25A slow blow circuit breaker?

I think it is a Type D MCB, as that’s what I was taught at college.

www.consumerunitworld.co.uk/hager-ndn125a-mcb-type-d-single-pole-25a-10ka-441-p.asp

I would have assumed that also but the data sheet states a type B.

if the same X ray rig is sold in other countries the instructions may be assuming unfused plugs.  I sometimes find a perusal of the instructions for other places to  be informative. I agree the load is likely to have current bursts, and a C or D will ride that out much as a hot wire fuse would have done.

If you have a 13A fuse in line then any larger breaker will also work, after all you are using the fuse you just want the breaker not to trip before the fuse blows. Mind you if it really draws 12 the 13 A fuse will run hot However,  I suspect that is only during the Xray of some seconds, and most of the rest of the  time it is a few hundred watts at most.

Mike.

if the same X ray rig is sold in other countries the instructions may be assuming unfused plugs.  I sometimes find a perusal of the instructions for other places to  be informative. I agree the load is likely to have current bursts, and a C or D will ride that out much as a hot wire fuse would have done.

If you have a 13A fuse in line then any larger breaker will also work, after all you are using the fuse you just want the breaker not to trip before the fuse blows. Mind you if it really draws 12 the 13 A fuse will run hot However,  I suspect that is only during the Xray of some seconds, and most of the rest of the  time it is a few hundred watts at most.

Mike.

Yes, that is right. The dental x-ray exposure time is very short, less than a second, so the load is really very small. I suggest a type D and lose the 13A fuse, it is likely to blow after a number of "shock" type use and it would be a serious problem for the dentist as he probably wont have a clue as to why it doesn't work. Common problem with FSUs!

A further thought. You say switch fuse asked for, I presume this is for isolation during any servicing. Personally I would fit a BS4343 plug and socket, as I would not like to be working on EHT supplies like this without positive isolation from the supply. A 16A one would be perfectly satisfactory, and probably a 16A trpe D in the CU, but I wouldn't worry about a larger breaker as BS4343s are never a point of overcurrent failure, unlike BS1363 stuff. The Xray tube probably operates at about 100 kV and 30-50 mA, a very dangerous supply.