Ethical dilemma [RE-wrenches]

[William Miller]

Fiends:

Here's a dilemma and how I dealt with it.  I am still wondering if there is
a better solution.  Your thoughts are appreciated:

I was called by the operations director for an off-grid elementary school
to replace fans on an SW inverter.  While on site, I took some time to
learn how the system was built.  There are 4 SW inverters with outputs
summed through 2 levels of transformers.   They run their generator during
the school day and ran on batteries and inverters during the afternoon and
evening for extra curricular, janitoring and etc.  The system runs great
while fed by the generator, but when the generator shuts down, inverters 1
and 2 are not synced to inverters 3 and 4.  You can measure the voltage
from phase to phase and over a half hour or so it goes from 240 to 0 and
then back up.  The output of the equipment room is two hots and a shared
neutral.  When the inverters are out of phase, the neutral is properly
shared.  When the inverters drift in phase, the neutral current will
increase, possibly until the current is double the rated current.  It is my
understanding that power is distributed throughout the school in this
manner.  At any point where a neutral is shared--on a feeder or multi-wire
branch circuit--this condition is possible.

I wrote a report describing this problem as clearly as I could.  I followed
up with phone calls to the operations director.  Last conversation I was
told that there was no money to correct this problem and that all they
could do is, "conduct extra fire drills."

I wrote to the school and told them I could not work for them until this
issue is addressed.  I do not want to be even associated with a system in a
public school that has an obvious design defect.  I feel pretty comfortable
about this decision, but I am curious what others might have done.

William

__________________________________________________________________
William Miller
SLO Communications: Communications and Power Systems Consulting
PO Box 50, Santa Margarita, CA 93453
Voice :805-438-5600		Fax: 805-438-4607	VMail: 805-546-4875
email: wrmiller at slonet.org
License No. C-10-773985
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