Apartment Building House Loads Demand

[cyriousn]

Don't forget to calculate the equivalent 3 phase load of the dryers and ovens which will jack up the load. 220.54 mentions it but the examples in Annex D also show this for ovens.

 

[cyriousn]

Got it! Thank you for your help! I guess it’s up to me to figure out if the 2750A seems correct for the overall house + apartment loads… wish i seen example of demand loads regarding house loads but there isn’t really any out there, only. for dwelling units

I just punched in some numbers into a file I made from doing this a few years back and I assumed 500 sq ft per each apt at 3VA per square foot along with the (3) 1500VA circuits totaled those up and subjected them to the 100%,35%,25% diversities, then assumed 2500VA (2 1200W fan coils) of HVAC for each apt at 100%, then assumed (4) Appliances (fridge,freezer,MW,DW) rated at 1200W each (might be high) subject to 0.75 demand factor, then used a 5kw dryer in each place which equates to 84 equivalent phase to phase connections using 0.25 factor then taking that load and divide by 2 to get the single phase equivalent and multiply by 3 to get 157,500 VA for the three phase equivalent, electric cooking doing the same method using 8kw load which turned out to be a 0.16 demand factor to get 161,280VA and totaled 1,282,730VA or 3564A total for the apartment loads.

 

[Tainted]

I just punched in some numbers into a file I made from doing this a few years back and I assumed 500 sq ft per each apt at 3VA per square foot along with the (3) 1500VA circuits totaled those up and subjected them to the 100%,35%,25% diversities, then assumed 2500VA (2 1200W fan coils) of HVAC for each apt at 100%, then assumed (4) Appliances (fridge,freezer,MW,DW) rated at 1200W each (might be high) subject to 0.75 demand factor, then used a 5kw dryer in each place which equates to 84 equivalent phase to phase connections using 0.25 factor then taking that load and divide by 2 to get the single phase equivalent and multiply by 3 to get 157,500 VA for the three phase equivalent, electric cooking doing the same method using 8kw load which turned out to be a 0.16 demand factor to get 161,280VA and totaled 1,282,730VA or 3564A total for the apartment loads.

Can you share your file with me so I can compare and see if I'm missing something? thanks you!

 

[MyCleveland]

Don't forget to calculate the equivalent 3 phase load of the dryers and ovens which will jack up the load. 220.54 mentions it but the examples in Annex D also show this for ovens.

Your discussing standard calc, 220 part 3, requirements. While he should be aware of this he has determined he qualifies for optional method, 220 part 4.

 

[cyriousn]

From looking over the calculation example in D5(b) for the Optional Multi-Family Calculation it says "All Conditions and calculations are the same as the D4(b) example that was done at 240V. Isn't that not true because you would still need to find the three phase equivalent of the dryers and electric cooking appliances which was not done in calculation example D4(b)? Also in D4(b) example the Min Size Main Feeder Required for the 40 unit building comes out to be 1028A. Is that even a realistic example of getting a 240V single phase service that large?

As far as the optional method, if I use the same data as above I get 3,300,500VA diversified with 0.23 to get 2108A for the apartment loads. Quite a big difference between the two methods so just be careful. Are these apartments that will be targeted as luxury where people will be in and out between their multiple residences or will these be targeted to every day people who will be in their every day where you will see a higher demand?

 

[cyriousn]

Can you share your file with me so I can compare and see if I'm missing something? thanks you!

If you plug in all of the data that I used, into your calc, do you get something close?

 

[MyCleveland]

From looking over the calculation example in D5(b) for the Optional Multi-Family Calculation it says "All Conditions and calculations are the same as the D4(b) example that was done at 240V. Isn't that not true because you would still need to find the three phase equivalent of the dryers and electric cooking appliances which was not done in calculation example D4(b)? Also in D4(b) example the Min Size Main Feeder Required for the 40 unit building comes out to be 1028A. Is that even a realistic example of getting a 240V single phase service that large?

As far as the optional method, if I use the same data as above I get 3,300,500VA diversified with 0.23 to get 2108A for the apartment loads. Quite a big difference between the two methods so just be careful. Are these apartments that will be targeted as luxury where people will be in and out between their multiple residences or will these be targeted to every day people who will be in their every day where you will see a higher demand?

Exactly that, optional calc does NOT use 220 part 3 methods.
Notice in optional calc they are using the nameplate values given ( x number of units) for ranges.
Then applying reductions as allowed in table 220.84.

 

[cyriousn]

Exactly that, optional calc does NOT use 220 part 3 methods.
Notice in optional calc they are using the nameplate values given ( x number of units) for ranges.
Then applying reductions as allowed in table 220.84.

I see what you are saying now. The three phase equivalent is only listed in Part 3. It seems odd that you wouldn't have to find the three phase equivalent in the optional calculation. Wouldn't having the single phase loads on the three phase system still have the same effect as calculation D4(b)? I agree that you wouldn't take the diversities in tables 220.54 and 220.55 though.

If I remove the three phase equivalents to the optional calc I get 2100A which I guess wasn't too far from the one with the three phase equivalents. Still a big difference between the standard calc and the optional calc. I would certainly take a look at what type of clientele plan on moving into these apartments. In high-end apartments I've seen people move in and immediately start asking for multiple ovens, steam baths, steam humidifiers, extra refrigeration appliances, etc... that will start to push the limits of the system once you have 125 units filled. Might be worth asking whoever the building manager is going to be if they are going to be limiting what electrical loads can be installed in the apartments or maybe it doesn't matter if each apartment is limited to let's say 100A.