Commercial load calc

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DAWGS

Senior Member
Location
Virginia
Can you guys check this service size for me. I come up with an 800A 120/208 3-phase.

Office lighting 4680 square ft.
Shop lighting 9660 square ft.
(97)General purpose receps
(1)Water heater 5KW
(2) welders 208V 3-phase 117A 60% duty cycle
(1) electric hoist 208V 3-phase 5A
(1) air compressor 208V 3-phase 50A
(2) exhaust fans 832VA each
(2) copiers 1200VA each
(3) treadmills 1800VA each
(1) Heat load 68KW
(1) Condensor 208V 3-phase 60A
(1) Condensor 208V 3-phase 30A
(1) AHU 208V 3-phase 30A
(1) AHU 208V 3-phase 15A

I ommited condensors in my calc because heat load was higher. Thanks.
 
16,380.00
4,830.00
17,460.00
5,000.00
84,299.90
1,801.28
18,012.80
1,664.00
2,400.00
5,400.00
68,000.00
10,807.68
5,403.84
241,459.50 VA

670 Amp, minimum

Keep in mind the motors need to be calced from Table 430.250 not the nameplates. It is safer to calc the actual lighting as well rather than footage. I don't see any kitchen appliances, are there supposed to be any?
 
1a. Lighting load should be calculated based IECC allowance. Check IECC code that applies to your project.

1b. Take the result from 1a x 1.25 --> continuous load.

2. Receptacle load --> First 10kVA @100%, remain kVA @ 50%

3a. HVAC load, Electric Heat load --> Apply non-coincidence load article.

3b. Allow 25% of largest motor load.

4. Misc. + General load --> Calculate at 100%.


* Sum all above load from 1a through 4, convert to Amp. and go to next standard panel/breaker size. This will be your calculated service size.

When the building is occupied, have electrician goes back and meter the load at main service panel, I am sure that real load shall be around 30%-40% your service size even at peak time (-:
 
anbm said:
1b. Take the result from 1a x 1.25 --> continuous load.
Click to expand...

Umm... multiplying by 1.25 is typically an ampacity calculation. Nonetheless, it's rather moot point since you started with a non-NEC-based load value. When sizing a service for NEC compliance, I highly recommend using prescribed NEC methods :D
 
Office Lght 16,380.00
Shop Lght 4,830.00
Air Comp 18,012.80
Sub total 39,222.80
Above Cont @ 125% 49,028.50
Welders 84,299.90
Hoist 1,801.28
Exhausts 1,664.00
Heat 68,000.00
AHU 10,807.68
AHU 5,403.84
Continous 221,005.20

Recept 17,460.00
WH 5,000.00
Copiers 2,400.00
Treadmills 5,400.00
Sub total 30,260.00
First 10k 10,000.00
Remainder @ 50% 10,130.00
Non continuous 20,130.00

VA 241,135.20
Amperes, Minimum 669

I'm tired! I think I had a brain freeze in my previous post.
 
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