Wednesday, June 20, 2018

Revit Electrical Feature - Load Sub-Classification Motor

Revit has an electrical feature that is pretty much undocumented. And I do not claim to be an expert on this topic, but wanted to share what I do know and hear how/if others use this feature. I am talking about an electrical connector's ability to have a Load Sub-Classification Motor enabled as shown in this first image.

Before talking about how this appears to work, I will mention that the biggest problem we have is...
the sub-classification is hard-coded to the specific classification "Motor". As outlined below, this does not work for our load classification naming convention.

The National Electric Code (NEC) here in the USA requires that the largest motor be identified and treated differently from the rest. Basically, this feature allows Revit to find the largest motor, even if it is buried  within a family with multiple electrical connectors, and re-classify it to the built-in "Motor" load classification. Otherwise it stays at its current classification.

If all motor loads are using the same load classification / demand factor, then this works as Revit is able to treat the largest motor differently as seen in the Electrical Settings image below.

If you use a different name for the motor load classification then you have a problem. Below is an example of the same loads producing different results. The first example is using MTR as the load classification, and then the Load Sub-Classification Motor comes along and only uses Motor, thus creating two entries where each have their own largest-motor. The second option uses the built-in load classification naming convention Motor and thus we get accurate results.

The next four images show another variation on this, with multiple connectors and load classifications. The partial schedule shown in the footer of a panelboard schedule.

Because of this hard-wired load classification we never use the sub-classification option. And why do we not just use the built-in names you ask? Because...
  1. The built-in load classifications are named with a “Capitalize Each Word” naming convention.  Most use only UPPERCASE in formal documentation.  Some client standards require UPPERCASE per specific client standards.
  2. The built-in load classifications have to long of a text string which appears in the panelboard schedule load descriptions and load classification information in the footers.
  3. These are typical load classifications that we use short UPPERCASE names for:
    • Cooling (we use AC)
    • COMP (this is for computer loads, high harmonics, non-linear).  Revit does not have this.
    • GND (for ground connections, just because it has an electrical connector)
    • Heating (we use HEAT)
    • Lighting (we use LITES)
    • Kitchen Equipment – Non-Dwelling (we use KTCH)
    • Motors (we use MTR)
    • Receptacles (we use RCPT)
    • SPEC for specific equipment loads.  Revit does not have this.
    • WELD for welding loads.  Revit does not have this.
  4. Also we use these:
    • FIRE ALARM (used for NAC circuits to report mA loads).  If it needed to display on a schedule we would abbreviate FA.
    • MASS NOTIFICATION (used for NAC circuits to report mA loads).  If it needed to display on a schedule we would abbreviate MNS.
These are what we use in the MEPPP sold by CTC. Look forward to hearing what others have to say on this topic...

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  1. Hey Dan, Did you confirm this with Autodesk support? (the fact that the 'Sub-class as motor option' ONLY links to the 'Motor' load classification?

  2. Not with Support, but with someone at Autodesk high up in Revit MEP product development.


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