[RE-wrenches] Tilt biased....

holtek at sbcglobal.net holtek at sbcglobal.net
Sun Apr 18 08:55:02 PDT 2010


Allan,
According to Unirac tech, the code manual only addresses solid wall structures. He was also the one who told me about the greater windloads on open structures. His suggestion was to get an engineer involved, but on a system this size I am hoping to avoid that additional cost. I did fill out their online design parameter form, so I'm hoping to get enough feedback from that to come up with an over-engineered way to anchor the array to the frame structure of the carport..........
Holt E. Kelly
Holtek Fireplace & Solar Products
500 Jewell Dr.
Waco TX. 76712
254-751-9111
www.holteksolar.com

  ----- Original Message ----- 
  From: Allan Sindelar 
  To: RE-wrenches 
  Sent: Sunday, April 18, 2010 2:17 AM
  Subject: Re: [RE-wrenches] Tilt biased....


  Holt,
  Feedback re the low tilt angle: Go for it, you're good.

  Re wind loading: check out UniRac's Code Compliant Installation Manual, http://www.unirac.com/pdf/ii227.pdf, especially pages 3-9.

  Less wind loading is one of the main reasons for going with a lower tilt angle. Another is closer module row spacing (at 3X height RoT) without inter-row shading.

  No experience with Enphase.
  Allan


  <![endif]--> 
  Allan Sindelar
  Allan at positiveenergysolar.com
  NABCEP Certified Photovoltaic Installer
  EE98J Journeyman Electrician
  Positive Energy, Inc.
  3201 Calle Marie
  Santa Fe, New Mexico 87507
  505 424-1112
  www.positiveenergysolar.com



  holtek at sbcglobal.net wrote: 
    Searching for opinions.....is this "over design"?
    Designing small system (2.35kW). Customer uses gas for heating. Typical A/C unit. I was thinking of biasing the tilt to summer production for greater offset of summer demand (lat 31.6, proposing 18). No net metering in this part of the world. PVwatts shows a drop of 2% /yr. in production , 5% higher production for A/C months. Feedback?

     Also, this array will go on a carport. I understand that windloading is actually greater for an open structure than one with walls (another reason for lower tilt) - is there any one that can direct me to data on finding out how much more? 

    Lastly, what is a good avg. target derate factor for Enphase inverters (real world)?

    Holt E. Kelly
    Holtek Fireplace & Solar Products
    500 Jewell Dr.
    Waco TX. 76712
    254-751-9111
    www.holteksolar.com
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