Chamber Heater Safety Setup - Heater Fan Fail in On Position
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I have an actively heated chamber controlled with a solid state relay running the heater, a thermistor reading temperature of the heater, and a fan to blow across the heater.
I would like to setup my fan such that if anything in this chain were to fail, things can shut down as safely as possible, but i dont know what options i could use. can the fan fail in the ALWAYS ON config? Currently i have it thermostatically controlled so once a temperature of 35C is reached, the fan kicks on. But is there a way to add an extra layer of safety to this setup? maybe if the fan ever fails, Duet can stop the heater. Or perhaps if the thermistor ever does fail, or a runaway heater, is there something i can add in the config.g file to kill the heater output?
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@RogerPodacter
Heater and thermistor faults during a print are handled by the firmware.
To know is a fan "fails" you'd need one with a tachometer output.
You could then monitor this in daemon.g and take whatever action you deem fit.
I use this system for my water pump. -
@RogerPodacter Add a TCO positioned above the heater- if the fan fails and the heater is on, the TCO will cut heater power before things get out of hand.
I have a fan wired in parallel with the heater in my printer. When the heater is on the fan is on. The fan helps keep the heater temperature down. I use a 220V fan powered by 117VAC- it turns slowly and quietly, and doesn't stir the air so much that it causes prints to warp or split. I suspect operating the fan at 1/2 its rated voltage will probably ensure very long life.
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@OwenD thanks. this gives me some ideas. yes i use a 4 wire fan with PWM and tach abilities, so i will put something in daemon.g.
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@mrehorstdmd thanks, i do have a 160C temp control protector if the heater we ever to runaway, and this is screwed right onto the heater metal fins. perhaps that is sufficient and i am overthinking things. I also have spare thermal fuses 180C i will integrate one of these as well.
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@RogerPodacter Don't use a self resetting TCO. The last thing you want is to have an out of control heat situation cycling over and over.
