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25A slow blow circuit breaker?

Farmboy

What is a 25A slow blow circuit breaker? It's to supply an Xray machine in a dental practice. The data sheet states it draws 12A, and a 13A switch fuse has been asked for as the point of connection, along with this 25A type B slow blow CB at the supply end, but I've never heard of it - wouldn't surprise me if they meant fuse not CB.

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  • 0

    I agree - "slow blow" is a description of some types of fuses - not ordinary circuit breakers. MCBs all trip in the same sort of time once their tripping level is reached - the difference between B, C and D types is just the level at which they trip instantaneously, rather than the speed of tripping. Below that level they might trip by the thermal mechanism - but then you're talking of much longer times - way beyond the second or two that's likely to be a concern here. Sounds like the instructions have lost something in translation.

    The other possibility is that the "B" is referring to the characteristics of an RCD rather than overcurrent device (presumably the machine generates d.c. internally...).

       - Andy.

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  • 0

    I agree - "slow blow" is a description of some types of fuses - not ordinary circuit breakers. MCBs all trip in the same sort of time once their tripping level is reached - the difference between B, C and D types is just the level at which they trip instantaneously, rather than the speed of tripping. Below that level they might trip by the thermal mechanism - but then you're talking of much longer times - way beyond the second or two that's likely to be a concern here. Sounds like the instructions have lost something in translation.

    The other possibility is that the "B" is referring to the characteristics of an RCD rather than overcurrent device (presumably the machine generates d.c. internally...).

       - Andy.

Children
  • 0 in reply to AJJewsbury

    the installing engineer asked for a 20/25A type B CB, along with the switch spur.

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