Prusa Mk3 on a UPS?  

RE: Prusa Mk3 on a UPS?

The MK3 has a 250 watt PSU - and uses about all of it.

I would size a UPS bigger than that. Big question is how long you want it to provide power.

RE: Prusa Mk3 on a UPS?

UPS ratings are continuous, but they need to be sized for a peak load.  600VA is probably about 330W, is fine because the MK3S is 240W peak, and typically is well below that.   The computer and other equipment plugged into it, brought it over it's maximum capability. 

The real question is run-time.  A standard UPS might run for about 6min with a 200W load, so if it's just brief outages it helps, but if it's a 30 min outage, there's no good option.  

RE: Prusa Mk3 on a UPS?

Thanks for the feedback, everyone.  We live in an area where lightning strikes are relatively common, so occasional power surges happen.  I've got a whole-house surge protector, but it only guards against major spikes.  The power will flash off for 2-3 seconds every so often, then back on.  Enough to reboot computers, kill print jobs, etc.  I'm mostly concerned about conditioning the incoming power so I don't fry my $1000 printer, as well as keeping power going during those brief outages.

Maybe I should look into a solar-grid with Tesla home batteries instead...lol

RE: Prusa Mk3 on a UPS?

I use cyber power 1500KVA UPS on my racks, but I do have to remove the power panic wire from the Einsy boards to keep them running through the cross-over to the battery power. 

If I left power panic attached, I would get an "ERROR MINTEMP" on the hotends in the switch, and I'd lose the prints. I have 15 MK3S in a rack, wtih 6 UPS feeding them on a 20A 110VAC dedicated circuit. 

Before I disconnected power panic, if I took a power hit, I'd lose about 3-5 of the 15 prints in progress. 

RE: Prusa Mk3 on a UPS?

Posted by: @derek-k2

I use cyber power 1500KVA UPS on my racks, but I do have to remove the power panic wire from the Einsy boards to keep them running through the cross-over to the battery power. 

If I left power panic attached, I would get an "ERROR MINTEMP" on the hotends in the switch, and I'd lose the prints. I have 15 MK3S in a rack, wtih 6 UPS feeding them on a 20A 110VAC dedicated circuit. 

Before I disconnected power panic, if I took a power hit, I'd lose about 3-5 of the 15 prints in progress. 

Interesting. Just the kind of scenario of which I was thinking (essentially using the UPS to assure that Power Panic “takes” until the mains power comes back on.). Your report makes total sense now. Thanks for that MINTEMP information!

RE: Prusa Mk3 on a UPS?

• I have MMU2S attached to my MK3S+ And there is currently only one printer but might go to 2 later.
• my MMU2S sometimes flashes all LED’s which may indicate a power issue.
• There is some risk of power issues in my area, not just outages but voltage and phase fluctuations. This is not measured but based on observation. there is a lot of housing that run older air conditioners. The infrastructure is 30+ years old.
• Thd Mk3S+ PSU appears to be a switched mode type but it’s being run at the upper limit of its specification therefore some mains issues might be pushed through to the inside circuitry.
• Therefore I am seeking out a UPS to shield the printer from such issues. Looking at getting the type that runs continuously providing complete mains isolation, and having capacity of 1 -2 KVA and 30 mins run time of the battery.

Can anyone comment on my reasoning: have I missed on any of the logic in this decision ?

RE:

Posted by: @bryn51

• I have MMU2S attached to my MK3S+ And there is currently only one printer but might go to 2 later.
• my MMU2S sometimes flashes all LED’s which may indicate a power issue.
• There is some risk of power issues in my area, not just outages but voltage and phase fluctuations. This is not measured but based on observation. there is a lot of housing that run older air conditioners. The infrastructure is 30+ years old.
• Thd Mk3S+ PSU appears to be a switched mode type but it’s being run at the upper limit of its specification therefore some mains issues might be pushed through to the inside circuitry.
• Therefore I am seeking out a UPS to shield the printer from such issues. Looking at getting the type that runs continuously providing complete mains isolation, and having capacity of 1 -2 KVA and 30 mins run time of the battery.

Can anyone comment on my reasoning: have I missed on any of the logic in this decision ?

 

 

Yes, I've also heard that the MMU2S is right on the edge and cannot take a joke when its power drops slightly.  However, modern switched power supplies hold voltage very constant among varying input voltage levels, and I'm quite confident that a sag to, say, 105 volts or so (Stateside, roughly 210 in Europe) would have little effect on power supply output voltage.

I do have a Cyber Power on-sale-at-Best-Buy UPS on the MK3s.

We are in an exurban development, on the very end of a line that runs between 5-6 miles (6-9 kilos) to the substation, splits three ways, and vulnerable to sags and outages which occasionally occur.  We do have a generator (Generac), but a manual start, manual transfer one.

We did have a primary power failure during one long print.  Since the battery in the Generac was low at the time (since replaced) I had to hunt in the garage for the jump box with a flashlight (torch) to get the generator to spin up, and it was close to 20 minutes from lights out to lights on.

The Prusa did not miss a beat and the Cyber Power held power just fine, both during the ~20 minute dark period and the switch-back to commercial power.

IIRC, that Cyber Power unit was in the US $70-80 range.

Now, for the network closet we do have an 'online' Tripp-Lite UPS which runs continuously and does not switch when it loses commercial power, it just keeps running.  This was a used Ebay thing for a few hundred, but an equivalent new unit of that type runs into four figures.  I've replaced the batteries twice, once when I got it (the supplied batteries were well-worn) and that set ran about five years until the front panel started showing a warning that the batteries were marginal, so they were replaced again quite recently.

If you are REALLY concerned about sags and outages, the 'online' type of UPS is definitely the way to go.

However, I have found, both by testing and during an actual failure, that the drop-out-and-switch UPS will run the Prusa without losing anything.

I'm sure that the Cyber Power has a square wave output, but I have not actually scoped it, and the Prusa likes it just as much as pure sine wave commercial power.  I'm also sure that the Tripp-Lite has a stepped quasi-sine output, but again, I have not actually scoped it.

I would be more concerned about switching transient causing a drop-out.

I have one data point of experience, but the MMU2S was out of the circuit and not in operation when it happened.

RE: Prusa Mk3 on a UPS?

For what it’s worth I bought a CyberPower at Sam’s Club and it held up fine when we lost power for about 20 minutes. I forget the model number and I’m too lazy to go downstairs and look, but it was the biggest they had. Granted it was on a FlashForge Adventure 3 at the time, but it was able to finish the print. Haven’t had the power go out yet with my Mini+ (knock on wood).

RE:

I have in mind one of the many varieties of Eaton UPS. It’s made locally in Taiwan (by an Irish company ). If part of its utility is deemed to act as a no break power supply then I need roughly 2-3 hours worth based on outages that have occurred. They use Lithium based batteries and pure sine wave output. it seems the local power company has poor control despite having nuclear, gas, solar and a vast wind turbine farm, things go dark sometimes.

Although I might cave and go for a cheaper one since Eaton have not responded to my enquiry so far.