Optional Method

[FVC]

Does this appear to be correct? Im concerned about how to apply to large load I have for the driveway snow melt system.

Here is my optional load calculation. I'm including the (2) HVAC condensor units.

2,880w (ACCU 1)
3,360w (ACCU 2)
1,200w (AHU 1)
1,200w (AHU 2)
8,640w (total AC)

AC vs. Heat (oil furnace with hot water baseboard, AC's a much larger load)

54,676w (including driveway snow melt, nameplate of all appliances, 3w per sq ft, (2) small appliance ckt, laundry ckt)

Table 220-30

100% of the nameplate rating(s) of the air conditioning = 8,640 watts
100% of the first 10kVA of all other loads = 10,000 watts
40% of the remainder of all other loads = 17,870 watts
TOTAL OPTIONAL LOAD 36,510 watts

Article 220-2

TOTAL OPTIONAL LOAD 36,510 watts DIVIDED BY 240 VOLTS = 152.125 AMPS

Therefor a 200A single phase service would be okay to accommodate these loads.

 

[Dennis Alwon]

I didn't check the math but that looks correct to me :thumbsup:

 

[Dennis Alwon]

Although art. 220.60 is for noncoincident loads but is only listed in the standard method it would appear to me that it could be used in the optional method as well. IMO, you may have been correct in the other thread about using the heat for the driveway and eliminating the a/c load. That makes total sense.

 

[jumper]

How is this driveway snow melt system controlled?

 

[Julius Right]

It is probably an old edition of NEC since in 2011 Edition nor Table 220-30 neither art.220.2 exists. In this edition- in the following article- is stated:
220.83 Existing Dwelling Unit.
(B) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is to Be Installed.
The following percentages shall be used for existing and additional new loads. The larger connected load of airconditioning or space-heating, BUT NOT BOTH, shall be used.

 

[jumper]

It is probably an old edition of NEC ...

Looks like 1999 to me. IIRC that was the last edition to use dashes instead of dots.