Using aR fuse instead of aM

[g3nt73m4n]

Hi,

We used lately aR fuses instead of aM fuse. Can you please inform will there be any problem?

The application is water boosting and originally aM fuse was used. The circuit has also thermal magnetic relays for motor and motors are 0.55kw. Fuses are 6amp.

Thanks,

 

[oscar21]

All I know of fuses is a gG is for general use and a gM is for motors

 

[g3nt73m4n]

All I know of fuses is a gG is for general use and a gM is for motors

But what if we used one for the other type? As far as i guess the only difference will be short circuit opening time. Fast acting will open fast.

I think the only problem will be selectivity. Fast acting fuse will blown first and you need to change it.

 

[oscar21]

Some fuses cope with inrush currents better than others, its like the B,C,D type breakers. I would imagine a gM fuse will take more of an inrush than a gG fuse without blowing but I'm no expert in the commercial side of electrics like some are on here.

 

[g3nt73m4n]

Some fuses cope with inrush currents better than others, its like the B,C,D type breakers. I would imagine a gM fuse will take more of an inrush than a gG fuse without blowing but I'm no expert in the commercial side of electrics like some are on here.

Yes that's exactly difference i think. It will withstand in rush current better. The only thing is i hope fast acting is not that fast and can withstand in rush current. There is no exact resource about all of these fuse types. I could only find this EE02:FUSES BY MARKING | Book of Engineering - https://bookofengineering.com/ee02fuses-by-marking/

Very beneficial to find type of fuse and description but it does give lots of info.

 

[Darkwood]

A very useful link provided by yourself, the previous fuse allows for motor inrush and you have effectively swapped it for a rapid action fuse that will be highly prone to blowing on inrush currents expected on the circuit it protects, this will lead to what is known now as nuisance tripping, blowing of breakers or fuses when there is no issue. You won't find any accurate definitive guide because every machine and circuit has its own inrush characteristics thus it is hard to provide a definitive guide, this is why they simply generalise them IE semi conductor protection, motor protection, general use etc etc
You are on the right side of the curve IE if it blows it probably will not cause any damage, if you put the wrong fuses in to protect expensive electronics then that is where the slower action of the wrong fuse can allow the fault surge to destroy and damage the equipment.