"wahzoo" wrote in message
om...
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?)
fusible 3-pole
unfused 3-pole
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 circuit breaker
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.
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.)
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.
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?
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.
http://www.harborfreight.com/cpi/cta...emnumber=42163
--
Mark
Kent, WA