[RE-wrenches] More Bypass Musings

[Jason Szumlanski]

I think there’s a real point of diminishing returns here. Even on
whole-home backup systems, I usually skip a dedicated bypass as long as
there’s a reasonable way to restore power in a true emergency.

For *off-grid*, it’s definitely convenient to send generator power to the
loads during inverter service. But if the generator feed is spliced to feed
both the inverter and one side of a bypass switch, you still have to
disconnect the inverter feed to make it safe for service, so the benefit
can be marginal. The real benefit here is for clients to be able to
self-service to restore power during a component failure.

For *on-grid* systems, I recently dealt with an Enphase System Controller
failure. There was a separate main disconnect ahead of it (no main breaker
in the controller), and the load lugs fed the whole house. The controller
failed with the microgrid interconnect contactor stuck open, forcing the
client off-grid even though utility power was available.

Bypassing it took nothing more than a pair of 3/0 Polaris taps and about
ten minutes to splice the line to the load. Would a 200 A bypass switch
have been worth it? Not really. The quick splice worked fine, and once
Enphase sent a field tech to replace the MID, I just reversed it – no big
deal.

Back to off-grid, or on-grid for that matter... This is where a
well-planned wiring trough shines. You can make quick splices to bypass
smart loads or even whole-house feeders when needed. On a recent grid-tied
multi-Midnite AIO installation, I made sure the AC in and AC out power
distribution blocks were close enough together that I could completely
bypass the inverters with some quick Polaris tap splices. Or, I could
quickly remove and cap off a single inverter from the distribution blocks.
That's even better than a bypass because you can selectively bypass a
single inverter for service.

Most bypass switches will live their entire lives never being used, so I
tend to design for practical flexibility rather than theoretical
perfection. There are definitely situations where a bypass switch is
mandatory, in my opinion, but when there are options and the risk is low, I
often save the customer a few bucks after having a conversation with them
about convenience, cost, reliability/resilience, and serviceability.

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208


On Wed, Oct 15, 2025 at 11:26 AM Dave Tedeyan via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Hi All,
>
> Now that some inverters have "smart" load capabilities, I am musing on
> whether to put in a separate bypass for each smart load. I am thinking
> specifically about the Midnite AIO inverter, where the Smart loads are
> powered directly from the inverter, rather than just providing a relay to
> cut power (like in the Avalon SEP, if anyone has used those). The Midnite
> AIO also has provisions to run other backed up loads directly from the
> inverter as well.
>
> But if there was a system failure, and you have a bypass switch installed,
> this will only power the loads in the backed up loads panel from the grid,
> but not the specific loads that originate from the inverter. Are people
> installing bypasses for every individual load that originates in the
> inverter? I was just looking at William's interlock system, but I don't
> think that you can utilize that kind of system to have some smart loads in
> there as well. It seems like you can utilize the panel he labels "inverter
> feed" on his one line diagram to power other backed up loads, but the would
> not work for a smart load.
>
> Cheers,
> Dave
> --
>
> [image: Logo] <https://www.sungineersolar.com/>
> Dave Tedeyan, P.E.
> Owner | Sungineer Solar
> p: he | him | his
> a: 1653 Slaterville Rd. | Ithaca, NY 14850
> w: www.sungineersolar.com <http://www.sungineersolar.com/>
> c: (607) 270-0370
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>
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