60A circuit feeding a 30A fusisble disconnect

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Ranger86

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Is it allowed to have a 60A circuit (480V, 3-wire) feeding a 30A fusible safety switch? The load on the switch are some space heaters.

240.21 requires the overcurrent protection to be at the source, this is the only NEC section that I see some comflict with and I am thinking that this a NEC violation.

Do you see a violation here?
 
The fusible safety switch/disconnect must be rated for at least 60Amps and 480V.
 
Ranger86 said:
Is it allowed to have a 60A circuit (480V, 3-wire) feeding a 30A fusible safety switch? The load on the switch are some space heaters.

240.21 requires the over current protection to be at the source, this is the only NEC section that I see some comflict with and I am thinking that this a NEC violation.

Do you see a violation here?
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No since the 60 amp circuit is protected at it's Ampacity, and the disconnect will protect its conductors at it's Ampacity, I don't see a problem.

Think of it this way how many panels have you installed with a 200 amp main and have 15 amp branch circuits, same set up.
 
edward said:
The fusible safety switch/disconnect must be rated for at least 60Amps and 480V.
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Where do you find that?
I agree it needs to be a 600 volt disconnect, but taps to smaller disconnects has always been allowed, very common to find one large circuit feeding several such disconnects, we even do this on services, as long as the tap rules are met its good to go.
 
Yes, it has a 60A circuit breaker and the conductors are #6, so everything is good until it gets to the 30A (600V) fusible disconnect. This is the part I was not sure about. The disocnnect is fused at 15A.
 
Ranger86 said:
Yes, it has a 60A circuit breaker and the conductors are #6, so everything is good until it gets to the 30A (600V) fusible disconnect. This is the part I was not sure about. The disocnnect is fused at 15A.
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you need to look 240.21(B)(2)(2) it is allowed and as I said done all the time.

Any time a feeder ends in a dissconnect of a les amprage then the feeders it is still a tap wether it is one or many disconnects.
 
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GeorgeB said:
which may have ...
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I wish to kick myself in the behind and remind myself that I pretend to be an engineer, not an electrician with real code knowledge, and I should keep my ignorant replies (presented as fact) out of the thread. Sorry guys! I'll try to remember.
 
hurk27 said:
you need to look 240.21(B)(2)(2) it is allowed and as I said done all the time.

Any time a feeder ends in a dissconnect of a les amprage then the feeders it is still a tap wether it is one or many disconnects.
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How is that a tap?

A tap would be a #14 pigtailed off the end of the #6 and then feeding the disconnect. This is just #6 feeding a fused disconnect. If this had been an unfused 30 amp disconnect with 50 amps of load after it, then we'd have something to talk about.
 
Cow said:
How is that a tap?

A tap would be a #14 pigtailed off the end of the #6 and then feeding the disconnect. This is just #6 feeding a fused disconnect. If this had been an unfused 30 amp disconnect with 50 amps of load after it, then we'd have something to talk about.
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Can you tell me where to find that definition in the code?

Just because the tap uses #6 all the way to the disconnect, its still a tap to a low current circuit just like buss taps are.
 
hurk27 said:
Can you tell me where to find that definition in the code?

Just because the tap uses #6 all the way to the disconnect, its still a tap to a low current circuit just like buss taps are.
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240.2 makes it pretty clear. None of the conductors in the OP's example have an OCPD over the conductors ampacity.
 
This is a very common set up, if it was 60a going to a box and had a couple of 20 or 30amp taps going to their own fused disconnects, I'd call them taps. If its a 60a going to a single fused disco I'd call it a feeder. Who cares what you call it, it's legal.
It is done all the time because often you don't know how big the final unit is going to be, but you do know it won't be over a certain size.
 
hurk27 said:
No since the 60 amp circuit is protected at it's Ampacity, and the disconnect will protect its conductors at it's Ampacity, I don't see a problem.

Think of it this way how many panels have you installed with a 200 amp main and have 15 amp branch circuits, same set up.
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200 Amp panel is ok with smaller breakers assuming the rating of the panel is 200Amps. But i see a problem with a 200Amp protected and rated feeder to a 100Amp rated panel.

I understand the OP as a 60Amp rated feeder protected with a 60A OCPD feeding a 30Amp rated disconnect. If the 60A feeder is feeding a 60Amp rated disconnect with a 30Amp fuse feeding the heaters, then i think it is OK.

I think it is OK if the OP has a 60A feeder feeding other smaller rated disconnectS.

Unless i dont see or understand it i believe he needs a 60Amp rated disconnect but can have a 30Amp fuse feeding his heaters.

If i am wrong, It won't be the first time that i will learn something form this forum.
 
Gac66610 said:
depends on distance, could just be a feeder IMO
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It is a feeder. The 30A fused disconnect is the branch circuit ocpd, unless there is additional non-supplemental ocpd prior to the load(s) supplied, which would then make the disconnect's load side conductors another feeder.
 
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