marina calculations

[goldy09]

If individual sub meters are to be provided for each slip, do I still use table 555.12 note 2 after rec. demand factors?

Example: 20 20amp 120v recs. each on it's own sub meter. 1 rec. for each slip. 120/240v. service.

20rec. x 20A. x 120v.= 48,000va
48,000 x .70= 33,600va.?????
33,600/240v.= 140a.
140a. x .9= 126a.?????

 

[charlie b]

Re: marina calculations

Yes. I agree with your interpretation and with your math.

 

[bphgravity]

Re: marina calculations

I've seen this done is a slightly different way by taking the demand on each line of a 240V system.

Ex. 20 - 20A 125V receptacles

Line 1 = 10 - 20A receptacles
Line 2 = 10 - 20A receptacles

10 x 20A = 200A x .8 = 160A x .9 = 144A

This provides a slightly higher demand, however may compliment the FPN.

 

[hardworkingstiff]

Re: marina calculations

I've not seen any boats that use 20-amp receptacles. Most are either 1-30, 2-30, 1-50, 2-50, 1-100, 2-100, 1-100 3-phase, 2-100 3-phase.

 

[charlie b]

Re: marina calculations

Originally posted by hardworkingstiff: I've not seen any boats that use 20-amp receptacles.

Good point. I was only looking at the math. I forgot that the NEC no longer allows a marina's receptacle to be rated below 30 amps. Reference 555.19(A)(4).

Aside to Bryan: That is certainly an allowable method, but it is not a required method.