Dwelling Load Calculation

[BatmanisWatching1987]

Each dwelling unit is about 815 square feet with 20 Apartment.

All appliances will be Electric.

When doing the Load Calculation for the Electric Range (8kW), can I use the Table 220.55 (Demand Factors and Loads for Household Electric Range) of 80% for each unit.

Please let me know if I miss calculated my Load Calculation for all 20 Apartments.

 

[augie47]

220.55 is in Part III and your calculations appear to be Part IV, Optional. The two don't mix as best I know.

 

[BatmanisWatching1987]

220.55 is in Part III and your calculations appear to be Part IV, Optional. The two don't mix as best I know.

If I use Part IV Load Calculation, I would need to show the Range as 8kW.

But if I want to use Part III Load Calculation, what calculation I'm I doing incorrectly since I was following example in Annex D.

 

[Dennis Alwon]

First off the dishwasher does not go in the upper calculation-- you use sq. ft x 3, small appliance branch circuit 1500 va each and the laundry at 1500 if there is one

Add them up and then do the 3000 @ 100% etc.

Table 220.55 says to use 35kw for 20 ranges or you can use Col. B at 28%. The 35 kw is smaller...
Also look at 220.53 and your dishwashers can be at 75%

This is for standard calculation

You have both types of calculation but you seem to be mixing them

 

[Designer69]

if you size your service at 600A for 208 3/ph it will be too small for a 20Unit all electric.

Your calculations should come out to a number that will make your service size closer to 1200A

 

[BatmanisWatching1987]

First off the dishwasher does not go in the upper calculation-- you use sq. ft x 3, small appliance branch circuit 1500 va each and the laundry at 1500 if there is one

Add them up and then do the 3000 @ 100% etc.

Table 220.55 says to use 35kw for 20 ranges or you can use Col. B at 28%. The 35 kw is smaller...
Also look at 220.53 and your dishwashers can be at 75%

This is for standard calculation

You have both types of calculation but you seem to be mixing them

Not sure how you got 35kW. Since 8kW * 28% * 20 will equal to 44,800.

Thanks for the tip for Section 220.53

if you size your service at 600A for 208 3/ph it will be too small for a 20Unit all electric.

Your calculations should come out to a number that will make your service size closer to 1200A

Any chance you can explain why the service should be at 1200A?

 

[Dennis Alwon]

Look at column C

 

[david luchini]

If I use Part IV Load Calculation, I would need to show the Range as 8kW.

For the Part IV load calculation, you have to use the nameplate rating of the range.

 

[david luchini]

For a three phase service, the standard calculation Range Demand would be 43.5kW.

 

[dkidd]

First off the dishwasher does not go in the upper calculation-- you use sq. ft x 3, small appliance branch circuit 1500 va each and the laundry at 1500 if there is one

I'm pretty sure that it does. See Example D2(a)

 

[david luchini]

I'm pretty sure that it does. See Example D2(a)

Example D2(a) is using the optional calculation from 220.82.

The OP is doing the standard calculation. Dennis is correct, a dishwasher would not be included in the standard calculations lighting load demand.

 

[dkidd]

Example D2(a) is using the optional calculation from 220.82.

The OP is doing the standard calculation. Dennis is correct, a dishwasher would not be included in the standard calculations lighting load demand.

Dennis seems to say that the dishwasher is included in the lighting demand load:

"First off the dishwasher does not go in the upper calculation-- you use sq. ft x 3, small appliance branch circuit 1500 va each and the laundry at 1500 if there is one"

 

[david luchini]

Any chance you can explain why the service should be at 1200A?

I think 600A is in the right neighborhood, with the load values you have given.

 

[david luchini]

Dennis seems to say that the dishwasher is included in the lighting demand load:

"First off the dishwasher does not go in the upper calculation-- you use sq. ft x 3, small appliance branch circuit 1500 va each and the laundry at 1500 if there is one"

Dennis is saying the dishwasher do not get included in the lighting demand load.

Also look at 220.53 and your dishwashers can be at 75%

He is saying the dishwashers can be included in the appliance demand load.

 

[BatmanisWatching1987]

For a three phase service, the standard calculation Range Demand would be 43.5kW.

Could you please clarify how you come up with 43.5kW?

Since I got (8kW * 20) * .28 = 44.8kW.

Also look at 220.53 and your dishwashers can be at 75%

In section 220.53, it states, "Four or more appliances fastened in place..."
So if we are doing a load calculation for just 1 dwelling unit, then I can't use the 75%. So would I add the load with the Appliances.
But if we consider all 20 Apartments, then we can use the 75% demand factor.

 

[david luchini]

Could you please clarify how you come up with 43.5kW?

Since I got (8kW * 20) * .28 = 44.8kW.

220.55 says that for a three phase service the range demand shall be based on twice the number of ranges connected between any two phases.

There would be 7 ranges between any two phases, so select the demand load from column C for 14 ranges. Then multiply that value by 1.5 to get the equivalent three phase demand.

 

[Dennis Alwon]

Dennis is saying the dishwasher do not get included in the lighting demand load.



He is saying the dishwashers can be included in the appliance demand load.

Correct that is what I was saying

 

[BatmanisWatching1987]

220.55 says that for a three phase service the range demand shall be based on twice the number of ranges connected between any two phases.

There would be 7 ranges between any two phases, so select the demand load from column C for 14 ranges. Then multiply that value by 1.5 to get the equivalent three phase demand.

Thanks for the explanation.

I updated the Single and Three Phase Incoming Electrical Service based on everyone comments I received. Hopefully I correctly updated the incoming Standard Calculation.

I also notice, I was using Table 220.84 for doing the Standard Calculation which should only be used for the Optional Load Calculation. I will update the Optional Load Calculation Later.

Here were my results
For Single Phase 120/208V, I got I got an incoming service of 2,133 Amps.
For Three Phase 120/208V, I got I got an incoming service of 1,229 Amps.

Note for Single Phase, I used the load of 44.8kW, I know you can use 35kW based on Table 220.55.

 

[david luchini]

I updated the Single and Three Phase Incoming Electrical Service based on everyone comments I received. Hopefully I correctly updated the incoming Standard Calculation.

I also notice, I was using Table 220.84 for doing the Standard Calculation which should only be used for the Optional Load Calculation. I will update the Optional Load Calculation Later.

For both calculations, a 75% demand factor can be applied to the dishwashers and water heaters.

 

[BatmanisWatching1987]

For both calculations, a 75% demand factor can be applied to the dishwashers and water heaters.

According to 220.53, "It shall be permissible to apply a demand factor of 75 percent tothe nameplate rating load of four or more appliances fastened in place, other than electric ranges, clothes
dryers, space-heating equipment, or air-conditioning equipment, that are served by the same feeder or
service in a one-family, two-family, or multifamily dwelling."

I don't have more than 4 or more appliances for 1 Apartment.

But I guess your saying, I can take 75% off for the total calculation for all 20 Apartments.