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#### guitarboyled

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##### Banned
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188 Posts
Discussion Starter · ·
Please tell me if any of my calculation is off

These are the loads in a 120/208V panel board

Phase A : 15 800 W
Phase B : 15 200 W
Phase C : 16 400 W

I take the highest value for calculation purpose

16 400 W x 3 = 49 200 W / 0.80 (Power Factor) = 61 500 VA

61 500 VA / (208V x 1.732) = 170.7A

The wire has to be derated therefore, 170.7A x 1.25 = 213.4A

According to CEC (I presume it’s the same with the NEC) I need 0000 AWG wire

Would you use a 200A disconnect with 200A fuses

or

A 400A disconnect with 225A fuses?

#### BlackHowling

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##### Senior Member
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507 Posts
What is this disco for? Just the secondary conductors before they hit the panel?

#### guitarboyled

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##### Banned
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188 Posts
Discussion Starter · ·
What is this disco for? Just the secondary conductors before they hit the panel?

Yes it is

#### HARRY305E

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##### Registered
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413 Posts
Please tell me if any of my calculation is off

These are the loads in a 120/208V panel board

Phase A : 15 800 W
Phase B : 15 200 W
Phase C : 16 400 W

I take the highest value for calculation purpose

16 400 W x 3 = 49 200 W / 0.80 (Power Factor) = 61 500 VA

61 500 VA / (208V x 1.732) = 170.7A

The wire has to be derated therefore, 170.7A x 1.25 = 213.4A

According to CEC (I presume it’s the same with the NEC) I need 0000 AWG wire

Would you use a 200A disconnect with 200A fuses

or

A 400A disconnect with 225A fuses?
If you're derating the wire your number should be lower not higher.

I would use a 200 amp disconnect amusing you're using 4/0 al...

#### oldtimer

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##### Electric Al
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4,823 Posts
Why.

If you're derating the wire your number should be lower not higher.

I would use a 200 amp disconnect amusing you're using 4/0 al...

Why is the disconnect amusing ?

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413 Posts
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