kwh meter workaround (started as ratcheting cyclometers) [RE-wrenches]

[Kelly Keilwitz]

Wrenches,
We installed a form 2S (240-V), 4-tab, NON-ratcheting meter today, as
described by Geoff below, for a grid-tied, battery backup situation. The
meter is a reconditioned Schlumberger. The inverter is a single FX 2548 -
we're waiting for the GT upgrade. The single backup subpanel load is an
Outback X240 boost transformer to a well pump (I can send a one-line diagram
in Word format to anyone who wants a visual, off-list). The neutral is
connected to the top screw on the back of the meter, with the jumper
removed.

It doesn't work. Yet (one can always be hopeful) :)

Here's the situation - battery fully charged, we ran the pump and watched
the meter disk in the following situations:

1. Batt connected, grid connected => meter runs forward the fastest.
Expected: meter fwd until battery voltage drops and grid kicks in, when the
meter should stop.

2. Batt disconnected, grid connected, through inverter => meter runs forward
fast, but not as fast as #1. Expected: no movement fwd - possibly small
movement in reverse for inverter load.

3. Batt disconnected, grid connected, bypass inverter => meter runs forward
just perceptibly slower than #2 (i.e. minus inverter load). Expected: No
movement in meter.

4. Battery connected, grid disconnected => meter runs forward the slowest.
Expected: meter moves forward.

Any ideas? Geoff what solution did you arrive at?

For those who are wondering "Why bother?" it means an additional 10
cents/KWH for all solar energy production for our grid-tied customers.

Thanks,
-Kelly



----- Original Message -----
From: "RE wrenches" <Geoff at Third-Sun.Com>
To: <RE-wrenches at topica.com>
Sent: Monday, February 02, 2004 9:08 AM
Subject: RE: kwh meter workaround [RE-wrenches]


>
> My situation is similar to Doug's:  SW in grid tie with subpanel too.
>
> I have a non-ratheting "form 2-s" meter (rebuilt, cheap, from AEE).  I was
> planning on wiring it as per the original instruction, 120 to subpanel on
> one leg, 120 from inverter to main panel on the other leg - assuming the
> production would be measured in power to sub panel, power to backfeed the
> main, and any grid supported or charging losses subtracted or cancelled
out
> against output (this is a non-ratcheting)...
>
> Now, assuming this won't work  I need to change my plans fast!
>
> Option A: install the unit as simple 120 Volt Kwh meter on AC output to
main
> only.  (flaw - we don't measure/record the power sent to the sub panel) -
> Workaround - a second Kwh meter for this sub panel only- and "addition" by
> the customer.
>
> Option B - go with the unknown 5 tab approach and buy a new meter
>
> Option c:?
>
>
> Sincerely,
>
> Geoff Greenfield
> NABCEP Certified Solar PV Installer TM
> GLREA Certified Photovoltaic Systems Integrator/Installer License Number
> 0211-01
>
> THIRD SUN SOLAR AND WIND POWER Ltd.
> 340 West State Street, Unit 25
> Athens, OH 45701
>
> Phone (740) 597-3111
> Fax   (740) 597-1548
>
> www.third-sun.com
>
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