Thursday, September 13, 2012

Revit MEP Circuiting tips...poles or phase?

Ran into this one recently...we have a project with a new user that is adding devices to circuits. In the project she's working on, we have number of poles and voltage assigned as a parameter, but somewhere along the line added a phase parameter that was also equal to the number of poles...which, if you're the electrical designer, you know is wrong.

So here's my simple explanation, with a little help and clarification from my buddy Dan Stine...the Number of Poles in a circuit relate to the physical slot locations on a panel. The Phase refers to the A/B/C branches of a panel. Phase is a product of typical AC (or alternating current). Without going into great detail, know that Revit support single phase (panels with A/B branches, just like your house) or 3 phase (A/B/C - most commercial applications).

With electrical connections, you'll have these types of connections:

120/240 - these are single phase panels, with two poles - most commonly found in residential
120/208 - a three phase panel, more common in commercial applications. This type of panel also requires 4 wires to use all three slot sizes, from 1-3. In some cases, a 120/208 single phase connection can also be used - for example, in a apartment building.

120V is common in the US, but not common in other areas, such as Europe.

120V - A single phase, single pole Circuit - unless it's a GFI circuit, which could be single pole but 2 phase
208V/240V -  typically a 2 pole, 1 phase circuit, but also could be three phase (for example, in the event of a 208V GFI Circuit). 208 volt or 240 volt systems can both be either single phase 2 pole, or 3 phase 3 pole circuits.

Higher voltage panels for commercial and industrial applications are typically 277/480, indicating a one to three pole circuits. 277 volt circuits are almost always single phase, single pole, while most 460-480 volt circuits are 3 phase circuits. Depending on the power requirements, you can have 480 volt, single phase, 2 pole circuits - so make sure you check for this when specifyign your equipment.


In my simple little, non-electrical mind, it's a bit confusing, but from Revit, it's pretty straight forward.

If something is 120v, set the number of poles to 1. This will take up one slot in the panel, or one "circuit"

If something is 277v, set the number of poles to 1. The phase will also be set to one. For 208v/240v circuits, these can be single phase 2 pole, or three phase, 3 pole.

For 480V, in most cases, the number of poles will be 3. a 3 pole circuit takes up three slots, and can only be used in a panel that is defined as a 3 or 4 wire, 3 phase panel. You can have some systems, such as electric heat, use a 480v single phase, 1 pole circuit - again, check with your vendor before defining the circuit.

These are all set under electrical settings, for the distribution systems:

Revit requires that the proper combination of poles and voltage in order to add something to a circuit. There are two configurations for any type of a three phase panel - Delta, which doesn't include a neutral branch, and Wye, which does include a neutral.

Revit only recognizes single or three phase systems when you define your distribution system. For example, you might have a device or circuit, that requires 208v service but is single phase - you still have to assign the number of poles to 2. Otherwise, it can't be connected to a panel.

For more information, talk to a more reliable source than me - your local electrical engineer.

Hope this helps - if anyone wants to add to the conversation, knock yourself out!

thanks - David B.

2 comments:

jake ostler said...

Thanks for sharing this information. If I wanted to, would it be possible to add-a-phase to my transformer? Thanks

David Butts said...

Not really - as far as I'm aware of, you can only do 1,2 or 3 pole systems. Phases are not tied to the electrical connection, so in our case they're simply added for data. I might be wrong on this one since I'm not an electrical engineer, but as near as I know, the answer is no.