Section 220.83

[Dennis Alwon]

I am not sure I ever looked at this section and it has me baffled.

I am reading this to mean for an existing dwelling where I am adding new loads, I can calculate the service using this method. If that is true then it is one odd duck....

A new home I calculate the optional method and I get a number, lets say 186 amps. Now I add a car charger and no hvac loads added then I use the method given and I don't add the existing hvac system. This can mean I have a 20 kw heat strips that don't get added in but my car charger -say 48 amps- gets added. This means by adding the car charger my calculated load is less than the original home calculation.

Is this correct... If not show me where I am off---please.

220.83 Existing Dwelling Unit. This section shall be permitted
to be used to determine if the existing service or feeder is of
sufficient capacity to serve additional loads. Where the dwelling
unit is served by a 120/240-volt or 208Y/120-volt, 3-wire service,
it shall be permissible to calculate the total load in accordance
with 220.83(A) or (B).
(A) Where Additional Air-Conditioning Equipment or Electric
Space-Heating Equipment Is Not to Be Installed. The following
percentages shall be used for existing and additional new
loads.



Load calculations shall include the following:
(1) General lighting and general-use receptacles at 33 voltamperes/
m2 or 3 volt-amperes/ft2 as determined by
220.12
(2) 1500 volt-amperes for each 2-wire, 20-ampere smallappliance
branch circuit and each laundry branch circuit
covered in 210.11(C)(1) and (C)(2)
(3) The nameplate rating of the following:
a. All appliances that are fastened in place, permanently
connected, or located to be on a specific circuit
b. Ranges, wall-mounted ovens, counter-mounted cooking
units
c. Clothes dryers that are not connected to the laundry
branch circuit specified in item (2)
d. Water heaters

 

[wwhitney]

I share your confusion. Similar threads I started:

220.83(A) Existing Dwelling Unit Load Calculation

Why is 220.83(A) different from 220.83(B)? It seems like when you are adding non-HVAC loads to a dwelling unit, 220.83(A) doesn't break out the A/C and electric space heating loads separately, so they end up lumped in with everything and with a 40% diversity factor. While 220.83(B) does...

forums.mikeholt.com

PI: 220.83

Two more 220 PIs today. I'm a little baffled on this one as to why or how the current wording could be there. So if I'm missing the point somehow and this PI isn't reasonable, please explain. Cheers, Wayne [I'm omitting a bunch of the text that doesn't change.] 220.83 Existing Dwelling...

forums.mikeholt.com

I guess we'll see what the CMP says to my PI.

Cheers, Wayne

 

[Dennis Alwon]

I guess I missed that thread...

 

[Tainted]

And this too has baffled me for a long time. Made several post questioning this.

I think it was intended to be used to squeeze a little more power out of the existing systems where running new power is notoriously invasive and difficult.

I use 220.83 quite frequently because we have people requesting electric clothes dryers in their existing 50-70 amp apartments.

Sometimes the numbers work out if people use the 120V electric dryers.

If AC is not to be added, I just use it towards the 40%