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Generator Transfer Switch: Combining Multiple House Circuits on One Switch Circuit?

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Posted by (PeteCresswell) on December 6, 2012, 5:42 pm
Just had a cutover switch installed, but it only supports six
circuits and I actually have 9 that I'd like to have power to
when running a gennie.

The three combined circuits would be a couple of bedrooms and a
bathroom.  i.e. expected use would be just a few electric lights
and a couple of radios.

Seems like two breakers will now become unused and all 3 circuits
will be running off of a single 15-amp breaker - which, in turn,
would be served by one circuit from the generator transfer

Not knowing anything about electrical stuff, I'm wondering what
the downside exposure is here.

My hope would be that putting a 20-amp fuse in the transfer
switch's circuit (which is allowed per the maker's specs) would
make it so if, for instance, somebody plugged an electric heater
into a bathroom outlet, the breaker in the breaker box would trip
and that would be the end of the problem.

What I'm worried about is maybe a wire melting somewhere - which
seems tb a really dangerous situation.

Other considerations?

Code violations?

Pete Cresswell

Posted by mike on December 6, 2012, 7:34 pm
On 12/6/2012 9:42 AM, (PeteCresswell) wrote:

I'm trying to get my head around the math.  If you have six and combine
two more on one of the six, doesn't that make 8?

Not sure what you're planning, but if there is ANY wire smaller than
#12 anywhere in the system before or after your 20A breaker, you've got
a problem.

Acting on answers  you get on the web is risky.
Some people here know exactly what they're talking about...some don't.
It's impossible to tell which is which.

There are two people who care.
1)The local building inspector who'll sign off on the inspections that
come with the permit.  Call 'em up.
2)Your insurance carrier.  They'll probably not care if the building
inspector is happy.
You are gonna get a permit and have the work inspected??right???

Around here, an electrical permit costs way more than a lifetime supply
of batteries for bedroom emergency flashlights.

You don't say where you are, or exactly what's happening, but I expect
your solution will be "frowned upon" by the inspector.  Call 'em up and ask.

As usual, the time to think about 9 circuits is BEFORE you have six

Posted by (PeteCresswell) on December 6, 2012, 10:54 pm
 Per mike:

Five house circuits, each served by a single transfer switch

One transfer switch circuit left.   Proposal is to combine three
of the remaining house circuits on to it.

A licensed electrician did the job, so I'm assuming it's all
good-right-and-holy with the powers that be.

I like the idea of calling the building inspector....  I'll do

Actually, I did.   But this type of transfer switch only comes
with six circuits for a 120-v generator (which I have).  


It's claim to fame is that it doesn't cost that much more than a
conventional switch, but can shed circuits and re-acquire them
automatically in light of circuit loads, generator capacity, and
user specs.   Supposedly, this lets one get significantly more
use out of a smaller generator without having the generator's
breaker repeatedly tripping and/or running the generator over
it's continuous load capacity.

My generator is a dinky little Honda EU2000.  

Push-comes-to-shove, I can buy a second one and run them parallel
to double the capacity.... but experience over the past few years
(using no transfer switch but lots of extension cords)  suggests
that a single one can do it.

The 10-circuit models are looking for 220v input.  People report
jury-rigging the 10-circuit/220v switches to work with a 120v
generator, but I didn't want to go there - perhaps mistakenly...
because now I'm probably talking about a much more serious crime
against nature in combining circuits...

Bottom line though is that we're thinking "lifeboat" and not
"cruise ship".... dinky little gennie, low gas consumption...

With the five individually-served circuits, we have phone
service, internet service, lights in the kitchen, and TV... plus
I can do my work (which needs a PC and LAN server).

The two extra circuits are nice-to-haves (bathroom
light/radio/electric toothbrush,  bedroom lights/radio...) but
certainly not a big deal.    

I'll still try to get the local building inspector's comments,
but it sounds like we already know what he's going to say.... and
flashlight batteries are sounding a lot more sensible.
Pete Cresswell

Posted by mike on December 7, 2012, 2:39 am
 On 12/6/2012 2:54 PM, (PeteCresswell) wrote:

I read the installation and operator's manuals.  Way cool device.
Would be interesting to know the details of the load shedding.
My place was wired by an idiot.  I've got the living room, bedroom
and two bathrooms on one 15A circuit.  The stuff I could shed is
on the same circuit as the thing I want to power.
Having the computer crash every time I turn on the microwave isn't
an attractive option ;-)  I'm stuck with manual load management.

I have a new 5kW generator and a manual transfer switch in the garage.
Impulse garage sale purchase.
Learned that the permit cost more than the hardware, so there they sit.
Power doesn't go out much here anyway.
Power outage is a good excuse to take a nap ;-)

Posted by (PeteCresswell) on December 7, 2012, 10:29 pm
 Per mike:

So would I.... -)

But the manual is the absolute pits for understanding what's
going on.   It's all "Trust us, we'll do the right thing.".
Pete Cresswell

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