Wiring thermal cutoff on mains hot bed: splice in at SSR or bed?
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The new build plate and mains bed heater I ordered comes with a resettable 150*C thermal cutoff. I also plan on getting some single use thermal fuses and wiring in series.
Which is better practice and why:
- Splicing the thermal cutoff/fuse to the SSR input
- Splicing the thermal cutoff/fuse to the bed heater hot wire
I'm thinking splicing to the SSR input has the advantage of no mains power going to the bed if a thermal runaway happens also splicing onto the SSR input seems less problematic and easier to modify than using the bed heater +
I plan on using one of the IOs on my 6HC to control the SSR.
I may be missing something here so let me know if I am! Thanks!
Stock photo below for reference
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In practice it doesn't much matter as long as the flow of electricity is interrupted, so use whichever wiring arrangement is most functional for your setup.
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@wwak84 connect the TCO in the mains bed circuit in case the SSR fails short circuit.
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I'd put it in the heater power lead. SSRs tend to fail "on", so if you interrupt drive to the SSR, the TCO won't help if the SSR itself has failed. Mount the TCO on the heater using high temp silicone so that if the adhesive fails and the heater falls away from the bed plate, the TCO will do its job and kill heater power.
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@mrehorstdmd @dc42 good points, to the heater leads it is
