Downsizing Neutral in Prints

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naplespete57

naplespete57

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Ran into this today. Engineer apparently thinks that they can downsize the neutral in this circuit (please see attachment)

This 120V circuit is fed from a 30 amp breaker. It's hot wire is a #10 THHN but then they call for a #14 as a neutral.

I don't find any justification for this in the code but I wanted to see if anyone else does..
 

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  • PRINTS FOR NEUTRAL DISCUSSION.jpg
    PRINTS FOR NEUTRAL DISCUSSION.jpg
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I don't think it is a typo or a copy & paste error. I think it was a design choice, and therefore a design error. I find it hard to believe an engineer would make that design choice, but we are none of us perfect.

The error comes from the fact that the function of the 30 amp breaker is to protect both the "hot" wire and the "neutral" wire from overcurrent. The simple truth is that any and all current that flows in the #10 wire will also flow in the #14 wire. A 30 amp breaker is not allowed to be the overcurrent protection for a #14 wire.
 
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charlie b said:
I don't think it is a typo or a copy & paste error. I think it was a design choice, and therefore a design error. I find it hard to believe an engineer would make that design choice, but we are none of us perfect.

The error comes from the fact that the function of the 30 amp breaker is to protect both the "hot" wire and the "neutral" wire from overcurrent. The simple truth is that any and all current that flows in the #10 wire will also flow in the #14 wire. A 30 amp breaker is not allowed to be the overcurrent protection for a #14 wire.
Click to expand...

Well said
 
charlie b said:
I don't think it is a typo or a copy & paste error. I think it was a design choice, and therefore a design error. I find it hard to believe an engineer would make that design choice, but we are none of us perfect.

The error comes from the fact that the function of the 30 amp breaker is to protect both the "hot" wire and the "neutral" wire from overcurrent. The simple truth is that any and all current that flows in the #10 wire will also flow in the #14 wire. A 30 amp breaker is not allowed to be the overcurrent protection for a #14 wire.
Click to expand...

If one was completely ignorant to the fact, and going strictly off of the drawing,

One could assume that the PSU/SE2 is not an actual load but a switching device and therefore the #14 coming out of the load side of it was not actually a neutral but a switchleg.

In that case, that #14 switchleg would be going to a load termination point where the load side of the actual load was a #14 neutral attached to an undefined size of neutral on the right side of the drawing.

An udefined size neutral originating from the same terminal point as the ungrounded conductor feeding the 5, 15 and 30 amp circuit breaker.

JAP>
 
Who knows,,, SRT/121 may be the load, and the 30a feed to the switching device may have integral 15 amp protection without the neutral or (Grounded Conductor) termination drawn in as of yet.

JAP>
 
If PS2/SCU is an actual switching device, and, SRT-E121 is actually a load, then, the #14 on the load side of PS2/SCU to SRT-E121 is a switchleg, and, not a neutral at all.


JAP>
 
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