[pvusers] PV inverter reliability

[Joel Davidson <joeldavidson@earthlink.net>]

Inverter failures has been blown way out of proportion. Sure, inverters
fail as do any electronic device. I have sold thousands of inverters,
have about 1.5 megawatts of on- and off-grid PV in the field with
inverters and have personally used inverters since 1963. Many of my
customers read these posts. Perhaps they can write in and attest to
inverter reliability.

I predict an inverter failure rate decline analogous to the decline in
failures of another complex electronic device, the television. Four
decades ago, TV power supplies and tuners failed fairly regularly. Today
billions of TV are in use and 100s of millions of TVs are sold yearly
and the failure rate is very low.

If you are concerned about buying a good inverter, ask your supplier for
a recommendation.

If you install inverters, follow these 3 simple rules:
1) Size the inverter properly. Running an inverter at full rating all
the time is poor system design. An inverter "running on red line" in a
poorly ventilated equipment room suffers heat stress which shortens
component life.
2) Size your inverter cables properly. Undersized cables stress
inverters. Wire is cheap compared to the price of an inverter. If "the
book" says 2/0, then use 2/0. Or better yet, use 4/0. You are only
talking about a few feet of cable.
3) Tighten all battery and inverter cable connections properly. If you
don't know how to use a torque wrench, then you are not qualified to
tighten cables.

This email was written in a net-metered PV powered office. See system
wiring diagram at http://www.solarsolar.com/sysdwg.html Our SW4048
inverter was installed June 1998 and has functioned perfectly through 2
SCE scheduled blackouts (remember the California energy crisis?), 2
utility power outages (1 was 16 hours long when a pole mounted
transformer when out on the next block) and my regular system tinkering.
An added benefit is that I have not had to replace a computer mother
board or hard drive since going solar because power quality from the
inverter is better than grid power.

Editorial - I think Xantrex's ST-series and SW-series troubles could
have been avoided or quickly corrected if the talented engineers that
use to work at Xantrex and the talented people still there had been
given the freedom to make better inverters. Trace had a tradition for
making great inverters. It is time for Xantrex to pick up the Trace
banner or lose the race. Employers either help their eagles fly or herd
turkeys.


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