Grounded Neutral

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BA Evans

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i have a 120vac control circuit with a grounded neutral, the neutral of this circuit has a fuse in it. is this still considered a grounded neutral.
 
Yes. Indeed in some contexts the word "neutral" is a conversational-English (slang) term for what is properly called the "grounded conductor." If the fuse in your neutral leg were to open, then that conductor would no longer be connected to "ground." But then, the circuit wouldn't operate either, so there is no need to be concerned about the lost connection to planet Earth.
 
charlie b said:
. . . there is no need to be concerned about the lost connection to planet Earth.
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I'm not so sure I agree.

While the advantage of the bond restricts the possible voltage-to-earth (in case of accidental contact with higher voltage, as with a typical grounded service), it also means that, if this fuse were to open, the entire control circuit would be hot relative to the enclosures.

It would be easy for someone to get zapped while learning what happens when a grounded conductor is fused. While I understand that this wiring is probably not subject to NEC, it makes clear why simultaneous opening of all hots must accompany opening a grounded conductor.

At the very least, I certainly hope this is not the only fused conductor. If it is, it may be a mistake. Could a 2-pole breaker be substituted without voiding listing and warranty? We didn't get much (okay, any) detail on the equipment.
 
LarryFine said:
. . . it also means that, if this fuse were to open, the entire control circuit would be hot relative to the enclosures.
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Not the entire control circuit, but only up to the first relay contact. I'm not going to say this clearly, since I haven't had any coffee yet this morning. With the neutral open, all relays within the circuit deenergize, and all points that require the "on/off" contacts to be "on" will lose power.
 
hardworkingstiff said:
I fail to understand why a fuse would be installed on this conductor. I think there should be one on the ungrounded conductor.
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I have seen control circuits that have fuses on both legs of the control circuit. I don't generally work with this type of equipment, so I can't tell you why some control circuits fuse both legs and others fuse only the ungrounded leg.
 
steve66 said:
I think this sounds like a violation of 240.22.
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But isn't this stuff inside (or otherwise a portion of) a listed component, and therefore not under the jurisdiction of the NEC?
 
Schematic Designer

Schematic Designer

these circuits have fuses on the Hot as well as the Neutral. the design is for a utility and yes i realize the NEC is not to be used for utilities, this client has required it to be.
 
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