line to line and line to neutral circuits

[Twoskinsoneman]

I want to install the following circuit. I'm not concerned with wires or loads my only concern is having a MWBC in this manner. I think 210.4 (c) exception 2 allows it but I want to make sure there is no other place in the NEC that restricts it. Thanks

 

[peter d]

Looks good to me, NEC wise. Maybe not the best design without actually knowing what those motors do.

 

[Twoskinsoneman]

Looks good to me, NEC wise. Maybe not the best design without actually knowing what those motors do.

very small motors. What would be your concern.

 

[peter d]

What would be your concern.

A fault in one motor will shut them all down. But again, without knowing the actual application it's pure speculation.

 

[480sparky]

I vote legal. Unorthodox, to be sure, and maybe a problem for a troubleshooter, but I'd say it's fine by the NEC.....

 

[mikeames]

I thinks its normal given the situation of one 240v motor first in the run and 2 -120v motors at the end of the run. If those motors were small enough and the operation of the circuit is acceptable for the application then I would do it the same way.

 

[Twoskinsoneman]

I thinks its normal given the situation of one 240v motor first in the run and 2 -120v motors at the end of the run. If those motors were small enough and the operation of the circuit is acceptable for the application then I would do it the same way.

240 load is 5amp fan. two 120 loads are actuators to move louvers. Can't recall load but is less than 1 amp each.

 

[Twoskinsoneman]

I vote legal. Unorthodox, to be sure, and maybe a problem for a troubleshooter, but I'd say it's fine by the NEC.....

Don't think it would pose a trouble shooting problem. The power source, OCPDs, junction boxes, and loads are all in one tiny room. :grin:

 

[Twoskinsoneman]

Thanks for everyone's input. I feel confident it is NEC compliant.

 

[480sparky]

Don't think it would pose a trouble shooting problem. The power source, OCPDs, junction boxes, and loads are all in one tiny room. :grin:

OK, maybe not a 'problem', but someone unfamiliar with it may scratch their head at first.... "What the.....?"

 

[alfiesauce]

Am I seeing this right- if the neutral wire gets disconnected at the panel, the two 120V motors start to work in a series environment?

 

[jim dungar]

Am I seeing this right- if the neutral wire gets disconnected at the panel, the two 120V motors start to work in a series environment?

Just like with every other MWBC.

 

[Twoskinsoneman]

Am I seeing this right- if the neutral wire gets disconnected at the panel, the two 120V motors start to work in a series environment?

since they are identical motors operated simulatanouesly it doesn't matter anyway. The neutral is just for show :grin:. And of course for code compliance.

 

[480sparky]

since they are identical motors operated simulatanouesly it doesn't matter anyway. The neutral is just for show :grin:. And of course for code compliance.

Where did the OP say they were identical motors?

 

[Twoskinsoneman]

Where did the OP say they were identical motors?

It wasn't perinent for the OP. I was just letting him know as a matter of fact. It has no bearing on anything. I was just making a theoritical point that since the loads were identical ( I know this because they are my motors) if the neutral connection failed, the series circuit would still provide the proper voltage to each load due to identical loads.

 

[480sparky]

It wasn't perinent for the OP. I was just letting him know as a matter of fact. It has no bearing on anything. I was just making a theoritical point that since the loads were identical ( I know this because they are my motors) if the neutral connection failed, the series circuit would still provide the proper voltage to each load due to identical loads.

Never assume. Yes, they probably are identical. But you know what they say about assume. :smile:

 

[Twoskinsoneman]

Never assume. Yes, they probably are identical. But you know what they say about assume. :smile:

Not sure what that means. I'm assuming. They are the same model brand new motors. I certainly am not saying they should be wired in series. It was just an off comment on the simple theory of a series circuit. Someone else brought it up.

Is your point that the circuit would not work?

 

[480sparky]

Not sure what that means. I'm assuming. They are the same model brand new motors. I certainly am not saying they should be wired in series. It was just an off comment on the simple theory of a series circuit. Someone else brought it up.

Is your point that the circuit would not work?

In your drawing, you simply have two motors. You also state later thay are 120v. But that's only part of the equation. What if one motor is 1/8 HP, and the other is 1/4 HP? Then you'd see a huge difference in the voltage applied to the two motors if the neutral was opened and they operated in series.

 

[iwire]

I think his point is they will not 'be the same'.

More of a thought experiment, I wonder how the voltage would split between the two motors with the neutral open and different mechanical loads on each motor?

 

[Twoskinsoneman]

I think his point is they will not 'be the same'.

More of a thought experiment, I wonder how the voltage would split between the two motors with the neutral open and different mechanical loads on each motor?

That is a fun thought exercise.

If the load increases on the motor it would draw more current and thus the voltage across it would drop and the voltage across the other motor would rise. But as the voltage dropped wouldn't the current also drop, sort causing some sort of balance?