lol. He signed this project back in 2006 so he was registered. He was up for renewal in Florida I think in February of this year and he never renewed. Probably for the best. His PE number in Florida 10,000 something, pretty old. In Florida, they are up to almost 80,000 for license numbers.
Multi-Family Dwelling Calculation
- Thread starter Npstewart
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Only if you use the "standard method" for the entire calculation. Those demand factors are within Part III of article 220. The optional methodology is in Part IV, and tells us you can use it instead of the method in Part III. You can't mix the two methods.
Edited to add: I suggest doing the calculation both ways, to see which one gives you the better (i.e., lower) result.
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- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Please clear up one question for me. Does the value of 5960 represent 65% of the heating load (i.e., has the demand factor been applied, in determining this value), or is it 100% of the heating load?
Each unit is equipped with a 5KW electric resistance heating element, plus the fan which I will estimate to be 960 watts (tenitively), which will make a total HVAC load of 5,960. If we take 65% of that, that will put us at 3,874, that is what he should have used for the number under "Air Conditioning"... If you total his numbers up, he doesent use the 5,960 number. For some reason he used a 58% multiplier for the AC...
This project is a nightmare...
I went through and did a quick re-calculation using the original EOR's load calculation template and fixing all the errors. The final calculation result came up to 803 Amps....I wish it was a little higher so it would be easier to justify replacing 800A services because of 3 amps. (see attached). Im going to have to go through this with a fine tooth comb.
I went through and did a quick re-calculation using the original EOR's load calculation template and fixing all the errors. The final calculation result came up to 803 Amps....I wish it was a little higher so it would be easier to justify replacing 800A services because of 3 amps. (see attached). Im going to have to go through this with a fine tooth comb.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
There is no 220.32, T220.84 perhaps.
- Location
- Connecticut
- Occupation
- Engineer
Your "correction" is incorrect.
The original calculation for the multiple dwelling units was correct. You have 4 units at 37747 VA each and 8 units at 37735 VA each for a total of 452868 VA. 41% demand for that per 220.84 is 185676 VA, 774A @ 240V single phase.
The house loads should be added to that. If the house loads are truly 64 Amps, then your total is 838 Amps, not 803 Amps.
If you don't know how the 64A house load was arrived at, I'd recalculate that number. Maybe its sufficiently low that an 800A service would be OK.
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- Location
- Connecticut
- Occupation
- Engineer
If the house load keeps you above 800, maybe you could look at using an 800A service for the apartments and a separate service for the house loads, possibly under 230.2(D).
I dont understand how I am incorrect.
For the feeder calculation I have the following
Unit A
Misc loads & appliances: 32187
Air conditioning: 3874
= 36,061 x 8 = 288,488
-------------
Unit B
Misc loads & appliances: 32175
Air conditioning: 3874
= 36,049 x 4 = 144,196
288,488 + 144,196 = 432,684 Total VA
So: 432,684 *.41 = 177,400 Demand
177,400 @ 240-1 = 739 A + 64A(house) = 803.2 Amps
For the feeder calculation I have the following
Unit A
Misc loads & appliances: 32187
Air conditioning: 3874
= 36,061 x 8 = 288,488
-------------
Unit B
Misc loads & appliances: 32175
Air conditioning: 3874
= 36,049 x 4 = 144,196
288,488 + 144,196 = 432,684 Total VA
So: 432,684 *.41 = 177,400 Demand
177,400 @ 240-1 = 739 A + 64A(house) = 803.2 Amps
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I haven't checked any of the math, but you are incorrect because you are making the same error that I had thought the other engineer had made. You are taking a 65% demand factor on each heating system, and then later on taking another 41% demand factor on the whole building. Therefore, you are double-dipping the demand factors. Try the service part again, this time including the entire 5960 VA times the number of units, then apply the 41%, and see what you get. It will likely be well above 800 amps.
- Location
- Connecticut
- Occupation
- Engineer
Didn't you say your space heating load was 5960 VA per unit? (In post #25?)
So...
Unit A
Misc loads & appliances: 32187
Fixed electric space heating: 5960
= 38,147 x 4 = 152,588
-------------
Unit B
Misc loads & appliances: 32175
Fixed electric space heating: 5960
= 38,135 x 8 = 305,080
152,588 + 305,080 = 457,668 Total VA
So: 457,668 *.41 = 187,644 Demand
187,644 @ 240-1 = 782 A + 64A(house) = 846 Amps
(I notice you upped the disposal to 1000VA from 600, but you also swapped the quantity of units from A to B. Was this intentional?)
- Location
- Connecticut
- Occupation
- Engineer
I would expect that you'd have a different "rate schedule" for the apartments (residential rate) and house loads (commercial rate)? I seem to remember designing a project with a separate service to the house panel in the past.
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