Grid-Tie Stumper (for me) [RE-wrenches]
Jeff Clearwater
clrwater at earthlink.net
Tue Apr 15 17:46:39 PDT 2003
<x-flowed>
Matt,
I hope you and Bill are right because this kind of problem is
fixable. The deceptive meter scenario is a pain and a half for all
the hassles it presents!
So I'll look forward to hearing from Mo what the culprit really is,
but this has alerted me and I'm sure a few others to the technical
challanges contributing to the already thick net metering/sell back
issue.
And to watch for hots to neutral on SBs ! -assuming that this would
either smoke or simply not work (like I might have assumed) is -
like any other assumption - a poor assumption to make for an
electrician!
Thanks for all the good lessons on this thread.
jc
>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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