wind generators

[bvb]

We are trying to figure out whether a 57vac input would be considered as/fall under a service entrance or feeder calculation for direct burial using USE #6 in conduit (for voltage drop). Section 300-5 exception #3 lists a feeder circuit being permitted at 12" depth with less than 15 amps and less than 300vac, which is the case for these wind units at voltage listed above. At This voltage does this even qualify as a service entrance? The unit is 3-phase AC at 57vac max. The unit than goes to a 3 pole disconnect just inside the building.

 

[George Stolz]

Re: wind generators

Originally posted by bvb:
We are trying to figure out whether a 57vac input would be considered as/fall under a service entrance or feeder calculation for direct burial using USE #6 in conduit (for voltage drop).

Are you still under the '99 NEC? In general, at least by the '02 and '05, these conductors are not considered service conductors, according to Article 690.

Section 300-5 exception #3 lists a feeder circuit being permitted at 12" depth with less than 15 amps and less than 300vac, which is the case for these wind units at voltage listed above. At This voltage does this even qualify as a service entrance? The unit is 3-phase AC at 57vac max.

Are you looking to go shallower than 24"? Why?

The unit than goes to a 3 pole disconnect just inside the building.

3 poles? There isn't just a positive and a negative?

2002 690.14(C)(1) requires the disconnect to be outside, or inside nearest the entrance of the conductors.

 

[bvb]

Re: wind generators

Thanks, I had not looked in the section noted...the wind gen disconnect is just inside behind the jct. box and we cannot reasonably get the conduit deeper than 12-18" because of rock. This 3-wire circuit is just 3 leads from the wind gen. No ground because the units are 290; from the building and they are grounded seperately. Unless this is not correct...we have always grounded at the units if they are more than 50 feet from the main single ground point. A very long ground wire would be useless in case of ground fault or lightning.

 

[George Stolz]

Re: wind generators

Originally posted by bvb:
[QB] Thanks, I had not looked in the section noted...the wind gen disconnect is just inside behind the jct. box and we cannot reasonably get the conduit deeper than 12-18" because of rock.

How about 12" in PVC under 2" of concrete? Column 3, Table 300.5

A very long ground wire would be useless in case of ground fault or lightning.

Do you have a fault current path back to the generators?

I still don't get the three poles. Two hots and a neutral?

 

[al hildenbrand]

Re: wind generators

George,

The unit is 3-phase AC at 57vac max

Three pole, one for each phase. It sounds like that's why there is a three pole disco.