Which Amp Fuse for UK 3 Pin Plug  

RE: Which Amp Fuse for UK 3 Pin Plug

Posted by: @nathan-b20

A failed search has me thinking this is probably a rare query, but I'm hoping it's a fairly easy question to answer. 

I was offered a pre-owned MK3 that needs a little repair. It originated from France and comes with a 2 Pin EU plug that I need to replace with a 3 Pin UK Plug. I've got a spare 3 Pin UK Kettle Lead that fits the printer and is suitable for up to 350w, but I'm not sure what Amp Fuse to install in the wall plug (5A/10A/13A etc).

Lock down means I'm unable to check my MK3S which is currently at my work place so I'd be really grateful if someone knows the correct UK Amp Fuse to use please? 

if you don't want to lose the power panic function, you can use this board including the power plug:

https://www.amazon.co.uk/Prusa-Power-Voltage-Switch-socket/dp/B07PSQ7M8Z

RE: Which Amp Fuse for UK 3 Pin Plug

Mine came with a 5A fuse in the UK plug (its a MK3 but I cant see the s being different)

RE: Which Amp Fuse for UK 3 Pin Plug

@neophyl

Thanks very much. I just used a power conversion calculator which suggested a fairly low amp rating (250w/230v=approx 1.1A) that I wasn't sure I could believe, so that's really helpful to know. I'm a little surprised the amp draw isn't higher considering the use of a heated bed and heat block. It's quite energy efficient. 😎 

RE: Which Amp Fuse for UK 3 Pin Plug

@nathan-b20

I think 5 amps for the 230VAC power supply is sufficient. The printer components on the einsy are specially secured with 5 and 15 amps at 24VDC.

RE: Which Amp Fuse for UK 3 Pin Plug

@karl-herbert

That's great. It appears 5A or even 3A would be sufficient in the UK. I'll stick with the 5A prusa chooses to fit. Thanks very much everyone.

RE: Which Amp Fuse for UK 3 Pin Plug

The fuse in the plug is to protect the cable from the plug to the appliance, so it really depends on the size of the cable, it is not actually to protect the appliance i.e. the PSU.

But, personally, where I can I use the lowest fuse size where I can to protect the cable AND the appliance so for a 3 amp fuse you can pull 3 x 220 (Assuming 220v is standard, in my house it's actually 251V!) or 660w which is more than enough for the PRUSA printer, and no you can't trust fuses as there are so many environmental factors which can influence things for instance, if the fuse is in a sub zero environment, say -18 Deg C, it will allow much much more current to flow before it ruptures, or like in my case, the voltage is higher.

But for now, in the UK, and you want to fit a fuse, a 3A will more than suffice. This is also assuming the power factor is close to 1, but that's another load of electrical stuff to worry about, but not in this particular case.