service main feeders multi family

[electricman31]

hello to everyone,

I have been stumped on this one for several days now,I recently looked at a 3 family house that a builder that I work for had me look into a service change for him and I calulated the loads however he needs to save money and may be Iam a little conservitive with my calculations can someone see something else to maybe help to downsize the feeder or should it stay the way I calculated it out at?
3 family house with 3 units all the same size 1456 sq. ft.with gas and oil heat,no clothes dryers,gas stove.I have figured 1) 4368w general and recpt. load 2) 3000w total appliances 3) 1500w laundry.
1456 gen lighting/recpt. load
3000 small app. 3 apts total
1500 laundry 3 apts total
5956 total
- 3000
2956* .35= 1034.6+3000= 4034.6

special app. 1 oil fired furnace 1200w
fixed app. 1 water heaters 6000va

6000*.75=4500
1200
+ 4034.6

9734.6 total watts per
appt.

9734.6*3=29,203.8 watts

29,203.8 divided by 240=121.7 amps

with that said shouldn't you have to add something in for landlords common area? Seems to me unless I forgot something 2/0 cu would be a conservitive size feeder? did Icalculate correctly?

thanks for any help in this matter

 

[bphgravity]

Re: service main feeders multi family

Even using the optional method, the load does not calculate to less than around 135-amperes.

Whay are you only using 75% of the water heater load? Are you sure 220.17 applies?

 

[electricman31]

Re: service main feeders multi family

the load calcs come out not less than 135A by your calcs, remember that I will be using 2/0 cu in a dwelling unit. In that application the wire is good for 200A it should be just fine I don't feel safe downsizing it anymore than that. I don't think I have missed anything else?