I'm trying to find the specifics of the double-throw manual transfer
switch I need to run my whole house off my generator.
I'm planning to have a 6000 watt gas generator with a L14-30 type
4-wire output socket in a 3-wire 200 amp house electrical system. I
would like the transfer switch indoors.
My question is which kind of double-throw transfer switch do I need?
fusible 2-pole 3-wire w/SN (sn=solid neutral?)
If I had to guess it'd be "unfused 3-pole" with a breaker panel that
has a main breaker and "fusible 3-pole" with a breaker panel that
contains breakers only for the branch circuits, whatever is cheaper.
I'm I close?
(I've tried to find relevant text in the my 1996 NEC with no success.)
Secondly, I'd wire the generator up like this:
"G" of L14-30 (chassis ground) to earth ground of my house system
"W" of L14-30 to transfer switch neutral
"X" of L14-30 to transfer switch hot
"Y" of L14-30 to transfer switch other hot
Is this right?
Any help appreciated,
Take a look at the Line Transfer Switches that Lowes sells.. I'd be willing
to bet that they meet your local codes, in addition to the NEC requirements.
I'm not sure that it is necessary to swith the nuetral but it may be a
safety requirement.. When I lived overseas I had a generator and line
transfer switch to handle the whole 200 amp load.. I didn't have to switch
It is necessary to switch the neutral if you have a bonded neutral/ground in
your generator. If non-bonded, you must not switch the neutral.
All the generators I have seen have been non-bonded, and all the transfer
switches have not switched the neutral; which fortunately go together.
An excellent article on it is at:
Thanks, that link is the first humanly readable article I've seen on
the subject. This refers to the CEC, so all I have to do is verify
that the NEC is proposing the same.
The first question to ask is what loads do you want to run off the generator --
anything in the
panel, a handful of circuits, or somewhere in between? I don't like those
Gentran transfer switches,
and you can get them for up to 12 circuits, but usually only 1 can be a double
pole (240V) circuit.
These are the most common and probably least expensive solution. They are also
typically limited to
15A circuits. The intermediate approach is to put a transfer switch between your
main panel and a
subpanel. Then run all the circuits you want to run from the generator in the
subpanel. Finally, you
can put a transfer switch in front of your 200A panel and be able to run any
load in your house that
is under 6KW, but you'll have to switch things on and off to keep from
overloading the generator.
You'll also have to mess with Service conductors which will require you to at
least pull the power
meter and probably run some new conduit.
Transfer switches for option 1 are about $150 to $300. A transfer switch for
option 2 is $200, but
you also need the subpanel, the feeder cable, and a large breaker to protect the
feeder. Option 3
costs $300 plus service conductor rework.
As far as the switch itself, it doesn't need any fuses. But you have to have a
somewhere near the generator to protect what is going to the transfer switch,
and each branch
circuit must have a circuit breaker. A 2-pole switch is the minimum required,
and will require you
to separate the neutral/chassis bond in the generator if using option 2. A
3-pole switch will work
with any configuration and is the preferred switch because you can switch the
neutral too, thus
eliminating any downstream rebonding of the neutral which isn't allowed. But
this creates a
Separately Derived System.
They're all legal so you won't find it. The problem is breaking all the other
little rules scattered
throughout the book depending on what approach you take.
Yes, but the neutral/ground bonding issue needs to be addressed and depends on
how you do things
whether they should be bonded or not.
You can get a 200A Cutler-Hammer unfused 2-pole manual transfer switch from
Harbor Freight Tools for
$299. I believe this is your best option if no provisions have been made for a
transfer switch. But
there may be issues with mounting this beast next to your main disconnect and
rerouting the service
conductors. They have a smaller 100A unit for $199 that you could put in front
of a 100A subpanel,
but you'll need to relocate everything you want to power to this subpanel.
Sorry, didn't mention this was all new construction. But I did say I
wanted to run my whole house. I share your dislike of the GenTrans
That's great because I priced a Cutler-Hammer model (DT324FGK) for
$3420! What brands are you referring to? The Harbor Freight model
you mention for $300 lists for $1695 so that's quite a buy, maybe too
A fuse between generator and transfer switch? Could you explain it's
function?It's only a 6000-watt generator, if I ask too much of it,
what's the harm?
and each branch
However you decide to go be sure your transfer panel has watt meters,
or else you run a high risk of overloading a generator leg. I have to
rebalance my panel , Friday I had an outage I was pulling Max off one
leg and 10% off the other. Bad for a generator.
It just shows you how overpriced a lot of electrical equipment is (or how
residential stuff is
highly subsidized by other customers). A 200A main panel is $80 at Home Depot
with 6 breakers
included. Buy the equivalent rated panel from CH without the breakers and it
will list for $300. I
bought the 100A switch from Harbor Freight and have been happy with it -- its
huge and seems very
industrial. A co-worker bought the 200A version.
Generally, all conductors must be protected from short circuits. You could argue
that the generator
can't source enough current to melt the feeder, but I'm unsure if the code
allows you to run the
output from a generator unfused (I don't think it does). Usually, a generator
has built in
overcurrent protection anyway. It also requires a disconnect, but the transfer
switch may qualify if
it is in sight of the generator, and a power cord would also qualify.
If this is new construction, I'd definitely go with the 200A model. It makes the
issue so much easier when this is Service Equipment. You can always bond the
generator if you need
to, but unbonding some can be impossible. Only requirement with this switch is
that it must be
mounted immediately adjacent to your 200A main breaker box.
Some panel brands (SquareD) sell interlock kits. Essentially they let
you backfeed using a breaker in the 2/4 position. The kit contains a metal
lever or plate that doesn't allow the main breaker and the 'generator'
breaker to be on at the same time. For this kit to work, you need a panel
mounted main breaker. Essentially it creates a two-pole switch.
That interlock kit sounded good on paper but it's the klugiest looking
thing installed. I'm thinking to that I'd like to have a sub panel
and have that switched as well so I'm going with the old fashioned
Once you install the interlock kit anything that is supplied from that
panel, including sub panels, can be supplied by the generator
connection. The only limitation is the capacity of the generator set
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