuff I been doing has been from online references. Now I need to find out how to solder the fuse inline and make it look nice.
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@falkia what do you mean secondary side of the PSU?
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@jens55 no, you're not being to cautious, that's a very good idea. I rather buy a fuse than trying to fix a PSU.
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@jsinicro -V (negative) on the load side.
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@falkia So you connect the negative on the DC output side to the same ground that the AC ground uses?
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This is the kind of fuse I ment. It's like two fuses that have the same lever.
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@jsinicro said in Heated Bed 220VAC USA 2phase hot wires wiring question:
@falkia So you connect the negative on the DC output side to the same ground that the AC ground uses?
Yes, correct.
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@jsinicro I suggest you add a thermal cut out (TCO) in series with the power to the heater, and mount the TCO on the heater. Don't get a heater with adhesive. Mount the heater using silicone.
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@mrehorstdmd OK, I got the heater bed custom made 700x700mm from Keenovo and includes a 3M self adhesive.
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@jsinicro The manual says you should seal the edges with silicone- I think it prevents the adhesive from drying out/oxydizing/letting go. Without sealing the edges the adhesive is good for about 2 years of heat cycling before it starts to let go. As it lets go, there will be air between the heater and the plate. The heater will scorch in those areas.
When I replaced that heater I got one without the adhesive and used silicone to mount it. It's been about 2 years since then and it appears to be holding fine.
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@mrehorstdmd Wow, OK Thx
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@jsinicro What brand or type of TCO do you suggest
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@jsinicro Cantherm makes a wide variety of them, most cost about $1 (in the US). They have all the safety certifications and actual quality control so they should behave according to specs. I wouldn't buy the no name cheap stuff that sells 5 or 10 for $1. I would also avoid self resetting units. You don't want an unsafe condition to keep cycling power to the heater on and off. Example: https://www.digikey.com/en/products/detail/cantherm/SDF-DF144S/1014764
There are two critical temperatures- the safe operating temperature limit (holding temperature) and the temperature at which the TCO opens. The two are usually 20-30C apart because they self-heat. The self-heating is a function of the amount of current they carry. If you intend to operate the bed at 120C, you will probably need to get a TCO that is rated to open at about 150C or so. Read the spec sheet/ap notes. It isn't rocket science.
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@mrehorstdmd Thanks for the post above. Found it looking searching for just such info, ordered SDF DF184S for my modded Creatbot f430. No-smoke, great!
BTW- my Keenovo was installed on the bottom of a glass bed with their adhesive and silicone 5? years ago. Never had any issue with oxydizing of the glue. Finally though some of the coils died. Waiting for the replacement.
