Hello Holt:
First make sure you estimate your time and materials and get paid 100% for the work you do. In other words dont count on any follow on work. Then, (a) Figure out where the inverter is going to go. Plan for the inverter, disco, production meter, subpanel (if any). (b) Stub out a ¾ (or 1) nipple at the appropriate point on the wall, put a pull box in the wall space. (c) From the pull box, run either metal flex (empty flexible metal conduit) or MC cable (prewired cable) to the attic and the point of roof penetration. (d) Penetrate the roof and put another pull box and nipple (or appropriate length of rigid conduit) at this point; and of course do a good job of flashing in the penetration. (e) If you used MC cable, strip enough of the clad off to leave ample wire at both ends for what you want to do there. (f) Mark the cable/conduit run with peel and stick labels that say Solar or Danger Solar or Danger Solar 600 Vdc). I am pretty generous with these labels, using them every 10 on long runs in the attic and every 6 in walls. (g) You will also need to provide a means of disconnection on the roof before penetration. You can use a DC-rated disconnect (my choice) but I have heard that touch-safe fuses or circuit breakers serve as adequate means of disconnection. Does anyone else know something definitive? If you use a disco, you should NOT need to provide over-current protection if you size you wire according to code and have a letter from the inverter manufacturer stating that the inverter cannot back-feed the PV array. Personally, I like MC cable, as it comes pre-wired with 2 current carrying conductors plus a ground (e.g. MC10-2, for AWG-10) or 4 current carrying conductors plus a ground (e.g. MC10-4 for AWG-10). Since it is pre-wired, the resulting diameters are impressively small. There are special connectors for MC. There seems to be a distinction between MC being cable and MF being a raceway, and possibly MC cable not being allowed by the AHJ. I get pre-approval for MC before I start from the planning department, use the protection plates wherever an errant nail or sheet rock screw could do damage, and use lots of labels. Inspectors are usually impressed with these pre-cautions and I have never had a problem. Oh, two other things. When I do use MF, I like to pre-wire it using a long level space (like a driveway). It a whole lot easier to pull the wire than after it is in place. I guess that there is a limit to the number of bends one can make in MF before putting in a pull box (its conduit after all). Good luck. - Peter Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 CA Lic. 854779, NABCEP Cert. 031806-26 [email protected] _____ From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Saturday, February 07, 2009 7:35 AM To: RE-wrenches Subject: [RE-wrenches] Solar Ready remodel Wrenches, I am working with a client that is doing major remodeling on a recently purchased house. His budget is not allowing PV at this time, but he is very serious about adding it when he sells other property. I am suggesting that we make the house "solar ready" for such a time. I'm thinking to run oversized conduit to dedicated solar equipment room making wire runs easier when that time comes around. It is unclear as to the size of system budget will allow at future date (roof will accomodate approx. 9kw). Are there any further steps that are suggested while the walls are open to make a future install as economical as possible? Holt E. Kelly Holtek Fireplace & Solar Products 500 Jewell Dr. Waco TX. 76712 254-751-9111 www.holteksolar.com
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