service calculation

[strauby21]

I am Installing a service for 4 appartments and 1 house meter. 5 total. what is the best way to calculate what size main service I will need. any help or direction would help thanks

 

[LarryFine]

You'll find everything you need in NEC Art. 220. Calculate each apartment's load, as well as the house load, and report back with your results.

 

[strauby21]

Thanks,

I Have two apts @ 13250Vac each and two @ 15500Vac (all have electric heat) for a total of 57500Vac. I added 2000Vac for the house meter which is just lights and a washer/dryer. total is 59500Vac. The amps for 59500 is 248 amps but do I use 220-84 and a demand factor of 45% which would be 26775Vac and would be 111 amps. My number for the apt are as follows: these are old apts so the only have one small appliance circuit (if that):
1500Vac + 1000sq ft @ 3 vac= 3000Vac + 8000Vac heat + 1750Vac Range


Thanks for your help I appreciate it

 

[cdwelectric]

Michigan Master and contractor

Michigan Master and contractor

I also have a multi family service change to do. Its a 22 unit building with seperate laundry facilities. I am looking for the code reference, for the house panel load. The examples (d4) in chapter 9 show 3 va for general lighting in the apartments so I assume the same would apply to hall way lighting (per ft2
However, there is also,,,,,,,,,,,(giants just scored the go-ahead) perimeter lighting, 4 cloths washers, and 4 gas dryers. Still wondering if I am doing the right calculations.

 

[haskindm]

Thanks,

I Have two apts @ 13250Vac each and two @ 15500Vac (all have electric heat) for a total of 57500Vac. I added 2000Vac for the house meter which is just lights and a washer/dryer. total is 59500Vac. The amps for 59500 is 248 amps but do I use 220-84 and a demand factor of 45% which would be 26775Vac and would be 111 amps. My number for the apt are as follows: these are old apts so the only have one small appliance circuit (if that):
1500Vac + 1000sq ft @ 3 vac= 3000Vac + 8000Vac heat + 1750Vac Range


Thanks for your help I appreciate it

First, what is Vac? I understand VA and I undertand Watts, but not Vac. Don't mix the standard calculation and the optional calculation, use one or the other. All loads will need to be considered - Heating, Ranges, Water heaters, general use lighting and recpatclaes based on square footage, small appliance circuits, etc. There are no shortcuts, all of the steps of article 220 must be followed. The fact that you have only one samll appliance circuit does not change the fact that the minimum that must be calculated is 2.

 

[donw]

And you can't take the same demand factor you use for the units, on the house panel (using the optional method). Figure the house loads as any commercial project.

 

[cdwelectric]

I did answer a few of my own questions. Hallways, corridors, stairwells, and storage areas are calculated at 1/2 va per sq. ft.
Then there are some perimeter lighting that need to be calculated for the house load. My largest problem is getting the square footage of each apartment from the owner. I know the largest is around 2000 square feet, and the smallest is somewhere around 600, plus half of them have had garbage disposals and dishwashers added, and looking at the existing panels there is a 2 pole 30 amp breaker for some reason. Still gathering all the information. Thanks for everyones input.