Hi,
I've been doing some commercial building design lately and would like to check something with you guys.
My question relates to panelboard loading derived from from mechanical equipment.
Of course, I size motor conductors and breakers based on FLA and other rules, which are fairly straightforward. But it seems to me that resultant load on a distribution panel load is subject to some interpretation and judgment, with factors like actual motor load and duty cycle becoming very important.
For example, I have a bunch of 2.5 hp hydraulic engine hoists in this one building (a car dealership), each on a separate 25A circuit, sized based on FLA. If each pump were fully loaded and running all the time then the load on the panel is a bit less than 2KW load to the panel, for a total of something like 7.5KW. But, they run very intermittently, with a duty cycle well under 10%, so the total average load on the panel is actually much less. Based on duty cycle alone I think a value of 600W each is reasonable. I understand that it is important to design for worse case peak loads, but I tend to leave some capacity in each panel for that purpose.
I realize in this case the motors are fairly small - I am interested in the process rather than this particular example. The same sorts of decisions apply to larger mechanical equipment like HVAC systems. Perhaps some of you take a very conservative approach and just apply the full KW rating?
thanks!
I've been doing some commercial building design lately and would like to check something with you guys.
My question relates to panelboard loading derived from from mechanical equipment.
Of course, I size motor conductors and breakers based on FLA and other rules, which are fairly straightforward. But it seems to me that resultant load on a distribution panel load is subject to some interpretation and judgment, with factors like actual motor load and duty cycle becoming very important.
For example, I have a bunch of 2.5 hp hydraulic engine hoists in this one building (a car dealership), each on a separate 25A circuit, sized based on FLA. If each pump were fully loaded and running all the time then the load on the panel is a bit less than 2KW load to the panel, for a total of something like 7.5KW. But, they run very intermittently, with a duty cycle well under 10%, so the total average load on the panel is actually much less. Based on duty cycle alone I think a value of 600W each is reasonable. I understand that it is important to design for worse case peak loads, but I tend to leave some capacity in each panel for that purpose.
I realize in this case the motors are fairly small - I am interested in the process rather than this particular example. The same sorts of decisions apply to larger mechanical equipment like HVAC systems. Perhaps some of you take a very conservative approach and just apply the full KW rating?
thanks!
