Replacing Fuse with CB

Fuse is a protective device that remains intact and allows circuit current through it untill the rated current is exceeded. Yes, fuses can be replaced with the circuit breker of the same current rating and operational voltage. However, in some cases of lower rating (especially fractional values of current), it may not be possible to find exactly the same current rating CB.

Quite.

For domestic applications in the UK:

• Nominal "5A fuse wire" → 6A B-characteristic circuit breaker.
• Nominal "15A fuse wire" → 16A B-characteristic circuit breaker.
• Nominal "30A fuse wire" → 32A B-characteristic breaker

will suit most situations.

Yes You can and You should .

Hang on a tick. Doesn't this depend a bit on the asker's application?

Fuse / CB interchangeablity may not be true for, say, an individual electronic device. CB often take a comparatively long time to trip, yes? I would think that in many such applications a quick blowing fuse would be much more preferable to protect the electronics from cascading failure.

yes exactly, thats why i put it on discussion table before to replace it, please discuss it from application point of view.

1. Every fuse is designed and rated for a particular value of current, if the current drawn through the circuit is more than the fuse rating, the fuse will blow thus protecting the equipment in question. The provides for protection from overload as well.

2. Yes, rewirable fuses are obsolete now, instead one can go for HRC fuses for comaratively higher current ratings and glass cartridges for the smaller ones like those in electronic circuits.

3. Circuits breakers with Microprocessor Control are available for fastest possible isolation of the faulty circuit, however main function of current limiting feature is to completely avoid the possibility of contact welding.

Manirul,

There are many more types and sizes of fuses than there are circuit breakers. This is because fuses can be manufactured to perform more specific protection tasks. The general ways to sort fuses and circuit breakers would include: circuit voltage, interrupting capacity (short circuit clearing capacity), current rating, time-current curve, speed of action, physical size, cost, and others.

For general use circuits (offices, residences, and similar) using a circuit breaker is probably better because of the ease of resetting after an overload and the greatly reduced risk of being over-sized. However, for many other types of loads and circuits, the fuse will be the better choice. Others have already noted that you have many more (and closer together) sizes of fuses. They will give better coordination between branch circuit, load center, and mains---so only the one closest to the fault opens. When I was first learning the trade, I thought fuses were old fashioned. After 30+ years, I frequently will find fuses to be the better choice for a particular application.

Good question--JMM

That's correct, in some application fuse is better choice over CB rather comparing MCB, at the same time cost effective. Say, for VT primary connection its new trend to use MCB than fuse though costly, but easy to reset and mounting doesn't consume much space in panel.

With Present development of inbuilt microprocessor based relay in CB the operating time has become tremendously low which is very much comparable to fuse. Hence the practice is not to used FUSE as back-up of CB. Isolating a faulty circuit in 1.5 cycle is quite less time than the sckt fault withstand time duration of circuit. I have never seen fuse used as a back-up. May be some old installation retained the upstream fuse while doing modification & revamping.

Fuses are an inexact science- read the specs of time & fast- but they save equipment in the case of a vast overload. I would say that c/bs would be more responsive to transients-as in elcb for eg.

One problem is that a circuit breaker would not fit into the fuse base position, and even when replacing fuse with another fuse, you need to match rating and size so you don't have clearance issues which could result in sparking or fire hazards. Also check descrimination is ok. Good luck.

A much bigger problem going on here is that the question is far too vague to get a good answer. Say for instance we are speaking of a fuse on a large AC motor installation where the available line fault current capacity is 200,000A. No circuit breaker is capable of interrupting a fault that big, but there are many many fuses that are. On the other side, if the current is 2ma, no circuit breaker goes that low (reliably). You just cannot make blanket statements on such an open ended issue.