[PLUG-TALK] [PLUG] Line conditioners

Keith Lofstrom keithl at gate.kl-ic.com
Thu Nov 13 18:26:33 PST 2014

On Thu, Nov 13, 2014 at 12:52 PM, Keith Lofstrom <keithl at gate.kl-ic.com> wrote:
> Transfer switch - in my generator subpanel, I have a pair of breakers
> with a little mechanical gizmo that only allows one of the pair to
> be active at one time.  A little iffy, but installed with the help
> of an electrician, and the electrical inspector allowed it....

On Thu, Nov 13, 2014 at 03:35:59PM -0800, Denis Heidtmann wrote:
> Keith, how about pix of this little gizmo?  Is it commercial or home made?

Commercial, I think it is called a breaker interlock, here's one:


Mine is a little different, but it is the same idea.  You cannot
turn on both breakers at once. 

You have to think through the grounding and the neutral return to
make these work properly, especially with GFCIs.  My toggle controls
two-phase (120-0-120) ganged breakers in a subpanel, one feeds
computers, one feeds refrigerators and furnace.  My computers are
further isolated behind some 120 pound medical-grade isolation
transformers.  Wastes a little power, but lightning-resistant.

The gizmo was something like $40, not cheap for a few cents of
metal, but most of that is due to low volume and manufacturer's
liability insurance. 

If the toggle is misinstalled, it can cause fire or electrocution. 
You do not want to send power back to the pole and zap a utility
worker.  The neutral can do that if the wrong thing burns out on
the transformer or neighborhood wiring.  The wiring (or miswiring)
will remain decades after the homeowner who installed it is dead.


Keith Lofstrom          keithl at keithl.com

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