KWH meter discrepancy [RE-wrenches]

[Kelly Keilwitz]

Hi Jeff & Bob-O,

Thanks for the responses.
All our grid-tie's require utility-grade meters for green-tag sales and,
now, for the WA State production incentive (modeled after Germany's Feed-in
tarif). After thinking about it several of our systems have inverter
metering as well as the utility meter. A GTFX 3048 system we recently
installed also showed more substantially more production on the mate than on
the (form 12S) utility meter. I chalked that up to issues with sorting out
the energy in, out and to the critical loads. But, maybe it's the same "con"
(conspiracy, confusion, confoundedness...?). I'm going to compare a Fronius
5100 output (nice display) with the utility-style production meter on a
recently installed system next week.

I find it difficult to believe that all of our utility- type meters are
inaccurate -- on the low side. Accuracy is what Austin & Hialeah are selling
with the reconditioned meters. What are inverter manu's selling?...

With your confirmation stories I'm satisfied that we didn't goof up somehow
with this meter.

Thanks,
-Kelly


On 5/18/06 5:48 PM, "Jeff Clearwater" <clrwater at earthlink.net> wrote:

> 
> Hi Kelly & Bob-O,
> 
> Yes, Since I install systems in MA sometimes and for all those
> systems we need to install "utility grade" KWH meters for the rebate,
> I too find the inverter's meter running 15-20% higher than  the
> refurbished Austin Instruments meters like those bought through
> AEESolar or EO.
> 
> And come to think of it the ones that were the most off were the 120
> VAC units (SB1800) though the 240 VAC units are off too though by
> varying percentages - usually around 15-20%.
> 
> And that's a major drag as the MA rebate program depends on those KWH
> meters - not the inverters!  So if they are low instead of the
> inverters being high - the folks are not getting their full
> performance portion of the rebate back.
> 
> I recently installed two on some Windy Boys (120 VAC SB1800) and got
> 21% more on the inverters than the meters.
> 
> For now I've stopped installing them - but need an alternative.  They
> are nice in that they are cheap
> 
> Anyone with a solution?
> 
> Best,
> 
> Jeff Clearwater
> Village Power Design
> 
> 
> 
>> Hiya Kelly,
>> It may be the 120V thing on the 240 meter, but in Oregon we are
>> required to put a revenue grade meter in almost every installation.
>> Most are 240V, but some are wired 120V like you have depending on
>> the inverter. I've NEVER seen the meter from the inverter and the
>> revenue grade meter agree regardless of the inverter manu. And
>> -here's the salient part- the inverter meter is always the high one.
>> Uh huh.....
>> Bob-O
>> On May 18, 2006, at 10:02 AM, Kelly Keilwitz wrote:
>> 
>>> 
>>> Wrenches,
>>> 
>>> We recently installed a small PV GT system with a SMA SB700, with display.
>>> We also have a utility style "green tags" meter on the AC output. It's been
>>> running for a couple of months and the SB display is recording 18% higher
>>> energy production than the green tags meter. The green tag meter is a form
>>> 2S, 240-V meter, wired for the 120-V output of the SB700.
>>> 
>>> We've wired 240-V meters for 120V operation before but never had a
>>> (reliable) KWH meter to gauge against. Is the SB display meter reliable? Any
>>> problems with wiring 240V meters for 120V output?

Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
987 Wanamaker Rd, 
Coupeville, WA 98239
PH & FAX 360-678-7131
sunwind at whidbeysunwind.com
 


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