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Panel Schedule Demand Load Calculations

Panel Schedule Demand Load Calculations

The NEC requires that receptacle demand load to be calculated as follows: 100% for the first 10,000VA and 50% for the remainder.  The industry standard has always been to display this information as two separate line-items on electrical panel schedules:

 

          Load Classification     Connected Load     Demand Factor     Demand Load
          Receptacle                         10,000VA                  100%                  10,000VA  

          Receptacle                           3,040VA                    50%                     1,520VA

 

Revit displays the information on the panel schedules in a single line, like this:

 

          Load Classification     Connected Load     Demand Factor     Demand Load
          Receptacle                         13,040VA                  88.34%                  11,520VA

 

While the calculation is correct, the way that it is displayed does not convey that the calculation has complied to the NEC requirement.  We have been asked on multiple projects to display the receptacle demand load calculation as two separate line items on each panel schedule.  As a result, we have had to export our Revit Panel Schedules to excel, to manually change the way that this information is displayed, in order to appease plan-checkers, costing us a lot of time and labor doing rework.  This makes using Revit smart-circuiting unfeasible for many of our projects.


Revit should display this information in a way that is intuitive, and consistent with the industry accepted presentation of demand load calculations on panelboard schedules.

9 Comments
scbunker
Collaborator

I'd say you have overly-persnickety plans reviewers...

I believe I'd gently push back if I encountered such a reviewer. I have had reviewers take certain issues with the way Revit displays things before, but they've always understood when I described it as a software limitation and showed how the calculation was correct.

armando
Contributor

Looking for a solution to this ourselves. We are receiving the same comments from our local building depts.

meten
Community Visitor

San Jose, CA and Austin, TX  are just a couple of jurisdictions that will reject Revit's demand calculations. See permit comment below:

"I appreciate the use of software. Please show demand factor as seen in code."

Permit Comment.png

jdcarlingJQBC3
Enthusiast

I don't even see how to adjust  this. I modified the parameter "power factor" and it did nothing. I also cannot find one listed as demand factor to adjust.

robp
Community Visitor

Washington State also requires category breakouts similar to what @meten  is indicating, for all load calculations including branch circuit panels, distribution panels, transformers, switchboards, transfer switches, generators, etc.  WA State L&I Electrical Plan Review (LNI EPR) is responsible for reviewing plans for buildings in the public sector that do not have local electrical plan review and will reject plans not showing these breakouts.  A lot of local plan reviewers follow the LNI EPR guidelines.  This forces redundant design in alternate software, or separate calculation in Excel to satisfy these requirements. 

 

Which boils down to 2 issues: Revit increases the time for electrical engineers to their work and Revit is non-code compliant software. 

matt.hand52
Contributor

36 upvotes over 2 years and still no response? That's gotta be a record!

 

I haven't had to find a solution to this issue until now although I recognized this was going to be an issue when circuiting existing loads at a previous firm. If you just happen to have as bad of luck as me, you'll find it is possible to severely overload a phase if you just happened to circuit the panel in such a way that many existing motors and lighting circuits land on the same phase, and mainly receptacles on the other two. At face value, my panel was balanced by reviewing the Total Load by Phase at the bottom of the schedule. But a quick look at my Load Classification table shows that one phase really is seeing demand almost 50% more than the other two. A quick breakdown in the Load Classification summary would suffice to both my engineers and the planning dept, and would also be a great design check:

 

Ckt Demand Totals.png

BDezayas
Participant

@scbunker , yes, we have picky plan reviewers.  I have received this comment several times and they will not accept anything other than what the NEC specifically indicates. 

The closest I have been able to present this so far is by changing the name of the demand load to say, "Receptacle - First 10k @ 100%, Rest at 50%.  This has gotten accepted by previous reviewers in other projects, but i am now having the same issue from another reviewer that is not accepting it.Screenshot 2021-06-18 120255.jpg

nanschutz
Observer

Has this been addressed in the newest version of Revit? It would be nice if the tables actually showed the correct NEC values so they can pass the engineers review. Please respond.

matt.hand52
Contributor

@nanschutz No it has not in Revit 2023. I haven't checked the latest Revit Preview in a while so I can't be sure if there is a beta feature yet to try. We really just need them to create parameters for Demand Load per Phase similar to what is available for Apparent Load but I did confirm those aren't there yet: 

matthand52_1-1663080907034.png

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