I want to be able to get power into my house from a portable generator
without the need of extension cords through open doors. I would like
to install an external box that can accept at NEMA-type plug from the
generator and then wire it to a couple of outlets inside the house that
are independent of the rest of the house's electrical system. I won't
need any transfer switch because the power from the generator will
never travel on the main wires in the house.
My question: The box that accepts a NEMA plug has two hot (red and
black) wires. Can I wire an outlet using the red wire and an another
outlet using the black wire (with the white and ground wires common to
Thanks. I was pretty sure that's how it worked, but I couldn't find
any website that talked about wiring it in this way.
The furnace will have to remain off during a power failure. If I want
to get that fancy, I will get an electrician to hook up a transfer
switch. I'm just trying to power the refrigerator, TV, some lights and
a fan without having an open door cluttered with extension cords.
There are better options than a true transfer switch available today for
small generators. A true transfer switch is needed for large loads, but
if you only have a small generator and have to do load management anyway
there is no need for a transfer switch.
There are a number of small generator sub panels in the ~$200 price
range that allow you to move 6-10 circuits that require backup to this
new sub panel and each one essentially has a little transfer switch.
An even cheaper option that can be used for large generators as well as
small ones is an interlock kit for your main panel. I just did a full
panel replacement with a Square D QO panel and I installed a ~$30
interlock kit from Square D that interlocks the main breaker (200A in
this case) with another 2 pole breaker (any size up to 125A) in panel
I have a 20A breaker as the back feed breaker currently since I'm only
connecting a 5 kW generator, but if I switch to a larger generator I
just change that back feed breaker to a larger size. You could even use
an oversized breaker there if you wanted since it is really only doing
switching duty, the over current protection is provided by the breakers
on the generator itself.
This interlock kit is a much cheaper solution than a full transfer
switch or even one of the generator sub panels. Since it's produced by
the manufacturer of the panel it's a quality, approved option. Square D
makes the interlock kits for their Homeline panels as well and I expect
a few other manufacturers have similar options.
Price out your exterior box, socket plugs,, cable to the gen. Now look
at a Generac transfer switch kit, for 300$ you get everything , a pre
wired 6 circuit panel with 2 watt meters, exterior box, extra sockets,
plugs , cable. It is cheaper buying the kit, easy to install and you can
power everything you need.
I think you miss the point of the Square D interlock kit. The little
generator sub panels only handle what circuits you relocate to that sub
panel, the $30 interlock kit takes the place of a full transfer switch
for generators supplying up to 125A. Since it provides power to the
entire panel it also lets you power any circuit you need and do load
management as required.
Does the sqare d have watt meters, he did say portable gen, it would be
to easy to overload the gen without a way to monitor it. I never looked
into square d, I just put in the Generac kit since it was complete and
pre wired .
The Square D kit is nothing more than an approved interlock plate that
only allows one of the two (main or back feed) breaker to be on at the
same time, and a retainer bracket that prevents the back feed breaker
from being inadvertently removed from the panel. There are no meters,
inlet connectors, etc. The kit I used is a QOCGK2 if you want to see it
on the Square D site, it's very different from the little generator sub
As noted this is about a $30 kit that can take the place of a $200+ full
125A transfer switch. Even adding the cost of the back feed breaker and
inlet box for a small generator it would total perhaps $100.
Overloading a small generator isn't much of a concern since the
generator will have it's own circuit breakers and it will just pop them
or stall the engine if you switch in too big a load like a central A/C
The interlock kit is a particularly good option for those who are
comfortable doing load management, or in cases where a generator large
enough to handle most everything is being installed.
I've been Googling around looking for less expensive transfer
panels/switches/relays etc and also found this puppy. It's great to
see someone already using it. I hate to have to replace my entire load
center but even so it's still cheaper and more flexible than anything
else I've found.
The upside is it also gets me a main circuit cut-off inside the house
that the contractor crap doesn't have.
One question though, maybe two ;-), where did you get the interlock?
No one seems to have it and Square-D doesn't sell direct.
And a general question directed at anybody (who knows) - there wouldn't
be a problem installing another set of mains breakers in series with
the the main service breakers outside by the meter, would there?
Oh, and a third - does the inside breaker have to have the same rating
as the outside one (150Amp?) There is a great SquareD value pack I'd
like to use but it has a 200 Amp main breaker.
Pete C. wrote:
The inside Main can be larger than the outside main as the conductors are
protected by the 150 amp . The inside would essentially just serve as a
disconnect. Call electrical supply houses that are Square D distributors for
> Pete C. wrote:
>> RBM wrote:
>>> This is actually a cheap, simple, safe,and approved method of
>>> only seen it made by Square D for the QO series
>> They also make it for their Homeline series panels.
>> Pete C.
You can get the Interlock at any Square D stocking electrical supply
house. I've even seen them at the box stores.
The only issue with the series main breaker arrangement is that both
breakers must have an adequate withstand rating for the available fault
current. The 150 ampere breaker is undoubtedly sized for the service
entrance conductors so you can't eliminate it without changing out your
service entry conductors.
No the breakers don't have to be the same amperage rating as long as the
one at the meter is sized for the size of the service entry conductors.
"This alternating current stuff is just a fad. It is much too dangerous
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