monitoring equipment--oh say have you seen? [RE-wrenches]

[Joel Davidson]

I use Ethan Brand's 4 channel unit (3 AC and 1 DC) on my own 2kW net metered PV
system. With more meters than necessary I read:
a) electric service panel for net kWh (grid and SW4048 AC1)
b) 120VAC kWh meter on the standby loads subpanel (SW4048 AC2)
c) C40 controller meter for DC volts, amps, watts, amp hours
d) TM500 monitor for DC volts, amps, amp hours and % battery full
e) SW4048 for its various readings (I leave it on AC load for production amps)
f) Brand DC shunt for cumulative amp hours into battery bank
g) Brand on AC1 from service panel to inverter
h) Brand on AC1 from inverter to service panel
i) Brand on AC2 from inverter to subpanel.

I started monitoring my system daily 11/19/00 through 12/30/00. Then I switched
to monthly to match the utility bill period starting around the 20th of the
month. Some time between 2/20/01 and 3/20/01 the Brand meter reset itself. There
was no utility or PV system power outage during the period so the cause for the
reset is unknown. Lesson re-learned the umpteenth time is if you use volatile
memory and collect long-term data, then make daily readings to catch problems
and only lose one day of data. Since the one and only "hiccup," Ethan,s meter
has been working fine. All measurements confirm what we already know, that PV
performs as predicted.

1. Has anyone else has had a Brand meter hiccup? What was the cause?

2. Has anyone come up with a way to keep standby batteries on line but shut the
SW4048 float charge off?

Commentary. PV is wonderful. That said, two continuing disappointments are Trace
line-tie PV systems with batteries not having MPPT and the SW4048 consuming 7 to
8 kWh per month to float charge batteries that are just standing by not being
used. On the other hand, it is nice to have a net metered PV system that
requires virtually no attention and batteries on line when a utility blackout
occurs. Our neighborhood is 5 miles north of LAX in Southern California Edison
territory. In the past month we had a 1.5 hours stage three rolling blackout and
a 16 hour outage due to wire and transformer failure. Both times our system
performed flawlessly with no interruption or interference to computers, modems
and phones. This very urban SCE circuit we are on was only black for 20 minutes
during the 1994 earthquake and has been down only a few times for short periods
since 1984. But if recent events are a forewarning and not an anomaly, then this
summer should be very interesting and an great time for California PV installers
to sell PV UPS to commercial customers.

Go to Tom Hoff's excellent Clean Power Estimator at
http://www.energy.ca.gov/cleanpower/
and play with the numbers. Your commercial customers should be pleasantly
surprised at the economics of a PV UPS when you factor in the buydown rebate,
10% investment tax credits and accelerated depreciation. Any business that puts
in a UPS without PV is throwing away money.

Brightly,
Joel Davidson


"Travis Creswell, Ozark Solar" wrote:

> Marco,
> Have you checked out the newest multi-channel Brand unit?  Has anyone for
> that matter?  I'm pretty happy with the other Brand power meters that I have
> and am giving thought to getting one of his multi-channel recording units
> Also trace has a multi-channel unit but I don't know if it counts kWh's.
> Before I bought the Trace one, I'd spend some time with the Grainger
> catalogue.  The last time I looked at Grainger they had comparable units
> (maybe even a few more features) for a little less money.
>
> I'm currently recovering from emergency appendix surgery and won't being
> doing much other than reading and surfing the internet for the next week so
> I'll look around some and let you know what I find.  Laproscopic, only 3
> small cuts.  Checked in the hospital at 10pm and out the next day by 5:30
> pm.  I'm impressed.
>
> Travis Creswell
> Ozark Solar
> ----- Original Message -----
> From: <mmangelsdorf at hei.com>
> To: <RE-wrenches at topica.com>
> Sent: Friday, April 20, 2001 4:29 AM
> Subject: monitoring equipment--oh say have you seen? [RE-wrenches]
>
> > Wrenches,
> >
> > I'm looking for affordable monitoring equipment to be able to measure both
> > instaneous and cumulative power from a solar array and from a
> grid-connected
> > inverter to critical loads and to the grid.  Do any of you have experience
> > or feedback on the Hexaplex kWh meter?  Check out their website for more
> > info: http://home.att.net/~fisher-wright.  It looks interesting on paper.
> >
> > Marco Mangelsdorf, Ph.D.
> > Marketing and Sales
> > ProVision Technologies, Inc.
> > 69 Railroad Avenue, Suite A-7
> > Hilo, Hawaii 96720 USA
> > (808) 969-3281, fax 934-7462
> > www.provisiontechnologies.com
>
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