Why is it considered unsafe to double post neutral wires (two neutral wires to one lug on the neutral bar) in an electric panel?

This is unsafe due to the need to turn off multiple circuit

Breakers to work on any of the circuits using these wires.

If a person is working on one circuit and turns off a breaker

It is possible that the second neutral is carrying current and

Is a shock hazzard when removed from neutral buss

Simply because the lug is only rated to handle one wire safely. Any more than rated will result in loose connections.

It's a code violation also, The code is based on safety, Not necessarily efficiency.
I forget the exact wording in a paragraph at the start of the Electrical Code, that states just that.

Quote:

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Originally Posted by biggsie

This is unsafe due to the need to turn off multiple circuit

breakers to work on any of the circuits using these wires.

If a person is working on one circuit and turns off a breaker

it is possible that the second neutral is carrying current and

is a shock hazzard when removed from neutral buss

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Biggsie... I don't believe this has anything to do with that scenario does it? Since the neutrals are all on the same buss anyway, that problem is always present. The only way to ensure your problem doesn't occur is to have the MWC on tied breakers. Or am I misunderstanding what you're saying?

Hey Cobra, I'm thinking he meant 4 breakers would need to be turned off to safely work on a neutral problem, if 2 neutrals under one screw. Provided they were all multi circuit.
Take Care.

What biggsie said makes sense to me. Here's the scenario:

Assume every breaker in your panel is on, and all circuits are under load. You turn off one breaker and attempt to remove it's corresponding white from the neutral buss. In the process, the second white pops out and makes contact with you. ZAP!

This is an excellent question. I don't believe in following code just because it says so. It's always wise to question code so that you can learn the reason why it is that way, and then follow it! Understanding why code exists is always a good thing.

Another reason is if neutral is removed on a multi circuit while energized, the 120 Volt circuits using that neutral may go to 240 volts if load or breaker(s) are not turned off.

It may be a bad practice, but come on, who is going to shut off one circuit and loosen 2 wires?

If I was redoing a neutral connection that was overheated due to loose connection, I would turn off 2 circuits to repair. If 2 neutrals under same screw. 4 circuits need to be turned off.

Strat... I may be totally confused here... which isn't that unusual! LOL You are assuming then that both neutrals under the same screw are on MWC's? I totally agree with 4 breakers needing to be switched off if so. If they aren't MWC's, only two would need to be switched off, right?

I think my original question to Biggsie was worded poorly... and I did misunderstand a bit what he was saying.

EDIT: I did read this again and saw where you were assuming the circuits were MWC's. So I do agree with you guys that 4 breakers would need to be off. (or better yet, the MWC's would be on tied breakers and you would need to just flip the two sets of breakers)

I think we are in agreement. If neutral was only for one circuit, then the 240 volt danger would be eliminated. I was just mentioning a potential danger that may be overlooked(multi circuit needs 2 breakers off to safely disconnect neutral for repair. Take Care

Why isn't it required to mark those infernal things? Say you want to work on circuit #24. If it is shared with #22 or #26, you want it off too. So what do you do, throw all 3 and hope it isn't sharing a neutral with #18?

What about say a red felt tip bracket {= ?

Basically, only qualified and trained personnel belong in a panelboard, and if any work needs to be done, such as disconnecting wires, that person will know what to lookout for before just haphazardly disconnects any wiring.

And I believe NEC 2008 does require MWC's to be tied in some way Labman.

Ah, progress. I am surprised how long it took to do something about the 3 wire dryers and ranges.

For a real horror story, see https://www.askmehelpdesk.com/plumbi...ed-161901.html

In defense of the plumber. He made it work, told the owner it wasn't right, and left the cover on the panel.