Sharing Neutrals, Isolated Grounds etc.

[iwire]

Here's where I disagree:
What would have happened in this same situation (open neutral) had this not been a MWBC?

Which is a direct result of bad installation techniques, not the MWBC.

We will remain in disagreement.

 

[LarryFine]

Here's where I disagree:
What would have happened in this same situation (open neutral) had this not been a MWBC?

Answer:
Devices would have lost power - smoke stays where it belongs.

Simple as that.

Question: And what would occur if the same thing happened to your service where you live?

Answer: The same thing. Have you requested that your POCO run two grounded conductors to your house?

 

[gregldoyle]

Hi, new to the forum.
I design broadcast and av systems and many of my clients request iso grounds. This is due to the extremely low-level audio signals and ground differential between distant locations across a facility. Differential hum is a killer for microphone level audio. Also a problem for digital audio and video where it causes bit errors when connecting two points together with different ground potentials. We design the systems with "floating" racks and bond the iso ground to the equipment racks. I see two definitions for this, iso-ground and enhanced ground. For most installations, I agree, isolated grounds are a waste of good (and expensive) copper. For some technical installations, it's worth it.
Greg D.
Senior Designer
Black Diamond, WA

 

[Greg1707]

neutral conductors

neutral conductors

Since we are on this subject here is my question. I have a panel and six feet above the panel in the attic I have a jbox. The jbox is connected to the panel by conduit. I want to run multiple 120v circuits to this jbox from the panel. From the jbox I will split off to multiple home runs. Assuming that I will not be using MWBC how many neutrals do I need? I assume that I can just use one neutral as long as it is sized correctly? If this is correct do I size it according to the calculated combined load of the circuits?

 

[bradleyelectric]

Since we are on this subject here is my question. I have a panel and six feet above the panel in the attic I have a jbox. The jbox is connected to the panel by conduit. I want to run multiple 120v circuits to this jbox from the panel. From the jbox I will split off to multiple home runs. Assuming that I will not be using MWBC how many neutrals do I need? I assume that I can just use one neutral as long as it is sized correctly? If this is correct do I size it according to the calculated combined load of the circuits?

How can you be a master electrician, an aspiring electrician and not know the answer to this question all at the same time?

 

[LarryFine]

How can you be a master electrician, an aspiring electrician and not know the answer to this question all at the same time?

I'd be happy just knowing about the first two! :-?

 

[Greg1707]

How can you be a master electrician, an aspiring electrician and not know the answer to this question all at the same time?

First of all thanks for your quick response. I have virtually no experience working with conduit or FMC. The electrical field quite large, as you know from reading this forum. The field encompasses installing ceiing fans all the way to wiring industrial plants. Most of us make a career out of just working in one little area of the field. I am not very experienced in many areas and appreciate this forum to learn more.

So to repeat the question. Can I run 6 120 volt #12 THHN ungrounded conductors from the panel using FMC to a large junction box and run only one properly sized neutral conductor to the junction box. At the junction box the THHN would be spliced to 6 #12 romex cables. The properly sized neutral would be spliced to the 6 romex cables as well. All conductors of the circuits are in the same cable and raceway.

 

[steelersman]

Can I run 6 120 volt #12 THHN ungrounded conductors from the panel using FMC to a large junction box and run only one properly sized neutral conductor to the junction box. At the junction box the THHN would be spliced to 6 #12 romex cables. The properly sized neutral would be spliced to the 6 romex cables as well. All conductors of the circuits are in the same cable and raceway.

You would need 3 neutral conductors. You can share 2 circuits per neutral, assuming the service is 120/240 single phase. Just make sure that each pair of circuits that share a neutral are on seperate legs, ot on the same leg. Also you don't need to upsize your neutrals as long as you do as I said above. 3 #12 neutrals would cover the six #12 120 volt circuits.