[RE-wrenches] Bypass Musings

[Tyrone Houck]

Very cool. We typically use Siemens panels with the "back to back" style
interlock for single inverters allowing up to 125A bypass in a readily
available 8/16 panel. In this fashion, multiple inverter installs
necessitate an AC combiner panel with the output feeding a larger transfer
switch. I like your solution as it certainly has the potential to save wall
space and condense the footprint into one larger panel. We commonly install
two bypasses in series for all grid tied battery backup systems; one for
grid bypass and the second for generator bypass. I look forward to trying
your product in the future.. I still need to plan the brand switch to QO
for the right scenario(which I probably need to do anyway as I have a
decent collection of QO breakers collecting dust!). Nice work and a hearty
salute for coming up with a creative solution to a question most of us have
asked at one point or another!

Sunny Regards,

Tyrone Houck
Oregon Solarworks LLC
CCB #204937 LRT #076
541-787-1366
tyrone at oregonsolarworks.com




On Mon, Oct 13, 2025, 10:54 PM William Miller via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> 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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