[RE-wrenches] Bypass Musings

[William Miller]

Friends:



For many years I had committed to the Outback product line.  The decline of
Outback forced me to branch out.



I just completed my first install of Fortress Envy inverters.  Not long ago
I installed a Sol-Ark 12K in my shop.  Both experiences were mostly
positive.



What is interesting is the Envy and Soul-ark inverters do not come with BOS
equipment.



Now, if you want a PV disconnect, you need to add one manufactured by a
third party.  This can be accomplished with a 600 volt safety switch.



If you want AC disconnecting means or distribution, you need to provide
outboard equipment.  This is easily provided with off-the-shelf circuit
breaker panels.



Since my second Radian install I have avoided putting AC breakers in the
GSLC because wiring them was beyond tedious.  Instead I ran my AC leads
right through the GSLC and straight to one of two breaker panels:  A
generator-fed panel and in inverter-fed panel.  Therefore I am not
inconvenienced by lack of AC BOS with the new generation inverters.



There is one other function that is missing with the lack of BOS cabinets:
Bypass switching.  I think it is imperative that bypass capabilities be
provided.  Inverters can fail and occasionally need service and a bypass
makes these scenarios much easier to handle.  As a matter of policy I will
not support a batter-inverter client if they do not have a bypass.



The Fortress and Sol-Ark manuals recommend use of an outboard double throw
switch for bypass.  These are expensive and bulky.



Over the years I have developed circuit breaker interlocks that can be
fitted in a standard breaker panel and take care of the bypassing function
cheaply and efficiently.



For a long time I have been meaning to write an article on the subject of
transfer switches and bypass options.  I finally got around to it and it
can be found here
<https://millersolar.com/MillerSolar/practices/Technical_Procedures/Interlock/Interlock.html>.
I hope my efforts writing this might provide some insight on the subject.



I think I have fine-tuned my interlock design to a final iteration, as
described in the article.  If any of you are interested in trying out my
Universal Bypass Interlock I am willing to send one for you to try at no
cost.  Contact me off list if you are interested.



Sincerely,



William Miller



Miller Solar

17395 Oak Road, Atascadero, CA 93422

805-438-5600

www.millersolar.com

CA Lic. 773985
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