[RE-wrenches] BAKERSFIELD FIRE

Tue Oct 19 22:10:42 PDT 2010

Ray,

The only inverters sold in the U.S. that have European-style ground-fault
detection circuits in the small size range is Power-One and SMA TL-series.
Perhaps SunPower will have a special version of the SMA TL-series listed to
work with SunPower modules.

Bill.

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of R Ray
Walters
Sent: Tuesday, October 19, 2010 9:42 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] BAKERSFIELD FIRE

Is it possible for us to add this circuit to systems now? Or is this
something that needs to be done by the inverter manus, get UL listing, etc.?

Anything that keeps my kill ratio to zero as an installer is worth
considering. 

I'd even do as you suggested, and retrofit existing larger systems, if it
was within the realm of us wrenches.

Thanks,

Ray

On Oct 19, 2010, at 10:00 PM, Bill Brooks wrote:

Ray,

The reason I mentioned resistively grounded systems is that anything
requires a ground, like SunPower, could use a resistive ground instead of
being ungrounded. This solves SunPower polarization issue and is the way
many of their systems are installed in Europe.

Bill.

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of R Ray
Walters
Sent: Tuesday, October 19, 2010 10:50 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] BAKERSFIELD FIRE former "Target fire"

R. Walters

ray at solarray.com

Solar Engineer

HI Bill;

Where do we sign your petition?

I've advocated for ungrounded systems for over a decade. Besides Europe,
electric vehicles and mobile systems are long standing examples that this is
safe. It also solves IMHO some lightning issues, and is easier to work on
(less accidental short circuits to frames and boxes)

I've done numerous ungrounded systems, and never had any problems. (We still
of course bonded all exposed metal to ground, with EGCs run with the
conductors)

My question is how do Sunpower modules behave ungrounded? I was under the
impression that they had to have positive bonded to ground to function
properly. Your proposed "Temporary Ground Lift" circuit would probably be
the best way for Sunpower modules?

Thanks for your always thorough education of us numb nuts in the field,

Ray Walters

Moving to ungrounded or resistively grounded arrays is relatively easy and
the NEC covers the requirements in 690.35. We already have several
transformerless designs from Power-One and SMA (new TL line in the U.S.),
but there is nothing holding back larger inverters using transformers with
ungrounded arrays. Existing arrays could be made much safer if they were to
be retrofitted with a circuit at the inverter that would lift the grounded
conductor each morning and test for ground faults on the grounded conductor
prior to starting the inverter. While not quite as safe as "European-style"
systems, it is a large improvement over where we are today. Don't be
surprised if things change about how we do GFPs soon. If I have anything to
do with it, it is going to happen. The current hazardous situation, and bad
information about the Bakersfield fire, cannot continue.

Bill.

Bill Brooks, PE

Principal

Brooks Engineering

873 Kells Circle

Vacaville, CA 95688

707-332-0761 (office and mobile)

707-451-7739 (fax)

bill at brooksolar.com (email)

www.brooksolar.com <http://www.brooksolar.com/>  (web)

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