Grid-Tie Stumper (for me) [RE-wrenches]

Tue Apr 15 15:42:28 PDT 2003

Bill, Jeff, Chris and Mo,

I tried sending a reply regarding this but the List wouldn't accept the mail
the other day. Anyway, I suspect that Bill's comment is the closest to the
actual problem; a ground connection situation. We did a 3 phase, 4 SB2500U
SBDs with a mechanical meter at the output, that was behaving exactly the
same way. In our case, the mechanical meter was spinning like a top (it's a
10 k system using 72 Sharp 165's), but the utility TOU meter was going a lot
slower.

When the sun went down was when the big fun started. The customer called to
inform me that the meter was showing about a 4.1 kW load in the middle of
the night WITH NOTHING ON. I called the electrician who had done the hook-up
and we went out to the site to check the problem. All the SB's were
operating properly and were extremely close to each other in their
respective read-outs. There were no faults of any kind (according to the
inverters!)

We (me actually) discovered that one of the phases had been connected
(inadvertently of course) to a neutral/grounded buss at the AC disconnect.
Since SBs will still power-up with one leg going to ground (!), all the
power from that one phase was going right to earth without blowing any of
the numerous breakers in the system. Pretty weird. When the sun was absent
from the mix, the grid took over and thought it was running a nice big load,
hence, big electric bill for one billing cycle.

The problem was corrected and the system has been pumping out (it mainly
runs pumps) over it's rated power virtually every day the sun's been out.
The moral of this story is that it's better to work when you can actually
see what color phase tape is on the end of those wires. The electrician
turned several shades of red and white when he saw what had happened.

Matt T
----- Original Message -----
From: "Bill Brooks" <billb at endecon.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, April 15, 2003 2:56 PM
Subject: : Re: Grid-Tie Stumper (for me) [RE-wrenches]

> Jeff, Chris, and Mo,
>
> These pulse meters as they are called are not used very often in
residential
> applications in California so I am skeptical that this is the problem.
>
> The first grid-tied system I did over 12 years ago had a pulse meter, and
> the utility came out immediately and started asking questions. The pulses
> were way above normal and the register on dial face was way off from the
> pulse counter. The counter would in fact get to the registration point and
> go back and forth and add pulses out the wazoo.
>
> The strange thing about Mo's situation is that the PV system was turned
off
> and the bill went way up. That could happen with a pulse meter, but it is
> more likely that the home is using way more power than previously.
>
> First check the ground wires for current, then check for new loads. Sounds
> like these folks have changed their consumption and don't realize it. This
> is a very common problem with PV installations. It is always a key part of
> the education for an off-grid customer, but is often overlooked for
on-grid
> customers--but just as important.
>
> Without a meter measuring the PV output--you are totally sunk. All
electric
> bill problems suddenly become the fault of the PV system--happens all the
> time.
>
> Bill.
>
>
> -----Original Message-----
> From: Jeff Clearwater [mailto:clrwater at earthlink.net]
> Sent: Tuesday, April 15, 2003 2:31 PM
> To: RE-wrenches at topica.com
> Subject: Re: Grid-Tie Stumper (for me) [RE-wrenches]
>
>
> Exactly.
>
> and it was Chris F. not Bill that noted the following:  My
> observations and his post is what is leading me to conclude this -
> anybody else who can confirm this info?
>
> At 2:51 AM +0000 4/15/03, Christopher Freitas  -  OutBack Power wrote:
> >Some of the electronic KWH meters only count when a hole in the rotating
> >disk passes by a sensor - it does not know (or care about)the direction
> >the power is flowing.  There also are some add on data logging systems
> >for KWH meters which use this method as well.
> >
> >I also have wondered what this type of meters would do if it happened to
> >stop in just the right position and a pair of SW inverter/charger are
> >doing their "jitter bug" routine when they are trying to float the
> >battery but not sell back current. Could be interesting...
>
>
>
> >Hi Jeff,
> >
> >So you are saying that the numbers might be different from what the
> >mechanical part of the meter says from what the electronic part says?
> >
> >ie, that the the mechanical might read correctly ( count down) but the
> >electronic would only count up?
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Jeff Clearwater
> Village Power Design Associates
> Sustainable Energy & Water Solutions for Home & Village
>
> Office:  (413) 256-6777,  Cell: (720)480-8455
> Fax:  (413) 825-0372
> 61 Baker Road
> Shutesbury, MA 01072;
> PO Box 764
> Boonville, CA  95415
> (707) 895-9015
> Fax: (707) 897-0224
>
> Council Member - Ecovillage Network of the Americas -
> http://www.ecovillage.org
> Advisory Board - Living Routes - Ecovillage Education -
> http://www.livingroutes.org
> Founder:  Ecovillage Research, Development, and Demonstration Program:
> http://www.home.earthlink.net/~clrwater/RDD/rdd.html
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
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