Does the panel allow tandems?
Actually you are correct, the question does not concern 2 neutrals under one lug. It concerns a neutral and a ground under one lug. @rmeier2 states that most bus bars are rated for 2 conductors per lug and I looked at some on the Menards website and he is right. Robert also states that loosening wires is not an issue since the bus bar is rated for 2 wires. So I guess us non-electricians don’t know why you can’t have a ground and neutral together. But the electricians that wrote the code must have had their reasons I guess. Maybe one will chime in with it?
408.21 Grounded Conductor Terminations.
Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor.
The article in the link that Ryan posted directly responds to the question of an EGC and neutral in the same hole.
Since I can’t place two neutrals in a
single termination, can I install the
neutral and ground conductor in the
same termination?
The connection of a neutral and equipment-grounding conductor in the
same termination creates a similar issue. One of the objectives of the
particular arrangement of bonding jumpers, neutrals and equipment
grounds is to allow circuit isolation while keeping the equipment grounding
conductor still connected to the grounding electrode (see UL 869A -
Reference Standard for Service Equipment). When the neutral is
disconnected, the objective is to still have the equipment ground solidly
connected to the grounding electrode. If both the neutral and grounded
conductor is under the same terminal, this cannot be accomplished.
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Good catch. I should have read further I guess, lol.
Ryan, What I was trying to elicit from you was an explanation, in your own words, what your concerns with isolating circuits are, not what an article said. I am not trying to put you on a spot. I am more interested in having you and others truly understand.
Understanding why we do some of the things we do in the electrical trades will make you a better inspector but, simply repeating something that you read or heard somewhere without actually understanding it can do more harm than good.
The article you posted explains WHAT will happen with a loss of neutral (elevated Voltage, etc.) but it does not sufficiently explain WHY the Voltage is elevated. Knowing what will happen is certainly important but understanding why is more important.
If you read through various home inspector and electrician forums, you will find that there is a lot of guessing going on. Most of the guesses are wrong. The challenge for someone who is trying to learn is sorting out bad information from good.
Having covered this particular topic many times in my classes for both electricians and home inspectors, I can tell you that it takes a minimum of about two hours for most electricians to start getting a good grasp on what is going on and a little longer (though not much) for home inspectors.
This is an ideal example of where the House of Horrors can be the best possible way to learn. By doing hand-on demonstrations in the HoH, I can show inspectors something in 10-15 minutes something that would take at least an hour if I am standing in front of a class. The other advantage of a hands-on demonstration is that it is easy to dispel misinformation and myths.
Oh, ok. I wasn’t sure what you were after. Thanks!
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The issue is that the neutral is a current carrying conductor and will expand and contract under load. Improper torque would exacerbate any looseness. Multiple grounding conductors would remain tight as they only carry current under a fault condition. It would be extremely rare for both to carry a fault at the same time.
Incorrect. One neutral per hole Period.
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You’re right. That was a misquote on my part. Thank you for fixing it.
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The elevated voltage would only happen on a multi-wire branch circuit. A circuit with one hot and one neutral would simply fail to work.