# Multifamily dwelling unit calculation



## electricalperson (Jan 11, 2008)

besides doing the standard method of calculating a service for an apartment building, (3 va per sq ft, small appliance branch circuit etc) what is the method used to add in the feeder/service size for a laundry room with electric dryers and washers? is it all nameplate? what about common areas and house panel loads such as fire alarms and outside lighting? the mike holt book is not clear on that part of multifamily dwelling unit calculations


----------



## Salvatoreg02 (Feb 26, 2011)

electricalperson said:


> besides doing the standard method of calculating a service for an apartment building, (3 va per sq ft, small appliance branch circuit etc) what is the method used to add in the feeder/service size for a laundry room with electric dryers and washers? is it all nameplate? what about common areas and house panel loads such as fire alarms and outside lighting? the mike holt book is not clear on that part of multifamily dwelling unit calculations


Take the total square foot of house.. The rest is name plate.plus all the other ****.


----------



## McClary’s Electrical (Feb 21, 2009)

Salvatoreg02 said:


> Take the total square foot of house.. The rest is name plate.plus all the other ****.


 

He said multi family. There are demand factors that can be applied


----------



## Salvatoreg02 (Feb 26, 2011)

mcclary's electrical said:


> He said multi family. There are demand factors that can be applied


I said total of all nameplates. If he chooses to use the demand factors of section 220 " god bless " if he doesn't that he'll and up running larger feeder cables. 
Did he specify how many clothing dryers there were. No! Up to four it's 100% DF
Did he specify how many electric ranges there were no!!
So, to me it sound like a small multi-family dwelling, less the 3 I'll assume, based on what was said
HAPPY NOW!


----------



## McClary’s Electrical (Feb 21, 2009)

Salvatoreg02 said:


> less the 3 I'll assume,


 



There's your mistake. Never assume anything


----------



## Salvatoreg02 (Feb 26, 2011)

mcclary's electrical said:


> There's your mistake. Never assume anything


Regardless, you can use section 220 for demand factors or add all your required branch circuits plus any additional loads based on there nameplate " not all the time" but what I said is correct ANYWAY. PROVE ME WRONG!


----------



## McClary’s Electrical (Feb 21, 2009)

Salvatoreg02 said:


> Regardless, you can use section 220 for demand factors or add all your required branch circuits plus any additional loads based on there nameplate " not all the time" but what I said is correct ANYWAY. PROVE ME WRONG!


 

shut up ***:whistling2:


----------



## electricalperson (Jan 11, 2008)

im not talking about the optional method. i want to use the standard method for all my calculations. 3 va per sq ft, demand factors for general lighting load, (first 3000 va at 100%, 3001 - 120,000va at 35% and the rest at 25%) electric range demand factors, dryers, appliances etc. what im talking about is factoring house loads such as parking lot lighting, hall lights, fire alarm and offices. 

factoring loads for halls, do you factor in the VA per sq ft for halls? (.5VA) and 3.5 VA for offices? this is all calculated at 125% correct? do i just add the VA too the dwelling unit calculation?

only thing i find is 220.84 B


----------



## Salvatoreg02 (Feb 26, 2011)

electricalperson said:


> im not talking about the optional method. i want to use the standard method for all my calculations. 3 va per sq ft, demand factors for general lighting load, (first 3000 va at 100%, 3001 - 120,000va at 35% and the rest at 25%) electric range demand factors, dryers, appliances etc. what im talking about is factoring house loads such as parking lot lighting, hall lights, fire alarm and offices.
> 
> factoring loads for halls, do you factor in the VA per sq ft for halls? (.5VA) and 3.5 VA for offices? this is all calculated at 125% correct? do i just add the VA too the dwelling unit calculation?
> 
> only thing i find is 220.84 B


Any additional lighting shall be added to your general lighting load. Then do your adjustment. 
Let's put it this way if your using a recessed light and the largest light bulb that can be installed is 100watts x 100 fixture you have to add that to your general lighting load. Then deduct % 
Which ever if the two calculations is greater u should use. 
I'll find the code section
Common halls are already in the general lighting load. Exterior parking lot lights no. 
Office space different method
Fire alarm will fall under the general lighting load. You can add it separately if you know the load. 
If you know all the electrical devices you are going to install you need to take the greater of the two methods,,


----------



## Salvatoreg02 (Feb 26, 2011)

Salvatoreg02 said:


> Any additional lighting shall be added to your general lighting load. Then do your adjustment.
> Let's put it this way if your using a recessed light and the largest light bulb that can be installed is 100watts x 100 fixture you have to add that to your general lighting load. Then deduct %
> Which ever if the two calculations is greater u should use.
> I'll find the code section
> ...


Section Annex D Ex. D4(a)


----------



## raider1 (Jan 22, 2007)

electricalperson said:


> im not talking about the optional method. i want to use the standard method for all my calculations. 3 va per sq ft, demand factors for general lighting load, (first 3000 va at 100%, 3001 - 120,000va at 35% and the rest at 25%) electric range demand factors, dryers, appliances etc. what im talking about is factoring house loads such as parking lot lighting, hall lights, fire alarm and offices.
> 
> factoring loads for halls, do you factor in the VA per sq ft for halls? (.5VA) and 3.5 VA for offices? this is all calculated at 125% correct? do i just add the VA too the dwelling unit calculation?
> 
> only thing i find is 220.84 B


You would use Part III of Article 220 to calculate the house loads. So for the office loads you would take the 3.5 VA per square foot and apply that for the office areas. The halls I would use .5 from Table 220.12. For the parking lot lighting you would need to use 220.14(D) and use the actual wattage of the fixtures to come up with the required lighting load for the service calculations. The Fire alarm would fall under 220.14(A) and you would use the full load of the FA system. 

You would just add the house loads to the rest of the dwelling unit loads as part of the calculations.

Chris


----------

