Inverter protection [RE-wrenches]

[allan]

Travis,
    Bob-O is right on this.  Code requires that all "service equipment" be
isolatable from all power sources.  Trace is using the 250 as one disconnect
for the C40.
    It's a stupid design.  As Bob-O sez, that #6 pigtail is being protected
by a 250A breaker.  Now we have never had inverter trouble from the array
powering the inverter if the 250 is shut down while the inverter is on.  A
couple of years ago I asked Trace tech support about this, and was told that
the inverters can handle running off the PV input--but the techie didn't
sound all that reassuring himself, and we didn't mention a big wind gennie.
    We have used a few power panels, mostly for last year's Y2K systems,
none since.  We do use a lot of Trace's DC disconnects in single-inverter
systems (not enough warehouse space with two).  In most cases, we either use
two Heinemann breakers for the controller (one on the PV side and one on the
battery side), or if we anticipate that we'll need more than the four
breaker spaces in the Trace box, we'll use a separate QO2-4/70 box for the
array input.  In either case, we run to the battery side of the big breaker.
    This brings up a related issue:  Grid folks are used to the big breaker
on their AC panel shutting everything off.  So they'll think the same of the
big DC breaker.  If they freak out for some reason they'll hit that breaker,
which causes all sorts of trouble if the inverter is operating at the
time--at least loss of programming from the also-stupid volatile memory.
(It happens--one customer shut off this breaker--and the generator input
disconnect--the first time the SW cooling fans hit stage 3).  So we 1) label
the 250 as "Inverter Breaker", not "main disconnect"; add the label
"Warning: shutting off this breaker may cause inverter to lose programming
and require a service call" or something like that; 3) run all other loads
and inputs on separate disconnects; and 4) warn the client about this.

Allan at Positive Energy
-----Original Message-----
From: Bob-O Schultze, Electron Connection <econnect at snowcrest.net>
To: RE-wrenches at topica.com <RE-wrenches at topica.com>
Date: Monday, December 04, 2000 9:49 AM
Subject: Re: Inverter protection [RE-wrenches]


>Doug,
>I don't sell or install Power Panels and THAT is one of the reasons.
>As I recall, the wire that they provide to go from the inverter side
>of that 250A CB to the RE inputs is 6AWG as well. The one Wes Edwards
>and I installed as volunteers for a non profit had that #6 going
>right up into the battery positive input of a C40 controller. Meaning
>that should you have a fault in the controller, that #6 was protected
>only by a 250A CB. Lovely, and it apparently is OK with UL which
>tells me something about the whole testing lab deal. As to protecting
>the inverter DC inputs from gross overvoltage, I THINK the C40 (or
>whatever) should block PV voltage if powered down. The wind genny is
>another matter entirely. Usuall, I remove the skinny #10 wire from
>the battery side of the big Henie and replace it with something more
>substantial BEFORE I assemble the DC 250. Of course, with your PP
>that defeats the whole purpose of buying a prewired, UL approved
>unit. Your only options I think, would be to shove a wire up with the
>4/0 on the hot side of the big CB, feed it to a smaller downstream CB
>or safety switch and on to your Whisper load center (or whatever).
>OR, feed the Whisper load center (thru a DC rated CB or RK-5 fused
>safety switch) directly from the battery. A bit uglier, but at least
>safe.
>Good Luck, Bob-O
>
>>I have a question for the expertise of this group.  We are in the final
>>throws of completing a system (2 racks of 4 ASE 300W modules on trackers
and
>>3000W Whisper (I think), 2 Trace 5548s for 240V on a Trace Power Board,
>>about 2000 Ahr battery bank, 20Kw generator, purchased as a package from
>>Kiocera ("It will take an electrician only a few hours to get it up and
>>running!")).  The power inputs (PV and wind) are connected to the inverter
>>side of the 250A battery disconnects, which is our question.  It seems to
>>leave the inverter unprotected - you're able to isolate the batteries, but
>>to isolate the inverter you need to turn off the PV and wind input
>>separately.  This would seem to make sense, but it seems that an
inattentive
>>or inadequately trained homeowner might easily turn off the battery main,
>>thinking they were disconnecting power to the inverter, when in fact the
PV
>>and wind would still be powering the units.  We actually did this (left
only
>>the wind connected), and one of the inverters smoked.  So, I would
>>appreciate any thoughts and/or remedies.
>>Doug McCorkle
>>Sunnyside Solar
>
>Bob-O Schultze, Electron Connection
>PO Box 203, Hornbrook, CA 96044
>800.945.7587 fax 530-475-3401
>www.electronconnection.com
>
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