[RE-wrenches] Positive-ground question re Sunpower

[Glenn Burt]

It has been my experience that if Sunpower modules are installed contrary to
their manufacturer recommended positive ground configuration, that in a
short time you will only be generating a few watts. I have seen this in more
than one instance when the array was mis-wired and the negative was the
grounded conductor.

 

Fortunately reversing the wiring allows the static charge to bleed of in a
couple of weeks, and the strings returned to their expected production
values.

 

I would recommend against trying to use them intentionally in this fashion.

 

-Glenn

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan
Sindelar
Sent: Friday, November 19, 2010 10:08 AM
To: RE-wrenches
Subject: [RE-wrenches] Positive-ground question re Sunpower

 

Wrenches:
This has been addressed before in a slightly different context, so a short
answer is enough. Can a Sunpower module be used successfully in a
negative-grounded low-voltage system?

The situation: Mark in our Taos office sent me the following: "We have an
old time friend and customer. [John] and his wife used to help us on various
installations years ago. They're both retired now and living on fixed
limited income. About two months ago, we sold them a replacement battery
bank of golf carts. They have a  small off grid system with a few hundred
watts of PV. Recently, [John's wife] was put on an oxygen machine for a
heart condition. The machine consumes somewhere around 800 Watt-hours per
day. Their system can't keep up now without running the generator most every
day. I was wondering about a couple blem/cosmetic damaged panels that PosE
has at their shop in Santa Fe. I'm not sure yet whether the best solution
would be to upgrade their existing system, or perhaps a separate system for
the O2 machine. Either way, if there is a way to help them with the
equipment, then I'd be happy to donate my time to help [John] do an upgrade.
If there is some way we can help them out, it would be a good thing. They're
just a couple of really good people who've helped a lot of others out in
their lifetime. Now they're the ones in need, and I'm just trying to find a
way to help them."

We have two Sunpower 215s with cosmetic damage that can't be sold. I think
that one or both can be used here, but are just somewhat less efficient if
negative grounded. 

What's the straight scoop here, please?
Thanks,
Allan

 <mailto:Allan at positiveenergysolar.com> 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 <http://www.positiveenergysolar.com/> 

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