# Residential calculation questions



## Dennis Alwon (May 9, 2009)

First off are you using the standard or optional calculation?

1. I agree that the basement wouldn't count as it would not be declared habitable space,

2. Yes the gas furnace is separate and a/c as well-- the greater of the 2 would be used 

3. I would use 5000 watts but to be safe you can use 6000 watt

4. You do not count the refrigerator.


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## mburtis (Sep 1, 2018)

Thanks for the input. For this go around I am doing the standard method. I'll try the optional method and see what that works out to. 

So for the gas furnace what number do I use? The fla of the blower motor? The furnace itself has a sticker saying 12.1 amps max but no nameplate rating for the motors that's visible. 

Forgot to mention, there is no built in microwave, just a counter top unit. So I included that in the small appliance circuit even though it's wired to a receptacle on a future dedicated circuit. Is this right? 

I also just remembered I forgot the range hood. That I assume is seperate from the small appliance circuits and would be based on the motor load or a nameplate rating?


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## kb1jb1 (Nov 11, 2017)

Laundry 1500 watts. Garage 20 amp circuit for EV, 1500 watts.


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## wiz1997 (Mar 30, 2021)

There are examples of load calculations in the back of the NEC book.


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## mburtis (Sep 1, 2018)

I've been going through the examples. All most all of them include electric heat and air conditioning. That's why I wasn't sure about the gas central heat.


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## mburtis (Sep 1, 2018)

kb1jb1 said:


> Laundry 1500 watts. Garage 20 amp circuit for EV, 1500 watts.


I've been using a 2017 book since my 2020 book is at work. I'm aware of a requirement to install at least 1 luminare and 1 receptacle per bay in a garage that has power. These are allowed to be accounted for in the general lighting load. Did that change in 2020 with a seperate circuit calculation for EV?


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## kb1jb1 (Nov 11, 2017)

mburtis said:


> I've been using a 2017 book since my 2020 book is at work. I'm aware of a requirement to install at least 1 luminare and 1 receptacle per bay in a garage that has power. These are allowed to be accounted for in the general lighting load. Did that change in 2020 with a seperate circuit calculation for EV?


I believe a dedicated 20 amp circuit for the garage was added. It use to be either a 15 or a 20 amp but now it is a 20 amp. We are also still on the 2017 NEC.


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## wiz1997 (Mar 30, 2021)

mburtis said:


> So for the gas furnace what number do I use? The fla of the blower motor? The furnace itself has a sticker saying 12.1 amps max but no nameplate rating for the motors that's visible.


Is there an air conditioning unit?

If there is, you'll need to compare the AC load to the heater load, then use the larger of the two but not both.

They are typically not on at the same time.

Something I was taught during a Master's exam class, was to add 25% for the largest motor.

Which could be any motor from the AC compressor, to the garbage disposal.


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