Check my work, embarrass me on a §220.84 load calc

[brycenesbitt]

I need to do a load calculation for a multifamily building I can't examine the actual stuff in. So I need reasonable defaults, even though
they can not practically be checked. How'd I do?
See any issues?

Do I derate the baseboard heaters once per unit THEN again for load diversity, as shown?

(The baseboard heating is part of what I'm unsure of (I wish it were watts per square foot of floor area making it easier to compute and less random))

Building 7	Beds	ft ²	Heat	Laundry	Cooling	Range	Disposal	H2O	D/W	Extra		§220.84 Load Calculation
1	2	920	✓	-	-	✓	✓	✓	✓			20.32	VA	84.67	A
2	2	920	✓	-	-	✓	✓	✓	✓			20.32	VA	84.67	A
3	2	920	✓	-	✓	✓	✓	✓	✓			21.28	VA	88.67	A
4	2	920	✓	-	-	✓	✓	✓	✓			20.32	VA	84.67	A
5	2	920	✓	✓	-	✓	✓	✓	✓			24.16	VA	100.67	A
6	2	920	✓	-	-	✓	✓	✓	✓			20.32	VA	84.67	A
7	2	920	✓	-	-	✓	✓	✓	✓			20.32	VA	84.67	A
8	2	920	✓	-	-	✓	✓	✓	✓			21.28	VA	88.67	A
Common	-	100	-	2	-	-	-	-	-	2400		17.00	VA	70.83	A
Constructed	1986										Raw sum	185.32	VA	772.17	A
											After 43% demand factor for 8 units	79.69	VA	332.03	A
											Net load with power managed EV (no change)	79.69	VA	332.03	A
Load		Name-plate	derate									Count	Load Diversity	220.84(B)
Heat		9600	65%	VA	Baseboard heaters, quantity less than 4							3	45
Laundry		9600		VA	40A electric dryer							6	44
Cooling		2400		VA	Minisplit							8	43
Range		8000		VA	Typical range							11	32
Disposal		2400		VA	Typical disposal							12	41
H2O		7200		VA	30A resistance tank water heater							14	40
Dishwasher		3600		VA	Typical dishwasher							16	39
Kitchen		3000		VA	Fixed value from 220.84(C)(2)							18	38

 

[wwhitney]

Do I derate the baseboard heaters once per unit THEN again for load diversity, as shown?

No. 220.84 is self-contained and nothing in 220 Part III applies. 220.84 has no reference to a 65% factor for heating. You put in the full nameplate rating of all heating as specified in 220.84(C)(5), unless the cooling load is higher.

It is interesting that 220.84(C)(3) and (4) specifically refer to the nameplate, while (5) does not. And Part II of 220 still applies. So if, for example, 220.14 had special rules for heating, those would still apply to determine the heating "load". But it doesn't, heating would fall under the 220.14(A) catchall which just refers to the "ampere rating".

Note that for cooling (or heat pump heating), 220.14(C) does refer you to 430/440 for motor loads, so the load would be the nameplate MCA.

No opinion on any of your default values, as I have no applicable experience.

Cheers, Wayne

 

[brycenesbitt]

Error noted !
VA should be kVA

 

[brycenesbitt]

No. 220.84 is self-contained and nothing in 220 Part III applies. 220.84 has no reference to a 65% factor for heating. You put in the full nameplate rating of all heating as specified in 220.84(C)(5), unless the cooling load is higher.

That's what's getting me
220.84 (C)(5) The larger of the air-conditioning load or the fixed electric space-heating load

It does not say "nameplate" it says "load". So what's the load?

That's where I dragged out:
65 percent of the nameplate rating(s) of electric space-heating if less than four separately controlled units.
40 percent of the nameplate rating(s) of electric space-heating if four or more separately controlled units."

----------------------------------------------
I updated the dyer to 7680 VA ( 80% of the 40A breaker, allowing a commercial 32A machine)>

Building 7	Beds	ft ²	Heat	Laundry	Cooling	Range	Disposal	H2O	D/W	Extra		§220.84 Load Calculation
1	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
2	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
3	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
4	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
5	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
6	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
7	2	920	✓	-	-	✓	✓	✓	✓			20.03	kVA	83.47	A
8	2	920	✓	-	-	✓	✓	✓	✓			20.99	kVA	87.47	A
House	-	100	-	2	-	-	-	-	-	2400		15.46	kVA	64.43	A
														736.17
Constructed			Raw	sum								176.68	kVA	736.17	A
1986			After	43% diversity	factor for 8 unit							75.97	kVA	316.55	A
			Net	w/EV load	management							75.97	kVA	360.00	A
			Net	w/EV communication fail	(add 6 unmanaged chargers at 1.4kW)							84.61	kVA	352.55	A
Load		Name-plate	derate										Count	Load Diversity 220.84(B)
Heat		7680	100%	VA	Baseboard heaters, separate controls, quantity less than 4								3	45
Laundry		7680	100%	VA	40A circuits 32A Max Dryers, demand factor per 220.54								6	44
Cooling		1920		VA	Minisplit 240V at 16A								8	43
Range		8000		VA	Typical range, Table 220.55								11	32
Disposal		1440		VA	Typical disposal								12	41
H2O		5760		VA	30A resistance tank water heater at 80%								14	40
Dishwasher		1440		VA	Typical dishwasher								16	39
Kitchen		3000		VA	Fixed value from 220.84(C)(2)								18	38

 

[wwhitney]

That's what's getting me
220.84 (C)(5) The larger of the air-conditioning load or the fixed electric space-heating load

It does not say "nameplate" it says "load". So what's the load?

That's where I dragged out:
65 percent of the nameplate rating(s) of electric space-heating if less than four separately controlled units.
40 percent of the nameplate rating(s) of electric space-heating if four or more separately controlled units."

OK, but that language is from 220.82. Nothing in 220.84 references 220.82.

The first sentence of 220.84 says in part "in accordance with Table 220.84(B) instead of Part III of this article." It's basically saying 220.84 is self-contained.

I don't have an explanation for the difference in language between 220.84(C)(3)/(4) and (5), but I don't think it's significant.

Cheers, Wayne

 

[brycenesbitt]

Thanks for your help