Is it a Fuse-Terminal or Switch or Both

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stickelec

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Most Control Panels I see in C1-D2 areas that use the 5x20mm fuse also use the Fuse Terminal Block that is "hinged or pivoted" to provide for ease of opening or breaking the circuit. It appears to me that style terminal is nothing more than a "fuseable switch" with open-contacts.

I think my question revolves around "can a switch be - not called a switch if it has a fuse in it"? Is the definition of a switch based on its intended use or on its construction and potential use? (I don't find the answer in Art 100)

I know 501.105(B)(1) does not use the word "terminal or switched-terminal", am I reading something that is not there?

Thanks
 
stickelec said:
Most Control Panels I see in C1-D2 areas that use the 5x20mm fuse also use the Fuse Terminal Block that is "hinged or pivoted" to provide for ease of opening or breaking the circuit. It appears to me that style terminal is nothing more than a "fuseable switch" with open-contacts.

I think my question revolves around "can a switch be - not called a switch if it has a fuse in it"? Is the definition of a switch based on its intended use or on its construction and potential use? (I don't find the answer in Art 100)

I know 501.105(B)(1) does not use the word "terminal or switched-terminal", am I reading something that is not there?

Thanks
Click to expand...

its a fuse block. there are plenty of fuse blocks where the fuse carrier is part of the circuit and can be used as a convenience to remove the fuse.

mounting something on a din rail does not make it a terminal.

a switch has contacts that make or break the circuit. these things would use the fuse to do so.
 
realolman said:
If it was on a pole it'd be a fused disconnect.:smile:
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You are right, the "fuse-terminal" I speak of has a hinge, fuse-carrier, and blade...no different than a Nema-1 General Duty Safety Switch (IMO).
 
Stick IMO this is a question that could only be answered by the manufacturer.

I bet some of these units are designed to make and break a load and I bet some are not.
 
this has always bothered me

this has always bothered me

The hinged fuse terminals can be utilized as knife switches. In fact, I have seen them actually used in that manner with fuse slugs in place of actual fuses. (I haven't seen that in a CI-D2 area).

Of course any fuse holder must be designed such that the fuse can be replaced. After all, that is the point. But, I feel like it is just too easy to use these hinged fuse terminals as switches. You wouldn't be allowed to put a knife switch in a CI-D2 area, unless it was part of a nonincendive circuit. So, why can you use these hinged fuse terminals? I guess because it is just a fuse holder for a fuse which you are allowed to use.
 
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Thanks to all for the input. I am still concerned there could be siginificant exposure when using a fuse-terminal that is nothing more than an open knife-switch as pointed out by pburger. I see them commonly used to switch I/O for testing, maintenance, etc. I really doubt the average person even gives it a second thought.

One manufacturer uses the words, Lever and Disconnect, how close can you get to saying "switch"?

Thanks again
 
stickelec said:
Most Control Panels I see in C1-D2 areas that use the 5x20mm fuse also use the Fuse Terminal Block that is "hinged or pivoted" to provide for ease of opening or breaking the circuit. It appears to me that style terminal is nothing more than a "fuseable switch" with open-contacts.

I think my question revolves around "can a switch be - not called a switch if it has a fuse in it"? Is the definition of a switch based on its intended use or on its construction and potential use? (I don't find the answer in Art 100)

I know 501.105(B)(1) does not use the word "terminal or switched-terminal", am I reading something that is not there?

Thanks
Click to expand...

I do not think that these can be classified as "fused switches", but rather "disconnetable, fused terminals". They clearly not designed to interrupt load, but suitably uinsulated to facilitate the manual disconnection and isolation of the circuit for testing purposes.

Certainly can not be used to comply with 501.105(B)(1) including exceptions, but I am always bothered by the contradictions of that requirement and the 501.115(B)(2). Their function seem to me identical.
 
Article 501.115(B)

Article 501.115(B)

What is the classification of the enclosure these are found in? Assuming the enclosure is general purpose, doesn't Art. 501.115(B)(3) state that the fuse types typically found in the 'hinged' terminals are not acceptable unless installed in an enclosure rated for Cl. 1, Div. 1? I've seen, generally in unclassified areas, typically GMD, GMA, etc. class fuses in the types of terminals I think you are referencing, but don't see these as being acceptable in a hazardous area without the enclosure being rated for Cl. 1, Div. 2. See the following for more info.

http://bussmann.com/library/bifs/8003.pdf
 
alaskajohn said:
What is the classification of the enclosure these are found in? Assuming the enclosure is general purpose, doesn't Art. 501.115(B)(3) state that the fuse types typically found in the 'hinged' terminals are not acceptable unless installed in an enclosure rated for Cl. 1, Div. 1? I've seen, generally in unclassified areas, typically GMD, GMA, etc. class fuses in the types of terminals I think you are referencing, but don't see these as being acceptable in a hazardous area without the enclosure being rated for Cl. 1, Div. 2. See the following for more info.

http://bussmann.com/library/bifs/8003.pdf
Click to expand...

Yes, the Control Panels referenced are NEMA-12 and 4. I don't know that the "the hinge" has anything to do with it as applied to the NEC, although that is the basis of my concern.

I agree with your point regarding Art. 501.115 (B) (3) since the "interruption of current" would not occur within a factory-sealed explosion-proof chamber...if manually or accidently opened.

An argument would bring up 501.105 (B) (5), regarding if each fuse is preceded by a switch... which in real life is impractical considering a typical panel might have 100 or more such fuses. The assumption being that a person would open said switch before opening said fuse.

Of course the way "it is done" is a single Sealed Switch driving one or more Sealed Relays (for more current) is installed as a main power switch to the panel, like the average tech is going to SD a Process to work on a DI that has no critical function in the code.

Personally, I can't tell the "difference in design" of the fuse-terminal in question and a NEMA-1 Safety Switch.
 
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