[RE-wrenches] Grid tied PV to subpanel on detached garage?

[Aladdin Solar]

I meant the question largely to be a generic one but I can give you an example:

Buried conductors are 6AWG. No additional grounding conductor exists between the main and detached building. As Brian Mehalic already responded, the 60A subpanel would tough to deal with for inverter sizing. Assume the AC disconnect is required near the main meter and so would have to disconnect all circuits in the subpanel.

So say we put a 50A main breaker in the 60A subpanel to allow a Fronius IG 3.0 (3000 watt) and a string of 12 Sharp ND240s or similar.

The PV ground would have to hit a ground rod at the garage and a grounding conductor would need to be buried back for bonding at the main building--right?
 
  ----- Original Message ----- 
  From: Mark Frye 
  To: RE-wrenches 
  Sent: Wednesday, April 11, 2012 9:25 AM
  Subject: Re: [RE-wrenches] Grid tied PV to subpanel on detached garage?


  1 - What is the AC output rating of the PV inverter?
  2 - What is the size of the feeder conductors?
  3 - Does the sub panel at the garage have a main breaker of it's own?
  4 - Does your AHJ or utility require anAC disconnect or not?

  Mark Frye
  Berkeley Solar Electric Systems



  On 4/11/2012 7:09 AM, Aladdin Solar wrote: 
    Wrenches:

    There's probably an obvious answer but please help me think this through. Here's the situation--comes up all the time: The PV array and grid-tied inverter will be located on a detached building (garage or pole barn, etc.). The existing power to the building is a 240V 60A subpanel connected to the main panelboard at the house or main building via buried cable. If we obey buss bar loading and wire sizing, etc, is there any reason why we can't or shouldn't install the small grid tied PV system and tie it into the garage subpanel instead of trenching new lines back to the house and hit the main panel there? One hitch I see is that if we want a PV system AC disconnect near the main meter, the whole garage would end up on that. Have I overlooked an NEC or inverter requirement?

    Thanks for your comments.

    Charlie Pickard
    Aladdin Solar


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