Article 220-31(A) OR (B)

[wmeek]

I have an existing 3,088 sq. ft. residence with a 125A service (also has Gas). Customer has a 20x40 two story garage. First floor is 20x40, and second floor is 14x39. He is wanting to make a game room out of the second floor. He will be adding a central air unit. I was wandering about 220.31. Is it saying to take 3va per square foot of existing building and all your 1500 va small appliance and laundry
loads and all fixed appliances at name plate rating and add these up with the existing ac vs heat at 100 %. Then add all your loads for the addition and ac at 100 %, and then you can take the first 8000va at 100% excluding any ac or heat loads and the remainder at 40% and then add 8000va and all heat and ac loads to see if existing service is capable of handling the new addition. I have never used 220.31 before.
Thanks

 

[e57]

Sounds like you got it? Whats the question?

 

[wmeek]

I guess the question was do you take all existing loads of equipment from house that is fastened in place at name plate amperage plus all SA ckts and Laundry Ckts, and then add all new loads for new part and take off the first 8000va and the rest at 40% and then add all your A/C or Heat loads whichever is the largest at 100% for existing as well as new addition and then divide by 240V to see what size Service is needed to accomondate the new addition.

 

[wmeek]

I guess I am a little confused here. I am using 220.31(B)
In the existing Loads, I have

Ltg/SA/Laundry

3088 x 3 = 9264
1500 x 2 = 3000
1500 x 1 = 1500

Total = 13,764

Fixed appliances

Dryer 5000
Double oven 8800
Dishwasher 1380
Disposal 804
bath exhaust fan 360
Pool Pump Motor 11.2 x 240 x 125% = 3600
Pool Blower 3.8 x 240 x 125% = 1140
Micro and Venthood = 1800
Freezer = 600
AHU 2.3 x 120 = 276

Total = 23,760


A/C vs Heat

A/C 38A x 240 = 9120

Heat (Gas)

Total = 9120
____________________________________________


37,524
- 8,000
________
29,524 x .40
11,810
+ 8,000
+ 9,120 A/C
___________
28,930 / 240 = 120.5A

Added Loads

Ltg. 1600 x 3 = 4800
Bath Exhaust fan = 360
Refrigerator = 1440
Beer Keg Cooler = 1440
Water Heater = 4500
Air compressor 15A x 240 = 3600
_________
Total 16,140

A/C vs Heat

A/C 22A x 240 = 5280
Heat 5kw = 5000
Total 5280


16,140
+ 5280
_____________
Total 21,420

Do you add the calculated existing loads per 220.31(B) to the new loads(100%) and divide by 240 to see if existing service is large enough. I appreciate all the help. I just have not dealt with this section before.