[RE-wrenches] Rooftop wiring methods between multiple subarrays

[August Goers]

William -

I agree with you about a no-shortcuts and full workmanship plan of attack. That is how we will all stay in business and continue to make local scale PV a success. However, when we dissect the details of running between multiple array sections I still don't see a good solution. I'm glad to use EMT or aluminum or stainless conduit but there are several code questionable violations which we must address. If we're using a metal raceway we need to address bonding. How do we bond both ends of the conduit? How do we run our ground wire through this raceway? Is it okay if the copper wire touches the conduit? How do we bond the conduit to actually meet NEC requirements? I'm starting to think that the NEC doesn't have the answers...

-August


From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of William Miller
Sent: Friday, October 09, 2009 5:31 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Rooftop wiring methods between multiple subarrays

Colleagues:

I think the correct answer is: there are no short cuts to good workmanship.  It requires intelligent design, a judicious selection of materials and careful installation.  EMT is appropriate in low corrosion environments, PVC if you can control UV damage and accommodate expansion.  There are aluminum and stainless conduits for the extreme environments and demanding aesthetics.  I am sorry that there are no easy ways to pursue quality.

It is my understanding that the European model is to "plug and pray" with quick connect cables, running them across roof tops and stapling them to exterior walls.  I don't know this for a fact, but if it is true, I hope that market does not drive the US market towards reduced standards.  I belive it is short sighted to skimp on wiring methods with dangerous power feeds.  I think the loss of conduit boxes on modules is a direct result of European installation techniques and a trend towards reducing labor costs.  I welcome information from those of you with experience in other markets to verify these hunches.

William Miller



At 04:21 PM 10/9/2009, you wrote:

EMT needs to be "pickled"  with vinegar or acid, to get the paint to hold. I love it for inland work, but near the ocean, it'll rust through in 5 years. I'm not sure how much more time paint would buy you.
Anybody use other plastic materials HDPE? Supposed to not have the expansion problems of PVC.


R. Walters
ray at solarray.com<mailto:ray at solarray.com>
Solar Engineer




If you have to run around the roof with EMT, you can protect it from rust
with a coat of paint.

Regards,
-Hans

Please note new e-mail address and domain:

William Miller
Miller Solar
Voice :805-438-5600     Fax: 805-438-4607
email: william at millersolar.com
http://millersolar.com
<http://millersolar.com/>License No. C-10-773985
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