Service Load Calculation for a Residence with multiple panels

[Luis De Castro]

I have an MDP panel feeding 4 panels, how to do the service calculations , do I do calculations for each panel separetely and the main panel also separetely

 

[Ponce]

First, calculate each panel individually:
This will give you the ampacity of each panel.
Next you will to calculate load for the, Entire Building, Main Panel:
I don't know your situation, but there will probably be a greater Diversity allowed on the main panel because you are taking into account the entire building. NEC Article 220 covers the allowable demand factors for receptacles, dwelling units, HVAC units and such.
Keep in mind the connected load for the individual panels will most likely exceed the size of the main breaker.
I hope this answers your question.

 

[Ponce]

Table 220.84(B) covers the demand factors for Three or more multifamily dwelling units.

 

[Luis De Castro]

I have an MDP panel feeding 4 panels, how to do the service calculations , do I do calculations for each panel separetely and the main panel also separetely

Need clarification, in my case is not multipole dweilings, all panels are in the same residence

 

[jaggedben]

You can use an optional calculation method (e.g 220.82) for the MDP and service. The subpanels would need individual calculations according to 220 Part III and you would need a sensible way (by room, for example) to assign the home's square footage to each panel, to calculate the lighting load.

(Honestly I never see people doing load calculations for residential subpanels, most people seem to just wing it with a 100A or 125A or 200A feeder. In my experience they are generally massively oversized and I've never seen an AHJ care.)

 

[Luis De Castro]

You can use an optional calculation method (e.g 220.82) for the MDP and service. The subpanels would need individual calculations according to 220 Part III and you would need a sensible way (by room, for example) to assign the home's square footage to each panel, to calculate the lighting load.

(Honestly I never see people doing load calculations for residential subpanels, most people seem to just wing it with a 100A or 125A or 200A feeder. In my experience they are generally massively oversized and I've never seen an AHJ care.)

Thanks

 

[Ponce]

Jeggedben is correct.

Run the calculation for the entire building to size the MDP. This is what the utility company needs.

Pick a standard size for the sub panels.