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

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
switch.

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?

 

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
installed.

 

Per mike:

Five house circuits, each served by a single transfer switch
circuit.

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
that.

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

http://tinyurl.com/csv3g2y

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.

 

Per mike:

Electrician I asked said something that I interpreted as similar.
I'm having trouble with this one and think either something
hasn't soaked in yet or I talk too fast/write too verbosely and
am muddying the waters.

For the sake of argument:

- One 15-amp breaker (NOT 20.... the twenty amp fuse
is in the switch's circuit feeding the 15-amp
breaker)

- Three circuits hung on that single breaker.

- Each circuit's wire is spec'd to handle up to
15 amps.

- Seems to me like no single wire can experience more
than 15 amps because the breaker will trip at 15.

- The 20-amp fuse in the switch (instead of a 15-amp fuse)
is so that the breaker will take the hit on overload
and the fuse will be less likely to blow.

Do I have it right? If not, where am I going wrong?

 

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 ;-)

 

I see nothing dangerous here, but it may turn out to be inconvenient if
your load is more than you think it is. There is no chance that you
will want to run window units in any of those bedrooms?

When I installed my 6-circuit transfer panel I believe I combined a
couple circuits.

 

I'm no expert. I know about how electrons behave.
I don't know a lot about the details of the electrical code.

The electrical code is like a lawbook. Evolved over the ages to
codify acceptable behavior. But the devil is in the details.
You may do something that you think is perfectly reasonable
and still be in violation. That's why we have inspectors.
And they don't always agree.

What follows is based on logic and conjecture. The electrical
inspector is the one you need to ask.

Assume for the sake of argument that a 15A breaker actually tripped
at 15.00 AMPS. Assume you have #14 wire in the circuit.
If you load any point on any downstream line to 15.1A, the breaker
should trip. There is no way you can overheat any part of the
wire as long as the breaker is functional.

If you have a #14 wire from the input side of the 15A breaker to the
output side of a 20A breaker, you could logically argue that
the wire can never experience more than 15A because of the second
15A breaker.
And the inspector might agree with your logic as he wrote
"fail" on the inspection report. ;-(

I made all that up. Ask the inspector or a licensed electrician.

Just flashed on another issue.
If you have 240VAC service, your 120VAC loads will be split with an
attempt to balance the load on the two halves.
If you have a 120VAC generator, the switch will have to combine
circuits from two phases onto a single phase generator.
That might make for some interesting transients when the power
comes back on.

 

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.".

 

Per Vaughn:

Right now, we're thinking "Lifeboat", not "Cruise Ship".

OTOH, I did buy an itty-bitty microwave for use during outages
and maybe a very small window box would not be out of the
question.... OTOOH, we very seldom have outages during hot
weather and when we have they've been fixed within hours.

 

Per mike:

Waited for my better half to go shopping today and fooled around
with the gennie/xfer switch for a few hours.

It seems to tolerate cutting/resuming utility power with no
problems that I can see. Delicate stuff like the TV, LAN
server, computer are on UPS', so maybe that helps.

Once I figure out how to have come control over which circuits
get shed in what order when there's too much for the gennie, I
think I'll be a happy camper with this thing - albeit critical of
the manuals.... but then I'm one of those compulsive fault
finders and I can write a single-spaced 8x10 page of negative
rants on almost any product I buy.... -)

 

The interesting thing about the "shedding" section of the manual
was that the graph has no dimensions.
Shedding works well when the incremental loads are insufficient to
stall the system, or when you sit between the event that initiates
the function and the function itself so you can shed loads BEFORE
adding loads and sensing overload.

When you have a 2kW generator and a 1500W microwave and a 1300W bathroom
heater and a 700W furnace air handler and...and...and...
You might want minimum on/off times for the furnace and fridge.
Starting the microwave might leave you with nothing that can be shut
down and a stalled generator.
That kinda puts you in the position to manually shed loads before
you start the new one.

It wasn't much more expensive than a manual switch, so, no big deal,
but I'm not optimistic that it's all the marketing hype would lead
you to believe.
It'd be more interesting if you could install it before the wiring
went in so you could have direct access to the loads you want to
focus on.

I have this vision of the stairwell lights going out just as
you step off the top platform with a heavy box of junk.
"Honey, I'm microwaving some coffee...want some?"
;-)

 

Yes, but if you combine your circuits, you will be power-limited all the
time, not just when you are on emergency power.

I asked about the window shaker because that's one of the more common
big power users you will find in a bedroom. Other possibilities include
space heaters and medical equipment such as oxygen concentrators.

Things are a bit different here in south Florida.

Vaughn

 

Per mike:

I had a similar vision of The Better Half chopping celery in the
kitchen and Yours Truly stupidly turning on the bathroom lights
where a heater was plugged in.

I discovered a circuit parm called "Delayable" that *sounds* like
it exempts the circuit from being shed if set to False.

"Delayable Circuits The factory default setting is NO. Setting
a circuit to YES, enables the UTS to run ALM for the individual
circuit selected."

Next time I have the house to myself, I'm going to try some more
stress testing and see what happens when I do various things.

I'm thinking a 1,500 watt electric heater or two will be useful
tools in that regard. Also, I have found that just a toaster
takes almost 1,000 watts.

 

Whole lot could be sensed and controlled using existing wiring; I`m sure
you`re aware of the
various mains carrier transceiver kits available?

 

Yep.
Problem with delaying shedding is that it's determined after the fact.
If the heater stalls the generator, you're hozed.
I think a good outcome will be critically dependent on which stuff is on
which circuit.

Keep posting your evaluation results. Interesting topic.

 

GE, SquareD, and Cutler/Hammer ALL make double Breaker Modules that
have TWO Breakers in a single Breaker Form Factor. Usually these are
15Amp Duals.... Just Say'en..... That would double your available
individual Breaker circuits, and they are ALL UL Approved, so No Code
Violations.....

 

Per Mr Clarke:

Maybe in somebody's dreams.

I'll Google it.

Thanks.

 

Another little surprise will be the defrosting heaters in your
frost-free refrigerator. They take the best part of a kilowatt and come
on at unpredictable times.

 

mine is "only" about 500 watts.

- oh, and a similar surprise to anyone using (most of the) newer
natural gas stoves/ovens. They tend to have electric "spark"
ignition for the stove top - which isn't too messy electriclaly.

But... they also tend to use electrically heated "glow plates"
in the oven to ignite the gas. And these stay on the during the
entire "lit up" cycle..

Add in another 500 watts there...

 

Per Vaughn:

Luckily (?) we don't have gas for cooking, but the refrigerator
defrost thing is news to me.

Knowing that will probably save me an hour or so beating my head
against the wall wondering where the extra load is coming from.

Thanks.