Multi-Circuits Separate Neutrals

[KENNY_HUNTER_WSP]

Electrical team is currently challenged with showing multi-circuit furniture feeds with separate neutrals. We typically do not show wiring or tick marks on marks on plans, just home runs. Trying to get the tag on the home run to replace the " , " with "&". From my googling it looks like Revit can only show comma's.

Currently, we need to perform a workaround to support this by using two separate tags, one that tags the main circuit and one that tags a manually inputted comment. 

My suggestion, enable Revit to change comma's that identify multiple circuits within a home run by allowing the use of other symbol types. Allow symbols "&" and "+" in addition to the ",". See attached image example of what we are trying to accomplish.

[smbrennan]

I voted up for this with one stipulation, there needs to be better recognition of what circuits are pairing with what neutrals, and how those are represented. 

We represent 3x 1-pole circuits as 1,3,5

We represent 1x 3-pole circuit as 1-3-5

However, electrically, there is nothing wrong with 3,5,7 as a 3-pole breaker. So if I have a home run annotated with odd circuits 1 through 11, it could be 1,3,5 & 7,9,11, or 1-3-5 & 7-9-11, or any combination of the 2 based on the breakers. 

[KENNY_HUNTER_WSP]

@smbrennan Thanks for expanding on my idea. This is exactly what we are looking for. Your circuit speak is much better than mine. 🙂

[Martin__Schmid]

@KENNY_HUNTER_WSP  - I think to solve this problem, it is  aligned w/ what @smbrennan  indicated.. Revit would need to understand more about the topology of the conductors.. and possibly what breakers are shared. 

In your image:

A-1,3,5  - I am interpreting that as 3-shared neutrals... is there anything Revit should understand regarding if/how these are shared on a common 3P breaker vs. three separate 1P breakers?

A-1&3&5 - is this three individual 1P circuits each w/ their own neutral and breaker?  In one common hometrun/conduit?

A-1+3+5 - not sure what you're showing there... not really clear from the request as stated... what is different about the condition by which you are showing a + and the extra 'pin head' tickmark?  

when you share a neutral, i think the NEC requires that all circuits sharing a neutral need to be able to be disconnected together (e.g., thus, a multi-pole breaker or tie)... are there other related needs.. e.g., is it possible to fulfill this requirement if the circuits aren't adjacent (e.g., 1,3,11 as an example?) in some way that you would likely design for?

[smbrennan]

Martin,

In my opinion, and the OP would have to elaborate his meaning, 

1,3,5 is indicating a 3-pole breaker. 3 Hots + 1 Shared Neutral. 

1&3&5 is indicating 3x 1-pole breakers. 3 Hots, each with their dedicated neutral

1+3+5 is the same as above, but each with a dedicated ground. 

If I have single pole breakers and I know I'm sharing neutrals, then I want to specify commas as a circuit separator. 

If I have a 3-pole breaker for single-pole circuits, then I need Revit to support that. 

In any scenario where I have a 2-pole or 3-pole breaker, I want to use dashes as a circuit separator. 

Furthermore, if I am combining multiple circuits with shared neutrals into a home run, then I want to clearly distinguish those, and wiring should clearly indicate that as well. 

Circuits 1,3,5 & 7-9-11 is using 2 neutrals, but I prefer those neutrals to be shown next to their respective circuits. See attached (below?) image for reference. 

[scbunker]

I've been trying to develop an appropriate workaround for shared neutrals in applications such as furniture feeds, surface raceway, and site lighting and I stumbled upon this post.

@Martin__Schmid, I think that the 'pin heads' in the OP's third example is indicating three separate grounds (one separate ground for each circuit).

To answer your other questions: you are correct about what the NEC requires, and I'm not aware of (nor can I conceive of) any way to do this if the circuits are not adjacent to each other in the panel. 

I have an idea for how to support shared neutrals that may be rather simple to implement: expand upon the Group functionality in panel schedules. I came across this help article that said grouping was to support shared-neutral circuiting. Circuit grouping in panel schedules is inadequate support for this, but it did give me an idea.

What if you added two more grouping functions: "Group With Multipole Breaker" and "Group With Handle Tie". 

The "Group With Multipole Breaker" function would leave the Circuit and Description as separate lines but would merge the trip and pole rows (depending upon that setting in Electrical Settings). Trip would need to be equal for all three (editable by user) and poles would depend upon the number of circuits merged.

The "Group With Handle Tie" function would group them, but leave them all as 1-pole breakers, each trip editable and can be different (though this is uncommon), and there needs to be some indication of a handle tie. Mere shading wouldn't work because then you wouldn't know which are tied when multiple ties are adjacent. It'd take a little thought to figure out how to show the tie.

In both of the above cases devices would need to be tagged with the individual circuits. Same for wires, unless the wires were connected to multiple circuits. I think that the multiple options for showing the multiple circuits (commas vs ampersands, etc.) could be settings that trigger based on how the breakers are merged, probably with per-circuit overrides.

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This doesn't involve shared neutrals, and I don't mean to hijack the thread, but I can think of two more group functions that could be added:

"Group and Merge": There are cases where a 1-, 2-, or 3- pole breaker can take up more than 1, 2, or 3 panel slots. The most common example is shunt trip breakers. The shunt trip device takes up an extra space in the panel, but that space isn't connected to anything - it's just attached to the side of the breaker. We usually show this with the 4 rows merged in the description column, the circuit still a separate row, and the load still a separate row (but with no load in the column). To do this in Revit currently, I add a space beside the shunt trip breaker, rename it "shunt trip" and group it with the breaker. If the breaker is in slots 1,3,5, usually we call it circuit 1,3,5 rather than 1,3,5,7. But perhaps that should be an option.

Another use for "Group and Merge": Sometimes high-current breakers can take up double slots. So a 3-pole breaker could take up 6 slots. Physically, the breaker is connected to each phase twice. We show this by merging all 6 rows in the description column, but only showing load on the first three rows (so we don't divide the load between the two phase A connections). I don't know that these are still used; I've only seen them in existing installations. If I had to do this in Revit currently, I would just add spaces to three rows and group them with the breaker. If the circuit is occupying slots 1-11 odd, we'd still call the circuit 1,3,5 I think. But perhaps that should be an option.

(I don't know if that pic is actually of that kind of breaker, but it looks like that.)

You can have a similar situation where high current breakers take up 6 slots across from each other rather than adjacent to each other.

"Group With Tandem Breaker": A tandem breaker is a way to get two circuits out of one panel slot. Both circuits are connected to the same phase. I don't know how I would do this in Revit if I ever needed to. 

Engineers hate these things because they screw up our schedules. Contractors will often install these to squeeze in another circuit. I can think of a couple of different ways to show this in a panel schedule, but I've already waxed eloquent, so we can discuss later if you like.

Let me know if it helps for this to be posted as a separate idea.

[Martin__Schmid]

@scbunker  - thanks for these details.  I'm not too concerned about this thread being separate ideas, as to really nail this is not just a small handful of individual ideas, but a more broad view of these types of relationships between breakers, conductors, and physical enclosures... and due consideration for the significant differences that exist in other geos.