Max wattage for extuder heater



  • What is the max crrent recomended for extruder heaters on a duet 2wifi board



  • Hi,

    From the documentation:

    Duet 2 (WiFi and Ethernet)

    A 2-pin 3.5mm terminal block is provided for connecting each of the two supported hot end heaters.

    The design is rated to 5A per extruder heater connection

    Frederick



  • Found it ... 5A.



  • Thanks. πŸ™‚



  • So here is my concern
    At 12v and @ a 60w. Heater that converts to 5amps.
    Since 5amps is max or 100% for the heater output, It makes me wonder if a ssr is needed considering continuous load.. by elecrical standards we can only load up to 80% of full load current if used for more than two hours.
    In my book this would be considered a continuous load. Do i need to take precautions to protect the board by using a ssr. Second what can i do to prevent the possable runaway scenario if the ssr. Were to short closed i plan on using a thermaly controlled over temp sensor in line for the bed heat but this is upractical for the hotend i believe the firmware protects against a runnaway extruder heater.. but will that still work when a ssr. Shorts closed .. with out some sort of secondary input the duet would be able to fault.. but not stop the runnaway heater. any input and ideas would be appreciated...πŸ€”



  • Also is that 5a. Total or per heater



  • It states per heater im assumug the circuit has avalable 10a. but devided up 5a. Per heater
    So my con clution is ther is enough current available provided im only running one heater
    But im absolutly at the terminal limits on the duet board. Do The same rules apply for the solid state stuff on the board as they do for an electrician as far as loading components to 80% or 100% ????


  • administrators

    60W is a high powered heater. A machine using a heater of that power would normally use 24V power.

    The heater mosfets can easily handle more than 5A. It's the connections that are the limiting factor. If you use the proper ferrules to terminate the heater wires, 5A should not be a problem.



  • @ziggymanpopo said in Max wattage for extuder heater:

    So here is my concern
    At 12v and @ a 60w. Heater that converts to 5amps.
    Since 5amps is max or 100% for the heater output, It makes me wonder if a ssr is needed considering continuous load.. by elecrical standards we can only load up to 80% of full load current if used for more than two hours.
    In my book this would be considered a continuous load. Do i need to take precautions to protect the board by using a ssr. Second what can i do to prevent the possable runaway scenario if the ssr. Were to short closed i plan on using a thermaly controlled over temp sensor in line for the bed heat but this is upractical for the hotend i believe the firmware protects against a runnaway extruder heater.. but will that still work when a ssr. Shorts closed .. with out some sort of secondary input the duet would be able to fault.. but not stop the runnaway heater. any input and ideas would be appreciated...πŸ€”

    A 60W heater, on most normal printheads, if run at 100% duty cycle for 2 hours, hopefully will have triggered an over-temp shutting off the board, and if you are not using a well designed all metal hotend... might well have melted something important.

    An extruder heater is not a 100% duty cycle, continuous load. It is PWM controlled and will run well below 100% duty cycle for the majority of the time.

    There are ways to design fail-safe setups that would cut off the power to the board in the event of the type of failure you describe...
    That said, based on my experience the way to deal with this is to size your heater correctly and have an extruder that will not melt.
    A failure of the board is rare enough that its not worth the trouble to build in a fail-safe if you have an extruder that can withstand the temps of a thermal runaway.
    PTFE has no place in a hotend πŸ˜‰



  • Awsome answer!! thank you
    I am upgrading to a 1000w. line voltage heat pad
    With all this in mind ive decided on a 50 w heater and switching to a mosquito mega hotend w/copper heater block so i can hit temps up to 400c+
    This way i can hopfully extrude all different types of filiment.. including things like peek,ultem and nylons ect. Is 50w sufficient in wattages for400c+???
    What recomendations can you make for an inline thermal sw??? I was thinking of using a bi-therma
    (Adjustable) Similar to what they use inside an electric furnace.... one with a fiscal reset
    Im surching for the right device i can put between the 120v mains feeding my bed and one of the lines
    On the heater pad
    Odds that the ssr. would short closed is so verry small are that its probably not an issue ...just the same, if i leave my house I'd like to leave with the utmost confidence the house will still be there upon my return.....any advice to this topic ??? ,Thanks 😁



  • Im starting to wonder if i "NEED" to convert to 24v to be able to print the higher temps ...


  • Moderator

    It would be strongly recommended.



  • If i removed the heated bed load completely
    It would be a great reduction in current demand
    Wouldnt that make up for the loss in avalable current since im at 12v. Therefore be able to run much higher temps.. .is a50w heater cartrage large engough to reach 400c or so. Right ??


  • Moderator

    Well it's less about the total wattage of the power supply and more about the current carrying capacity of the wiring for the heater.

    50 watts at 12v is 4.2 amps
    50 watts at 24v is 2.1 amps

    If this doesn't make sense to you, read up on watts/amps/volts/resistance/current until it starts to make sense why you'd want 24v over 12v.



  • No makes perfect sense. I was an electrical contractor for 30 years so that helps. i have alread chainget ot the wire to 14ga. I believe the weakest part of the chain for me would be the terminal block
    Let me ask you this way. given the hardware is sufficient and im running 12v no bed load.. a 50watt cartrage am i limiting what i can do ?? If i chainge to 24 v. (Have p.s.) would i need to need to change any thing other than the two fans and the heater to 24v
    Last. Does the voltage change affect the pid. It would make sense to me that it does


  • Moderator

    Alright, I just wanted to make sure you're aware of underlying details.

    14ga should be fine, though is stiffer, which can be a bit of a problem long term for a moving part like extruder/bed.

    If you did switch to 24v you would need to provide the 12v fans with 12v from a buck converter (usually easier) or find 24v replacement fans (sometimes harder).

    24v would have faster heating. And yes you'd need to redo the PID tuning.



  • Its a bit of deal to chainge everything over
    I wholy agree 24v is way better


  • Moderator

    Forgot to mention that stepper motors will perform better at 24v as well.



  • I guess the question would be am i exceeding the 12v desinged capabilitys with what im doing i feel like I'm still missing little bits here and there so apologies ......
    from what im seeimg myself this will work but im just working everyting a little harder than one needs to. If you say, i wouldnt or shouldn't,,,ill change everything to 24v. Not that big of a deal... the 14ga.wires are in a cable snake and tied off absolutely no movement in fact all three axesesπŸ™‚



  • Steppers hu?? Realy did not know that. πŸ€”


  • Moderator

    A 50w hot end heater isn't such a big deal compared to trying to run a high wattage bed heater on 12v. So 12v isn't as much of a detriment in this case.

    Do you already have the 50w 12v heater cartridge?
    Do you already have a 24v PSU?

    24v has advantages but it would be more work comverting.



  • Why dont i finish my extruder upgrade and I'll collect everything necessary and I also need to do a firmware upgrade before i start im still on ver. 2.1😬😬😳
    Start dialing in everything in ...so maybe rigjt after the firmware upgradeπŸ˜³πŸ™„ lol.
    I know it printed great before the extruder change.
    So logically i would think this a logical approach???
    Thaknks Phaedrux


  • administrators

    If you are using an AC mains heated bed controlled by a SSR, you could use the bed heater output to connect the extruder heater, and a different output to connect the bed SSR.


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