is there a requirment to remove 20% load from the main panel

[fittowork11]

Hi Everyone

I have caluculate my load factors for a 3 unit building at 184 amps, My question is according to The Nec can I use a 200 amp service or do I need to remove 20% off of the 200 amps to get 160 amps that would be intern to small (please if someone can exsplain how this works)

Thanks

Brian

 

[curt swartz]

Welcome to the forum.

You need to provide more info. Is this a residential building or non residential. Is the 184 amps continuous?

Please share your calculations.

 

[infinity]

If the load calculation is according to Article 220 the calculated load is used to size the service. If you calculation comes up with 200 amps then that is your minimum service size. You do not need to do anything to the calculated load.

 

[fittowork11]

If the load calculation is according to Article 220 the calculated load is used to size the service. If you calculation comes up with 200 amps then that is your minimum service size. You do not need to do anything to the calculated load.

This is what I got according to artical 220 (at the moment the main house panel is suplied by a 250 mcm THW (Aluminum)

Calculated load	Unit 1 970 sqft	Unit2 970 sqft	Unit3 580 sqft	Total
General lighting	970 x 3va =2910	970 x 3va = 2910	580 x 3va = 1740	7560 VA
Small appliance	3000 va	3000 va	3000 va	9000 VA
dishwasher	1200 va		1200 va	2400 VA
Laundry circuit	1500 va		1500 va	3000 va
disposal	760 va		760 va	1520 va
Stove hood	300		300 va	600 va
Fridge (is this needed)	600 va	600 va	600 va	1800 va
			Total	25880/120= 216 amps

 

[RWC/NC.]

Noticing laundry circuit unit(s) one & three. Curious are there no electric clothes dryers, in the two separate units. Also noticing range hoods, might dwelling ranges & hot water heaters along w/unit heating equipment be gas, in lieu of electric. Are there any AC loads being considered (?)

 

[Little Bill]

This is what I got according to artical 220 (at the moment the main house panel is suplied by a 250 mcm THW (Aluminum)

Calculated load	Unit 1 970 sqft	Unit2 970 sqft	Unit3 580 sqft	Total
General lighting	970 x 3va =2910	970 x 3va = 2910	580 x 3va = 1740	7560 VA
Small appliance	3000 va	3000 va	3000 va	9000 VA
dishwasher	1200 va		1200 va	2400 VA
Laundry circuit	1500 va		1500 va	3000 va
disposal	760 va		760 va	1520 va
Stove hood	300		300 va	600 va
Fridge (is this needed)	600 va	600 va	600 va	1800 va
			Total	25880/120= 216 amps

You divide by 240, not 120
25880/240=107.83A

 

[RWC/NC.]

Bill, it appears possibilities he's also missed utilizing Table 220.42 lighting load demand factors.

 

[kwired]

You divide by 240, not 120
25880/240=107.83A

or 208 and square root of three if that applies, but either way makes a significant difference from using 120. May or may not be other demand factors available not mentioned in his spreadsheet, and as mentioned probably is also heating or cooling load that isn't in the sheet, would only need to consider whichever is larger load.

 

[fittowork11]

or 208 and square root of three if that applies, but either way makes a significant difference from using 120. May or may not be other demand factors available not mentioned in his spreadsheet, and as mentioned probably is also heating or cooling load that isn't in the sheet, would only need to consider whichever is larger load.

Hi Kwired

yes you are right I definatly made a mistake with dividing by 120

Thanks makes the service mutch small LOL

 

[fittowork11]

Bill, it appears possibilities he's also missed utilizing Table 220.42 lighting load demand factors.

Hi I was under the impression from the nec that multi unit building that are not apartments are treated as individule residence when using demand factors or am I wrong Thanks for your advice

 

[jaggedben]

Hi I was under the impression from the nec that multi unit building that are not apartments are treated as individule residence when using demand factors or am I wrong Thanks for your advice

The NEC does not care about ownership arrangements, if that's what you're asking. Only the way the building is built.

 

[dm9289]

Hi I was under the impression from the nec that multi unit building that are not apartments are treated as individule residence when using demand factors or am I wrong Thanks for your advice

If the calculation method you used was the optional see table 220.84 also. Keep in mind you likely have a 4th panel needed for loads in common areas. You may want to look at annex D example D4(b)

 

[kwired]

Hi I was under the impression from the nec that multi unit building that are not apartments are treated as individule residence when using demand factors or am I wrong Thanks for your advice

There not many categories in the table. Dwelling units, hospitals, hotel/motels and warehouses. You apply whatever demand factor applies to each category if present and 100% for all other situations.

Even in a multifamily dwelling situation you likely have "house loads" that are taken at 100% where the rest of the calculations can take advantage of dwelling unit demand factors.

 

[Tulsa Electrician]

Multi family, service calc.
Take it the stove is gas. You mentioned hood for stove.
Gas dryer maybe?
no HVAC ?
There is some examples in the back of the book to help guide you. Informative Annex D Examples.
I use them a lot.
edit
Sorry dm9289 did not see you already stated annex D.