Minimum service allowed

[oldsparky52]

Okay, this scenario. A fixed pier with 34 slips and 34 boat lifts. Each lift has (2) 3/4HP motors. No other loads.

Since (2) motors start/stop as one I think you should count each slip at (2*6.9A @230V) 13.8A.

So, 1@1.25% is (13.8*1.25) 17.25A plus (33*13.8)455.4 = 472.65A calculated load.

Well there is no way in the world all of those lifts will operate at the same time. A 500-amp service IS NOT NEEDED for this to safely operate.

What is the minimum service required for this using the NEC?

 

[david luchini]

No need to take 125% of two motors, even if they start/stop at the same time. So 6.9A @ 68.25 = 470.9A.

The minimum service size would be what ever the AHJ would allow, per 430.26.

 

[LarryFine]

I would think 100a is adequate, electrically speaking.

 

[oldsparky52]

I would think 100a is adequate, electrically speaking.

I agree. But ... how do you sell it to the AHJ?

 

[oldsparky52]

I would try to sell it by claiming that you would never see 25% of the lifts being used simultaneously. 25% of 471 is 118-amps. Tell you what, I'll just install a 200-amp service.

Of course I have no scientific basis for pulling 25% out of the air.