Whenever I try to print with Bambu Lab Polycarbonate PC, it blows the trip fusion the house.
I’ve tried heating the nozzle and bed up to the correct temperatures manually to try and draw the same current and the printer warms properly - that should be close to the max current draw.
The house electrics are good - checked by electrician.
Everything else works fine though the only other materials I’ve printed with are PLA variants and PETG.
Is this for 240v or 120v?
Is the RCD tripped or the fuse? Even at 120V I can not imagine a fuse tripping, unless you have really high load on that circuit already.
It’s the breaker on that plug circuit. The RCD doesn’t trip. We are on 240v (in the UK / Ireland)
Let us know the breaker capacity (in Amps)
On 240V, the printer draws up to 1000W (roughly 4.2A@240V) during bed warm-up. If you have other loads on the same breaker already drawing power, you might be exceeding the breaker limit. Try disconnecting everything except the printer and see if the breaker still trips
.
If it does still trip, check to see if the breaker is an Ground Fault (GFCI) type, Arc Fault (AFCI) type or combination.
If it is GFCI/AFCI or combination, it’s possible the printer is generating electrical noise the breaker interprets as arcing, which causes it to trip. I have personally witnessed AFCI breakers get tripped by tiny loads, because the breaker “thinks” it senses arcing.
It’s the RCD that’s tripping. It’s a Hagar 63A 2 Pole Type A RCD. The tripping sensitivity is 30ma.
The circuit that the printer is on supplies a few rooms with power to their wall sockets. Problem replicates with everything else unplugged.
Sounds like you have a phantom device drawing a lot of load. I’m not familiar with 240v circuit amp limits, but if you’ve disconnected everything and the printer still trips it, I’d first guess that the circuit is powering something you are not aware of.
If you can’t find the additional amp draw, buy a cheap outlet amp/voltage/watt meter ($20-$30), and see if the printer is drawing way too much. I can’t imagine what could make it draw circuit tripping amps by itself and not display a problem, but I’m not a professional, so its worth $20 to test.
You can do some simple low cost trouble shooting on your own. First, get a Kill-A-watt meter and measure the current draw on your device. Circuit breakers are designed to trip when there is too much current drawn. Read the instructions for setting it for current draw and if your current draw is under your circuit breaker rating(in Amps), then the problem is with either your wiring or you have other appliances on the same circuit. If you’ve unplugged everything else and the breaker is still tripping? Well… call another electrician or fire department fast and get out of the house. 
But seriously, you may have more serious wiring issues that requires investigation by a licensed electrician and that’s no joke.
The Kill-a-Watt meters are cheap enough where you can afford to buy more than one. I’m actually up to four of them because I keep misplacing them. I find them indispensable when performing power supply diagnostics on systems I build. Short of any digital diagnostics, they tell you exactly what’s happening at your outlet. This should be good for 99% of household power diagnostics.
https://www.amazon.co.uk/s?k=killawatt+meter
https://www.amazon.co.uk/dp/B0BDYKRPR6/
Here’s a picture of the current draw from my P1P with both hotend and bed heating up(2.621a). If your printer is pulling more than 3a, you’ve possibly got a bad power supply but that is quite unlikely, not impossible, just unlikely. The Kill-a-watt will lay that question to rest.
One other thing. Circuit breakers themselves do wear out. I had one pesky breaker that kept tripping at random. I eventually just replaced it and broke the old one apart. What I found was that the old breaker for whatever reason had completely oxidized while another identical breaker I took out of the same panel was fine.
I had to do some research as I was not familiar with the term RCD. In the US we call this a Ground Fault Circuit Interrupter (GFCI). Residual-current device - Wikipedia These trip when there is an imbalance in current between two legs of the circuit. It’s not uncommon for these to trip on heavy inductive loads (large motors), but I find it surprising that a 3D printer would cause one of these to trip. Even more surprising is that it is related to a particular filament type, especially if heating the nozzle and bed without printing doesn’t cause the problem. I’m baffled.
The definitive question is “Does the machine trip the breaker on a seperate circuit/different location”. If it doesn’t it’s the original circuit, if it does, it points to the printer.
Bambu have even stated, that they reduced the temp on the hotplate due to too high ground leakage current:
If there is another device or some problems in the wiring, it might cause the RCD to trip.
Mhm, I am not that surprised. Its the filament with one of the highest temps. Plus, while printing, you will have higher leakage current, you will have electrical noise from the motors, etc. So if your installation is already right on the edge, this might just be enough to cause it to trigger.
How old is your electrical installation? If it is too old, the insulation might have already started to break down and thus the leakage currents add up. There is nothing I could really recommend, as it might put you in danger.
Honestly, the best thing with ground leakage and tripping RCD’s is to contact an electrician. The RCD is there to potentially save your life, so I would not tamper with it.
I think Holmes4 likely nailed this problem! In case it’s not clear, I’ll restate:
RCDs in Europe are the same as GFCIs in the US but with a couple of differences. The major difference is in the trip threshold. RCDs in Europe trip if over 30ma leakage current to ground. GFCIs in the US trip on leakage current over 5ma to ground…
The link that Holmes4 posted indicates Bambu experienced some challenges with the heat bed heating element insulation: at 120V the electrical insulation is sufficient, but at 240V there can be enough leakage between the heating element and the grounded heatbed to approach or possibly exceed the regulatory limit of 30ma.
Bambu derated the heatbed from 110 to 100C on 240V applications as a work-around. At lower temperatures, the problem is less likely to exhibit.
My best guess is the heatbed heating element on your printer is beyond spec. It has too much leakage and that is causing the problem. I suggest contacting Bambu support and seeing how they want to proceed.
There is little sense in using a watt meter to measure printer power draw. If the printer was drawing in excess of breaker capacity (63A), you would definitely know it from the smoke, loud pops and bright flashes. This would not be anything subtle
If you have a DVM or milliamp meter, you could measure current flowing on the ground between the printer and the outlet. If you do that, you will probably see current on the ground start at zero when the heatbed is ambient and then begin to rise as the heatbed gets hot.
If you see that current get to 5ma, that would be a concern and I would personally consider that heatbed defective. If it starts to approach 20-25ma, you have definitely found the problem. You would never actually see it reach 30ma, because that would cause the RCD to trip.
One more thing:
My X1C has a power inlet/fuse/switch assembly on the back that is equipped with a 6A 250V fuse. There is no possibility the printer is drawing enough current to trip your 63A breaker while NOT blowing that 6A fuse. That 6A fuse would be the first to open and long before 63A.
Your problem has to be leakage between mains and ground being detected by the RCD. I think you have a defective heat bed.
Thankyou. I think you have it nailed. With the printer being the only device plugged in on the circuit, the RCD trips on printing the PC. The house electrics were checked over by an electrician and all seems good.
I found another post where someone was having a similar issue and after much log sending and messages, Bambu sent them a new heated bed.
