Demand Factors for Three or More Multifamily Dwelling Units???????

[AWinston]

I am doing a design on a 27 unit apartment complex. There are 6 separate buildings with 2-6 units in each. All cooking appliances are gas and I am trying to apply the demand factors in Table 220.84. If I am reading the exceptions correctly, am I only able to use the demand factors in this table if I throw in a 216kw (8kw x 27 units) simulated load for electric cooking? Can I use the microwave as the "electric cooking"? The other exceptions are already satisfied.

Right now the apartment complex's load is at 1642.8A without applying any demand factors. If I were able to use the microwave as the "electric cooking", that drops down significantly if I am able to use the demand factors.

 

[Smart $]

While Code doesn't specify what is and isn't considered electric cooking equipment, I believe it must meet the terms set forth in 220.55. So unless you have microwaves over 1750W, you either cannot use 220.84 or you have to include a phantom 8kW per dwelling unit.

 

[AWinston]

Thanks! I'll just set the microwaves to 1751w.

 

[AWinston]

While Code doesn't specify what is and isn't considered electric cooking equipment, I believe it must meet the terms set forth in 220.55. So unless you have microwaves over 1750W, you either cannot use 220.84 or you have to include a phantom 8kW per dwelling unit.

I spoke with a plan checker I know and he sent me this response. I also spoke with another engineer (my mentor) and he stated that using a microwave as the "fake" cooking appliance doesn't allow the facility to upgrade to actual electric cooking equipment (stoves, ovens etc) in the future.

"I looked in an old trade magazine for this very topic. The reason the Code requires a “Fake” load at 8 kW is to allow a future installation of the then-new electric cooktops.

Replacing that fake load with a required-to-be-included load for the microwave, would not meet that goal. IMO microwaves (microwave-ovens) are small appliances and not cooking equipment. Toaster-ovens have a similar name, as do Dutch-ovens. None are electrical cooking equipment. Nor are they ovens. By definition ovens are heated. Microwaves instead heat the food – not the oven.

Since the underlying reason is not listed in the adopted Code, that might give the local AHJ an opportunity to agree or deny. I would deny.

My reason for denial is one that one cannot mix the Part III Calculations (required / normal) method, with the Part IV Optional method. Picking from both as convenient is not allowed unless Code text specifically says it is. As in that 220.84 section; If the calculation under Part III exceeds the Part IV calculation (including the 8 kW adder) then the lowest of the two may be used.

I may have mentioned this already but always remember: Article 100 is Definitions. Every Code cycle, I scour the text to see if Common Sense made it in the new edition. No joy so far.

Hope this is helpful."
​

 

[lielec11]

I spoke with a plan checker I know and he sent me this response. I also spoke with another engineer (my mentor) and he stated that using a microwave as the "fake" cooking appliance doesn't allow the facility to upgrade to actual electric cooking equipment (stoves, ovens etc) in the future.

"I looked in an old trade magazine for this very topic. The reason the Code requires a “Fake” load at 8 kW is to allow a future installation of the then-new electric cooktops.

Replacing that fake load with a required-to-be-included load for the microwave, would not meet that goal. IMO microwaves (microwave-ovens) are small appliances and not cooking equipment. Toaster-ovens have a similar name, as do Dutch-ovens. None are electrical cooking equipment. Nor are they ovens. By definition ovens are heated. Microwaves instead heat the food – not the oven.

Since the underlying reason is not listed in the adopted Code, that might give the local AHJ an opportunity to agree or deny. I would deny.

My reason for denial is one that one cannot mix the Part III Calculations (required / normal) method, with the Part IV Optional method. Picking from both as convenient is not allowed unless Code text specifically says it is. As in that 220.84 section; If the calculation under Part III exceeds the Part IV calculation (including the 8 kW adder) then the lowest of the two may be used.

I may have mentioned this already but always remember: Article 100 is Definitions. Every Code cycle, I scour the text to see if Common Sense made it in the new edition. No joy so far.

Hope this is helpful."
​

You got it right there... Even if the entire building uses their microwaves exclusively for cooking the AHJ won't care. You need to add the 8k for a simulated electric range.

 

[AWinston]

You got it right there... Even if the entire building uses their microwaves exclusively for cooking the AHJ won't care. You need to add the 8k for a simulated electric range.

In my case, when I ran the calculations the total load came to 867kVA (Simulated load) vs 669kVA. I went with the smaller value.