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Is External PSU mount really necessary?  

Active Member
Is External PSU mount really necessary?

Having built my enclosure and managed to fit in the MMU2 and various other mods I remembered that I didn't bother moving the main PSU to outside the enclosure.  Whilst I appreciate it will get hot in the enclosure (I am in the UK so never that hot) - is there any reason why I shouldn't just leave the main PSU mounted on the side of the printer frame as pre-enclosure? 

Posted : 08/06/2023 3:26 pm
Estimable Member
RE: Is External PSU mount really necessary?

I am interested in this as well, since removing the psu is some work AND the quick-connect option isn’t (yet?) compatible with the MK4.

I don’t know the specs on the MK4 psu, but most PC power supplies are rated to operate in a max 40C ambient environment.  Prusa stated when the enclosure was released that — in a 20-22C room — the temp in the enclosure could be expected to hit 38C when printing ASA.  Extrapolating from that, if the room were a little warmer, like a 35C summer day, the enclosure temp could easily hit 50C or higher.

I suspect that’s why Prusa went with the external mount.  But (again assuming a typical 40C rating) it would probably be fine inside as long as the room temp was <22C, particularly if the bed is at lower temperatures.

Posted : 10/06/2023 3:39 am
Walter Layher
Honorable Member
RE: Is External PSU mount really necessary?

I followed the existing instructions for the MK3 and adapted them accordingly, the configuration of the wires is a bit different. Mounting the MK4 PSU on the outside of the enclosure works with the parts for the MK3 that are either included or have to be printed for the MK3.

Posted : 10/06/2023 8:17 am
Prominent Member
RE: Is External PSU mount really necessary?

The warmer the environment, the hotter the PSU runs. This can reduce its life time and the more the hotter the enclosure gets. If your enclosure gets really hot it might even abruptly fail. Chances are that nothing will happen for a long time if you reach only moderate temperatures but don't be surprised if the PSU doesn't survive as long as you'd expect from a quality product.

I didn't take any chances and mounted my PSU outside of my enclosure. I did take chances with the electronics though as that was too much hassle. So far I have had no issues with MMU2s or Mk3s electronics but I have heard the MMU2s can throw tantrums inside enclosures.  

Mk3s MMU2s, Voron 0.1

Posted : 13/06/2023 10:49 am
Estimable Member
RE: Is External PSU mount really necessary?

I have not found it that difficult to put the PSU outside and to pull it back in if I need to pull the printer out of the enclosure.  It may be that I am used to working in much tighter spaces.  I can even remove stuck filament in the extruder using a mirror and pliers faster than I can move the printer.

Heat is an issue where I live as the ambient temperature can be 35 degrees so extra heat will be an issue for some materials as the enclosure is to limit contamination and drafts in the workshop.

Posted : 13/08/2023 6:53 pm