Creating a Demand Factor

One of the most exciting changes you’ll find in Revit MEP 2011 is the Demand Factors feature.  The existing functionality has been overhauled with a new user interface that allows for the creation of demand factors using a variety of calculations.  The release also includes many out-of-the-box demand factors based on the NEC.  But what if a demand factor you need is not included?  The following is an example of how to create a custom demand factor for arc welders.

Article 630 in the NEC describes the minimum conductor ampacity requirement for a group of welders.  This requirement is the sum of 100 percent of the two largest welders, plus 85 percent of the third largest welder, plus 70 percent of the fourth largest welder, plus 60 percent of all remaining welders.  To create this demand factor, set the calculation method to By quantity and the calculation option to Incrementally for each range.  Revit determines the largest item as the first, the next largest as the second and so on.  This image shows this demand factor in the new UI: 

I have created a project that contains seven arc welders of various loads that use the new demand factor.  Their calculations are as follows:

2500 VA  x  100%  =  2500 VA

2200 VA  x  100%  =  2200 VA

2000 VA  x  85%    =  1700 VA

1200 VA  x  70%    =  840 VA

1200 VA  x  60%    =  720 VA

1200 VA  x  60%    =  720 VA

1000 VA  x  60%    =  600 VA

Totals:

11300 VA connected load, 9280 VA demand load   

This is the display of the Arc Welder demand factor in the load summary section of a panel schedule:

 

Comments

[Federico Negro]

This is very cool...

[Cheap Coach Bags]

What will be your harvest this year, my friends?