Can I De-Rate a 30 A Disconnect switch to 20 A by using a 20 A fuse?

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Eaton sells a 30 AMP, 2-Pole, General Duty Safety Switch, Fusible with Neutral rated for 240 VAC,
It uses type FLNR fuses, which come in 20 A. So by using a 20 A fuse, do I effectively make the 30 A switch into a 20 A switch?
Likewise, can I take a 60 A switch and use it as a 40 A switch by using a 40 A fuse?
As everyone knows, 30 A and 60 A are industry standards and 20 A and 40 A switches are not..
Thank you in advance
 
Installer said:
Eaton sells a 30 AMP, 2-Pole, General Duty Safety Switch, Fusible with Neutral rated for 240 VAC,
It uses type FLNR fuses, which come in 20 A. So by using a 20 A fuse, do I effectively make the 30 A switch into a 20 A switch?
Click to expand...

No, you have a 30 amp rated switch with 20 amp fuses ;) nothing wrong with that. Get into fuse reducers and you can have a very big switch with relatively small fuses.
 
If it is a 30A switch it can carry a 30A load continuously with a 30A load. By installing a 20A fuse, you have now limited the switch to 20A. Seems like common sense to me.
 
Installer said:
Eaton sells a 30 AMP, 2-Pole, General Duty Safety Switch, Fusible with Neutral rated for 240 VAC,
It uses type FLNR fuses, which come in 20 A. So by using a 20 A fuse, do I effectively make the 30 A switch into a 20 A switch?
Likewise, can I take a 60 A switch and use it as a 40 A switch by using a 40 A fuse?
Click to expand...
At a super simplified level, yes to both.
 
You are not changing the RATING of the switch, you are just changing how you USE it. Disconnect switches only come in a few sizes; 30, 60, 100, 200, 400, 600, etc. So WHENEVER you need a CIRCUIT rated for less than those values, that's what you do, you install the correct FUSE for that circuit in a switch that is that size or larger.

For the most part, a 30A fused switch is designed to hold fuses that are 30A and under and conversely, the fuse manufacturers will design their fuses 30A and under to all be the same size. But fuses also come in "Classes" that have to do with their size and things like interrupting ratings, current limiting ability etc. So a 30A and under "Class CC" fuse may be a different physical size than a 30A and under "Class RK5" fuse like the FLNR. So the thing you have to look out for is that the switch you select matches the fuse class you want to use. In this case, because you said that the switch is for FLNR fuses, any FLNR fuse 30A and below is going to be designed to fit in the fuse holders of that switch.

The only thing you can't do is install a 60A fuse into a 30A switch...
 
Thanks everyone

Thanks everyone

Thank you for your replies.

So if you don't get to do electrical work on a daily basis, you lose your grasp very quickly, even if you are someone who has been working with your hands a long time.


Jraef said:
You are not changing the RATING of the switch, you are just changing how you USE it. Disconnect switches only come in a few sizes; 30, 60, 100, 200, 400, 600, etc. So WHENEVER you need a CIRCUIT rated for less than those values, that's what you do, you install the correct FUSE for that circuit in a switch that is that size or larger.

For the most part, a 30A fused switch is designed to hold fuses that are 30A and under and conversely, the fuse manufacturers will design their fuses 30A and under to all be the same size. But fuses also come in "Classes" that have to do with their size and things like interrupting ratings, current limiting ability etc. So a 30A and under "Class CC" fuse may be a different physical size than a 30A and under "Class RK5" fuse like the FLNR. So the thing you have to look out for is that the switch you select matches the fuse class you want to use. In this case, because you said that the switch is for FLNR fuses, any FLNR fuse 30A and below is going to be designed to fit in the fuse holders of that switch.

The only thing you can't do is install a 60A fuse into a 30A switch...
Click to expand...
 
Installer said:
Eaton sells a 30 AMP, 2-Pole, General Duty Safety Switch, Fusible with Neutral rated for 240 VAC,
It uses type FLNR fuses, which come in 20 A. So by using a 20 A fuse, do I effectively make the 30 A switch into a 20 A switch?
Likewise, can I take a 60 A switch and use it as a 40 A switch by using a 40 A fuse?
As everyone knows, 30 A and 60 A are industry standards and 20 A and 40 A switches are not..
Thank you in advance
Click to expand...

the switch itself is still a 30 amp switch.
 
Just like circuit breakers have frame sizes that limit the maximum amps they can carry, but you can buy them in common lessor amp ratings.

i.e. Eaton G Frame breakers are 100 amp rating, but available as small as 15 amp trip rating.

Of course, you cannot usually change a breaker's trip rating in the field, like you can buy fuses up the switch rating if the load changes.
 
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