Panel calculation, panel change

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brother

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I plan on having a upgrade on a rental. originally i wanted a 200 amp service. Presently it has a 100 amp old screw type fuse panel in there now.

Its been a while since ive done residential (duplex), and when i did it, it was always 200 amp upgrade (duplex) the city required it ;).

Now im in a different city and i was told by another electrician to just put in a 100 amp panel, no need for all that power on a 764 sqft unit. I said i plan to add more circuits and electric heat (cadet). He claims the 100 amp breaker panel would work cause of the demand factor even with the added circuits.

I disagreed and said it AT LEAST should be a 125 amp. Even apartments have that. But i have to admit its been a while since the calculations for demand factor on service loads (as found in the back of the Nec). This 'city' doesnt have that blanket requirement of having all panel up grades to be 200 amp :).

So tell me, who is right? me or him. 125 amp or 100 amp?? Help me with these calcs. Im adding about 4 heaters later someday. 3 1500 watt. and 1 2000 watt. right now i still plan to do the 125 amp unless im proved otherwise, but if i can save some work and a few bucks i would like to put in a 100amp
 
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I didn't do the calculation but IMO a 764 sq ft unit should not require anything larger than 100 amps. The amount of heat you've mentioned is negligible, from a load perspective, on a 100 amp service.
 
Additionally, going from 100a to 125a is not worth the work no matter what. If you're going to bother, go to at least 150a. However, your new heating load is only 26/27a, which I agree is minimal.
 
Brother,
Sit down with article 220 and do the calculation. On a 764 sq. ft. unit, you probably could have done the calculation quicker than you typed the original question. With the calculation you will know exactly what your load is and how much capacity you will leave for future expansion. Everyone has an opinion, do the math and work from the facts.
 
I agree - do the calculation. The size of the apartment doesn't matter all that much. What affects the calculation more is major electric appliances like water heater, clothes dryer, range, and heat/AC. You've mentioned you want to add electric heat, so there is strike number 1. If the apartment has no laundry facilities in that unit, then you get to skip the clothes dryer and the laundry small appliance circuit. That alone could be enough of a difference to tilt the answer to 100A from 125A.
 
brother said:
I plan on having a upgrade on a rental. originally i wanted a 200 amp service. Presently it has a 100 amp old screw type fuse panel in there now.

Its been a while since ive done residential (duplex), and when i did it, it was always 200 amp upgrade (duplex) the city required it ;).

Now im in a different city and i was told by another electrician to just put in a 100 amp panel, no need for all that power on a 764 sqft unit. I said i plan to add more circuits and electric heat (cadet). He claims the 100 amp breaker panel would work cause of the demand factor even with the added circuits.

I disagreed and said it AT LEAST should be a 125 amp. Even apartments have that. But i have to admit its been a while since the calculations for demand factor on service loads (as found in the back of the Nec). This 'city' doesnt have that blanket requirement of having all panel up grades to be 200 amp :).

So tell me, who is right? me or him. 125 amp or 100 amp?? Help me with these calcs. Im adding about 4 heaters later someday. 3 1500 watt. and 1 2000 watt. right now i still plan to do the 125 amp unless im proved otherwise, but if i can save some work and a few bucks i would like to put in a 100amp
Click to expand...

764 sq. ft. @ 3 va per foot ...............2292
Small appliance and laundry ??... 4500
Water heater ?????????.4500
Dryer ????????????5000
Big range ??????????12000
Dishwasher microwave disposal @ 3600
First 10,000 @ 100% the remainder at 40%

Total part (B) 18856.8

Part (C) larger of heat or AC
4 units at 40% equals 2600 or a 20 amp AC unit @ 240 volts equals 4800

18756.8
+4800
23556.8/ 240 volts = 98.153 amp Main
 
"Give a man a fish, and he eats for a day...

"Teach a man how to fish, and he sits in a boat all day and drinks beer."
 
1793 said:
Is this a duplex? Is each area 764Sq ft?
Click to expand...

Yes its a duplex, and the actual sqft is 780. lol I missed the 20 sqft some where (not that it make that much of a difference). LOL ;)

They will NOT be sharing the same feeder. each unit has its own feeder. So it sounds like when i USE the OPTIONAL method (article 220.82 NEC 2005) a 100 amp panel will work. :

water heater = 4500 watts
stove 42amps * 240 = 10080 watts
dryer 26 amps * 240 = 6240 watts
laundry (washing machine) = 1500 watts
appliance 2 circuits 1500 each = 3000 watts
lighting 780sqft * 3 va = 2340 watts
Heaters 40% * 6000 = 2400 watts
TOTAL 30060 watts
30060 - 10000 = 20060
20060 * 40% = 8024
10000 + 8024 = 18024
18024 / 240 = 75.1 amps

Check my math, is it right?? Did i follow the code correctly??

heaters cadet 6000 watts
heaters cadet (for future) three (maybe 4) 1000 watt and one 2000 watt

NO dishwasher, or garbage disposa or air conditioningl!! and there will NEVER be one, I will see to that. too much maintenance on them and tenants dont take care of them. :( Fun being a landlord LOL
 
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Go back and read 220.82 again. Do part (B) first and then do part (C) and add the two together.

Edited to add from 220.82(A)
The calculated load shall be the result of adding the loads from 220.82(B) and (C).
 
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brother said:
Yes its a duplex, and the actual sqft is 780. lol I missed the 20 sqft some where (not that it make that much of a difference). LOL ...;)

...They will NOT be sharing the same feeder. each unit has its own feeder. So it sounds like when i USE the OPTIONAL method (article 220.82 NEC 2005) a 100 amp panel will work. :

:( Fun being a landlord LOL
Click to expand...

I don't have my book in front of me, I thought a duplex could only have one Service Drop.:confused:
 
Does this mean that there could be only one meter and service disconnect or does this mean only one service drop or lateral?

230.2 Number of Services.
A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D). For the purpose of 230.40, Exception No. 2 only, underground sets of conductors, 1/0 AWG and larger, running to the same location and connected together at their supply end but not connected together at their load end shall be considered to be supplying one service.
 
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