KWH meter discrepancy [RE-wrenches]

[Kirk Herander]

Another thing:

I believe the mechanical KWH meter is a small phantom load on the
utility, and perhaps the Sunny Boy consumes a small amount of AC at
night. If I detented meter were used, preventing a turn back of the
meter, it would be more accurate, although as much as 20% is a lot of
discrepancy. 

Kirk Herander
Vermont Solar Engineering
802.863.1202
fax 802.863-7908
NABCEP(tm) Certified Solar PV Installer
Xantrex Certified Dealer Charter Member
NYSERDA-eligible installer
VT Solar and Wind Partner


-----Original Message-----
From: Mark Byington [mailto:sales at cobaltpower.com] 
Sent: Monday, May 22, 2006 10:32 AM
To: RE-wrenches at topica.com
Subject: RE: KWH meter discrepancy [RE-wrenches]



We have also observed cyclometer KWH meters reading typically 2 to 10%
below the cumulative inverter readings.

Here's some anecdotal evidence that I saw with my own eyes - not
indicative of every case of course, but probably somewhat typical of
mechanical type meters.

About 2 years ago I was looking at the PV system on my own house, which
has 2 SMA 2500's with display and a GE I70S mechanical meter with
cyclometer readout.  It was early evening and the inverters were putting
out about 120 watts total, but the KWH meter was dead stopped.  I rapped
on the glass bell housing of the meter with my knuckles, and the meter
started moving slowly.

I tend to trust the solid state inverter readout more than the
mechanical KWH meter.

Mark
Cobalt Power Systems, Inc.



[Non-text portions of this message have been removed]


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