Feed-Through Electrical Panels

[dtiemeyer]

Does Revit have any settings to accomodate a 'Feed Through' panel arrangement (sometimes called 'double-lugs') ?

My engineer tells me this is a situation where Panel B is fed by the same feeder as Panel A, but Panel B doesn't take any breaker-slots on Panel A.  

I dont see how to do this in Revit.

[dtiemeyer]

Does Revit have any settings to accomodate a 'Feed Through' panel arrangement (sometimes called 'double-lugs') ?

My engineer tells me this is a situation where Panel B is fed by the same feeder as Panel A, but Panel B doesn't take any breaker-slots on Panel A.  

I dont see how to do this in Revit.

[pteague]

It seems like there could be two options for what you're trying to do.

1) Feeding 2 panels from the same breaker with separate load calculations for each panel.  This is easily doable.  You just add Panel B to the same circuit that Panel A is being fed from.  That will combine the loads in the upstream breaker, but the panels themselves will have independent load calcs.

2) Sub-feeding Panel B from Panel A without using a breaker and keeping the load calcs combined in Panel A.  I don't know of any way to do this without using a workaround.

[pteague]

It seems like there could be two options for what you're trying to do.

1) Feeding 2 panels from the same breaker with separate load calculations for each panel.  This is easily doable.  You just add Panel B to the same circuit that Panel A is being fed from.  That will combine the loads in the upstream breaker, but the panels themselves will have independent load calcs.

2) Sub-feeding Panel B from Panel A without using a breaker and keeping the load calcs combined in Panel A.  I don't know of any way to do this without using a workaround.

[dtiemeyer]

I agree @pteague it seems those are the only 2 options. Perhaps Autodesk could chime in.  Is there any way to link a B panel through an A panel without it occupying a breaker slot?

Or is your plan to let 3rd party providers (like Design Master) handle the more advance functions like this?

[dtiemeyer]

I agree @pteague it seems those are the only 2 options. Perhaps Autodesk could chime in.  Is there any way to link a B panel through an A panel without it occupying a breaker slot?

Or is your plan to let 3rd party providers (like Design Master) handle the more advance functions like this?

[Anonymous]

The easiest thing to do is to simply change the Max Number of 1 Pole Breakers parameter from the default 42 to 84 and adjust the dimensions of the panel.  This effectively treats them as a single panel, and the NEC now permits single tubs with more than 42 breaker spaces in them.  If the engineer is dead set on treating them as separate panels you'll have to connect both to the same circuit and describe your desired configuration with notes/specs.  Ultimately what you're attempting to model is the feeders to the panels, which I strongly advise you not to bother with - I would be absolutely floored if your engineer was showing that graphically in CAD before adopting Revit.  If you circuit both panels to a single circuit in your distribution board the systems data will be correct, and that's the truly important part.  The physical objects in Revit MEP are very much a secondary consideration next to the systems data.

[Anonymous]

The easiest thing to do is to simply change the Max Number of 1 Pole Breakers parameter from the default 42 to 84 and adjust the dimensions of the panel.  This effectively treats them as a single panel, and the NEC now permits single tubs with more than 42 breaker spaces in them.  If the engineer is dead set on treating them as separate panels you'll have to connect both to the same circuit and describe your desired configuration with notes/specs.  Ultimately what you're attempting to model is the feeders to the panels, which I strongly advise you not to bother with - I would be absolutely floored if your engineer was showing that graphically in CAD before adopting Revit.  If you circuit both panels to a single circuit in your distribution board the systems data will be correct, and that's the truly important part.  The physical objects in Revit MEP are very much a secondary consideration next to the systems data.

[dtiemeyer]

I agree that, from the perspective of the electrical engineer, the physical objects are secondary in importance to the systems data. But there is more to designing an electrical system than just circuit loading. A potentially undersized feeder is a huge liability issue, but since Revit doesn't attempt to handle feeder sizing in the first place, it hasn't the settings required to create this type of arrangement. Ideally we'd like to be able to build a model that is accurate both physically & in the data/system, because we want to get to a point where the data/system arrangement settings are correct so that the One-Line can be generated from it.

But I think all this discussion has essentially answered my original question.

[dtiemeyer]

I agree that, from the perspective of the electrical engineer, the physical objects are secondary in importance to the systems data. But there is more to designing an electrical system than just circuit loading. A potentially undersized feeder is a huge liability issue, but since Revit doesn't attempt to handle feeder sizing in the first place, it hasn't the settings required to create this type of arrangement. Ideally we'd like to be able to build a model that is accurate both physically & in the data/system, because we want to get to a point where the data/system arrangement settings are correct so that the One-Line can be generated from it.

But I think all this discussion has essentially answered my original question.

[Anonymous]

We've pretty much given up on Revit generating accurate wire sizes or one-lines.  At some point we still have to design things, if the software gets too good at it we'll be out of a job anyway, right.  In this particular case you could probably trust the generated feeder size from Revit, but due to the way it calculates circuit length any long feeder is going to be incorrect because Revit doesn't account for conduit routing, it just measures the shortest straight line distance.

There's a guy on here who promotes his add-in for electrical calcs, I think it's called Design Master.  I've never used it because my firm doesn't want to shell out the additional cash.  We're hoping that SKM will eventually jump on the Revit train.

[Anonymous]

We've pretty much given up on Revit generating accurate wire sizes or one-lines.  At some point we still have to design things, if the software gets too good at it we'll be out of a job anyway, right.  In this particular case you could probably trust the generated feeder size from Revit, but due to the way it calculates circuit length any long feeder is going to be incorrect because Revit doesn't account for conduit routing, it just measures the shortest straight line distance.

There's a guy on here who promotes his add-in for electrical calcs, I think it's called Design Master.  I've never used it because my firm doesn't want to shell out the additional cash.  We're hoping that SKM will eventually jump on the Revit train.

[dtiemeyer]

Yeah, when I was investigating that, I thought it was doing a 'shortest path between panels using only x, y, z', not the 'pure shortest distance' but it wasn't great. As you say, conduits dont always follow the shortest distance even in an XYZ (like going around an elevator shaft, for example), and then if both panels were on non-orthogonal walls, the results were erroneous as well.  We're actually looking into the Design Master for its ability to generate a one line from Revit equipment, which is part of the genesis of the OP question.

Cheers,

Dustin

[dtiemeyer]

Yeah, when I was investigating that, I thought it was doing a 'shortest path between panels using only x, y, z', not the 'pure shortest distance' but it wasn't great. As you say, conduits dont always follow the shortest distance even in an XYZ (like going around an elevator shaft, for example), and then if both panels were on non-orthogonal walls, the results were erroneous as well.  We're actually looking into the Design Master for its ability to generate a one line from Revit equipment, which is part of the genesis of the OP question.

Cheers,

Dustin